engleski

Early neuromagnetic responses to deviant faces in an oddball paradigm.

Quick recognition of face identity and facial expression is very important social skill. Magnetoencephalography (MEG) is well suited to investigate spatio-temporal dynamics of face processing [e.g. 1]. Our previous results have shown a negative deflection in MEG and ERP responses to deviant faces in an oddball paradigm with a maximum around 280 ms [2]. The aim of this study was to investigate neural substrates of early detection of a change in the facial stimulus. Facial expression change (happy vs. neutral) and upright vs. inverted faces were considered. Measurements were carried out at the BioMag laboratory using a 306-channel whole-head MEG system (Vectorview, Elekta Neuromag Ltd, Helsinki) simultaneously with a 60-channel EEG. Eight subjects with available MRI scans participated in the study. Face stimuli were presented in an oddball paradigm with four experimental conditions: 1) happy standard, neutral deviant ; 2) neutral standard, neutral deviant ; 3) inverted happy standard, inverted neutral deviant ; 4) inverted neutral standard, inverted neutral deviant. The task was silent counting of the face with glasses target stimuli in all conditions. Spatio-temporal source localization was conducted for neuromagnetic responses evoked by neutral face deviant stimuli in all conditions. Up to four sources were identified during the first 140 ms post-stimulus in the occipital, occipito-temporal, and parietal regions. Figure shows locations of three currents dipoles in the time interval 80-140 ms post-stimulus for one subject in four conditions. Our preliminary results indicate early differences in locations of current dipoles reflecting experimental condition dependent processing of physically the same neutral deviant faces.

MEG (magnetoencephalography); face processing; spatio-temporal source localization

nije evidentirano