FORCED EXTINCTION AS A MEANS TO EVALUATE CONSOLIDATION GRADIENT OF A PASSIVE-AVOIDANCE RESPONSE IN THE RAT

Passive avoidance response (PAR) consolidation gradient, and US (foots hock) intensity/engram strength relationship were investigated by mean s of specific forced extinction procedure (30 min detention in the sho ck box without receiving punishment) in Wistar rats trained in the lig ht-dark box apparatus. Different groups of rats (punished either with 0.8 or 1.2 mA footshock intensity) underwent detention at different po stacquisition time delays: immediately or 1, 2, 4 days after acquisiti on training. By means of this purely behavioral paradigm, designed to investigate a specific PAR memory trace, previous results obtained by using diverse and sometimes unspecific memory-disrupting agents were f ully confirmed: PAR strength and consolidation gradient are positively related to US intensity. The influence of differential generalization effects on extinction is discussed. An unexpected finding was that fr om engrams that are experimentally shown to be of unequal resistance t o disruption, equal conditioned responses are obtained.