Action selection is impaired by unilateral lesions in the rostral thalamic reticular nucleus.

Abstract

The rostral thalamic reticular nucleus (rTRN) exerts the same inhibitory control of thalamocortical transmission from the motor nuclei as the caudal sectors have over sensory nuclei. It is well established that the caudal sectors are involved in selective attention. This suggests an analogous role for rTRN in the selection of situationally appropriate behavior. Rats were trained to make an observing response followed by the illumination one of two centrally located light emitting diodes (LEDs) signaling the location of the correct nose poke to the left or right. Unilateral injections of ibotenic acid or saline were aimed at the rTRN. Postoperatively, the proportion of incorrect responses made into the hole contralateral to the lesion increased, and there was a concomitant decline in the number of correct responses directed ipsilateral to the lesion when compared with the rats with sham surgeries. Basic sensory and motor deficits do not account for these effects because response times and uncued responses did not differ between the groups. The data suggest that the diminished inhibition of the motor nuclei on the side of the rTRN lesion weakened the ability to deselect the incorrect contralateral response. We propose that the sensory and motor sectors of the TRN are functionally similar and the rTRN increases the contrast between a selected and nonselected actions.