Additional neuromagnetic source activity outside the auditory cortex in duration discrimination correlates with behavioural ability.

In magneto- and electroencephalographic experiments on an oddball paradigm we compared the components of the auditory evoked fields and potentials of "attend" with "nonattend" conditions in 17 subjects. The former consisted of the performance of a duration discrimination task, where we observed augmented activity for the auditory sustained response. A multiple source analysis showed this effect mainly stemming from a third source outside the auditory cortices. The dipole moment of this specific activation was increased by 150% under the attend condition. Having anatomical 3D MRI data sets of 12 subjects the likely location of the third source was shown to be within the area of the precuneus or the posterior cingulate gyrus, which, along with its waveform, suggests it to be a CNV equivalent. Further, the dipole moment is correlated significantly to the subjects' psychometrically derived discriminative abilities.