Neural Field Dynamics and the Evolution of the Cerebral Cortex

We describe principles for cortical development which may apply both to the evolution of species, and to the antenatal development of the cortex of individuals. Our account depends upon the occurrence of synchronous oscillation in the neural field during embryonic development, and the assumption that synchrony is linked to cell survival during apoptosis Apoptosis . This leads to selection of arrays of neurons with ultra-small-world characteristics. The “degree of separation” power law Power law is supplied by the combination of neuron sub-populations with differing exponential axonal tree distributions, and consequently, in the visual cortex Cortex visual , connections emerge in anatomically realistic patterns, with an ante-natal arrangement which projects signals from the surrounding cortex Cortex onto each macrocolumn, in a form analogous to the projection of a Euclidean plane onto a Möbius strip. Simulations of signal flow explain cortical responses to moving lines as functions of stimulus velocity, length and orientation. With the introduction of direct visual inputs, under the operation of Hebbian learning Hebb rule , development of mature selective response “tuning” to stimuli “features” then takes place, overwriting the earlier ante-natal configuration. Further assuming similar development principles apply to inter-areal interactions in the developing cortex, a general principle for the evolution of increasingly complicated sensory-motor sequences, at both species-evolution and individual time-scales, is implicit.