Stimulus change influences escape performance: deficits induced by uncontrollable stress and by haloperidol.

Exposure to uncontrollable foot-shock or treatment with haloperidol was found to disrupt subsequent escape behavior. Performance among naive mice, as well as mice that had been exposed to inescapable shock or treated with haloperidol could be enhanced by either interrupting the shock train during escape testing or by presentation of a novel stimulus. The effectiveness of these treatments were dependent on the time at which the change in stimulation occurred. That is, shock interruption or cue presentation just prior to escape being possible enhanced performance, but the same manipulation several seconds prior to escape being possible had only a limited effect. In addition, the time of cue termination also influenced escape behavior. When cue offset coincided with or followed successful escape a performance enhancement was evident, but when cue offset occurred several seconds prior to escape, performance was not affected. It was suggested that inescapable shock and haloperidol treatment hinder performance by disrupting response maintenance. Shock interruption and novel cue presentation minimize disturbances of escape performance by altering the course of the decline of shock-elicited activity.