Where neurophysiology can help to answer questions in cognitive and language science

Dia: 21 novembre 2006
Hora: 12:00
Lloc: Sala de Graus, Facultat de Psicologia, Campus Mundet

Dr. Friedemann Pulvermuller
Professor of Cognitive Neuroscience

Medical Research Council
Cambridge, UK
url: http://www.mrc-cbu.cam.ac.uk/people/people-pages.php?id=105

Resum
Which aspects of language and cognitive processing take place irrespective of whether subjects focus their attention on incoming stimuli and are, in this sense, automatic? The Mismatch Negativity (MMN), a neurophysiological brain response recorded in the EEG and MEG, is elicited by attended and unattended stimuli alike. Recent studies investigating the cognitive processes underlying spoken language processing found that even under such attentional withdrawal, MMN size and topography reflect the activation of memory traces for language elements in the human brain. Familiar sounds of one's native language elicit a larger MMN than unfamiliar sounds, and at the level of meaningful language units, words elicit a larger MMN than meaningless pseudowords.

This suggests that the MMN reflects the activation of memory networks for language sounds and spoken words. Unattended word stimuli elicit an activation sequence starting with superior-temporal cortex and rapidly progressing to left-inferior-frontal lobe. The spatio-temporal patterns of cortical activation depend on lexical and semantic properties of word stems and affixes, thus indicating that the MMN can give clues about lexico-semantic information processing. At the syntactic level, MMN size was found to reflect whether a word string conforms to grammatical regularities. This growing body of results suggests that lexical, semantic and syntactic information can be processed by the central nervous system outside the focus of attention in a largely automatic manner. Analysis of spatio-temporal patterns of generator activations underlying the MMN to speech may be an important tool for investigating the brain dynamics of spoken language processing and the distributed cortical networks activated