Learning and retention of active avoidance are differently impaired after dorsal and ventral lesions of the nucleus reticularis pontis caudalis of rats.
Four groups of 8 adult male hooded rats of the Long-Evans strain were investigated before and after bilateral symmetric lesions of the nucleus reticularis pontis caudalis (RPC) in a Y-maze and in a jump test box. After dorsal (d) RPC lesions the retention of preoperatively learnt simple tasks in the Y-maze or in the jump test was not impaired whereas brightness discrimination in the Y-maze was neither retained nor relearned. Postoperative acquisition without preoperative experience was impossible for dRPC rats in any of the tests. After ventral (v) RPC lesions there was no retention of active avoidance response in the Y-maze but rather normal retention of the jump test performance. The retention of brightness discrimination, however, was not impaired in the Y-maze after vRPC lesions. The relearning of the impaired active avoidance in the Y-maze was impossible for vRPC rats; though these rats showed intrasessional improvement, there was no retention between sessions. After retention of the simple jump test task the vRPC rats were not able to learn a go/no-go task in the jump test box. Acute extinction to the non-reinforced 2.5 KHz tone was prolonged. Intertrial responses in the jump test were reduced to zero after dRPC lesions, but significantly enhanced after vRPC lesions. The results indicate that CAR response initiation was reduced after dRPC lesions, but in vRPC rats the suppression of incorrect responses was reduced in the jump test. The lesions differently impair the control of learnt motor programs.
Müller
G
G
Department of Neurophysiology, Karl Marx University, Leipzig, GDR.
Klingberg
F
F
D000818:Animals; D001362:Avoidance Learning; D005108:Extinction, Psychological; D008297:Male; D008568:Memory; D011149:Pons / Q000502:physiology*; D051381:Rats; D012016:Reference Values; D012154:Reticular Formation / Q000502:physiology*