An ERP study of category learning

TABULLO, ANGEL; YORIO, ALBERTO; PÉREZ-LEGUIZAMÓN, PATRICIO; SEGURA, ENRIQUE

Varadero, Cuba

Congreso; 4º Congreso Cubano y 1º Taller Ibero-Latinoamericano de Neurofisiología Clínica.; 2008

Stimulus equivalence (Sidman, 1982, 1994) provides a behavioural model of category learning, and it has been argued that equivalence relations may be related to semantic and symbolic processes. In the present study, we examined ERPs in a category learning task, comparing equivalence related, identical and unrelated stimulus. Methods: ten healthy subjects participated on the experiment. In a training phase, a series of arbitrary relations between visual stimuli (A-B, B-C) were thought to subjects via matching to sample procedures. In the test phase, subjects were instructed to classify stimulus pairs as "equivalent", (C-A), "identical" or "unrelated". EEG activity was recorded during this phase. Results: a frontocentral negativity was observed between 100 and 300 ms. The waveform elicited by identical stimuli was significantly less negative than the waveforms of equivalent and unrelated stimulus (F(2,8)= 6.757, p=0.019). A centroparietal negativity emerged between 350 and 600 ms. The waveform was significantly more positive for equivalent stimuli, and more negative for unrelated stimuli (F(2,8)= 7.322, p=0.019). Conclusions: we found a N200 component associated with perceptual mismatch, and a N400 component, associated with semantic mismatch. N200 could reflect automatic attentional processes, and N400 could be a larker categorizatin and decisoin taking. Therefore, neural correlates of equivalence show similarites with those of other semantic relations.