Applications of event-related potentials in the study of attention

Sammanfattning: Event-related potentials were measured in a series of studies where issues concerning attention were of special interest. In particular, the P300 was used as an index of controlled attention. Papers I and III studied nicotine effects on the P300. If nicotine effects were reflected in the P300, decreased latencies and increased amplitudes would be expected. No systematic nicotine effects were found on the P300. In contrast, nicotine had clear dose-response effects on the EEG in Paper I. EEG findings indicated increased arousal, and similar, if less marked, results were obtained in Paper III. Paper II tested nicotine effects on reaction time in tasks involving response competition and visual search, respectively. A focusing effect of nicotine would implicate smaller effects of distracting or less salient information. No such specific effects were found, but response times generally decreased after nicotine administration. Paper IV focused on nicotine effects in a demanding memory test. Recognition memory improved after nicotine administration. A special question concerned whether nicotine would improve strategic encoding, as manipulated by the instructions. We found no evidence for such an effect. Nicotine administration did not affect event-related potentials. In general, nicotine administration decreased response times in studies II, III and IV. Paper V studied the restitution of cognitive function after insulin-induced hypoglycaemia. During hypoglycaemia P300 amplitude decreased in a relatively complicated visual task, while remaining unaffected in the easier tasks used. Amplitudes were restituted after approximately 40 minutes. Paper VI studied P300 in patients diagnosed with toxic encephalopathy with or without neuropsychological impairment. Patients were studied in both simple and complex tasks, and the P300 amplitude was lower in both patient groups.