How the Cortex Regulates the Thalamus

Abstract

The thalamus provides sensory information to the cerebral cortex, but the cortex also sends massive input to the thalamus. Top-down corticothalamic projections may allow the cortex to regulate sensory processing by modulating the excitability of thalamic neurons. I will describe unique modular circuits within the deep layers of the somatosensory cortex that give rise to corticothalamic axons. I will also show that corticothalamic regulation is a highly dynamic process; it relies on a time- and frequency-dependent balance of feed-forward excitation and inhibition that can switch the excitability and sensory throughput of the thalamus according to ongoing behavioral demands.