Beyond cortical layers and the canonical cortical circuit - Solange Brown

Wu Tsai Neurosciences Institute Seminar Series Presents

Solange Brown, PhD 

Associate Professor of Neuroscience, Johns Hopkins University School of Medicine

Host: John Huguenard

Abstract

The canonical cortical microcircuit has principally been defined by interlaminar excitatory connections among the six layers of the cortex. Using layer 6 as a model, a layers which has been traditionally associated with corticothalamic feedback, we identify two sublayers with distinct cellular composition and circuit organization. Using paired whole-cell patch clamp recordings, optogenetic circuit mapping, and viral tracing, we show that the cortical output of one of these sublayers is dominated by interlaminar inhibition rather than excitation. We go on to show that two types of layer 6 corticothalamic neurons found respectively in the upper and lower sublayers of layer 6 represent distinct information streams in the somatosensory cortex. Our results suggest that one type regulates, via its more restricted circuits, sensory responses related to a cortical column while the other, which receives input from many cortical and subcortical areas and integrates into pulvinar-related circuits, likely relays contextual information across cortical columns. Together, these data provide further evidence that interlaminar inhibitory projections contribute to the canonical cortical microcircuit and revise our understanding of the basic synaptic organization of neocortical circuits.