Subplate neurons: crucial regulators of cortical development and plasticity.

Patrick Kanold

doi:10.3389/neuro.05.016.2009

Abstract

The developing cerebral cortex contains a distinct class of cells, subplate neurons, which form one of the first functional cortical circuits. Subplate neurons reside in the cortical white matter, receive thalamic inputs and project into the developing cortical plate, mostly to layer 4. Subplate neurons are present at key time points during development. Removal of subplate neurons profoundly affects cortical development. Subplate removal in visual cortex prevents the maturation of thalamocortical synapse, the maturation of inhibition in layer 4, the development of orientation selective responses in individual cortical neurons, and the formation of ocular dominance columns. In addition, monocular deprivation during development reveals that ocular dominance plasticity is paradoxical in the absence of subplate neurons. Because subplate neurons projecting to layer 4 are glutamatergic, these diverse deficits following subplate removal were hypothesized to be due to lack of feed-forward thalamic driven cortical excitation. A computational model of the developing thalamocortical pathway incorporating feed-forward excitatory subplate projections replicates both normal development and plasticity of ocular dominance as well as the effects of subplate removal. Therefore, we postulate that feed-forward excitatory projections from subplate neurons into the developing cortical plate enhance correlated activity between thalamus and layer 4 and, in concert with Hebbian learning rules in layer 4, allow maturational and plastic processes in layer 4 to commence. Thus subplate neurons are a crucial regulator of cortical development and plasticity, and damage to these neurons might play a role in the pathology of many neurodevelopmental disorders.

Highlights

INTRODUCTIONSubplate neurons are among the earliest generated neurons in the cerebral cortex of mammals and are located in the developing white matter of all cortical regions (Luskin and Shatz, 1985; Valverde and Facal-Valverde, 1987, 1988; Mrzljak et al, 1988; Kostovic and Rakic, 1990; Allendoerfer and Shatz, 1994; Reep, 2000; Kostovic et al, 2002; Kostovic and Judas, 2006; Perkins et al, 2008)
Subplate neurons comprise additional cortical circuits that are only present during cortical development, and these circuits appear to play a major role in development and early cortical function, but are only beginning to be characterized
CONNECTIVITY OF SUBPLATE NEURON AND RELATIONSHIP WITH CORTICAL CELLS The cell bodies of subplate neurons are located in the cerebral white matter (Mrzljak et al, 1988; Kostovic and Rakic, 1990)

Summary

INTRODUCTION

Subplate neurons are among the earliest generated neurons in the cerebral cortex of mammals and are located in the developing white matter of all cortical regions (Luskin and Shatz, 1985; Valverde and Facal-Valverde, 1987, 1988; Mrzljak et al, 1988; Kostovic and Rakic, 1990; Allendoerfer and Shatz, 1994; Reep, 2000; Kostovic et al, 2002; Kostovic and Judas, 2006; Perkins et al, 2008). After thalamic axons grow into layer 4, thalamocortical synapses and GABAergic circuits in layer 4 undergo refinement and maturation and over this time are influenced by sensory experience (defining the “critical period”) (Friauf and Shatz, 1991; Allendoerfer and Shatz, 1994; Clancy et al, 2001; Chen et al, 2001a; Kanold et al, 2003; Kanold and Shatz, 2006) During this time subplate neurons are still present, receive

Subplate neurons regulate cortical development

Findings

CONCLUSION