Halide ions are ubiquitous in natural waters and wastewaters. Halogens play an important and complex role in environmental photochemical processes and in reactions taking place during photochemical water treatment. While inert to solar wavelengths, halides can be converted into radical and non-radical reactive halogen species (RHS) by sensitized photolysis and by reactions with secondary reactive oxygen species (ROS) produced through sunlight-initiated reactions in water and atmospheric aerosols, such as hydroxyl radical, ozone, and nitrate radical. In photochemical advanced oxidation processes for water treatment, RHS can be generated by UV photolysis and by reactions of halides with hydroxyl radicals, sulfate radicals, ozone, and other ROS. RHS are reactive toward organic compounds, and some reactions lead to incorporation of halogen into byproducts. Recent studies indicate that halides, or the RHS derived from them, affect the concentrations of photogenerated reactive oxygen species (ROS) and other reactive species; influence the photobleaching of dissolved natural organic matter (DOM); alter the rates and products of pollutant transformations; lead to covalent incorporation of halogen into small natural molecules, DOM, and pollutants; and give rise to certain halogen oxides of concern as water contaminants. The complex and colorful chemistry of halogen in waters will be summarized in detail and the implications of this chemistry for global biogeochemical cycling of halogen, contaminant fate in natural waters, and water purification technologies will be discussed. Halide ions are ubiquitous in natural waters. Ordinary levels of halides in seawater are 540 mM chloride, 0.8 mM bromide, and 100–200 nM iodide  and [O2]  and [H+]  is much above a few millimolar  . Reactiollimolar . Howeverseawater . Scavengtive see .−/XOH; pKa,HOCl = 7.82 (0 °C), 7.54 (25 °C); pKa,HOBr = 8.55; pKa,HOI = 10.5), via a transient halo-ozonide intermediate  [3−• to transformation of phenol [Carbonates also affect RHS levels indirectly by scavenging OHces rRHS . ConversHS [3−•] ,64 and if phenol .2O2 to HO2•/O2−• Reactions (22) and (23). Rate constants are 2 × 109 M−1 s−1 for Cl• and 4 × 109 M−1 s−1 for Br•, but are much smaller for X2−•  and (27)). The highest rate constants are observed when the acidic form of one reactant is paired with the basic form of the other—namely, OX− + H2O2 or HOX + HO2−. The reaction proceeds by nucleophilic attack of H2O2/HO2− on the electrophilic halogen atom of HOX/OX− to give initially H-O-O-X and then H-O-O-O-H [1O2 [Hypohalites can oxidize H-O-O-O-H , which dO-H [1O2 . Singlet2X Reaction (28) [2− concentrations, the principal decomposition pathway of NO2X is reversible dissociation to X− and NO2+, followed by hydrolysis of NO2+ to nitrate (Reactions (29) and (30)):Nitrite attacks hypohalites nucleophilically to generate NOion (28) ,69. Hypo3 giving XO2− and eventually XO3− [3−) is of concern in drinking water as a carcinogen [In acidic aerosols, it is also possible to regain the nrRHS through Reaction (5). Hypohalites react with Olly XO3− ,26,70. Brcinogen :(31)XOH+2). DOM can also sensitize the photolysis of dissolved compounds such as pollutants, either through direct reaction between the solute and the 3DOM* , or DOM-sensitized photolysis is an important mechanism for attenuation of organic contaminants in natural waters ,11. Incr3DOM*, parameters that can be measured by a sorbic acid isomerization probe method [3DOM* concentration in photolyzed water as the halide concentration increases to seawater levels [3DOM* lifetime by slowing intra-organic matter electron transfer, which is known to be an important decay pathway for 3DOM*. In the other [3DOM*, but at the same time increase the rate of singlet-to-triplet intersystem crossing (1DOM* → 3DOM*). Exactly how halide affects 3DOM* lifetime and intersystem crossing rates remain to be resolved.Halide ions have been shown to influence the yield and lifetime of e method . Two stur levels ,75. One r levels  attribut− and Br− enhanced DOM photobleaching rates, independent of ionic strength. About 12% of the rate increase was attributed to the formation of RHS (from reaction with OH•) that target electron-rich chromophores more selectively than does OH•. The rest was unresolved. Studies on environmental grab samples are mixed; some report no consistent effect, others rate enhancement, and still others rate suppression with increasing salinity ..− and Br•, X2−•) in aqueous solution have not received a great deal of attention, and rate constants are far more plentiful for X2−• than X•. rRHS are commonly generated by pulse radiolysis or flash photolysis, and rate constants are calculated from the decay or growth of the UV/visible signal. As mentioned above, the major nrRHS in aqueous solution are the hypohalites, HOX and OX−. A sizable literature on these reactions exists due to their importance in chlorine disinfection chemistry [It is useful to summarize what is known generally about the reactions of RHS with organic compounds. The reactivities of rRHS :Three major pathways for reactions of rRHS with organic compounds have been identified: H-atom abstraction from C-H groups Reaction (33); one electron removal from heteroatoms ; and addition to unsaturated bonds Reaction (35). Rate constants range from 10 M−1 s−1 ,80  and Br2−• (1.66 V) [As expected from their reduction potentials , reactiv(1.66 V) , suggestH-abstraction  seems to2−• and Br2−• increase with electron-donating ability of the alkene substituents [8–109 M−1 s−1) to give β-halo organoperoxyl radicals (X-C-C-OO•) that decompose through various pathways to give such products as halohydrins, haloketones or haloaldehydes, ketones/aldehydes, epoxides, and diols.rRHS add to the double bond alkenes reversibly Reaction (35). Rate constants for Cltituents . The res•, Cl2−•, and Br2−• with simple aromatic compounds depend on substituents [2), reaction proceeds by electron transfer as in Reaction (34); whereas, if the substituent is H, alkyl, -Cl, -NO2, etc., the radical can add to the aromatic ring.Reactions of Brtituents . In gene•, and used short times to minimize involvement of nrRHS. In solutions containing just 540 mM Cl− and 0.02 mM Br−, the contributions to phenol transformation were 74.4% by OH•, 21.9% by BrCl−•, 3.3% by Cl2−•, and 0.4% by Br2−•. In simulated seawater that included 2.3 mM carbonates, they were 52.6% by CO3−•, 6% by OH•, 21.5% by ClBr−•, 0.1% by Cl2−•, and 19.7% by Br2−•. The lessons to be learned from this with respect to phenol transformation are that, (a) carbonates divert oxidative power away from OH• toward CO3−• and X2−•; (b) X• seems to play no significant role; and (c) BrCl−•, is an important rRHS.Mitch and co-workers  kinetica−2 to 107 M−1 s−1 [Hypohalites react with organic compounds by electrophilic substitution, electrophilic addition, or oxidation. Known apparent second-order rate constants for HOCl reactions with organic compounds range widely from 10 M−1 s−1 . The mosThe neutral form of amines reacts rapidly with HOCl (primary > secondary >> tertiary) to form chloramines Reaction (36). α-Amino acid groups undergo further decarboxylation and deamination reactions :(36)R−NHn > 1. Phenols give o- and p-X substituted products. The phenoxide ion is ~105-times more reactive than the free phenol, and reactivity correlates with electron donor character of the substituents. Ortho- and para-substituted dihydroxyaromatics undergo oxidation to the corresponding quinone [α-Amino acid groups undergo further decarboxylation and deamination reactions . Aromati quinone .Above pH ~ 5 ketones and aldehydes are halogenated by electrophilic substitution at the α carbon Reaction (37), an important reaction in disinfection chemistry because it leads to hazardous byproducts:Alkenes are attacked electrophilically by the halogen atom of HOX at the least-substituted end of the double bond to form the halohydrin Reaction (38).The halohydrin can undergo internal or solvolytic elimination of halide to form, respectively, the epoxide or the α,β-dihydroxy compound.Hypohalites can also oxidize some functional groups—for example, primary and secondary alcohols to aldehydes and ketones, respectively; aldehydes to carboxylic acids; and sulfides to sulfones, sulfoxides, or sulfonic acids . Some ofGiven that RHS are photochemically produced in natural waters, the question arises as to whether this could lead to incorporation of halogen into natural compounds and water contaminants. Of the nearly five thousand natural organohalogen compounds identified to date , only a A number of volatile gases of importance in stratospheric ozone chemistry and climate warming are thought to originate from abiotic reactions in the oceans. 3 .Or it could come from chloride displacement of bromide in BrCl2O2 and irradiated with UV for 35 min. Phenol can be considered a model compound for terrestrial DOM and some pollutants. Both chloro- and bromophenols were produced, with bromophenols constituting the majority of products. However, the total yields based on initial phenol were only 0.52% in seawater and 0.03% in wastewater concentrate. The yields were unaffected by eliminating the carbonate component, despite carbonate’s ability to scavenge rRHS Reaction (19). While not established by these results, it is more likely that phenol was halogenated by nrRHS, given the greater reactivity of nrRHS than rRHS toward phenolic compounds  × 10−4 mol I/mol C (or 19–160 nmol Br L−1 and 6–36 nmol I L−1) [H-pyrazole (DMP), to irradiated natural seawater samples generated 4-Br and 4-I DMP. Since rRHS oxidize rather than halogenate DMP, this result verifies production of nrRHS in these systems [Native organobromine and organoiodine compounds were found in a variety of seawater samples at concentrations ranging (3.2–6.4) × 10l I L−1) ,95, and l I L−1) . Simulatl I L−1) . With adl I L−1) . Additio systems  and poin3DOM* is the active oxidant species, one may postulate a mechanism involving the formation and subsequent decay of a ternary exciplex, as previously discussed DOM*The ESI-FT ICR-MS study provided a wealth of information on the types of reactions that occur . Most naIn summary, the results suggest that sunlight-driven reactions of RHS with DOM play an important role in bromine and iodine geochemical cycling in marine environments. It has been estimated  that phoPhoto-driven AOPs using oxygen, ozone, and peroxides as bulk oxidants are frequently used to destroy pollutants in drinking water and wastewaters. Semiconductor materials are often used as photocatalysts. While earlier work employed UV light, recent emphasis has been on reactions that are viable in the visible or solar spectral regions to reduce energy costs. Wastewaters such as landfill leachates, production waters, industrial wastewaters, and reverse osmosis brines intended for reuse or safe disposal often contain high levels of halide ions. Application of AOPs for treating salty waters is challenging due, among other things, to the conversion of ROS to RHS, which can affect the efficiency of organic compound degradation and generate unwanted halogenated byproducts. It should be noted that solutions irradiated with UV wavelengths below the absorption edges of halide ions (~260 nm) may generate rRHS from direct photolysis of halides Reaction (41):2 to produce HO2•/O2−•. One study [This reaction proceeds through a reversible halogen atom-electron solvent cage complex that produces free halogen and hydrogen atoms upon reaction with water ,97. The •, including H2O2/UV, Fenton reactions, and heterogeneous photocatalysis , among others. There are several reports of decreased rates and organohalogen formation when OH•-based AOPs were conducted in the presence of elevated halide concentrations. A few examples are given. One study involving a Fenton-based AOP to destroy dyes indicated that dye removal decreased while total halogenated organic compounds (AOX) increased when 57 mM Cl− was present at pH 2.8 and 1 [• [− [Numerous AOPs generate OH.8 and 1 . Anotherand 1 [• . Machuleand 1 [• . In Fent 1 [• [− .•-generating reaction (H2O2/UV) in phosphate-buffered water containing 0.8 mM NaBr showed that OH• accounted for most (74%) of phenol transformation, Br2−• for 24%, and Br• for 0.8% [• was still the most important radical (67%), followed by CO3−• (31%), BrCl−• (2.1%), and Br2−• (0.3%).Kinetic modeling of phenol oxidation by an OHfor 0.8% . In a sy2, either by surface-associated hydroxyl radicals or valence band holes [It has been proposed that halide ions can be oxidized on the surfaces of semiconductor photocatalysts such as TiOnd holes ,102. It nd holes .− at 254 nm yields OH• and Cl• − rapidly converts to HOBr/OBr− [− generates OH• and Br• -based AOPs are attractive alternatives to hydroxyl radical-based AOPs. The sulfate radical is nearly as reactive toward organic compounds as hydroxyl. UV/peroxydisulfate (S2O82−) has a higher quantum yield of SO4−• from S2O82− (1.4) at 254 nm [• from H2O2 (1.0) [• and SO4−• simultaneously [Sulfate radical (SOt 254 nm  than doeO2 (1.0) . The phoaneously . SulfateSulfate radical reacts directly and rapidly with the halide ions:− by OH• is important only in acidic solution, oxidation of Cl− by SO4−• Reaction (43) is pH-independent and therefore impacts water treatment over a much broader pH range. Several studies have shown that halide ions can strongly affect SO4−•-based oxidation rates [While oxidation of Clon rates  and leadon rates .4−•-based processes are more strongly affected by halides than are OH•-based processes [2−• and CO3−• are much higher than those of SO4−• and OH• [2−• and CO3−• are typically less reactive and more selective toward organic compounds than SO4−• and OH•, means that oxidation efficiency can be significantly impacted [2O82− was strongly suppressed in 0.54 M chloride solution compared to phosphate-buffered water, while cyclohex-3-ene carboxylic acid was hardly affected at all [2−•, is poorly reactive toward benzoic acid, but highly reactive toward the double bond in cyclohex-3-ene carboxylic acid [2O82− reactivity of different pharmaceuticals in reverse-osmosis brine compared to water—namely, that X2−• and CO3−• were more reactive toward some than others [Experiment and kinetic modeling show that SOrocesses . In the  and OH• ,113. Thiimpacted ,113. Howd at all . This islic acid . A similn others .3−) as a final product under some conditions −O3S3) and iodoacetic acid [In the presence of iodide, peroxymonosulfate reactions can also lead to incorporation of iodine into DOM and form byproducts of concern derived from DOM, namely, iodoform  principally through DOM-sensitized photolysis and reactions with ROS of photochemical origin, especially hydroxyl radical, but also ozone and nitrate radical in atmospheric aerosols. Much more work needs to be done to establish the mechanism and importance of DOM-sensitized photolysis of halide ions with respect to generation of RHS. The nature of the chromophoric groups and the quantum yields of initial RHS products as a function of DOM type need to be established. It is noteworthy that chloride enhances bromination and further work is needed to establish whether the cause is formation of a ternary exciplex like the one in Halogen plays an important and colorful role in environmental photochemical processes in natural waters and in chemical reactions taking place during photochemical water purification. In the environment, halides can be oxidized to rRHS  interconverting with smaller amounts of molecular halogen species, X3DOM*). Exactly how this happens is not entirely clear and deserves further research; one study attributed it to a general ionic strength effect, while another to an increase in the rate of singlet-to-triplet intersystem crossing. Some studies report that high halide concentration accelerates photobleaching of DOM. The mechanism has not been established with confidence. An increase in the steady-state 3DOM* concentration could lead to a loss of chromophoric groups through intra-DOM reactions, or an increase in the generation of RHS that can oxidize DOM.Halide ions at relatively high concentrations can apparently increase the steady-state concentration of excited triplet-state dissolved organic matter  and undesirable byproducts can be formed. There is much to be learned about the influence of halide salts. It is noteworthy that halides can be photolyzed by UV below 260 nm. Whether halides are oxidized on photocatalyst surfaces is largely an open question. The rate constants of RHS with many organic compounds are unknown, but important for evaluating the contribution of RHS to organic compound degradation. The yields of halogenated byproducts depend strongly on the parent compound and the solution conditions. An insufficient database exists to predict precisely where rRHS will attack in a complex molecule. The halogenated byproducts may be of greater toxicity than the original contaminants. Although many studies reported the appearance of halogenated products, quantitative yields are often not reported ,104,122.


Little is understood regarding whether neural dynamics between the hub and spokes might flexibly alter depending on the nature of a concept and how it impinges upon behaviour. Using fMRI, we demonstrate for the first time that the ATL serves as a ‘pivot’ which dynamically forms flexible long-range networks with cortical modules specialised for different domains . In two experiments, we manipulated semantic congruity and asked participants to recognise visually presented items. In Experiment 1 , the ATL increased its functional coupling with the bilateral frontoparietal action-sensitive system when the objects formed a pair that permitted semantically meaningful action. In Experiment 2 (objects embedded in a scene), the ATL augmented its coupling with the retrosplenial cortex of the place-sensitive system when the objects and scene formed a semantically coherent ensemble. Causative connectivity revealed that, while communication between the hub and spokes was bidirectional, the hub's directional impact on spokes dwarfed the strength of the inverse spoke-to-hub connectivity. Furthermore, the size of behavioural congruity effects co-varied with the strength of neural coupling between the ATL hub and action- / place-related spokes, evident both at the within-individual level  and between-individual level . Together, these findings have important implications for understanding the machinery that links neural dynamics with semantic cognition.The neural architecture of semantic knowledge comprises two key structures: , regardless of tasks and stimuli•Processing semantic congruity about action and place recruits respective domain-specific regions•Neural dynamics between the ATL and action/place-specific regions co-varies with behavioural congruity effects•Semantic knowledge requires a division of labour between domain-general (ATL) and domain-specific regions In thise spokes . Howevere spokes .Since its genesis, the hub-and-spoke theory has been continually updated as neuroimaging techniques advance. Initially, this theory was built upon contrastive patterns of behavioural deficits from different types of neurological patients. Whereas patients with semantic dementia (SD) have focal atrophy of the ATL hub and show semantic deficits that extend over various conceptual domains and input modalities, patients with agnosia or apraxia have lesions circumscribed to the typical spoke regions and show selective impairments in certain domains  or bidirectional, and  whether the two-way communication is symmetrical  or asymmetrical.Our understanding about the relationship between the hub and spokes, nevertheless, is far from complete. There are three outstanding questions awaiting further investigation: To answer these questions, we conducted two fMRI experiments to investigate the relationship between the ATL hub and functionally disparate spokes. We presented pictorial stimuli and probed action knowledge (Experiment 1) and place knowledge (Experiment 2). Previous investigations into the neural basis of action and place knowledge have revealed that these two forms of semantic concepts rely upon separable cortical structures: action knowledge recruits a set of frontoparietal regions well-established as the action-semantics system, including the inferior frontal gyrus, inferior/superior parietal lobules, and motor cortices  gave informed consent before participating in the fMRI experiments. All were right-handed (assessed using the Edinburgh Handedness Inventory), completed safety screening for MRI before participation, and reported no history of neurological disease/injury or psychiatric condition. The study was reviewed and approved by the university research ethics committee.2.2Participants completed two experiments in a single session. There were eight runs of scanning. In Scan 1–3 (Experiment 1), participants viewed displays of dual objects, and performed a task probing the influences of action-related semantics. In Scan 4–6 (Experiment 2), participants viewed objects imbedded within a scene, performed a task probing the influences of scene-related semantics. In Scan 7–8, they performed a conventional 1-back localiser task to identify object-sensitive voxels of the lateral occipital cortex (LOC). The localiser data were used for a separate study and not reported here.generally despite various surface dissimilarities. Within each experiment, we sought to identify the regions that specifically discerned semantic congruity. These examinations at the general vs. specific level was attained via contrasting ‘object tasks vs. scramble patterns’ and ‘congruent vs. incongruent’, respectively. This approach is akin to prior studies wherein researchers exploited stimuli differing in formats or modalities  was orthogonal to the manipulation of semantic congruity, and the target location varied randomly and unpredictably on a trial-by-trial basis. In the non-object control task , subjects viewed a pair of scrambled patterns created via breaking images of the object recognition task into 360 randomly assembled fragments. The two scrambled patterns of each pair had identical visual configuration; however, we scaled their sizes so that one was always 2% bigger than the other. The control task required participants to judge which stimulus looked bigger.In Experiment 1, participants viewed a pair of visual stimuli in every trial, situated 4.2° to the left/right of the central cross. In the object recognition condition . A run of scanning consisted of 18 blocks of 18 s , as well as six 12-sec resting periods, giving 396 s in duration. The order in which task-conditions and stimuli-sets were presented was counterbalanced across participants so that each task-condition was equally likely to appear in every possible position of the sequences, with images randomly drawn from a designated stimuli-set for a given scan and shuffled across blocks. Each block contained six trials. Each trial began with a fixation dot (0.5 s). Subsequently, a pair of stimuli (object images or scrambled patterns) was displayed for 2.5 s during which participants indicated the target  by pressing a button on a MR-compatible response pad. All visual stimuli were displayed on a white background, presented via a mirror mounted above the head coil and projected through a screen at the foot of the scanner bed.t(6) = 22.69, p < 0.001). This difference was also manifest in by-item analysis for every individual participant , supporting its robustness that related objects are reliably deemed as permitting meaningful actions.In a pilot behavioural study, we tested a separate group of seven volunteers (none participated in the fMRI study) using an extended set of object images. The participants viewed a pair of objects in each trial  and rated the likelihood to which that the two artefacts could be employed together to perform certain meaningful actions, using a 5-point scale . Only pairs that were found to be consistently rated as permitting meaningful actions  were selected for the later fMRI experiments. This procedure yielded 216 pairs of objects for the final stimuli sets, consisting of 108 related and 108 unrelated pairs. Each individual object, be it electrical or not, appeared twice in the stimuli-sets, once presented with its semantically-related counterpart and the other time with an unrelated item. In the final stimuli-set, the average rating for related and unrelated objects was 4.37 (SE = 0.13) and 1.24 (SE = 0.03), respectively, with a significant difference in by-subject analysis (vs. non-living) was orthogonal to semantic congruency and varied unpredictably between trials. In the non-object control task , we displayed scrambled patterns made by breaking images of the object recognition task into 640 randomly distributed fragments. The scrambled pattern (778 × 518 in size) was surrounded by a black frame, either 1 mm or 2 mm in thickness. For the control task, participants judged whether the frame was the relatively thinner or thicker one.In Experiment 2, participants viewed a photo  in each trial of the object recognition task . To tackle field-inhomogeneity, a B0 field-map was acquired using identical parameters to the functional scans except for the following: TR = 599 ms, short/long TEs = 5.19/6.65 ms. Total B0 scan time was 1.6 min. A high-resolution T1-weighted structural scan was acquired for spatial normalisation, including 260 slices covering the whole brain with TR = 8.4 ms, TE = 3.9 ms, flip angle = 8°, FOV = 240 × 191 mm, resolution matrix = 256 × 163, and voxel size = 0.9 × 1.7 × 0.9 mm. Total structural scan time took 8.19 min.All scans were acquired using a 3T Phillips Achieva scanner equipped with a 32-channel head coil and a SENSE factor of 2.5. A dual-echo EPI sequence was used to maximise signal-to-noise ratio in the ventral ATL . Using t2.40 field-map (correction for field-inhomogeneity). The averaged functional images were then co-registered to each participant's T1 anatomical scan. Spatial normalisation into the MNI standardised space was achieved using the DARTEL Toolbox of SPM  using affine transformation. In the process of creating the group's template brain using individual T1, for each individual DARTEL estimated ‘flow fields’ that contained the parameters for contorting native T1-weighted images to the group template. SPM8 deformation utility was then applied to combine group-to-MNI affine parameters with each participant's ‘flow fields’ to enable warping into the MNI space for each individual. The functional images were then resampled to a 3 × 3 × 3 mm voxel size. Smoothing was subsequently applied using an 8-mm Gaussian FWHM kernel, consistent with prior studies . The functional images from the short and long echoes were integrated using a customised procedure of linear summation . The comx of SPM , which hx of SPM . Specifies e.g., .2.5For each participant, contrasts of interest were estimated using general linear model (GLM) convolving a box-car function of all experimental conditions with a canonical haemodynamic response function, with resting periods modelled implicitly. Motion parameters were entered into the model as nuisance covariates. In addition, we added each participant's reaction time (RT) of all active-task performance as parametric modulators, allowing us to rule out any brain activation driven by task difficulty or cognitive effort when assessing the effects of experimental manipulation. Low-frequency drifts were removed using a high-pass filter of 128 s. Contrast images from the individual-level analyses were then submitted to random effect models in the group-level analyses.2.6vs. unrelated context). This multiplication generated the interaction term – the psychophysiological (PPI) factor that accounted for task-driven changes in connectivity. This factor was used to identify possible ‘spoke’ zones whose neural connectivity with the ATL hub was modulated by semantic congruity. These three factors were used to construct a GLM model.The PPI analysis was conducted to investigate how semantic congruity affected the connectivity between hub and spokes. In the GLM results, we found that the object recognition tasks robustly activated the anterior section of left fusiform gyrus (FG), reliably observed in both Experiment 1 and 2, and the locus of peak activity fitted nicely with prior findings of the typical location of ATL semantic hub (see the Results section for details). For PPI, we used the peak coordinates identified by the GLM analysis, and set the ‘seed’ of connectivity at the left anterior FG; we extracted its time-series of neural activity via deconvolving its BOLD signal and deriving the first eigenvariate. For each participant, we identified the local maxima of ATL activity, guided using the peak coordinates of group responses  Six motion parameters that accounted for head movement. (ii) More importantly, the sizes of each participant's behavioural congruency effects were included as covariates to account for connectivity strength in relation to behavioural performance. In Experiment 1, semantic congruity primarily modulated accuracy; the covariate was hence defined as Accuracy – Accuracy. In Experiment 2, semantics primarily modulated RT; the covariate was thus defined as RT – RT. Note that, in both experiments, the covariate indices reflected the size of congruity effect, with a large numerical value of difference indicating a bigger effect, rather than the inversely-correlated measures of raw RT and accuracy. A whole-brain interrogation was performed to identify voxels whose activity could be explained by the PPI-interaction factor, without contamination of task condition and seed activity.In addition to the three principal factors, we included additional regressors into the PPI analysis:  based on the coordinates from representative studies about action and place processing, examining whether the PPI estimates were evident at those literature-defined ROIs. For Experiment 1, many participants reported in the post-scanning debriefing conversation that the display of congruent objects prompted them to engage in motor imagery of performing customary actions to use the two items together  whereas incongruent objects elicited little imagery. We speculated that such motor imagery might reinforce connectivity between the ATL hub and motor regions. Thus, we selected three sets of coordinates based on the meta-analysis by 2.7In the PPI analysis, we discovered that the ATL hub became more tightly connected with the action- and place-related spoke regions when the contexts encouraged the retrieval of action and place knowledge, respectively. Based on the results of PPI, we next used DCM to investigate causative interactions between the hub and spokes. Analyses were performed using DCM10, incorporated in SPM8. The first stage of analysis involved extracting the time-course of activation of the hub and spokes for each participant. This process was guided using the peak activation sites found in the initial GLM results and PPI analyses. Specifically, for each individual and each experiment we extracted the first eigenvariate  from a spherical ROI (radius = 6 mm) centred at the maximally responsive point of the ATL (identified by the GLM contrast) and action- and place-related spokes . Constrained based on the local maxima of PPI connectivity, for Experiment 1 the spoke node was located at the cluster peak in the right precentral gyrus  the intrinsic connectivity, representing the inherent coupling strength between the hub and spoke that is devoid of the perturbation of semantic contexts; (ii) the modulatory connectivity, representing an alteration to connectivity strength driven by the contextual difference of congruent vs. incongruent that is imposed upon the intrinsic linkages between network nodes.The straightforward, two-node DCM structure, plus the empirical evidence that demonstrates the existence of PPI connectivity between the two nodes, provided an appropriate context for focusing directly on the DCM parameters, following the recommendation of DCM guidelines . Here we33.1t(19) = −1.24, p = 0.23; Cohen's d = 0.28; related: 759 ms, unrelated: 776 ms), it drove a significant effect in accuracy (t(19) = 3.94, p = 0.001, d = 0.88), with object identification being more accurate for related objects that allowed meaningful actions (96%) than unrelated pairs (93%).t(19) = −4.38, p < 0.001, d = 0.98) – identifying objects in semantically congruent scenes (671 ms) was faster than in incongruent scenes (698 ms). In accuracy, we found a significant but much more subtle effect that identification was more accurate in the congruent (96%) than incongruent condition  = 2.34, p = 0.03, d = 0.52). It is important to note that such congruency effects have been replicated numerous times in previous studies that intermingled congruent and incongruent trials . With a longer 2.5-sec display that allowed sufficient visual information to accrue, in the present study we ensured that the robust effects cannot be due to guesswork at a decisional level. Also note that in all of our fMRI analyses, RTs (including performance on the control tasks) were modelled as parametric modulators, which controlled for variation of brain activity associated with response latency.In Experiment 1, semantic congruency concerned the relationship between objects and actions. While congruency did not modulate RT  at the cluster level and p < 0.001 at the voxel level. We detected, in both experiments, robust activity of the ATL hub driven by object recognition.First and foremost, we verified whether the object recognition tasks engaged the ATL semantic hub by contrasting the brain's overall response to the object recognition tasks  against the control scrambled-pattern tasks. Statistics was thresholded at k = 145,206 mm3). As shown in T = 5.53, situated at . A strikingly similar pattern was observed in Experiment 2 , covering the posterior object-sensitive regions and the anterior semantics-sensitive regions. Particularly, in the left hemisphere, we observed robust activation of the ATL, peaking at the anterior FG and nearby perirhinal region, with local maxima (T = 5.27) detected at . This task also engaged the right ATL homologue in Experiment 2, peaking (T = 5.12) at , although right ATL activation did not survive the applied threshold in Experiment 1. To highlight the overlap between the ATL clusters of both experiments, we display a conjunctive map in the middle inset-box of Specifically, for Experiment 1, object recognition elicited expansive swathes of activity extending across the ventral occipitotemporal cortices, merging as a single extensive cluster that encompassed much of the bilateral visual cortex , this relatively lenient threshold was applied to compare the congruent vs. incongruent trials that had nearly identical perceptual configurations and only differed in the subtle semantic aspect. We sought to identify the brain area that discerns such semantic granularity.Next, we identified areas sensitive to semantic congruency by contrasting related k = 4455 mm3, k = 3213 mm3, β estimate) within these motor clusters was correlated with the size of behavioural congruency effect, manifested as a statistically significant correlation at the peak of the precentral cluster  and a weak trend at the paracentral cluster . As In Experiment 1, we found object pairs that permitted meaningful actions elicited greater activity in two action-related regions of the right hemisphere, relative to unrelated object pairs. Both clusters belong to the broad frontoparietal action-related network – one active cluster was located in the precentral lobule  and right LG . As In Experiment 2, we found that, compared to unrelated contexts, visual items embedded in semantically-related scenes elicited greater activation in the bilateral lingual gyri (LG), known to be parts of the ventromedial place-processing system : the lef1944 mm3 B. IntereTogether, these analyses revealed that the ATL hub was commonly engaged by both kinds of object recognition tasks, consistent with its domain-general nature. By comparison, regions known for their roles in action- and place-related processing are differentially engaged to tackle distinct types of semantic congruity, consistent with their domain-specific nature.3.2.3i) whether the common hub liaises with different spoke modules under different semantic contexts via long-range connection, which would reveal distinct networks for action and place knowledge; (ii) whether the strength of functional connectivity with the ATL hub correlates with behavioural performance. The seeds of connectivity were set at the left ATL that showed robust activation to object recognition across experiments. Statistics were thresholded at p < 0.005 for voxel intensity and further constrained for cluster-level multiple comparisons at p < 0.05, as per our previous analysis that was focused on the comparison of congruent vs. incongruent condition  and the right parietal clusters . This pattern of connectivity suggests that, when stimuli connoted actions, the ATL became more tightly coupled with various frontoparietal regions, whose location dovetails nicely with the system of action-semantics (t(19) = 2.13, p = 0.04) and at the left precentral gyrus (t(19) = 2.73, p = 0.01).In Experiment 1 A, the PPemantics . Furtheremantics . Resultsemantics A show sit(19) = 2.14, p = 0.04) and t(19) = 3.19, p = 0.005).In Experiment 2 B, the PP3.2.4i) whether the strength of intrinsic connectivity between hub and spokes is symmetrical or asymmetrical; (ii) whether the connectivity was modulated by semantic congruity; (iii) whether the fluctuation in neural connectivity was reflected in the size of behavioural congruity effect.Results of the PPI analysis detected that the ATL semantic hub was more intimately coupled with the frontoparietal action-related and medial place-related cortical zones when participants recognised objects in contexts implicating action and place knowledge, respectively. However, while PPI revealed the statistical dependency between the hub and spokes, the nature of such connectivity was still correlative . To investigate the directional/causative impacts between the hub and spokes, we carried out DCM and focused on these questions: (ps < 10−8), observed both from the hub to spoke, as well as from the spoke to hub. Interestingly, there was a clear asymmetry in the ‘loudness’ with which the hub and spokes speak to each other, consistently found in both Experiment 1 and 2. Specifically, in Experiment 1 the directional impact that the ATL hub exerted on the action-related PrG spoke was significantly greater than the opposite effect from the spoke to hub (t(19) = 5.11, p < 0.0001). The asymmetry was also found in Experiment 2: the impact that the ATL hub wielded on the place-related RSC spoke was significantly greater than the inverse effect from spoke to hub (t(19) = 5.31, p < 0.0001). Note that while the feedback signals from spoke to hub was comparatively weaker, in both experiments they were still highly significantly above zero.First, we focused on intrinsic connectivity , checking whether causative linkage existed  reciprocally or not, and whether there was any asymmetry in the possible mutual connection. As shown in both vs. unrelated), and whether their susceptibility differed between the paths of hub-to-spoke and spoke-to-hub. As shown in F = 40.09, p < 0.001), and that the hub-to-spoke path is more susceptible to contextual modulation than the spoke-to-hub path  = 37.97, p < 0.001; note the different scales between the 2 bar-charts). Importantly, these two factors significantly interacted with each other  = 40.04, p < 0.001), indicating the contextual effect (unrelated > related) being more potent for the hub-to-spoke route than the reverse. A strikingly consistent pattern was observed on the data of Experiment 2. As shown in F = 52.99, p < 0.001, as evident in the different scales of the bar-charts) and when the stimuli showed discordance between objects and backgrounds  = 15.50, p = 0.001). In keeping with the asymmetry found in Experiment 1, there was a significant interaction that incongruity (unrelated > related) had a more powerful impact on the hub-to-spoke route than the opposite route  = 16.27, p < 0.001).Second, we examined the modulatory parameters , checking whether the reciprocal links are susceptible to the modulation of semantic contexts (related t(19) = 2.35, p = 0.03, see the right inset-box of t(19) = 2.27, p = 0.03, see the right inset-box of Third, we scrutinised whether the DCM modulatory parameters systematically co-varied with the behavioural congruency effects. In the preceding analyses, we learnt that the ATL hub amplified its regulation on the spokes when the stimuli conveyed semantically incongruous message . We speculated that a heightened level of modulation at the neural level  might systematically vary with behavioural congruency effects. Thus, for each participant and each run of scanning, we calculated the size of the behavioural effect of that given run, and then correlated behavioural outcome with the run-specific DCM modulatory parameter. This correlational analysis enabled us to verify whether, within individual performance, fluctuation in the size of behavioural effect (across the three runs of scanning) was mirrored in the neural connectivity gauged by DCM. In Experiment 1, the systematic co-variation was reliable – when participants made more error to unrelated stimuli , the DCM modulatory parameters tended to become greater under such unrelated contexts (see the left inset-box of 4i) A constellation of modality-specific and functionally-specialised regions that constitute the spokes; and (ii) the ventral section of the ATL, primarily the realm of anterior FG and perirhinal cortex, that functions as a transmodal hub  could only be manifested in the domain-specific ‘spoke’ regions while no difference was detected in the domain-general ATL ‘hub’. The ATL was ubiquitously involved in a wide range of contexts, irrespectively of task requirements and semantic congruity. This is consistent with patients' deficits that, following ATL damage, they show a wholesale decline in the ability to recognise all categories of visual items . We speculate that this correspondence might offer important clues about how semantic congruity is neurally implemented in the brain – when confronted with a semantic anomaly , the ATL hub might enhance its communication with relevant spokes to obtain useful knowledge for processing such anomalous information. However, applying prior knowledge would be unhelpful for solving the task when the stimuli were incongruent. Therefore, ironically, the more intensely the ATL speaks to the spoke, the more deterioration in the performance under incongruent contexts (a drop in accuracy or prolonged reaction), hence a bigger behavioural congruency effect. Future research is needed to test our speculation and elucidate the mechanisms.Our connectivity analyses revealed not only the flexibility in the coupling between the hub and spokes, but also the reliable relationship between neural coupling and behavioural outcome. Specifically, the PPI analysis revealed the correspondence between brain and behaviour that explained the variation 5In the present study, we demonstrated that efficient performance on semantic tasks hinges on the neuro-dynamics between the ATL hub and functionally specific spoke regions. Our novel findings unite the contemporary theories of semantic cognition  with exi


Thaumarchaeota, the ratio of their glycerol dialkyl glycerol tetraether (GDGT) lipids depends on growth temperature, a premise that forms the basis of the widely applied TEX86 paleotemperature proxy. A thorough understanding of which GDGTs are produced by which Thaumarchaeota and what the effect of temperature is on their GDGT composition is essential for constraining the TEX86 proxy. “Ca. Nitrosotenuis uzonensis” is a moderately thermophilic thaumarchaeote enriched from a thermal spring, setting it apart in its environmental niche from the other marine mesophilic members of its order. Indeed, we found that the GDGT composition of “Ca. Nitrosotenuis uzonensis” cultures was distinct from those of other members of its order and was more similar to those of other thermophilic, terrestrial Thaumarchaeota. This suggests that while phylogeny has a strong influence on GDGT distribution, the environmental niche that a thaumarchaeote inhabits also shapes its GDGT composition.For  Candidatus Nitrosotenuis uzonensis” is the only cultured moderately thermophilic member of the thaumarchaeotal order Nitrosopumilales (NP) that contains many mesophilic marine strains. We examined its membrane lipid composition at different growth temperatures . Its lipids were all membrane-spanning glycerol dialkyl glycerol tetraethers (GDGTs), with 0 to 4 cyclopentane moieties. Crenarchaeol (cren), the characteristic thaumarchaeotal GDGT, and its isomer (crenʹ) were present in high abundance (30 to 70%). The GDGT polar headgroups were mono-, di-, and trihexoses and hexose/phosphohexose. The ratio of glycolipid to phospholipid GDGTs was highest in the cultures grown at 50°C. With increasing growth temperatures, the relative contributions of cren and crenʹ increased, while those of GDGT-0 to GDGT-4 (including isomers) decreased. TEX86 (tetraether index of tetraethers consisting of 86 carbons)-derived temperatures were much lower than the actual growth temperatures, further demonstrating that TEX86 does not accurately reflect the membrane lipid adaptation of thermophilic Thaumarchaeota. As the temperature increased, specific GDGTs changed relative to their isomers, possibly representing temperature adaption-induced changes in cyclopentane ring stereochemistry. Comparison of a wide range of thaumarchaeotal core lipid compositions revealed that the “Ca. Nitrosotenuis uzonensis” cultures clustered separately from other members of the NP order and the Nitrososphaerales (NS) order. While phylogeny generally seems to have a strong influence on GDGT distribution, our analysis of “Ca. Nitrosotenuis uzonensis” demonstrates that its terrestrial, higher-temperature niche has led to a lipid composition that clearly differentiates it from other NP members and that this difference is mostly driven by its high crenʹ content.“IMPORTANCE For Thaumarchaeota, the ratio of their glycerol dialkyl glycerol tetraether (GDGT) lipids depends on growth temperature, a premise that forms the basis of the widely applied TEX86 paleotemperature proxy. A thorough understanding of which GDGTs are produced by which Thaumarchaeota and what the effect of temperature is on their GDGT composition is essential for constraining the TEX86 proxy. “Ca. Nitrosotenuis uzonensis” is a moderately thermophilic thaumarchaeote enriched from a thermal spring, setting it apart in its environmental niche from the other marine mesophilic members of its order. Indeed, we found that the GDGT composition of “Ca. Nitrosotenuis uzonensis” cultures was distinct from those of other members of its order and was more similar to those of other thermophilic, terrestrial Thaumarchaeota. This suggests that while phylogeny has a strong influence on GDGT distribution, the environmental niche that a thaumarchaeote inhabits also shapes its GDGT composition. Thaumarchaeota are a cosmopolitan phylum of archaea. All cultured members of this phylum are ammonium oxidizers carrying out, like their bacterial counterparts, the first and rate-determining step of the nitrification process  , “Ca. Nitrosotaleales” (NT) , Nitrososphaerales (NS) , and “Ca. Nitrosocaldales” (NC)  . Many of the cultured members of the NP order are marine mesophiles, such as the Nitrosopumilus, Nitrosoarchaeum, and Nitrosopelagicus clades . Archaeal membrane lipids are mainly composed of sn-2,3-diphytanyl glycerol diether with two C20 phytanyl chains (archaeol), extended archaeol (with a C20 and C25 phytanyl chain), or sn-2,3-dialkyl diglycerol tetraethers with two glycerol moieties connected by two C40 isoprenoid chains   and phosphohexose moieties (–A distinct characteristic of the ieties]) , 29. Thaieties]) , an isomieties]) , archaeoieties]) , 32–40. s phylum . Indeed,ironment –45. Comprchaeota –50, the moieties –38, 40.Thaumarchaeota and does not occur in other phyla of Archaea remains unknown. cren is characterized by the presence of an unusual cyclohexane moiety in addition to the presence of four cyclopentane moieties. Molecular modeling has revealed that this cyclohexane moiety disturbs the packing of a GDGT membrane     and NitrC order) , which cCa. Nitrosotenuis uzonensis” was cultured from a thermal spring  and its isomer  (Ca. Nitrosotenuis uzonensis” was subjected to ether cleavage in order to examine the biphytanes (BPs) released from the GDGTs   , followed by cren (25% ± 2%) and GDGT-1 (11% ± 3%) . All othCa. Nitrosotenuis uzonensis” cultures: monohexose (MH), dihexose (DH), two isomers of trihexose (TH1 and TH2), and hexose/phosphohexose (HPH) (see 2 fragmentation (2 fragmentation (Five different GDGT polar headgroups were detected in the “HPH) see , which iHPH) see . Therefoentation  with thoentation . The LC-entation  allowed Ca. Nitrosotenuis uzonensis” cells cultured at different temperatures that were analyzed in this study. The headgroup distributions (It should be noted that the intact polar lipids (IPLs) were examined in terms of their MS peak area response, and thus, the relative abundances reported here may not be their true relative abundances. However, this method allows for direct comparison between the “ibutions  at 37°C ibutions ; MH incrA marked variability in the distribution of core lipids of each intact polar lipid was observed . The LC-Ca. Nitrosotenuis uzonensis” is a moderate thermophile enriched from a thermal spring  (group 1.1a), generally considered to be a predominantly marine/aquatic, mesophilic order . It is well established that Thaumarchaeota increase their cren and crenʹ proportions at higher temperatures, which explains the fundamental role of crenʹ in the sea surface temperature (SST) proxy TEX86 (tetraether index of tetraethers consisting of 86 carbons)  and high-temperature (>15°C) versions TEXL86 and TEXH86, respectively, have been applied to temperature reconstructions in a wide range of marine and lacustrine settings  , particucultures  and appleviously  to calcuon model , the calon model . The temcultures . Howevereratures . Previouronments , 53, 61. springs . Our resCa. Nitrosotenuis uzonensis,” as the average number of cyclopentane moieties increased from 3.1 ± 0.3 at 37°C to 3.7 ± 0.3 at 46°C and 50°C  released from the GDGTs of “Ca. Nitrosotenuis uzonensis” grown at 46°C  increased in relative abundance, while one of the largest headgroups (TH2) decreased. However, when we calculated the average number of sugars per GDGT, we found no significant difference between the different growth temperatures  in the N. maritimus study was much lower. The results for “Ca. Nitrosotenuis uzonensis” are also different from those described previously for the Euryarchaeota species Thermoplasma acidophilum (thermophilic and acidophilic)  , which wmembrane –74 or coembrane –, algae . To produce this simplified data set, the isomers of the GDGTs were grouped together, with the exception of cren and crenʹ, which were treated separately, while hydroxy-GDGTs were not included. First, we used principal-component analysis (PCA)  order members were in the two positive quadrants of the first principal component, in the direction of crenʹ. The single Nitrosotaleales (NT) and Nitrosocaldales (NC) order members included in the data set were placed between the NP and NS orders (Ca. Nitrosotenuis uzonensis” (NP order) cultures grown at different temperatures clustered between the NP and NS members. Second, a “Ca. Nitrososphaera gargensis” culture , which was grown at 35°C (Ca. Nitrosocosmicus oleophilus” MY3 (NS order)  contained a high percentage (14 to 29%) of crenʹ . It is commonly observed that the proportion of crenʹ is higher in thermophilic Thaumarchaeota than in mesophilic Thaumarchaeota   to examiS orders . There w at 35°C , was plaS order)  was placof crenʹ . Many ofof crenʹ , 54, 63,of crenʹ , 37–39. rchaeota , 40, andsalinity , 71, 79.r = 0.72; n = 56; P = <0.001). However, there appears to be a “tipping point” in the crenʹ-to-cren ratio at 35°C  and found a significant correlation with growth temperature  composition of “ species  and alsoennensis . Neitherf the NP , 37, 38,ennensis . Previouennensis , and it mophilic , furtherlow 35°C .Ca. Nitrosotenuis uzonensis” cultures were not found to contain IPLs with a core hydroxy-GDGT (MH-OH or DH-OH), whereas these have been detected in all other members of the NP order examined to date 6Mo7O24·4H2O, 97.3 mg FeSO4·5H2O, 25.0 μg CuSO4·2H2O, and 4.0 g CaCO3. Fresh medium batches were allowed to equilibrate for 2 weeks to ensure reaching low levels of hydrogen peroxide forming during the preparation process. Four biological replicates were grown at 37°C, 46°C, and 50°C, in 250-ml Schott flasks, in the dark. All replicates went through two 10% transfers at the respective temperatures to dilute out lipids from the inoculum culture. The cultures were fed with 1 mM NH4Cl , and depletion was monitored with Nessler’s reagent. The final batches were refed multiple times, consumed 4 mM ammonium in total, and depleted ammonium before the biomass was harvested. This final biomass production step took about 8 weeks, ensuring that at the end, the vast majority of the cells produced were in stationary phase.Highly enriched “ archaea  were gro2 gas.Freeze-dried biomass lipids were extracted using a modified Bligh-Dyer procedure . Briefly2SO4.In order to remove the headgroups from the IPLs and to obtain the remaining core lipids, the Bligh-Dyer extract was hydrolyzed with 5% (vol/vol) HCl–MeOH by refluxing (3 h). The hydrolysate was neutralized with KOH to pH 7/8, extracted with DCM, and dried over Na−1. This remained isocratic for 5 min, and thereafter, there was a linear gradient to 1.8% propanol at 45 min. The injection volume was 10 μl.The hydrolyzed Bligh-Dyer extracts were analyzed using high-performance liquid chromatography/atmospheric-pressure chemical ionization mass spectrometry (HPLC/APCI-MS) on an Agilent 1100/Hewlett Packard 1100 MSD instrument equipped with automatic injector and HP-Chemstation software according to methods described previously , with thThe ratios and calculations that were carried out on the core lipid data are as follows:−1. IPL extracts were analyzed by HPLC-ion trap mass spectrometry (ITMS) according to methods described previously  [79:20:0.12:0.04 {vol/vol/vol/vol}] and eluent B is 2-propanol–water–formic acid–14.8 M NH3(aq) [88:10:0.12:0.04 {vol/vol/vol/vol}]). The lipid extract was analyzed by an MS routine where a positive-ion scan  was followed by a data-dependent MS2 experiment where the base peak of the mass spectrum was fragmented . IPLs were examined in terms of their MS peak area response. Thus, the relative abundance of the peak area does not necessarily reflect the actual relative abundance of the different IPLs; however, this method allows for comparison between the strains analyzed in this study. The peak areas were determined from extracted ion chromatograms of the [M + NH4]+ ion for each individual IPL species.The Bligh-Dyer extracts were directly analyzed for IPLs. Extracts were redissolved in a mixture of hexane–2-propanol–water  at a concentration of 10 mg mleviously , with moeviously . The anaThe ratios and calculations that were carried out on the intact polar lipid data are as follows:Principal-component analysis (PCA) was done using XLSTAT 2018 . The data used for the PCA were fractional abundances (percent) that totaled 100 for each species and were not transformed further before analysis. Spearman rank correlation was done using SigmaPlot .An amino acid alignment of 34 universal marker genes was extracted from previously reported ammonia-oxidizing archaeon (AOA) genomes using CheckM . A maxim


Correction to: Light: Science & Applications (2018) 7, 17153; 10.1038/lsa.2017.153; Article published online, 23 February 2018.In the version of this article originally published, in the “Materials and methods” section under subheading “Reagents”, there are errors about the information of reagents. And the original and corrected versions are shown below.Materials and methods, Page 2“The optical clearing agents (OCAs) used in this study include collagenase , EDTA disodium , and glycerol .”Should read“The optical clearing agents (OCAs) used in this study include collagenase , EDTA disodium salt  and glycerol .”We apologize for any inconvenience this may have caused.


N = 72). They self-nominated six activities to complete over the following week, and were randomized to either: a) a single-session Motivational Imagery condition (N = 24); b) an Activity Reminder control condition (N = 24); or c) a No-Reminder control condition (N = 24). As predicted, relative to control groups, the Motivational Imagery group reported higher levels of motivation, anticipated pleasure, and anticipated reward for the planned activities. The Motivational Imagery group also completed significantly more activities than the Activity Reminder group, but not more than the No-Reminder group. Relevance of results to behavioural activation approaches for depression are discussed.Facilitating engagement in rewarding activities is a key treatment target in depression. Mental imagery can increase engagement in planned behaviours, potentially due to its special role in representing emotionally salient experiences. The present study tested the hypothesis that mental imagery promotes motivation and engagement when planning pleasant and rewarding activities. Participants were recruited from a community volunteer panel ( •Mental imagery of planned activities increases motivation to engage in them.•Higher imagery vividness is associated with higher anticipated reward.•Mental imagery of planned activities is associated with higher activity completion. Motivating people to engage in specific behaviours  presents a significant challenge to different areas of science concerned with human behaviour, including public health, psychology and mental health science. For many activities it is not that they are difficult to do, but they are “put off”. Behaviour change interventions have often focussed on providing people with information about the risks and benefits of various alternatives. The hope that rational ‘cognitive’ analysis of such information will significantly influence subsequent choices is, sadly, all too often misplaced . A complIf effective, this could be highly relevant to mental health conditions that exert a substantial burden on individuals, families and wider society. In depression, for example, individuals may experience difficulty in imagining positive aspects of future experiences and, as a consequence, be less likely to plan and engage in these activities . They camotivational amplifier’, promoting actual engagement in activities  in1To test the “motivational amplifier” hypotheses, the present study tested the impact of guided motivational imagery of planned pleasant and routine activities on ratings of motivation, anticipated pleasure, anticipated reward and behavioural engagement. The motivational imagery group was compared against an activity reminder control condition as well as a no-imagery no-reminder control condition. Completion of target activities were measured over the subsequent week via an activity diary.We hypothesized that 1) compared to the control conditions, individuals in the motivational imagery condition would show greater increases in self-ratings  of their activities from pre-to post-experimental manipulation (i.e. near transfer); 2) within the motivational imagery condition, vividness ratings of the imagined target activities would correlate positively with activity self-ratings post activity scheduling ; 3) compared to both control conditions (activity reminder and no-imagery no-reminder), participants in the motivational imagery condition would engage in a higher number of scheduled target activities outside of the laboratory during participants’ everyday lives (i.e. far transfer). In addition to these a priori hypotheses, we explored a) baseline predictors of experimental effects, b) change in questionnaires measures of overall behavioural activation, depression, anxiety and stress; and c) group differences in experienced pleasure, reward, effort, and mood.22.1The study consisted of two parts: a laboratory session and an activity week during participants’ everyday lives see . The lab2.2N = 72, 44 females, mean age: 36.35, SD = 16.16) were recruited from a community volunteer panel  (e (SUIS)  – TwelvePlymouth Sensory Imagery Questionnaire (PSI-Q) ( (PSI-Q)  – ThirtyDepression Anxiety and Stress Scale (DASS-21) (DASS-21)  – TwentyPositive and Negative Affect Scale State Version (PANAS) ( (PANAS)  – Ten adBehavioural Activation for Depression Scale (BADS) (e (BADS)  – TwentyTemporal Experience of Pleasure Scale (TEPS) (e (TEPS)  – EighteDimensional Anhedonia Rating Scale (DARS) (e (DARS)  – A self2.3.1.1Participants identified six activities they would like to engage in over the subsequent week from a pre-defined list of broader activity categories see : three e2.3.1.2motivation, anticipated pleasure, anticipated reward, and anticipated effort for each of the target activities. Ratings were made for each of the six scheduled target activities pre and post activity scheduling on 100 mm Visual Analogue Scales (VAS) with the endpoints “not at all” to “extremely”. An example item illustrated how to use the rating scale. Participants did not receive a formal definition of the target constructs but had the opportunity to ask questions. The motivational imagery group repeated these ratings directly after activity scheduling with imagery simulation of the respective activity. Participants in the activity reminder control group and participants in the no-imagery no-reminder control group repeated these ratings directly after activity scheduling (with no imagery instructions of the respective activity). Prior to activity scheduling, participants also rated how important each selected activity was to them, how much they had been putting each activity off, and how difficult they typically found it to make time for the activity. These ratings were also made on VAS with the endpoints “not at all” to “extremely”.Before the experimental manipulation, participants rated their 2.3.1.3Participants in the motivational imagery condition rated the vividness of their mental imagery immediately following mental imagery of their target activities, on a 100 mm VAS asking “How vividly were you able to imagine the activity?” with response anchors ranging from 0 “not at all” to 100 “extremely”.2.3.1.4Participants then scheduled the selected activities in over the course of the following week using an activity diary and following the procedures and principles described in Behavioural Activation treatment manuals  then completed a general exercise in generating vivid mental imagery  and rece2.3.1.5The imagery script requests participants to vividly imagine themselves performing each of their six target activities, with each resolving in a positive way . Participants were instructed to concentrate and close their eyes during the imagery task and to focus on the most positive aspects of their image while imagining themselves doing the activity. The experimenter guided participants through an imagery script focussing on 1) contextual cues of the activity  as specified by participants at the time of scheduling the activities; 2) multi-sensory  engagement in the activity; 3) positive aspects associated with the activity; and 4) vivid imagery of the most powerful and motivating part of their image. The script was written by the research team following initial pilot testing. During the experimental session the experimenter read the script to the participant inserting the relevant information for the respective activity  while reading the script out loud. Each imagery-activity script took about 1–2 min.2.3.1.6Participants in the motivational imagery condition received text messages during the activity week to facilitate transfer from the experimental manipulation during the laboratory session to the activity week outside the laboratory. These reminder prompts also, of course, acted as a reminder of those activities. To control for the presentation of reminders per se, participants in the activity-reminder control condition also received text messages reminding them of the planned activities, but without imagery instructions. Participants in both the motivational imagery condition and activity reminder condition received two text messages per day during the activity week outside the laboratory. The text messages did not specify any detail about the nature or timing of the upcoming activity. In the motivational imagery condition the text message encouraged use of vivid mental imagery of the most powerful and motivating part of their image for the upcoming activity. In the activity reminder condition the text message included the words “activity reminder” to remind participants of the upcoming activity.3“routine” target activities , and provided activity ratings for each activity and scheduled them for the next week. The activity scheduling was done with or without mental imagery . Participants were then given an activity diary with instructions on how to record the following after each completed activity each day: (1) whether or not they had completed their planned activity, including when and for how long, (2) mood ratings immediately following each activity, and (3) where they had not managed to complete an activity, to provide a reason why. Participants in the motivational imagery condition and in the activity reminder condition were then informed that they would receive two text messages at random points in time before each planned activity (see above). At the end of the session, participants received payment for their time and a pre-paid return envelope to post the activity diary back.Participants completed self-report questionnaires  after pr42 and Cohen's d) were calculated for analyses involving group comparisons.All statistical tests were two-tailed . Significant omnibus tests were followed up by Bonferroni corrected pairwise comparisons. Effect sizes (η4.1There were three conditions 1) motivational imagery 2) activity reminders control and 3) no-imagery no-reminders control. For the purposes of examining the effects of the laboratory session on ratings, conditions 2 and 3  were collapsed into a combined control condition see . To test4.2To test differences between the three conditions in the number of completed activities (hypothesis 3), a one-way ANOVA was conducted, with condition  as the between-subjects factor and the number of completed activities as the dependent variable.4.3Additional exploratory analyses focussed on differences between conditions on overall behavioural activation, stress, anxiety and depression ratings from pre to post activity week using repeated-measures ANOVA with condition  as the between-subjects factor and time  as the within-subjects factor.To explore psychological mechanisms of motivational imagery effects, activity ratings collected following activity selection were entered in a multiple regression analysis predicting the number of completed activities. Condition was first dummy coded with the motivational imagery condition as reference group and two dummy variables  were entered in a linear regression model. The different activity ratings were entered in separate regression models (one for each activity rating). An interaction term between the activity ratings and the dummy variables was added to test whether the different activity ratings differentially predicted the number of completed activities by condition.55.1Comparing baseline activity ratings and scores on baseline questionnaire measures  confirmed no significant differences between the groups prior to the experimental manipulation . Scores 5.2M = 78.63, SD = 12.35) than the three selected “routine” activities  = 16.57, p < .001, d = 2.70). Within the motivational imagery condition, vividness ratings during the laboratory session were high , indicating that participants in the motivational imagery condition were able to form vivid images of engaging in their selected activities. For each activity, we asked participants in the motivational imagery condition to indicate if they used the reminder prompt to engage in imagery of that activity. Possible answers: yes, 1x; yes, 2x; no. On average, for 12 reminder prompts in the motivational imagery condition, participants indicated that they imagined engaging in the activity approximately half of the time they received a reminder prompt . Participants in the activity reminder condition were asked, for each activity if the reminder messages helped to remind them of the planned activities: Possible answers: Yes/No. On average, for six planned activities (12 reminder prompts), participants in the activity reminder condition indicated that the messages helped them to remind them of the activities for approximately two of the six planned activities .All participants were able to identify six behavioural target activities (three enjoyable and three routine activities) and to plan these in their activity diary. At baseline the three selected “enjoyable” activities were rated as more enjoyable (5.3Ratings of activities pre and post activity scheduling (hypothesis 1). Activity ratings before and after the experimental manipulation separately for the three groups are summarized in F  = 6.47, p = .01, η2 = 0.085, anticipated pleasure, F  = 4.91, p = .03, η2 = 0.066, and for anticipated reward, F = 9.31, p = .003, η2 = 0.117F = 2.61, p = .11, η2 = 0.036. For separate analyses of routine and enjoyable activities see Supplementary Materials.Relation between imagery vividness and activity ratings post activity scheduling (hypothesis 2). As predicted, there was a significant positive correlation between vividness and anticipated reward ratings, ; the more vividly participants imagined engaging in the scheduled activities, the higher their anticipated reward of engaging in them. There were no significant correlations between vividness and anticipated pleasure  or between vividness and motivation .5.4Effects of motivational imagery on the number of completed activities (hypothesis 3). The three groups differed in the mean number of completed activities F = 3.71, p = .03, d = 0.74. In line with our hypothesis, post-hoc comparisons with Bonferroni correction for multiple testing revealed a higher completion rate of activities in the motivational imagery condition  compared to the activity reminder control condition , p = .033, d = 0.94); that is, imagery had an effect over and above simple reminders. There was no statistical significant difference in activity completion rate between the motivational imagery condition and the no-imagery no-reminder control condition , p = 1.00, d = 0.19; imagery did not have an effect above the no-imagery no-reminder control condition. There was no statistical significant difference in activity completion rate between the two control conditions, p = .16, d = 0.52; suggesting text reminders in themselves were not linked with improved completion. For separate analyses of routine and enjoyable activities see Supplementary Materials.5.55.5.1β = −1.79, t(64) = −2.54, p = .01 and for “putting off” ratings and the dummy variable comparing activity completion between the motivational imagery condition and the no-imagery no-reminder condition, β = −1.71, t(64) = −2.94, p = .005. To interpret the interaction we plotted the number of completed activities as a function of “putting off ratings” (low/high median split) for each condition  these activities. There was a significant interaction between “putting off” ratings and the dummy variable comparing activity completion between the motivational imagery condition and the activity reminder condition, ondition . This in5.5.2M = 106.84, SD = 24.44) to post activity week , F = 9.76, p = .003, η2 = 0.132. The interaction with condition was not significant, indicating that the increase in behavioural activation as indexed by the BADS from baseline to post activity week did not differ between the three groups, F = 0.02, p = .977, η2 = 0.001.We explored if a broader increase in self-reported behavioural activation, assessed with the BADS, and scores on the depression, anxiety, and stress scales of the DASS-21 changed from baseline to post activity week. Overall there was a significant increase in behavioural activation from baseline  to post activity week , F = 6.25, p = .015, η2 = 0.089. The interaction with condition was not significant, indicating that the decrease in stress ratings from baseline to post activity week did not differ between the three groups, F = 0.74, p = .48, η2 = 0.023. Anxiety ratings on the DASS-21 did not change over the study period, F = 0.11, p = .736, η2 = 0.002 and neither did depression ratings, F = 0.39, p = .535, η2 = 0.006.Overall there was a decrease on the stress scale of the DASS-21 from baseline  and rewarding  with no differences between the three groups, F = 0.81 p = .45, η2 = 0.025 and F = 0.78 p = .46, ηM = 46.41, SD = 15.11) with no differences between the three groups, F = 0.49 p = .61, ηM = 70.69, SD = 11.97) with no differences between the three groups, F = 0.21 p = .81, ηOverall, completed activities were rated as pleasant  from pre to post activity scheduling. In addition, despite receiving equal number of text reminders, participants encouraged to use imagery completed significantly more activities than those who were not given explicit imagery guidance.This study examined whether guided motivational imagery enhanced motivation for, and behavioural engagement in planned enjoyable and routine activities. Results suggest mental imagery can act as a A caveat here is that the completion rates were not significantly greater in the motivational imagery group than those of the no-imagery no-reminder control group who received neither explicit imagery guidance nor reminders. In a between-participant design there are many factors relating to individual propensity for task completion and variation in task selection. For example, while not statistically significant, participants in the no-imagery no-reminder condition had relatively high scores on the Spontaneous Use of Imagery Scale (SUIS) compared to the other two groups. While speculative, it is possible that participants in this group tended to use imagery spontaneously during the activity week. An alternative explanation is that the significant effect of group on the number of completed activities is actually driven by a low number of completed activities in the activity reminder condition. Participants in this condition might have experienced the activity reminders as irritating resulting in a lower completion rate. In line with this explanation, when asked if they found the reminder prompts useful in reminding them of the planned activities, participants in the activity reminder condition indicated they only found the prompts useful for approximately two out of six activities. Further work using a greater range of activities over a longer period and potentially more sensitive measures such as ‘experience sampling’ will help to establish the likely reliability of the enhanced completion finding. Overall, however, these findings are in line with the overarching hypothesis that using mental imagery can promote engagement in behavioural activities.motivational amplifier. As one participant in the motivational imagery condition noted in a feedback email: “I thought doing visualisations was a great way to get myself to do the activities I miss out on, and it does seem to work. It made me happy and look forward to doing the activities”.Why might mental imagery of future behavioural activities promote motivation and actual engagement? Mental imagery is a core component of the ‘prospective brain’, a functional network allowing us to predict and plan for the future . Mental Mental imagery of future behavioural activities in this study increased anticipated pleasure and anticipated reward, relative to control groups. Thus individuals in the motivational imagery condition predicted that engaging in the planned activities would be more pleasant and more rewarding compared to those in control groups. However, ratings of actual pleasantness and reward upon activity completion did not differ between the groups, suggesting that there was a discrepancy between what participants predicted and how the planned activities actually turned out to be once completed. This finding is interesting in the context of the affective forecasting literature. When people make predictions of how they will feel about events in the future (i.e. affective forecasts) they typically overestimate the emotional impact of these events . ImportaWe also found that the more vividly participants imagined the scheduled activities the higher their anticipated reward ratings of engaging with them. Future research should further explore boosting positive imagery vividness in promoting motivation for behavioural activities, specifically in individuals who struggle to form vivid positive images such as those with depression .least inclined to do, may benefit most from this imagery intervention. This makes more intuitive sense when expressed in terms of the corollary; participants are more likely to engage in behaviours that they have not tended to “put off” thus reducing any additional benefit of imagery. It is nevertheless encouraging in terms of procrastination, delaying unpleasant activities despite negative consequences of such delay . Experimental protocols will need to be accompanied by training to use the motivational amplifier protocol.