Copyright 1993 by W. H. Calvin.
BINDING FORMS A CEREBRAL CODE WHICH ERROR CORRECTS: Scattered Feature Detectors Generate a Hexagonal Code via Synchronizing Excitation among Pyramidal Neurons. William H. Calvin* Univ. of Washington NJ-15, Seattle WA 98195
Pyramidal neurons of the superficial neocortex are excitatory to other pyramids and, since they tend to cluster axon terminals at a standard distance ("0.5mm"), some corticocortical cell pairs will mutually re-excite. Though refractoriness should prevent reverberation, even weak positive coupling can entrain oscillators when cells are active for other reasons. Because each pyramid sends horizontal axons in many directions, simultaneous arrivals may recruit a 3rd and 4th pyramid at 0.5mm from the synchronized parental pair. A triangular mosaic of synchronized superficial pyramids could thus form, extending for some mm (Calvin, Abstr.'92). Consider N neuron pairs responding to different aspects of an apple, scattered across extrastriate areas, forming N triangular mosaics that interdigitate. There is thus a recycling temporal pattern (since synchrony is not needed across pairs) imposed on a widespread cortical area. It has a spatial repeat, an elementary spatiotemporal pattern of N neurons which, for geometric reasons, is no larger than a 0.5mm hexagon. This compact pattern becomes standardized across the mosaic (a variant must overcome six simultan- eous EPSPs); such pattern "crystallization" is a form of error correction. The synchrony could induce longer-term NMDA connectivity changes; later, partial patterns could "pop out" the com- plete spatiotemporal pattern for Apple by resonance with this connectivity pattern, even in cortex lacking the original feature detectors. A hexagonal matrix could thus house a Hebbian cell assembly and function as a cerebral code.
William H. Calvin, The Cerebral Code: Evolving a Thought in the Mosaics of the Mind (in progress for 1995).
William H. Calvin and George A. Ojemann. Conversations with Neil's Brain: The Neural Nature of Thought and Language (Addison-Wesley, 1994).
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Revised 17 Jan 95 WHC