Functional topography of corticothalamic feedback enhances thalamic spatial response tuning in the somatosensory whisker/barrel system.
Corticothalamic (CT) projections are approximately 10 times more numerous than thalamocortical projections, yet their function in sensory processing is poorly understood. In particular, the functional significance of the topographic precision of CT feedback is unknown. We addressed these issues in the rodent somatosensory whisker/barrel system by deflecting individual whiskers and pharmacologically enhancing activity in layer VI of single whisker-related cortical columns. Enhancement of corticothalamic activity in a cortical column facilitated whisker-evoked responses in topographically aligned thalamic barreloid neurons, while activation of an adjacent column weakly suppressed activity at the same thalamic site. Both effects were more pronounced when stimulating the preferred, or principal, whisker than for adjacent whiskers. Thus, facilitation by homologous CT feedback sharpens thalamic receptive field focus, while suppression by nonhomologous feedback diminishes it. Our findings demonstrate that somatosensory cortex can selectively regulate thalamic spatial response tuning by engaging topographically specific excitatory and inhibitory mechanisms in the thalamus.
Department of Neurobiology, University of Pittsburgh, Pittsburgh, PA 15261, USA. temerean@nmr.mgh.harvard.edu
Simona
S
Temereanca
Daniel J
DJ
Simons
D000200:Action Potentials / Q000187:drug effects / Q000502:physiology; D000344:Afferent Pathways / Q000166:cytology / Q000502:physiology*; D000818:Animals; D001931:Brain Mapping; D004525:Efferent Pathways / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D005246:Feedback / Q000187:drug effects / Q000502:physiology*; D005260:Female; D018756:GABA Antagonists / Q000494:pharmacology; D009433:Neural Inhibition / Q000187:drug effects / Q000502:physiology; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D013003:Somatosensory Cortex / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology; D013788:Thalamus / Q000166:cytology / Q000502:physiology*; D014110:Touch / Q000502:physiology; D014276:Trigeminal Nerve / Q000502:physiology; D014738:Vibrissae / Q000502:physiology*
D018756:GABA Antagonists