Thalamocortical conduction times and stimulus-evoked responses in the rat whisker-to-barrel system.
Studies of the rodent whisker system indicate that somatosensory cortical circuitry operates at a millisecond timescale to transform sensory afferent signals from the thalamus. We measured axon conduction times and whisker-evoked responses of 48 thalamocortical (TC) neurons in the rat whisker-to-barrel pathway. Conduction times were derived from spike-triggered averages of local field potentials evoked in layer 4 cortical whisker-related barrels by the spontaneous firing of individual topographically aligned neurons in the ventral posterior medial thalamus. Conduction times varied fourfold, from 0.31 to 1.34 ms, and faster conducting TC neurons responded earlier and more robustly to controlled whisker deflections. Early arrival of highly responsive TC inputs, thought to contact inhibitory barrel neurons preferentially, could prime the cortical network, rendering it more selective for later-arriving signals.
Simons
Daniel J
DJ
Department of Neurobiology, University of Pittsburgh School of Medicine, E1452 Biomedical Science Tower, 200 Lothrop Street, Pittsburgh, PA 15261, USA. cortex@pitt.edu
Carvell
George E
GE
Kyriazi
Harold T
HT
Bruno
Randy M
RM
D000200:Action Potentials / Q000502:physiology*; D000818:Animals; D004525:Efferent Pathways / Q000502:physiology; D009431:Neural Conduction / Q000502:physiology*; D010812:Physical Stimulation / Q000379:methods; D011336:Probability; D051381:Rats; D011930:Reaction Time / Q000502:physiology*; D013003:Somatosensory Cortex / Q000502:physiology*; D013788:Thalamus / Q000502:physiology*; D014738:Vibrissae / Q000294:innervation*