Oscillatory activity in neocortical networks during tactile discrimination near the limit of spatial acuity

article i nfo Article history: Accepted 3 January 2014 Available online 13 January 2014 Oscillatory interactions within functionally specialized but distributed brain regions are believed to be central to perceptual and cognitive functions. Here, using human scalp electroencephalography (EEG) recordings com- bined with source reconstruction techniques, we study how oscillatory activity functionally organizes different neocortical regions during a tactile discrimination task near the limit of spatial acuity. While undergoing EEG re- cordings, blindfolded participants felt a linear three-dot array presented electromechanically, under computer control, and reported whether the central dot was offset to the left or right. The average brain response differed significantly for trials with correct and incorrect perceptual responses in the timeframe approximately between 130 and 175 ms. During trials with correct responses, source-level peak activity appeared in the left primary so- matosensory cortex (SI) at around 45 ms, in the right lateral occipital complex (LOC) at 130 ms, in the right pos- teriorintraparietalsulcus(pIPS)at160 ms,and finallyintheleftdorsolateralprefrontalcortex(dlPFC)at175 ms. Spectral interdependency analysis of activity in these nodes showed two distinct distributed networks, a domi- nantly feedforward network inthebeta band (12-30 Hz)that included all fournodes and a recurrentnetworkin the gamma band (30-100 Hz) that linked SI, pIPS and dlPFC. Measures of network activity in both bands were correlated with the accuracy of task performance. These findings suggest that beta and gamma band oscillatory networkscoordinateactivitybetweenneocorticalregionsmediatingsensoryandcognitiveprocessingtoarriveat tactile perceptual decisions.