Effects of posttrial electrical stimulation of the mesencephalic reticular formation on avoidance learning in rats

Rats bearing electrodes implanted unilaterally in the mesencephalic reticular formation were given either electrical stimulation (90 sec of 6 sec on-3 sec off; 0.01 msec biphasic, 300 Hz) or sham stimulation each day for 25 days immediately after a single trial in an active avoidance task. Although both implanted groups learned more slowly than unoperated controls, the performance of stimulated animals was significantly better than that of the stimulated control animals. When stimulation was discontinued (trials 26-50) level of performance did not decrease. The performance of animals given sham stimulation on trials 1-25 improved significantly when they were subsequently given posttrial stimulation (trials 26-50). These findings confirm previous reports indicating that avoidance learning is facilitated by posttrial electrical stimulation of the MRF.