Quantitative analysis of high-frequency oscillations (80-500 Hz) recorded in @entity1 XXXX hippocampus and entorhinal cortex.

@entity1 @entity11385 @entity410 @entity137 @entity4176 @entity1315 @entity194 @entity302 @entity35
High-frequency oscillations (100-200 Hz), termed ripples, have been identified in hippocampal (Hip) and entorhinal cortical (EC) areas of rodents and @entity1 . In contrast, higher-frequency oscillations (250-500 Hz), termed fast ripples (FR), have been described in @entity410 -generating limbic areas of rodents made @entity302 by intrahippocampal injection of @entity4176 and observed in @entity1 ipsilateral to areas of @entity410 initiation. However, quantitative studies supporting the existence of two spectrally distinct oscillatory events have not been carried out in @entity1 nor has the preferential appearance of FR within @entity410 generating areas received statistical evaluation based on analysis of a large sample of oscillatory events. Interictal oscillations within the bandwidth of 80-500 Hz were detected in Hip and EC areas of @entity1 with mesial @entity1315 using wideband EEG recorded during non-rapid eye-movement sleep from chronically implanted depth electrodes. Power spectral analysis showed that oscillations detected from Hip and EC areas were composed of two spectrally distinct groups. The lower-frequency ripple group was defined by a frequency of 96 +/- 14 Hz (median +/- width), while the higher-frequency FR group had a frequency of 262 +/- 59 Hz. FR oscillations were significantly shorter in duration compared with @entity11385 (P < 0.0001). In regard to the occurrence of FR and ripples in @entity302 Hip and EC, the mean ratio of the number of FR to ripples generated in areas ipsilateral to @entity410 onset was significantly higher compared with the mean ratio of FR to ripple generation from contralateral areas (P = 0.008). Furthermore, sites ipsilateral to @entity410 onset with @entity194 had significantly higher ratios compared with sites contralateral to both @entity410 onset and @entity194 (P = 0.001). These data provide compelling quantitative and statistical evidence for the existence of two spectrally distinct groups of limbic oscillations that have frequency and duration characteristics similar to those previously described in @entity302 @entity35 and @entity1 Hip and EC. The strong association between FR and regions of @entity410 initiation supports the view that FR reflects pathological @entity137 crucially associated with @entity410 genesis.
