Allan F. Mirsky

Selective intellectual deficits in children with temporal lobe or centrencephalic epilepsy

Abstract Specific patterns of intellectual impairment were observed in children with unilateral temporal lobe or centrencephalic epilepsy. The left temporal patients showed learning and memory deficits on verbal tasks while their performance on nonverbal tasks was unaffected. The converse was true for children with right temporal involvement. In contrast to the two temporal groups, the centrencephalic patients were without significant memory defect; instead, they showed lower scores on a test of sustained attention. The results are similar to those obtained in studies of adults with comparable cerebral dysfunction. The findings suggest that cerebral differentiation of intellectual processes is established in childhood.

Attentional Capacities in Children with Autism: Is There a General Deficit in Shifting Focus?.

Twenty-three children with autism and two control groups completed an attention battery comprising three versions of the continuous performance test (CPT), a digit cancellation task, the Wisconsin Card Sorting Test (WCST), and two novel, computerized tests of shifting attention (i.e., the Same–Different Computerized Task and the Computerized Matching Task). Children with autism could focus on a particular stimulus and sustain this focus as indicated by their performance on the digit cancellation task and the CPT. Their performance on the WCST suggested problems in some aspects of shifting attention (i.e., disengaging attention). The autism group performed as well as controls on the Same–Different Computerized Task, however, that required successive comparisons between stimuli. This implies that they could, in fact, shift their attention continuously. In addition, they did not differ from controls on the Computerized Matching Task, an analog of the WCST, suggesting that they do not have a general deficit in shifting attention.

On certain psychopharmacological and physiological differences between schizophrenic and normal persons.

SummaryThe schizophrenic patient is generally regarded to be less responsive than the normal person to many drugs as well as to certain nonpharmacological conditions. Evidence is presented that there is not an attenuated response in the schizophrenic with all centrally acting drugs. The schizophrenic may in fact be more responsive than the normal person to some nonpharmacological conditions. These studies are reviewed and a neuropsychological hypothesis proffered which may account for some of the differences between the normal and the schizophrenic.The hypothesis states that the schizophrenic patients are in a state of chronic hyperarousal. This results from dysfunction in those areas of the brain concerned with the maintainence of arousal, and attention, i. e. the brain stem reticular activating system.

On the dissimilar effects of drugs on the digit symbol substitution and continuous performance tests

A tentative hypothesis is presented to account for the dissociation of the effects of various centrally-acting drugs and other agents on performance of the Continuous Performance Test (C.P.T.) and the Digit Symbol Substitution Test (D.S.S.T.): L.S.D., secobarbital, pentobarbital meprobamate and phenobarbital produced significantly greater impairment of the D.S.S.T. than of the C.P.T., while chlorpromazine, sleep deprivation and centrencephalic epilepsy had the reverse effect. Psychological, neurophysiological, electroencephalographic and neuropharmacological data were cited which suggested that the tests were affected differently because they are dependent upon the functioning of somewhat different neural organizations which are, in turn, differentially sensitive to the action of various centrally-active agents.SummaryA tentative hypothesis is presented to account for the dissociation of the effects of various centrally-acting drugs and other agents on performance of the Continuous Performance Test (C.P.T.) and the Digit Symbol Substitution Test (D.S.S.T.): L.S.D., secobarbital, pentobarbital meprobamate and phenobarbital produced significantly greater impairment of the D.S.S.T. than of the C.P.T., while chlorpromazine, sleep deprivation and centrencephalic epilepsy had the reverse effect. Psychological, neurophysiological, electroencephalographic and neuropharmacological data were cited which suggested that the tests were affected differently because they are dependent upon the functioning of somewhat different neural organizations which are, in turn, differentially sensitive to the action of various centrally-active agents.

Clinical Correlates of Brainstem Dysfunction in Autistic Children.

Children with the diagnosis of autism were tested for brainstem auditory evoked potentials (BAEP), and information was gathered on their medical and developmental histories and current developmental levels of symptomatology. On comparing the nine autistic children having abnormal BAEPs and the seven autistic children with normal BAEPs, the former were found to have exhibited greater pathology in the areas of attention and social accessibility. No differences were found between the groups on measures of language, motor, or perceptual functioning, or on previous diagnoses or medical history. It is suggested that social and attentional pathology may be more specifically associated with the brainstem pathology that may characterize autism than are symptoms in other developmental areas.

Prediction of Spike‐Wave Bursts in Absence Epilepsy by EEG Power‐Spectrum Signals

Summary: The EEGs of subjects with absence seizures were examined to determine if changes occurred prior to spike‐wave bursts that could be used to predict bursts. A number of 20‐s epochs of EEG prior to spike‐wave bursts (preburst epochs) and during periods remote from bursts (control epochs) were examined in 5 subjects. Power‐spectrum analysis was carried out on each epoch and frequency bands from 0 to 50 c/s were combined into 2‐c/s bandwidths. Logarithmically transformed power values in each frequency band were entered into a discriminant analysis algorithm for each subject separately. Results were expressed in terms of a test for significant differences between preburst and control epochs (F statistic) and a “success ratio” of discriminant analysis classification, defined as the proportion of correct classifications in both groups, as obtained using a cross‐validation procedure. A significant preburst EEG pattern was found in 4 of the 5 subjects, and success ratios ranged from 0.64 to 0.83. Each subjects preburst EEG seemed to be characterized by a unique pattern of changes, and thus no common prodromal signal was found. The EEG changes did not appear to be caused by overt behaviors, such as eye closure or drowsiness. The findings suggest that the preburst EEG pattern represents a functional alteration in brain activity which could arise from the burst‐producing mechanism directly.

Visual evoked potentials during experimentally induced spike-wave activity in monkeys☆

Abstract 1. 1. Electroretinograms (ERGs) and visual evoked potentials (VEPs) were studied in 16 monkeys both before and after the induction of spike-wave (SW) EEG patterns by the intravenous administration of chlorambucil (13 animals) or by the direct cortical application of conjugated estrogen (3 animals). All of the estrogen preparations and 5 of the chlorambucil animals were studied under gallamine triethiodide paralysis; the other animals were studied under barbiturate anesthesia. 2. 2. In visual system placements (cornea, optic chiasm, optic tract, lateral geniculate nucleus, occipital cortex) there was a reduction or apparent abolition of the ERG of VEP during SW activity. VEPs were rarely seen in non-visual system placements (frontal cortex, parietal cortex, brain-stem reticular formation); averaged potentials from such locations appeared to reflect only increased “noise” during SW activity. 3. 3. When SW activity was confined to frontal cortex (as with the conjugated estrogen preparations) reductions in ERG were less likely to occur. However, generalized SW activity, regardless of how it was produced, was almost invariably accompanied by both VEP and ERG reduction. 4. 4. Reductions in evoked potential amplitudes or complete loss of components tended to be greater in more central placements (LGN, occipital cortex) than in more peripheral placements, and to be more pronounced with more intense visual stimulation. 5. 5. In 2 animals prepared with pre-chiasmal sections of one optic nerve, no substantial reduction in ERG was seen in the eye deprived of connection to the brain, although the usual decrease in amplitude was seen in the contralateral eye. 6. 6. The results were discussed in terms of hypothetical central events in petit mal epilepsy, including the possibility of centrifugal effects upon the retina being transmitted through optic efferent fibers during petit mal convulsive activity.

The Analysis of Visual Evoked Potentials during Spike and Wave EEG Activity

1 Ongoing research is described which employs the visual evoked potential to investigate the nature of the central changes in centrencephalic or petit mal epilepsy. 2 Studies have been conducted both with petit mal patients and with monkeys treated with chlorambucil to produce experimental spike and wave discharges. In each instance, the visual evoked potentials in the presence and absence of the spike‐wave complexes are compared. The data analysis is conducted with a magnetic tape system and LINC‐8 digital computer. 3 In general, the results indicate that visually evoked potentials may be seen during both the natural and the experimental spike‐wave activity. The amplitude of the evoked potential appears enhanced in man in the fronto‐central regions; less enhancement is seen in the parieto‐occipital placements. The amplitude of the evoked potential appears diminished in the monkey at visual system locations and enhanced at non‐visual locations. Factors which may relate to these findings, on both a peripheral and central level, are discussed and other problems under investigation are indicated.

Effect of electrical stimulation of the brain on visually controlled (attentive) behavior in Macaca mulatta

Abstract Electrical stimulation of various subcortical regions of the brains of five Macaca mulatta monkeys was conducted during the performance of a learned visual attention task. This required the animal to press for a red (positive) stimulus and to withhold responses to green or blue (negative) stimuli. Errors in performance were more frequently induced by the stimulation of the lower brain stem (midbrain and pons) than that of the thalamus. Omission errors (not responding to the positive stimuli) were most frequently elicited by stimulation of the mesopontine reticular formation or structures which are anatomically and functionally related to it. In contrast, commission errors (responding to negative stimuli) resulted most frequently from the stimulation of specific sensory systems or from areas closely related to them.

The effects of chlorpromazine and secobarbital on matching from sample and discrimination tasks in monkeys.

SummaryMonkeys were trained in the performance of a matching from sample task and in two simultaneous visual discrimination tasks differing in level of difficulty. In the case of the matching task, four doses each of chlorpromazine and of secobarbital were administered to the animals according to a balanced design. The procedure was then replicated. The results of the matching task indicated that chlorpromazine produced many errors of omission and few errors of commission. The latter kind of error as well as other measures of confused responding were seen primarily with secobarbital. In the case of the visual discriminations, secobarbital produced greater impairment of the more difficult (pattern) task than of the simpler (color) task; chlorpromazine had equivalent effects on the two tasks. The similarity between the secobarbital action and the behavioral consequences of certain cortical lesions in the monkey was discussed.