THE TRANSCEPHALIC direct current (TCDC) potential is the slowly changing aperiodic voltage recorded between the frontal and occipital emissary vein distributions on the midline surface of the head.1-3 It now appears that a negative frontal shift reflects a lowered activation threshold of the subjacent frontal cortex,4-6 and is related to the physiological substrate of the orienting reflex.7 At an elementary level, a brief negative shift occurs when the subject attends to an exteroceptive or nonvestibular proprioceptive stimulus, and a positive shift is promoted by interoceptive stimuli.2 Hunger and other externally oriented drive states promote a negative frontal baseline, and satiety states a positive one.1,2,8 At a more complex functional level, anxiety increases the TCDC variance of a group without imparting a specific polarity to the potential.2,8 An attempt to inhibit perception of an exteroceptive stimulus correlates