Three channels of corticothalamic communication during locomotion.
We studied the flow of corticothalamic (CT) information from the motor cortex of the cat during two types of locomotion: visually guided (cortex dependent) and unguided. Spike trains of CT neurons in layers V (CT5s) and VI (CT6s) were examined. All CT5s had fast-conducting axons (<2 ms conduction time), and nearly all showed step-phase-related activity (94%), sensory receptive fields (100%), and spontaneous activity (100%). In contrast, conduction times along CT6 axons were much slower, with bimodal peaks occurring at 6 and 32 ms. Remarkably, almost none of the slowest conducting CT6s showed step-related activity, sensory receptive fields, or spontaneous activity. As a group, these enigmatic neurons were all but silent. Some of the CT6s with moderately conducting axons showed step-related behavior (35%), and this response was more precisely timed than that of the CT5s. We propose distinct functional roles for these diverse corticothalamic populations.
Sirota
Mikhail G
MG
Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona 85013, USA.
Swadlow
Harvey A
HA
Beloozerova
Irina N
IN
D000465:Algorithms; D000818:Animals; D002415:Cats; D002540:Cerebral Cortex / Q000502:physiology*; D004553:Electric Conductivity; D004558:Electric Stimulation; D005552:Forelimb; D008124:Locomotion / Q000502:physiology*; D023421:Models, Animal; D009434:Neural Pathways / Q000502:physiology; D009474:Neurons / Q000502:physiology*; D012054:Reinforcement, Psychology; D013788:Thalamus / Q000502:physiology*; D014851:Wakefulness / Q000502:physiology