Participation of thalamic nuclei in the acquisition of conditioned avoidance reflexes in rats. IX. Lesions of the nucleus reticularis.

Bilateral symmetric lesions of the anterior part of the nucleus reticularis thalami (RET) strongly reduced the preoperatively learnt avoidance responses in Long-Evans hooded rats. A great retention loss, significantly prolonged reaction times and slow incorrect escape reactions in the first postoperative session in a simple runway task were corrected in the relearning period. The relearning of directional change and of a 2:2 alternation schedule in the Y-maze was rather difficult; it delayed and remained on a lower performance level with a not correctable side preference. A great retention loss in the pole-climbing test was not compensated in the relearning period. The experimental data suggest that the RET plays an important role in the inhibition of incorrect responses.