Corticofugal effects on the activity of thalamic taste cells.

To examine corticofugal influences on afferent thalamic cell responses in the gustatory system, effects of cortical conditioning stimuli on the responses of thalamic taste cells to peripheral stimulation were examined in the rat. Two types of excitability change of thalamic cells were observed; one is inhibitory (for about 60 msec) (20%) and the other is inhibitory (for about 10 msec)--facilitatory (for about 60 msec) (40%) to conditioning stimulus applied to the ventral gustatory area, and half of the cells belonging to the latter type also showed a similar pattern with more marked and prolonged excitability changes to conditioning stimulus applied to the dorsal gustatory area. It was suggested that some of the response characteristics of thalamic and cortical taste cells were attributed to the corticofugal feedback loop.