Coherence Potentials : Red Circle or Blue Triangle?
One of the many problems the brain seems to solve elegantly – Bring together multi-sensory information to create an integrated view in a manner that reconciles both functional localization and distributed memory. Distinguishing between a Red Circle and Blue Triangle is a seemingly easy task (which even my two-year old is able to solve). But how is the brain doing it? Simply put, there are one location in the brain to encode ‘shape’, and another to encode ‘color’. There has to be a way for cross-modal communication to happen!
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Proposed Invisible Code = Coherence Potentials
What are coherence potentials – Large size local field potential (average response of ~10-100 neurons) able to spread in saltatory manner across large distances in the cortex without distortion in their shape or size.
Original Paper discovering this phenomenon in monkeys
We analysed ECoG (signals from the brain surface) recorded at 59 sites in the sensori-motor cortex of a human subject performing a simple visuomotor task (imitate image on the screen, either fist clenching and foot dorsiflexion) to understand how coherence potentials arising in the recordings relate to the task.
What we found
1. Every time our subject clenches his fist, we found the one particular coherence potential arise ~400ms before. If the coherence potential is late, our subject took longer to respond.
2. This particular coherence potential was seen in the ‘expert region’ for movements of the hand.
Earlier studies have shown that local brain lesions do not necessarily abolish memory or behavior. Coherence potentials encode information relevant for behavior and are generated by the ‘expert’ sites that subsequently broadcast to other sites as a means of ‘sharing knowledge’.