Coupling of regional activations in a human brain during an object and face affect recognition task

Magnetic field tomography (MFT) was used to extract estimates for distribut ed source activity from average and single trial MEG signals recorded while subjects identified objects (including faces) and facial expressions of em otion. Regions of interest (ROIs) were automatically identified from the ME T solutions of the average signal for each subject. For one subject the ent ire set of MFT estimates obtained from unaveraged data was also used to com pute simultaneous time series for the single trial activity in different RO Is. Three pairs of homologous areas in each hemisphere were selected for fu rther analysis: posterior calcarine sulcus (PCS), fusiform gyrus (FM), and the amygdaloid complex (AM). Mutual information (MI) between each pair of t he areas was computed from all single trial time series and contrasted for different tasks (object or emotion recognition) and categories within each task. The MI analysis shows that through feed-forward and feedback linkages , the "computation" load associated with the task of identifying objects an d emotions is spread across both space (different ROIs and hemispheres) and time (different latencies and delays in couplings between areas)-well with in 200 ms, different objects separate first in the right hemisphere PCS and FG coupling while different emotions separate in the right hemisphere FG a nd AM coupling, particularly at latencies after 200 ms. (C) 2000 Wiley-Liss , Inc.