Impact of neuronal dynamics on anatomical organization of the cerebral cortex.

J.J. Wright, D.M. Alexander and P.D. Bourke.

9th Tamagawa Dynamic Brain Forum - DBF, Nov 2005


Action potential and local field activity in the gamma frequency range plays a major part in information processing in the alert state, and synchronous oscillation at gamma frequencies is believed to bind transient assemblies of neurones together in functional coalitions. The interaction of âœspike-and-wave❠dynamics with synaptic dynamics has been little considered.
Analytic and simulation considerations show that synchronous oscillation can act in concert with Hebbian synaptic modification to give rise to anatomically realistic features of the visual cortex (V1). From random lateral connections which decline in synaptic density with distance from the soma of origin, and which are distributed with terminal arborizations of approximately 300 micron dimension, evolution of synaptic strengths under organization by synchronous oscillation proceeds to a stable state in which all synapses are either saturated, or have minimum pre/post-synaptic coincidence. The most stable configuration gives rise to âœlocal mapsâ, each of macro-columnar size, and each organised as Möbius projections of retinotopic space. A tiling of V1, constructed of approximately mirror-image reflections of each local map by its neighbours is formed, accounting for orientation-preference singularities, linear zones and saddle points - with each map linked by connections between sites of common orientation preference. Ocular dominance columns are partly explained as a special case of the same process. The occurrence of direction preference fractures always in odd numbers around singularities, and effects of stimulus velocity, orientation relative to direction of motion, and extension, upon orientation preference are thus explained.
This model appears applicable outside the context of V1.