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Neurocomputational and neurophysiological studies of brain interactions of language and attention.
GARAGNANI, M., SHTYROV, Y., Kujala, T., Wennekers, T. & PULVERMULLER, F.
Experimental Psychology Society Meeting - April 2008, p52
Year of publication:
Recent EEG and MEG studies have revealed that 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 (Pulvermüller & Shtyrov, 2006; Pulvermüller et al., 2004), whereas greater late N400 responses to pseudowords than to words emerge in tasks where subjects have to attend to the stimuli (Sinai & Pratt, 2002). We built a neuroanatomically-grounded neural-network model of the left-perisylvian cortex and used it to simulate early word-acquisition processes by means of synaptic-weight adaptation based on neurobiologically-realistic learning. The variation of two model parameters replicated and explained the divergence between MMN and N400 results, providing the first unifying account, at the cortical-circuit level, of these neurophysiological data. Furthermore, we recorded neurophysiological brain responses to words and pseudowords when subjects were asked to attend to the spoken input or to ignore it. The results showed a robust activation of word-specific memory traces which was not significantly influenced by attention level, confirming the model’s predictions. These data provide further evidence supporting earlier suggestions that initial stages of lexical processing are not affected by attentional demands and may thus be automatic. References Pulvermüller, F. & Shtyrov, Y. (2006) Language outside the focus of attention: the mismatch negativity as a tool for studying higher cognitive processes. Progress in Neurobiology, 79:49-71. Pulvermüller, F., Shtyrov, Y., Kujala, T. & Näätänen, R. (2004) Word-specific cortical activity as revealed by the mismatch negativity. Psychophysiology, 41:106-12. Sinai, A. & Pratt, H. (2002) Electrophysiological evidence for priming in response to words and pseudowords in first and second language. Brain and Language, 80:240-52.