Corticothalamic gating of population auditory thalamocortical transmission in mouse

The mechanisms that govern thalamocortical transmission are poorly
understood. Recent data have shown that sensory stimuli elicit activity in
ensembles of cortical neurons that recapitulate stereotyped spontaneous
activity patterns. Here, we elucidate a possible mechanism by which gating
of patterned population cortical activity occurs. In this study,
sensory-evoked all-or-none cortical population responses were observed in
the mouse auditory cortex in vivo and similar stochastic cortical
responses were observed in a colliculo-thalamocortical brain slice
preparation. Cortical responses were associated with decreases in auditory
thalamic synaptic inhibition and increases in thalamic synchrony.
Silencing of corticothalamic neurons in layer 6 (but not layer 5) or the
thalamic reticular nucleus linearized the cortical responses, suggesting
that layer 6 corticothalamic feedback via the thalamic reticular nucleus
was responsible for gating stochastic cortical population responses. These
data implicate a corticothalamic-thalamic reticular nucleus circuit that
modifies thalamic neuronal synchronization to recruit populations of
cortical neurons for sensory representations.