Stress-induced facilitation of classical conditioning.

Stress has been shown to impair subsequent learning. To determine whether stress would impair classical conditioning, rats were exposed to inescapable, low-intensity tail shock and subsequently classically conditioned under freely moving conditions with a brief periorbital shock unconditioned stimulus and a white noise conditioned stimulus. Unexpectedly stressed rats exhibited significantly more conditioned eyeblink responses and the magnitude of their individual responses was also enhanced. These results stand in contrast to the learning deficits typically observed and suggest that stress can enhance the acquisition of discrete conditioned responses.