Binding of cortical functional modules by synchronous high-frequency oscillations.

Whether high-frequency phase-locked oscillations facilitate integration ('binding') of information across widespread cortical areas is controversial. Here we show with intracranial electroencephalography that cortico-cortical co-ripples (~100-ms-long ~90 Hz oscillations) increase during reading and semantic decisions, at the times and co-locations when and where binding should occur. Fusiform wordform areas co-ripple with virtually all language areas, maximally from 200 to 400 ms post-word-onset. Semantically specified target words evoke strong co-rippling between wordform, semantic, executive and response areas from 400 to 800 ms, with increased co-rippling between semantic, executive and response areas prior to correct responses. Co-ripples were phase-locked at zero lag over long distances (>12 cm), especially when many areas were co-rippling. General co-activation, indexed by non-oscillatory high gamma, was mainly confined to early latencies in fusiform and earlier visual areas, preceding co-ripples. These findings suggest that widespread synchronous co-ripples may assist the integration of multiple cortical areas for sustained periods during cognition.

Binding of cortical functional modules by synchronous high frequency oscillations.

High-frequency phase-locked oscillations have been hypothesized to facilitate integration ('binding') of information encoded across widespread cortical areas. Ripples (~100ms long ~90Hz oscillations) co-occur ('co-ripple') broadly in multiple states and locations, but have only been associated with memory replay. We tested whether cortico-cortical co-ripples subserve a general role in binding by recording intracranial EEG during reading. Co-rippling increased to words versus consonant-strings between visual, wordform and semantic cortical areas when letters are binding into words, and words to meaning. Similarly, co-ripples strongly increased before correct responses between executive, response, wordform and semantic areas when word meanings bind instructions and response. Task-selective co-rippling dissociated from non-oscillatory activation and memory reinstatement. Co-ripples were phase-locked at zero-lag, even at long distances (>12cm), supporting a general role in cognitive binding.