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.
Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona 85013, USA.
Mikhail G
MG
Sirota
Harvey A
HA
Swadlow
Irina N
IN
Beloozerova
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