CORTICAL NETWORK RESILIENCE TO SHORT-TERM ANOXIA INVOLVES REDISTRIBUTION OF SINGLE-NEURON FIRING

The neocortex exhibits large-scale spatiotemporal patterns of spontaneous activity that collapse when oxygen supply fails. How neurons in different cortical layers contribute to this breakdown and subsequent recovery upon reoxygenation remains poorly known. Using simultaneous high-density silicon probe recordings across the depth of the rat primary somatosensory cortex, combined with paired direct current potential recordings in superficial and deep layers and intracellular recordings from identified layer 2/3 and 5/6 pyramidal neurons, we examined the laminar dynamics of transient oxygen deprivation. Spiking activity across all layers rapidly declined due to progressive synaptic silencing and membrane hyperpolarization. This global quiescence was followed by a massive anoxic depolarization that consistently originated in layer 5 and then spread stepwise through the cortical column. During reoxygenation, neurons repolarized in a corresponding sequence and exhibited a transient rebound of synchronous firing, followed by a gradual return to near baseline activity within ~40 minutes. Despite normalization of population activity, most individual neurons showed persistent alterations in firing rate, indicating that cortical network resilience to short term anoxia involves a redistribution of single cell activity across layers. These results define the laminar sequence of neuronal failure and recovery during transient cerebral anoxia and reveal layer-specific vulnerabilities that may inform strategies to preserve and restore cortical function following anoxic or ischemic insults.