An ERP study of stimulus equivalence in aphasic and non-brain damaged individuals

In this study, one aphasic and four non-brain damaged adults engaged in a computerized equivalence-training procedure while cortical activation was recorded using event-related potentials (ERP). Equivalence training is a procedure used to promote transfer and generalization of learned skills. It is described by the properties reflexivity (A = A), discrimination (A = B), symmetry (if A = B then B = A), transitivity (if A = B and B = C then A = C), and equivalence (C = A). ERP is a non-invasive imaging procedure that records cortical activation in response to time or response specific events. The task consisted of a matching-to-sample paradigm of nonsense symbols. The symbols were presented at increasing complexity. Participants were required to touch a sample and then a matching choice on a computer monitor for a total of 201 trials. The present study compared the performance of the non-brain damaged individuals to the brain-damaged individual. The results show that both the aphasic and non-brain damaged individuals learned the equivalence relationships. The aphasic exhibited longer physical response latencies and cognitive latencies different from the non-brain damaged individuals. Additionally, cortical activation in the aphasic was marked by areas of high activation contrasted by areas of inactivation. This pattern was not observed in the non-brain damaged individuals. The implication of the study is that the aphasic processed stimuli different from non-brain damaged individuals and required added processing time, but he learned and generalized the emblematic relationships