Hemodynamic and electroencephalographic responses to illusory figures: Recording of the evoked potentials during functional MRI

The feasibility of recording event-related potentials (ERP) during function al MRI (fMRI) scanning using higher level cognitive stimuli was studied. Us ing responses to illusory figures in a visual oddball task, evoked potentia ls were obtained with their expected configurations and latencies. A rapid stimulation scheme using randomly varied trial lengths was employed, and cl ass-wise characteristics of the hemodynamic response were obtained by a non linear analysis of the fMRI time series. Implications and limitations of co nducting combined ERP-fMRI experiments using higher level cognitive stimuli are discussed. EEG/fMRI results revealed a sequential activation of striat e and extrastriate occipital cortex along the ventral path of object proces sing for Kanizsa figures. Interestingly, Kanizsa figures activated the huma n motion area MT. Targets resulted in activations of frontal and parietal c ortex which were not activated for standard stimuli. (C) 2001 Academic Pres s.