[Recent advances in clinical application of event-related potentials]

Auditory and somatosensory ERPs were studied in patients with dementia of the Alzheimer type (DAT), those with vascular dementia and demented patients with idiopathic Parkinson disease. In both auditory and somatosensory modalities, the P3 latency in the demented patient group was significantly prolonged compared with the control data. However, comparisons of the P3 latency among the patients with DAT, vascular dementia and demented Parkinson did not reveal any significant differences. Patients with vascular dementia had significantly prolonged N140 and P200 latencies in somatosensory ERPs, whereas N1 and P2 latencies in auditory ERPs did not show any significant differences. Patients with acute onset hippocampal amnesia showed normal auditory P3 and somatosensory P3, whereas patients with diencephalic amnesia had prolonged auditory P3 and somatosensory P3 in addition to the abnormal short latency somatosensory evoked potentials. Analysis of passively evoked P3 component and comparison between target P3 and passively evoked P3 may be useful for evaluation of demented patients with a variety of etiologies. Single-trial analysis showed a greater variance of P3 latency in demented patients than in control subjects. A greater variance of P3 resulted in 'absent P3' in conventional averaging in some of the demented patients. As vigilance levels changed from trial to trial, evaluation of P3 latency variance has been proven to be useful.