Corticothalamic Layer 6 Controls Cortical Activity and Thalamic Firing Mode in a Bidirectional Manner

Folkard, R.; Isaias-Camacho, E. U.; Groh, A.

doi:10.1101/2025.07.17.665299

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bioRxiv · 10.1101/2025.07.17.665299

Corticothalamic Layer 6 Controls Cortical Activity and Thalamic Firing Mode in a Bidirectional Manner

Folkard, R.·Isaias-Camacho, E. U.·Groh, A.

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Abstract

Corticothalamic layer 6 modulates information flow between cortical and thalamic circuits. Previous research reported contrasting inhibitory or excitatory effects of corticothalamic layer 6 on cortical dynamics, potentially reflecting technological discrepancies or physiological differences in corticothalamic layer 6 function. To resolve these discrepancies, we combined translaminar, multi-channel in vivo electrophysiology in the primary somatosensory cortex of the anaesthetised mouse with optogenetic stimulation across a range of stimulation regimes to manipulate firing rate and frequency of corticothalamic layer 6. Increasing corticothalamic layer 6 firing rates exerted a transition from inhibition to excitation across cortical layers. Furthermore, corticothalamic layer 6 activity imparted population synchrony onto distinct cortical subpopulations, independent of changes in overall corticothalamic layer 6 activity. In the thalamus, corticothalamic layer 6 modulated thalamic bursting in a bidirectional manner, dependent on optogenetic stimulation frequency. These results demonstrate that corticothalamic layer 6 in primary somatosensory cortex can bidirectionally modulate both cortical firing and thalamic firing mode, elucidating a more nuanced function of somatosensory corticothalamic layer 6 in thalamic and cortical signalling than previously recognised.

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Folkard, R., Isaias-Camacho, E. U., Groh, A.. 2025-07-21. Corticothalamic Layer 6 Controls Cortical Activity and Thalamic Firing Mode in a Bidirectional Manner. https://doi.org/10.1101/2025.07.17.665299

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