Drinking related direct current positive potential shift in the human EEG depends on thirst

Scalp recorded direct current (DC)-potential shifts were examined in 11 hum an subjects who had either thirsted for 16 h or had quenched thirst before recordings. The recording epoch included a 3-min baseline, an interval of a bout 5 min during which subjects drank 400 ml of water, and a 7-min post-dr inking interval. Consistent with previous data, when thirsty, subjects disp layed a widespread negative DC-potential shift during drinking which was re placed by a positive DC shift at the transition to the post-drinking interv al. The positivity after drinking lasted for about 2 min and averaged 146 L V at frontal recording sites. Quenching thirst before recordings reduced th e positive DC-potential shift upon drinking, whereas changes in preceding d rinking related DC negativity appeared to be secondary. The post-drinking p ositive DC-potential shift depending on the subject's motivational state ca n be considered an indicator of reward associated with quenching thirst, po inting to a lowered frontocortical excitability during reward. (C) 2001 Pub lished by Elsevier Science Ireland Ltd.