Tomomichi Kameyama

Correlations of event-related potentials with schizophrenic deficits in information processing and hemispheric dysfunction

In order to obtain further insight into hemispheric dysfunction in schizophrenics, two experiments were conducted employing event-related potential (ERP) recording during dichotic detection tasks as well as syllable discrimination tasks. Results concerning ERPs derived from the T3 and T4 regions are reported. Based on results in the two experiments, it is concluded that schizophrenics display a dysfunction of the left hemisphere, as well as a dysfunction in the ingration mechanism of both hemispheres. It is also speculated that the left-hemisphere dysfunction in schizophrenics is particularly correlated with positive psychotic symptoms.

Verbal memory disturbances in left temporal lobe epileptics

The relationship between laterality of paroxysmal discharges and characteristics of disturbances in memory functioning was investigated in temporal lobe epileptics. Subjects consisted of 22 temporal lobe epileptic patients, in whom the foci of the paroxysmal discharges were localized to one side of the temporal regions. The left focus group consisted of 10 patients; the right focus group, 12. Subjects were required to recognize verbal material presented to one hemisphere by means of a tachistoscope. The left focus group alone failed to demonstrate a right visual field superiority in these tasks. It was concluded that the left focus group specifically demonstrate disturbances in verbal memory functioning, particularly when stimuli were presented to the left hemisphere. Paroxysmal discharges seemed to interfere with normal memory functioning in the region where the foci of these discharges were found.

Distributions of the Nd and P300 in a normal sample

To obtain objective criteria for assessing the attentional and cognitive functioning of psychiatric populations, we attempted to standardize values of two components in Event-Related Potentials (ERPs), namely the attention-related negative potential (Nd) and the P300, in normal populations. The study consisted of 100 healthy volunteers (50 females, 50 males) who were given the task of making dichotic syllable discriminations requiring key-press responses. Their ages ranged between 18 and 59 years (mean +/- S.D., 32.3 +/- 11.3 years). Nd was found to be maximum in the Fz region, P300 being maximum in the Pz region. The means and standard deviations of Nd and P300 areas in their maximum regions were 554.1 +/- 307.8 microV ms and 2148.5 +/- 1248.5 microV ms, respectively. The transformation plot for symmetry indicated the suitable power of transformation to be 1/2 for both Nd and P300 distributions. After being transformed into square-root values, the distribution patterns of Nd and P300 areas were examined. When the lower limit of normal values was tentatively assigned to mean -2 S.D. using square-root transformed data for both Nd and P300, 97% of the subjects were found to display values above the lower normal limit for Nd, and 98% for the P300. Neither, Nd nor P300 areas correlated with age, while P300 latencies displayed a weak positive correlation with age. Females displayed relatively larger values than males for Nd and P300 areas and P300-peak amplitudes. However, the differences between females and males were not statistically significant. Females and males showed nearly equal P300-peak latencies.

Diagnostic reliability and significance of irregular beta patterns

Abstract: We designated EEGs with marked and irregular beta waves in basic patterns as “irregular beta patterns” on the basis that these patterns are related with particular symptoms such as dysphoria, irritability and autonomic symptoms and they implicate choice of therapeutic agents. Because of good response to antiepileptic agents in patients with “irregular beta patterns” along with EEG characteristics, we hypothesized that the prevalence of “irregular beta patterns” is higher in epileptics than in other psychiatric patients. In the present study, we tested this hypothesis, investigating actual frequencies of these patterns among different diagnostic categories for all patients whose EEG were recorded in all the first‐visit patients to the Outpatient Clinic, Deparmtent of Neuropsychiatry of the Tokyo University Hospital during one year period of 1986. Before starting this investigation, we checked the interrater reliability for these patterns. Therefore, two studies are reported here. In Study 1, five raters judged 98 EEG recordings blindly (43 epileptics and 55 healthy subjects). As a result, the generalized Kappa of 0.473 was obtained, indicating our agreement level was moderate or fair. This result lends support to our contention that irregular beta patterns are reliably judged. In Study 2, we judged the EEG recordings (137 schizophrenics, 62 affective disorders, 43 epileptics and 55 healthy controls) and calculated the prevalence rate of “irregular beta patterns” among the diagnostic categories. The results show that the prevalence rates of “irregular beta patterns” among psychiatric disorders and normal controls were 13% (18/137) in schizophrenics, 11% (7/62) in affective disorders, 14% (6/43) in epileptics and 4% (2/55) in healthy controls. These rates did not differ significantly among the three disorders. Thus, our hypothesis was not supported. The clinical significance of these patterns is discussed.

Linkage Analysis between Familial Myoclonus Epilepsy and Short Arm of Chromosome 6 Using HLA Phenotype as Genetic Marker

Genetic factors have been implicated in the etiology of epilepsies, specifically for familially transmitted ones. Recent development in molecular biology has provided US with various genetic markers available for a linkage study of genetically transmitted disorders. Using such markers, a linkage between seizure susceptibility and chromosome 9 was reported in El mouse.’ In linkage analyses of human epilepsies, the gene locus in chromosome 20 was suggested for benign familial neonatal convulsion3, the short arm of chromosome 6 for juvenile myoclonic epilepsy using human leucocyte antigen (HLA) as a marker (JME)’, and chromosome 21 for progressive myoclonus epilepsy of the Unverricht-Lundborg type2 as well as both Baltic and Mediterranean types4. Here, we studied the genetic linkage be275

Psychological Intervention Can Partly Alter P300-Amplitude Abnormalities in Schizophrenics

Abstract: In the present study, we investigated whether psychological interventions can alter P300‐abnormalities, specifically enhancing reduced P300‐amplitudes, in schizophrenics. A three‐tone discrimination task was employed for recording P300s, in which psychological intervention to facilitate target detection was performed through delivering a buzzer sound one second after each designated target tone that informed its occurrence. This procedure was done exclusively during the third and fourth sessions among the six sessions in total. When the data for all the patients were analyzed as a whole, no significant change was observed. However, when the patients were broken down into two groups based on the P300‐amplitudes in the first and second sessions, significant effects of the intervention emerged. The group with smaller P300‐amplitudes showed a significant increase in P300‐amplitudes as well as improved performance levels during and after the intervention sessions. On the contrary, the group with larger P300‐amplitudes displayed a significant decrease in P300‐amplitudes in these sessions. Interestingly, the above results were consistent with the subjective difficulty changes experienced by the patients through the sessions. Overall, the above results indicate that psychological interventions can partly enhance reduced P300‐amplitudes in schizophrenics.

Plasma homovanillic acid levels in temporal lobe epilepsy

The role of the central dopaminergic system in temporal lobe epilepsy (TLE) was investigated through measurement of plasma homovanillic acid (pHVA) levels. Plasma HVA levels in 30 patients with TLE were determined and compared with those in 53 healthy control subjects. Their relationship with clinical variables was investigated. The mean pHVA level of the TLE patients (9.44 ± 3.44 ng/ml) was not significantly different from that of the normal control subjects (8.40 ± 2.67 ng/ml). The differences were also nonsignificant when the patients were divided into subgroups according to seizure frequency, the interval between blood sampling and the preceding or following seizure, paroxysm laterality in electroencephalogram, the number of antiepileptic drugs administered, manifestation of psychotic symptoms, or antipsychotic medication. The obtained results were interpreted as indicating dopaminergic activities are not involved in the pathophysiology of TLE or decreased dopaminergic activities in TLE patients are balanced with compensatorily increased dopaminergic activities for suppressing seizure generation.

Psychiatric patients showing irregular β activities in EEGs and treatment with antiepileptic drugs : a report of 15 cases

Abstract: Fifteen psychiatric cases are reported who were clinically diagnosed as schizophrenic, affective disorders, or neurotic, but resisted standard medication regimens, all showing irregular β activities on EEGs. The cases tended to display symptoms in common, such as dysphoria, emotional instability or frequent physical complaints. These characteristic symptoms share something mutually with the symptoms shown in some epileptic patients or psychiatric patients with epileptic EEG abnormalities without clinical seizures. Antiepileptic drugs seemed more specifically effective to the above symptoms. More than half of these cases showed improvement on EEG findings such as a decrease in irregular β activities and an increase in rhythmicity or regularity of α activities along with clinical improvement with the administration of adjunctive antiepileptic drugs. These results suggest that the adjunctive administration of antiepileptic drugs to patients with irregular β activities on EEGs is clinically useful and an EEG examination has much value in psychiatric practice to find the criteria of drug therapy.

Event-Related Potentials and Cognitive Deficits in Schizophrenia

Measurements of Event-Related Potentials (ERPs) have been utilized in studies on attentional functioning. Hink, Hillyard and Benson (1978) recorded ERPs during syllable discrimination tasks, and found that the N100 component in normal subjects was enhanced to all stimuli in the attended ear, while the P300 component was enhanced only to the “target” stimuli in that ear. Based on these results, they hypothesized that the N100 component correlated with the ‘stimulus set’, while the P300 component correlated to the ‘ response set’ as defined by Broadbent (1971). Accordingly, ERP measurements are considered to be a useful method for clarifying the pathophysiological bases underlying those diseases that display disturbed attentional functioning. A number of studies measuring ERPs in schizophrenics has already been reported (Levit et al., 1973; Shagass et al., 1978; Roth et al., 1981; Saitoh et al., in press). These reports are nearly consistent in that schizophrenics demonstrate a reduction in P300 amplitudes.

Selective Attentional Deficits and Lateralized Hemispheric Dysfunction as Reflected in ERPs of Schizophrenic Patients

Event-Related Potentials (ERPs) were recorded at the Cz, T3 and T4 regions in schizophrenics (medicated and unmedicated), the siblings of schizophrenic probands and normal controls during syllable discrimination tasks such as employed by Hink et al. (1978). These tasks were employed in order to investigate schizophrenic deficits in channel selective attention and hemispheric dysfunction. Both the siblings and normal controls demonstrated an increase in amplitudes of NlOO elicited by stimuli presented to the attended ear as compared to those of the unattended ear. This result indicates that channel selective attention is well activated in these two groups. Both the siblings and normal controls also exhibited an increase in amplitudes of NlOO derived from the temporal regions elicited by stimuli presented to the ear contralateral to the EEG-deriving site as compared to ipsilateral stimuli. This result signifies contralateral hemispheric activation in the case of dichotic listening tasks. Neither of these two effects were observed in the schizophrenics. In addition, the latencies of NlOO at the T 3 region in the unmedicated schizophrenics were significantly shorter as compared to the other three category groups. These results suggest that selective attentional deficits reflected in NlOO are specific to schizophrenic patients and that th:: unmedicated schizophrenics specifically demonstrate the left hemispheric dysfunction. It is also suggested that the siblings have no disturbance in a “stimulus set” as defined by Broadbent (1971).