To evaluate the neurophysiological differences between panic disorder (PD) and generalized anxiety disorder (GAD), 52 patients with PD and 34 with GAD were investigated using event-related potentials (ERP). The ERP were recorded using a tone discrimination task, and peak latencies for N1, P2, N2, and P3 at a Pz electrode site were measured. In addition to analyzing the peak latencies of the ERP, the interpeak latencies (IPL; N1-P2, P2-N2, and N2-P3) were also analyzed. The same analysis was performed in 28 age-matched healthy volunteers (controls). When compared to those of the GAD and control groups, the mean latencies of P2, N2, and P3 were shorter in the PD patients. With regard to the IPL in the PD patients, the N1-P2 IPL was shorter than that in the other groups, and no individual with PD had a longer N1-P2 IPL than 1 SD above the mean of the controls. These findings suggest that certain attention-related processes in the cerebrum that affect ERP data are accelerated in PD patients. These findings demonstrate that it may be useful to neurophysiologically distinguish PD from GAD by measuring ERP peak latencies and IPL.

Most studies on event-related potentials (ERP) in psychiatric illness or dementia have focused on the single-peak latency of ERP components. In the present study, not only peak latencies of ERP components (N1, P2, N2, and P3) but also interpeak latencies (IPL; N1-P2, P2-N2, and N2-P3) were analyzed using the auditory oddball task. Thirty-five senile depressed patients and 34 patients with dementia of the Alzheimer type (DAT) were compared to 39 age-matched healthy volunteers. The mean latencies of P2 and P3 were shorter in patients with senile depression than in controls. In DAT patients, the N2 and P3 latencies were longer. When the IPL was assessed, however, only the mean IPL of N1-P2 was shorter in patients with senile depression, while the P2-N2 IPL were longer in those with DAT. The IPL results suggest that in senile depression the early cognitive process is hastened and in DAT the middle process is disturbed. Based on these results, we conclude that IPL of the auditory ERP might be used to reveal the disturbed steps within the cognitive process.

Winter AL: Contingent negative variation: An electric sign of sensorimotor association and expectancy in the human brain. Nature (Lond.), 203: 380-384, 1964. 10) Silberman AJ, Busse EW, Barnes RH: Studies in the processes of aging: Electroencephalographic findings in 400 elderly subjects. Electroenceph Clin Neurophysiol 7: 67-74, 1955. 12) Mayer RF: Nerve conduction studies in man.

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.

Background:In order to evaluate the degree of impairment of cerebral function and the organic factors involved in elderly depressed patients, auditory event-related potentials (ERP; P300) and N-isopropyl-p [lZ31] iodoamphetamine (1231-IMP) single photon emission computed tomography (SPECT) were examined. Methods: Three groups of patients, the depression (D) group, consisting of 23 cases where the magnetic resonance imaging (MRI) showed no abnormalities, the depression with silent cerebral infarction (D/SCI) group, consisting of 28 cases with silent cerebral infarction, and the post-stroke depression (D/PS) group, consisting of 19 cases at over six months after onset of cerebral infarction where no abnormalities in intellectual function were seen, but neurological symptoms such as hemiplegia were present, and 27 healthy individuals were investigated. All of the patients fulfilled the ICD-10 diagnostic criteria for depressive episode, and disease onset occurred when the patients were over 55 years. The ERP (P300) was recorded using a tone discrimination task. Regional cerebral blood flow (CBF) was measured by 1231-IMP SPECT, and the relative rCBF of each region of interest was evaluated by comparison with the mean cerebellar rCBF. In addition, the mean cerebral blood flow (MCBF) in the cerebral cortex was assessed. Results: The D group included many cases in which the P300 peak latency was relatively short and the MCBF was stable, relative to the other two groups. In the D/ PS group, there were many cases where the P300 peak latency was prolonged and the MCBF was reduced. In the D/SCI group, many differences in the results from both indicators existed among individual cases, and no fixed trend was identified. Conclusion: From the perspective of determining therapeutic tactics for elderly depressed patients and forecasting prognosis, it is important to review in detail, on an individual basis, components such as higher brain functions including cognitive functions, cerebral circulatory dynamics, and psychologicallenvironmental factors. We believe that it is useful to evaluate a combination of factors when making such a review, including diagnostic imaging such as MRI, ERP (P300), and rCBF.