Retrograde amnesia induced by lidocaine injection into the striatum: protective effect of the negative reinforcer.

A variety of manipulations which interfere with the activity of the striatum, including cholinergic blockade and spreading depression, produce amnesia. However, it has been demonstrated that with overtraining, striatal spreading depression and injections of anticholinergic drugs do not produce memory deficits in positively-rewarded tasks. In the present experiment 2% lidocaine was injected into the striatum shortly after training of passive avoidance, using three levels of footshock (0.2, 0.3, and 0.4 mA). Highly significant retention deficits were produced when the lower intensities were studied; in contrast, the animals trained with 0.4 mA showed near-perfect performance. The data show that the enhanced learning experience, which may be equivalent to overtraining, also protects against memory deficits in negatively-rewarded behaviors, and suggest that it induces a transfer of mnemonic functions from the striatum to other neural structures.