p506fig13.35 A shock, or other reinforcing event, can have multiple cognitive and emotional effects on different brain processes.<BR>||  Multiple functional roles of shock.  1. Reinforcement sign reversal: An isolated shock is a negative reinforcer; In certain contexts, a shock can be a positive reinforcer.  2. STM-LTM interaction: Prior shock levels need to be remembered (LTM) and used to calibrate the effect of the present shock (STM).  3. Discriminative and situational cues: The present shock level is unexpected (novel) with respect to the shock levels that have previously been contingent upon experimental cues:   shock as a [1.reinforcer, 2. sensory cue, 3. expectancy].