A mosquito bites and a butterfly flies: A specific response type of frontal patients in a similarity task.
BACKGROUND
Patients with neurodegenerative diseases affecting the frontal lobes have difficulties in categorization tasks, such as the similarity tasks. They give two types of unusual response to the question: "In what way are an orange and a banana alike?", either a differentiation ("one is yellow, the other is orange") or a concrete similarity ("they are sweet").


OBJECTIVE
To characterize the categorization deficit of frontal patients and develop a short diagnostic tool to assess the nature of these difficulties.


METHOD
We analyzed the responses provided by frontal and non-frontal neurodegenerative patients in a novel verbal similarity task (SimiCat). We included 40 frontal patients with behavioral variant fronto-temporal dementia (bvFTD) and progressive supranuclear palsy (PSP), 23 patients with Alzheimer's disease (AD) and 41 healthy matched controls. Responses that did not correspond to the expected taxonomic category (e.g.: fruits) were considered as errors.


RESULTS
All patients groups were impaired at the SimiCat test compared to controls. Differentiation errors were specific to frontal patients. Receiver operating characteristic analyses showed that a cut-off of two differentiation errors or more achieved 85% sensitivity of 100% specificity to discriminate bvFTD from AD. A short version of the test (<5 min) showed similar discriminative validity as the full version.


CONCLUSION
Differentiation responses were specific to frontal patients. The SimiCat demonstrates good discriminative validity to differentiate between bvFTD and AD. The short version of the test is a promising diagnostic tool that will need validation in future studies.
['Garcin|Béatrice|B|', 'Volle|Emmanuelle|E|', 'Funkiewiez|Aurélie|A|', 'Miller|Bruce L|BL|', 'Dubois|Bruno|B|', 'Levy|Richard|R|']
D000368:Aged D000544:Alzheimer Disease D000818:Animals D002080:Butterflies D016022:Case-Control Studies D003072:Cognition Disorders D003210:Concept Formation D004192:Discrimination, Psychological D005260:Female D005625:Frontal Lobe D057180:Frontotemporal Dementia D006801:Humans D007299:Insect Bites and Stings D008297:Male D000073216:Mental Status and Dementia Tests D008875:Middle Aged D019636:Neurodegenerative Diseases D009483:Neuropsychological Tests D010364:Pattern Recognition, Visual D013494:Supranuclear Palsy, Progressive
Similarities Categorization Behavioral variant fronto-temporal dementia Alzheimer's disease Neuropsychology