Evoked potentials and head injury. 1. Rating of evoked potential abnormality.

This paper describes a method for rating the degree of abnormality of auditory, visual and somatosensory evoked potential patterns in head injury (HI) patients. Criteria for judging degree of EP abnormality are presented that allow assessment of the extent and severity of subcortical and cortical dysfunction associated with traumatic brain damage. Interrater reliability data based upon blind ratings of normal and HI patients are presented and shown to be highly significant. Tables of normative values of peak latencies and amplitudes are given and illustrations of EP patterns of different degrees of abnormality are presented.

Evoked potentials and head injury. 2. Clinical applications.

The method of rating abnormality of evoked brain potential patterns and assessing the extent and severity of cortical and subcortical brain dysfunction in head injury patients described in Part I is applied in a clinical context. Evoked potential abnormality (EPA) scores are found to be significantly correlated both with admission and outcome disability approximately one year after head injury. Correlations increase with the increase in the number of sensory modalities tested. Correlations between EPA scores and clinical disability (measured by the Disability Rating Scale) decrease with time after injury. Significant correlations, however, persist for about 60 days after onset of injury. It was found that EP pattern abnormalities can reflect specific sensory (and at times motor) deficits in noncommunicative patients and thereby contribute significantly to early treatment and rehabilitation planning.

Visual scanning and matching dysfunction in brain-damaged patients with drawing impairment.

Visual matching and visual exploration were examined in 7 normal subjects and 20 brain-damaged patients with drawing impairment measured by the Bender Gestalt Visual-Motor Test. Right brain-damaged patients made significantly more errors of rotation and integration than left brain-damaged patients. Selecteded Bender figures were also used as stimuli for both visual matching and visual exploration tests. The ability to match Bender figures was found to be impaired in right but not left brain-damaged patients. All patients showed eye movement and fixation patterns different from those normals. Patients essentially had more fixations and shorter fixation durations. Significant intercorrelations were found between the total Bender Gestalt score and visual matching and visual exploration scores. These findings indicate that visual matching and visual exploration measures can be used to evaluate perceptual impairment in individuals who do not have adequate motor responses or where impaired motor responses may confound interpretations about visual cognitive impairment.

Are there schizophrenics for whom drugs may be unnecessary or contraindicated?

This study reports that there are schizophrenics who do relatively well long term without the routine or continuous use of antipsychotic medication. Specially selected young males undergoing an acute schizophrenic episode were followed, after hospitalization, for up to three years. While hospitalized they were assigned randomly to either placebo or chlorpromazine treatment. Many unmedicated-while-in-hospital patients showed greater long-term improvement, less pathology at follow-up, fewer rehospitalizations and better overall function in the community than patients who were given chlorpromazine while in the hospital. Factors related to post-hospital outcome were good premorbid history and short-lived paranoid characteristics. Considerations which may have an effect on the successful management of acute schizophrenic patients not on medication are mentioned. The findings underline the need for further study of how to utilize antipsychotic medication more selectively in the treatment of schizophrenia.

Phenothiazine effects on cerebral-evoked potentials and eye movements in acute schizophrenics.

An investigation was made of the effects of phenothiazine medication on the averaged visual-evoked potentials (AVEP) and on eye movements in hospitalized, young, acute schizophrenic patients. These results were compared with those of normal subjects who were not given medication. AVEP measures included maximum amplitude (Am), frequency of peaks (FOP'S), variability (V) and peak latencies for an early negative peak (N1) and a later positive peak (P6). Eye movement measures included percent of time looking at a stimulus slide, percent of time looking at a figure on the slide, the number of fixations and the percent of cells entered in which fixations occurred. For schizophrenics off and on phenothiazine medication, there were no consistently significant drug effects on any measure except frequency of peaks. Schizophrenics compared to normals had lower amplitudes, greater frequency of peaks, greater variability and lower eye movement scores.

Tobacco and evoked potential.

Significant changes were found in two indices of the averaged visual evoked potentials in nine smokers after 12 and 36 hours of abstinence and after resumption of smoking. There was a decrease of the amplitude envelope accompanying withdrawal and an increase with resumption of smoking. These changes are consistent with the contention that tobacco increases arousal. Amplitude changes were found in a specific component of the evoked potential occurring between 100 and 125 milliseconds after the onset of the flash. The latter changes suggest the possibility that smoking selectively enhances the perceptiont of weak stimuli.

Phenothiazine effects on auditory signal detection in paranoid and nonparanoid schizophrenics.

The differential effects of phenothiazine medication on auditory signal detection performance were compared in two types of schizophrenic subjects and in normal subjects. With increasing phenothiazine dosage a decrease in efficiency of signal detection performance occurred among nonparanoid schizophrenics and an increase in efficiency occurred among paranoid schizophrenics. These and related findings were interpreted in terms of differences in neuropsychological response and information processing characteristics in the two types of schizophrenics. The primary deficit in information processing in nonparanoid schizophrenics may be related primarily to their hypersensitivity to sensory stimuli, whereas in paranoids it may be related primarily to their impaired focusing of attention. Phenothiazines appear to decrease sensitivity to stimuli in nonparanoids but increase the ability to focus attention in paranoids. The possibility of treatment regimens which take into account the differential effects of phenothiazine medication was suggested.

Evoked response and behavior in cats.

Electroencephalographic averaged evoked responses to flashing lights of four different intensities were recorded in ten cats and correlated with behavior. Animals showing a high degree of exploratory behavior, aggressiveness, and activity and little withdrawal showed relatively large increases in amplitude of the averaged evoked response with increases of stimulus intensity. Those showing opposite behavioral traits had small increases or decreases of average evoked response amplitude with increases of stimulus intensity. These findings are compatible with those reported for human subjects. Inference is made about a neurophysiological mechanism for stimulus intensity modulation.