Subdural Recordings of the Cortex Motor Potential.

This chapter discusses subdural recordings of the cortex motor potential. One of the non-invasive methods used in normal subjects to shed light on the eventual important role of the non-specific ascending diffuse projection systems in generating and regulating contingent negative variation (CNV) activity, is the study of the relationship of CNV processes to classic parieto-occipital alpha activity (POAA) of the conventional electroencephalography (EEG). The latter is well known to be influenced by the desynchronizing arousal mesodiencephalic reticulocortical systems. Researches on the relationship between CNV and alpha activity changes have so far been rare and conducted with different recording and analyzing methodologies in few subjects. Doubtless also owing to the difficulties met in EEG data treatment, the results have often been inconstant, inconsistent or actually contradictory. Pfurtscheller and Aranibar observed in some subjects that CNV magnitude and alpha power behaved differently over various scalp regions. They noted, however, that the alpha power decrease in occipital areas was closely related to the initiation of movement (button pressing), and in most cases the decrement was already significant at 0.25 sec before S2 onset.