DC potential correlates of attention and cognitive load

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Abstract
Very low-frequency contributions to the human EEG have received comparatively little attention over the last 100 years. This article seeks to demonstrate that DC potentials, recordable from the scalp surface, may provide a measure of long-term activity in underlying cortical regions. A review of recent experiments shows that increased levels of cognitive-attentional demand lead to sustained increments in levels of scalp-surface negativity. Furthermore, the topographical distribution of DC shifts is consistent with knowledge about the localisation of function in human cerebral cortex. It is argued that the examination of phasic and tonic changes in surface potential may provide a real-time index of fluctuations in both the global and localised patterning of attention and arousal.