CONTROL OF MEMORY BY SPREADING CORTICAL DEPRESSION: A CRITIQUE OF STIMULUS CONTROL

MANY INVESTIGATORS HAVE FOUND THAT MEMORY FOR A TASK TRAINED DURING UNILATERAL SPREADING DEPRESSION (USD) IS UNAVAILABLE TO THE ANIMAL IF IT IS LATER TESTED WITH SPREADING DEPRESSION OF THE OPPOSITE SIDE. HOWEVER, IF BETWEEN TRAINING AND TEST SESSION AN ANIMAL IS GIVEN 1 TRIAL WITH NEITHER HEMISPHERE DEPRESSED, GOOD RETENTION IS OBSERVED. A. M. SCHNEIDER (SEE 41:7) HAS INTERPRETED THIS IN TERMS OF A STIMULUS CONTROL AND STIMULUS GENERALIZATION HYPOTHESIS. THIS EXPLANATION OF THE 1-TRIAL TRANSFER PHENOMENON IS EXAMINED AND FOUND UNSATISFACTORY BECAUSE: (1) THE STIMULUS CONTROL THEORY REQUIRES THE NONDEPRESSED STATE TO BE MORE SIMILAR TO THE USD AND CONTRALATERAL USD STATES THAN TO EACH OTHER. THE EVIDENCE FOR THIS SIMILARITY CONTINUUM IS UNCONVINCING. (2) SCHNEIDER INVOKES A DIFFERENT SIMILARITY CONTINUUM TO ACCOUNT FOR THE RESULTS OF SCHNEIDER AND KAY, AND FAILS TO SUPPLY RULES SPECIFYING WHICH CONTINUUM SHOULD APPLY IN ANY GIVEN CASE. (3) THE STIMULUS CONTROL THEORY INCORRECTLY PREDICTS THAT MAXIMUM TRANSFER SHOULD OCCUR WITHOUT A NONDEPRESSED TRANSFER TRIAL. (4) THE STIMULUS CONTROL THEORY CANNOT EXPLAIN THE EFFECTS OF POSTTRANSFER TRIAL USD ON RETENTION. (17 REF.)