Habituation of the alpha attenuation response in children and adults with psychiatric disorders

EEG alpha photic driving abnormalities in chronic schizophrenia

Periodic photic stimuli across the entire electroencephalographic (EEG) frequency range were used in an attempt to assess EEG functional differences between chronic schizophrenic patients and control subjects. The EEG responses to these photic stimuli were significantly attenuated in the schizophrenic patients, specifically at the frequencies within the EEG alpha range. The schizophrenic patients also showed an alpha range attenuation in the "no stimulus" EEG alpha measure, such that there was a significant correlation across subjects between the "stimulus" and "no stimulus" EEG alpha range abnormalities. These abnormalities are discussed with reference to possible dysfunctional thalamic mechanisms involved in the pacing of EEG alpha activity and the gating of information through the cerebral cortex.

Cardiovascular and electrodermal responses to simple stimuli in autistic, retarded and normal children

Phasic changes in respiratory period, electrodermal activity (EDA), the evoked cardiac response (ECR), and the vasoconstrictive peripheral pulse amplitude response (PPAR), were examined in matched groups of autistic, retarded, and normal children, using repeated presentation of simple visual and auditory stimuli. Analysis as a function of group membership and age indicated that respiratory pause and EDA showed habituation in the retarded and normal groups, but not in the autistic group, with no age effects in any group. PPAR and ECR showed no habituation in any group, but within-group age differences, and a higher mean response level for the autistic subjects. The autistic children did not display the diminution of response level with increased age that was characteristic of both the control groups. These effects were obtained across both modalities. Results could not be attributed to between-group tonic cardiac arousal differences, and were interpreted as further indications of diminished sensitivity to reductions in stimulus novelty, as well as developmental delay, in early-onset psychosis.

Accurate measurement of flash-evoked alpha attenuation

An accurate method for measuring flash evoked alpha attenuation has been derived, based on a model of the alpha generator. The method has been applied to 10 healthy volunteers in order to determine their alpha attenuation latencies (AALs). For the 9 subjects which showed at least some alpha rhythm, the AAL group mean is 95 msec. The AAL inaccuracy (S.D. 5 msec) is smaller than interindividual differences (S.D. 13 msec). There exists no relationship between the AAL and the frequency of the alpha rhythm.

Differential sensitivity to the effects of psychotropic drugs: psychotics vs normals; Asian vs Western populations

The effects and side-effects of psychotropic drugs are determined by many variables, and the host factor is one of the most important. A lower sensitivity of schizophrenics than normals to the sedative effect of chlorpromazine and a manic depressives to imipramine were demonstrated quantitatively by a higher percent time of waking EEG following medication. The mean therapeutic dose of chlorpromazine for the manic state was found to be much lower in Japanese than in Western populations in a controlled study comparing the antimanic efficacy of carbamazepine and chlorpromazine. A lower therapeutic dose in Asian populations has been reported also on other antipsychotic drugs, lithium, and tricyclic antidepressants. The lower therapeutic dose level was discussed from the standpoint of transcultural psychopharmacology.

Nervous reactivity changes in patients with late post-traumatic mental disturbances

A polygraphic study of 105 patients with late-post-traumatic psychiatric disturbances and 158 matched subjects in two control groups has shown marked differences in nervous reactivity. The differences, estimated by testing the electrographic components of the orienting reaction elicited by a repetitive auditory stimulus and its habituation were expressed by changes in the intensity, resistance to habituation, and sequence of habituation of the somatic, autonomic, and EEG components. The character and severity of alterations depended on the site of the traumatic impact, lesional aspect of the craniocerebral trauma, clinical picture of mental disturbances, and features of the EEG tracings.

Sensitivity to chlorpromazine effects on brain function of schizophrenics and normals. A preliminary report

For the purpose of quantitative demonstration of the sensitivity to chlorpromazine (CPZ) effects on brain functions of schizophrenics and normal subjects, polygraphic recordings of electroencephalogram (EEG) and electrodermal response (EDR) were performed before and 3 h after oral administration of 25 mg of CPZ: percent time waking EEG (per cent W-EEG) and number per minute of EDR were measured during the resting period and the period of calculation. In 10 normal adult subject, both per cent W-EEG and number of EDR showed remarkable decrease after CPZ administration. In 22 schizophrenics, however, per cent W-EEG showed no significant decrease after CPZ administration. Number of EDR in schizophrenics during the period of calculation did not show any significant decrease. The neural mechanism underlying the lower sensitivity to CPZ effects in schizophrenics was discussed.

Detection of EEG abnormalities with feedback stimulation

A feedback method for testing the reactivity of the occipital-parietal EEG in selected brain-lesioned patients revealed abnormalities of (a) insufficient reactivity, (b) bilateral differences in reactivity, and (3) asynchrony. These abnormalities were more evident during feedback stimulation than in the baseline conditions. The utility of feedback method for detecting EEG abnormalities rests on the increased stability or decreased "noisy" variation in the EEG during feedback. The EEG becomes more predictable even to the "on-line" human observer. This makes it easier to detect aberrations or deviations from normal effects. Some effects can only be seen with feedback such as the bilateral differences which occur when the left side controls the feedback compared to when the right side controls it. The results show that feedback EEG is a useful tool in clinical research and indicate that a clinical diagnostic test could be developed with more research. However, the feedback EEG method is not yet a proven diagnostic technique.

Hyperactive behavior and EEG arousal reactions in children

EEG arousal reactions and parameters of spontaneous EEG activity were studied in two extreme groups of behavior problem children (11 hyperactives and 11 non-hyperactives), selected on the basis of a rating of motor restlessness the core symptom of the "hyperactivity syndrome". The EEG was recorded in three reaction time experiments: a tone light conditioning paradigm and two series with random stimulation. An automatic analysis of EEG parameters was employed to describe the time functions of alpha amplitudes in the single trial. The main findings are: 1. In periods free from stimulation, hyperactive children have higher alpha and beta amplitudes, more alpha waves and a smaller amount of beta waves. This indicates a lower state of EEG arousal in the hyperactives. 2. The amplitude reduction to tone (in the single trial) develops more slowly in the hyperactive group. This group difference increases over the experimental situations. 3. The arousal responses to tone, in terms of the level of maximum amplitude reduction, become comparably weaker in the hyperactives across the experiments. 4. Under all experimental conditions the hyperactives exhibit shorter arousal responses to the light stimulus than the non-hyperactive children. 5. Reaction time performance of the groups is clearly different, hyperactives showing the longer latencies. 6. Although conditional changes in the arousal reactions to both stimuli are reliably demonstrable in all children, the groups show no difference in the corresponding measures. These findings are discussed under the aspects of activation and of attention behavior of the subjects.

An investigation of the genetic aspects of the alpha attenuation response

The alpha attenuation response (AAR) and its habituation rate during the course of 60 serially presented paired flash stimuli was measured in a small but homogeneous group of male identical and fraternal twins, all within the age range 19 to 40 years. Comparison of the intraclass correlation coefficients for each of the recorded AAR parameters between the two twin series and a constructed series of genetically unrelated individuals indicated that individual differences in the variables measured were significantly influenced by heredity. The findings are discussed in relation to previously reported studies of the genetic aspects of the normal spontaneous EEG.