Top-Down Mechanism of Perception: A Scenario on the Role for Layer 1 and 2/3 Projections Viewed from Dynamical Systems Theory

Abstract

Cortical layer 1 is the main entrance of top-down signals from other higher cortices and subcortical nuclei. Recent findings challenge the view that top-down signals play just a modulatory role. However, how top-down signals are implemented to help reconstruct the internal representations of images, or an episode of events is poorly understood. Recent experimental data suggest that the “ongoing” brain state without external inputs into layer 4 and attentional top-down signals continually fluctuates among the intrinsic patterns of activity. Viewed from a dynamical systems standpoint, the transitory intrinsic states could be an expression of “attractor ruins”, observed in a mesoscopic dynamical system. We hypothesize that when top-down signals arrive as attention(s), contexts, or indices, the local brain state is temporarily stabilized to be an attractor(-like) state. In view of the anatomical and physiological configurations of neuronal systems in the superficial layers, we propose a hypothetical scenario for such non-classical dynamics in the brain.