Further Work on the Shaping of Cortical Development and Function by Synchrony and Metabolic Competition.

James J Wright,Paul D Bourke

doi:10.3389/fncom.2016.00127

James J Wright, Paul D Bourke

Open Access

https://doi.org/10.3389/fncom.2016.00127

Copy DOI

Abstract

This paper furthers our attempts to resolve two major controversies—whether gamma synchrony plays a role in cognition, and whether cortical columns are functionally important. We have previously argued that the configuration of cortical cells that emerges in development is that which maximizes the magnitude of synchronous oscillation and minimizes metabolic cost. Here we analyze the separate effects in development of minimization of axonal lengths, and of early Hebbian learning and selective distribution of resources to growing synapses, by showing in simulations that these effects are partially antagonistic, but their interaction during development produces accurate anatomical and functional properties for both columnar and non-columnar cortex. The resulting embryonic anatomical order can provide a cortex-wide scaffold for postnatal learning that is dimensionally consistent with the representation of moving sensory objects, and, as learning progressively overwrites the embryonic order, further associations also occur in a dimensionally consistent framework. The role ascribed to cortical synchrony does not demand specific frequency, amplitude or phase variation of pulses to mediate “feature linking.” Instead, the concerted interactions of pulse synchrony with short-term synaptic dynamics, and synaptic resource competition can further explain cortical information processing in analogy to Hopfield networks and quantum computation.

Highlights

Two long-standing controversies impeding the development of brain function theory concern, respectively, the functional significance of cortical synchrony, and the significance of columnar cortical organization, or its lack
We showed that during a stimulus sweep across the visual field, the interaction of direct inputs with laterally transmitted waves generated by the stimulus at prior sites of input, could reproduce these effects via an effect similar to the Doppler shift in sound waves, and that they were equivalent to combined feature tuning of cells to stimulus orientation, spatial frequency, and temporal frequency
We introduced the positive-valued parts of Equations (8a–d) as long-range forces in a third stage in simulation, in analogy to the two prior stages resulting in Figure 4, assuming that the growth of synapses may likely influence the late selection of surviving cells

Summary

Introduction

Two long-standing controversies impeding the development of brain function theory concern, respectively, the functional significance of cortical synchrony, and the significance of columnar cortical organization, or its lack. Average axonal density as a function of distance from pyramidal somas is given by ρ((x + λβ −1/2)−2) = Nβ λβ e−λβ x + Nαλαe−λαx where ρ is average probability of synaptic connection between any two excitatory cells.

Results

Conclusion