Simultaneous Top-down Modulation of the Primary Somatosensory Cortex and Thalamic Nuclei during Active Tactile Discrimination
Published Date:Feb 27 2013
Source:J Neurosci. 33(9):4076-4093.
Facial Nerve Injuries
GABA-A Receptor Agonists
Principal Component Analysis
Funding:DP1 MH099903/MH/NIMH NIH HHS/United States
DP1MH099903/DP/NCCDPHP CDC HHS/United States
R01 DE011451/DE/NIDCR NIH HHS/United States
R01 NS073125/NS/NINDS NIH HHS/United States
R01NS073125/NS/NINDS NIH HHS/United States
RC1 HD063390/HD/NICHD NIH HHS/United States
RC1HD063390/HD/NICHD NIH HHS/United States
Description:The rat somatosensory system contains multiple thalamocortical loops (TCLs) that altogether process, in fundamentally different ways, tactile stimuli delivered passively or actively sampled. To elucidate potential top-down mechanisms that govern TCL processing in awake, behaving animals, we simultaneously recorded neuronal ensemble activity across multiple cortical and thalamic areas while rats performed an active aperture discrimination task. Single neurons located in the primary somatosensory cortex (S1), the ventroposterior medial, and the posterior medial thalamic nuclei of the trigeminal somatosensory pathways exhibited prominent anticipatory firing modulations before the whiskers touching the aperture edges. This cortical and thalamic anticipatory firing could not be explained by whisker movements or whisker stimulation, because neither trigeminal ganglion sensory-evoked responses nor EMG activity were detected during the same period. Both thalamic and S1 anticipatory activity were predictive of the animal's discrimination accuracy. Inactivation of the primary motor cortex (M1) with muscimol affected anticipatory patterns in S1 and the thalamus, and impaired the ability to predict the animal's performance accuracy based on thalamocortical anticipatory activity. These findings suggest that neural processing in TCLs is launched in anticipation of whisker contact with objects, depends on top-down effects generated in part by M1 activity, and cannot be explained by the classical feedforward model of the rat trigeminal system.
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