Authors:

GARAGNANI, M., SHTYROV, Y., Wennekers, T. & PULVERMULLER, F.

Reference:

Year of publication:

2008

CBU number:

6808

Abstract:

The brain responses to the same speech sounds differ if the stimuli are presented in different task contexts: when subjects are not paying attention to the auditory input, their early mismatch negativity (MMN) brain response is greater for words than for matched meaningless pseudowords, whereas the opposite pattern (N400) emerges in tasks where subjects attend to the stimuli. We implemented a neuroanatomically-grounded neural-network model of the left-perisylvian cortex that uses Hebbian learning to simulate word-acquisition processes. The variation of a single parameter explained the divergence between MMN and N400 results, providing the first unifying account, at cortical-circuit level, of these neurophysiological data. Furthermore, we recorded the brain responses to words/pseudowords when subjects were asked to attend to or ignore the same spoken input. The results showed consistent larger responses to pseudowords than to words under high attentional demand, and the opposite trend (wordsepseudowords) under non-attend conditions, confirming the model's predictions.