Spatio-temporal cortical patterns evoked in man by a discrimination task (Q1894089)

Magnetoencephalographic (MEG) recordings were obtained from a 37 sensor array during performance of a discrimination task. Pairs of stimuli were presented to the somatosensory and auditory systems which fell into two classes. Subjects were instructed to respond to one class and not the other. A ``virtual electrode'' estimation procedure was applied to generate time varying waveforms from locations within the brain as if from direct electrodes. Multivariate statistical procedures were then applied to the single trial MEG and virtual electrode estimates. This produces strong statistical inferences from the data from each subject, produces functional timing and localization for each subject, and demonstrates clear differences between subjects. It is an integrated experimental/analytic paradigm which is applicable to the study of perception, cognition, affect, and a wide variety of psychopathologies. Discriminant analysis was applied to the sampled single trial MEG data to (1) determine whether information was extracted and (2) to produce a discriminant function by which the 37 channel data stream can be collapsed to a single data stream to produce functional timing information. For all 5 subjects, these results conform to the following model for the sequence of activities required to perform the discrimination task: (1) Primary sensory processing. (2) Discrimination between stimulus classes, this being the imperative function upon which correct task performance depends. (3) Response preparation. (4) Motor activation.