Phase-dependent activity of neurons in the rostral part of the thalamic reticular nucleus with saccharin intake in a cue-guided lever-manipulation task.

Neurons in the rostral part of the thalamic reticular nucleus (rTRN) receive somatosensory and motor information and regulate neural activities of the thalamic nuclei. Previous studies showed that when activity in visual TRN neurons is suppressed prior to the visual stimuli in a visual detection task, the performance of the task improves. However, little is known about such changes in the rTRN preceding certain events. In the present study, we performed unit recordings in the rTRN in alert rats during a cue-guided lever-manipulation task in which saccharin was provided as a reward. Changes in neural activity during saccharin intake were observed in 56% (51 of 91) of the recorded neurons; the firing rates increased in 21 neurons and decreased in 23 neurons. Seven neurons both increased and decreased their firing rates during saccharin intake. Changes in firing rates during the reward-waiting stage between task termination and saccharin intake were also observed in 73% (37 of 51) of the neurons that responded to saccharin intake. Increased activity during saccharin intake did not correlate with increased activity during lever-manipulation or activity during the reward-waiting stage. However, decreased activity during saccharin intake was correlated with activity during the reward-waiting stage. These results suggest that rTRN neurons have phase-dependent changes in their activity and regulate the thalamic activities. Furthermore, the decreased activity of rTRN neurons before reward may contribute to refine somatosensory and motor information processing in the thalamic nuclei depending on the status of mind such as expectation and attention.