ORIGINAL ARTICLE: Inter‐peak Latency of Auditory Event‐related Potentials (P300) in Cases of Aged Schizophrenia and Alzheimer‐type Dementia

Abstract

Background: Both patients with schizophrenia and those with dementia show cognitive difficulties, and in many cases of schizophrenia the cognitive disturbance is progressive, as it is in dementia. Event-related potentials have revealed cognitive impairments in patients with schizophrenia and dementia, but most studies of event-related potentials in cases of psychiatric illness or dementia have focused on the single peak latency of the event-related potential components. In the present study, we investigated the cognitive function in elderiy patients with schizophrenia and Alzhe imer-type dementia (ATD) using auditory event-related potentials (P300). Methods: P300 was recorded using the tone discrimination task and peak latencies for N1, P2, N2 and P3 at the Pz electrode site were measured. In addition to analyzing peak latencies of P300, we also analyzed inter-peak latencies (IPL; N1 -P2, P2-N2, and N2-P3). Twenty-two elderly residual-type schizophrenics and 36 patients with ATD were compared with 39 age-matched healthy volunteers. Results: The mean latencies of P3 and mean IPL of P2-N2 in elderly schizophrenic patients were longer than those of the controls. In ATD the mean latencies of N2 and P3 and the mean IPL of P2-N2 were longer than those of the controls. When the mean latencies of ATD patients were compared with those in patients with schizophrenia, P2, N2, and P3 latencies and N1 -P2 and P2-N2 IPL were longer. Conclusion: These findings suggest that a similar impairment of the cognitive process is found in elderly patients with schizophrenia and those with ATD and that the degree of the impairment of patients with ATD is more severe than that of elderly patients with schizophrenia.

Revisiting P300 cognitive studies for dementia diagnosis: Early dementia with Lewy bodies (DLB) and Alzheimer disease (AD)

“…The use of an active task did not allow us to investigate possible differences between groups in the mis-match negativity response, but we made sure that patients kept constant their attention during recordings, as P300 amplitude is sensitive to the amount of attention resources engaged during the task. In every group, N200 latencies were correlated with P300 latencies, confirming previous studies that showed prolonged N200 and P300 latencies in patients with dementia [44].…”

“…Recordings in patients with dementia were compared with normative data obtained through P300 measurements in age-matched control populations. Standard deviation (SD) from the means was used to evaluate the biological effects on P300 measures in control subjects [35] and in patient groups, and to estimate the differences between patients and controls [44]. In demented patients, comparisons between ranges of different widths evidenced that, for P300 latency, the 2SD criterion had the greatest sensitivity in the detection of dementia [13].…”

Is There a Place for Clinical Neurophysiology Assessments in Synucleinopathies?

“…The use of an active task did not allow us to investigate possible differences between groups in the mismatch negativity response, but we made sure that patients kept constant their attention during recordings, as P300 amplitude is sensitive to the amount of attention resources engaged during the task. In every group, N200 latencies were correlated with P300 latencies, confirming previous studies that showed prolonged N200 and P300 latencies in patients with dementia [46]. Topographical analysis of P300 recordings including all scalp leads did not add information about possible differences between patient groups, confirming that study of P300 topography could be limited to midline electrodes.…”

Neurophysiological evaluation of late paraphrenia: Comparison with chronic schizophrenia and dementia of the Alzheimer type

“…P300 is believed to reflect the cognitive processes, such as sensory input, encoding or registration of sensory information, reference to memory templates, stimulus evaluation, responce sellection or cognitive context updating 18 . Prolongation of P300 latency is observed in healthy aging subjects and patients with dementia show significantly prolonged N200 and P300 latencies compared with healthy aging subjects 13,18–20 .…”

“…18 Prolongation of P300 latency is observed in healthy aging subjects and patients with dementia show significantly prolonged N200 and P300 latencies compared with healthy aging subjects. 13,[18][19][20] Correlations between P300 latency and N3 latency have been reported in healthy aged subjects. 21 In the present study, P300 and N200 latencies in patients with DAT were significantly prolonged compared with LP patients, chronic schizophrenics and healthy aged subjects, but there was no significant difference between LP patients and the controls on either N200 or P300 latency.…”