Estimates of brain activity using magnetic field tomography in a GO/NOGO avoidance paradigm

This paper presents the first estimates of three dimensional evolution of activity in the brain associated with a GO/NOGO avoidance (CNV) paradigm. These estimates are continuous probabilistic solutions (Ioannides et al. 1990) to the biomagnetic inverse problem, obtained from averaged multichannel magnetoencephalographic (MEG) recordings (Vieth et al. 1991). The emphasis here is placed on the comparison of the activity associated with the GO and NOGO conditions; estimates of activity are shown for the onset of warning stimulus (S1), the early response half a second after S1, the late response lasting for over one second before S2 (the time between S1 and S2 is 3.5 seconds) and the onset of the imperative stimulus (S2). We find responses in regions of the brain implicated with hearing the stimulus, task engagement and motor output. Differences in the images corresponding to GO and NOGO conditions are significant because they reflect differences in brain function when a motor response is required or must be inhibited.