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Biomedical subjects

C S Rebert

Publications and source records attributed to C S Rebert.

At least 37 records · Page 2Linked to original sources
PubMed1984

Selective nigral toxicity after systemic administration of 1-methyl-4-phenyl-1,2,5,6-tetrahydropyrine (MPTP) in the squirrel monkey.

1-methyl-4-phenyl-1,2,5,6-tetrahydropyridine (MPTP) was administered via the intraperitoneal route to squirrel monkeys. Akinesia, rigidity and hypophonia were seen after repeated doses of 2 mg/kg. Postural tremor was present in one animal. Neuropathologic examination revealed cell loss restricted to the zona compacta of the substantia nigra. MPTP appears effective in producing an animal model for Parkinson's disease in the squirrel monkey, and may be one of the more selective neurotoxins described to date.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed1984

Effects of vincristine, maytansine, and cis-platinum on behavioral and electrophysiological indices of neurotoxicity in the rat.

The effects of the antineoplastic drugs vincristine, maytansine and cis-platinum were studied to determine the appropriateness of a behavioral and electrophysiological test battery for characterizing the neurotoxicity of such therapeutic compounds. Single- and repeated-dose studies in rats were performed initially, to establish doses for the subchronic neurobehavioral study. Measurements obtained in the subchronic study included body weight, rectal temperature, forelimb and hindlimb grip strengths; performance of a multisensory conditional avoidance response task and other behavioral tests; and a series of evoked responses (ventral caudal nerve action potential, brainstem auditory response and responses from other modalities). The drugs were injected intraperitoneally 5 days per week for 7 weeks. The rats were tested weekly during baseline, treatment and recovery phases. Each drug caused a different pattern of effects, but they all altered body weight, rectal temperature, peripheral nerve conduction velocity, the somatosensory evoked potential and undifferentiated motor activity. cis-Platinum was the most toxic, and maytansine was the least toxic. The results indicated that some elements of the test battery were useful for evaluating the neurotoxicity of anticancer drugs. However, other tests - notably, a test of negative geotaxis and the cortical auditory evoked response - were unreliable.

Action Potentials↗
PubMed1984

Differential hemispheric activation during complex visuomotor performance: alpha trends and theta.

Two experiments were done to study asymmetry in left and right cerebral hemispheres while subjects performed in verbal and nonverbal tasks, including a complex visuomotor T.V. tennis game (Pong). Previous analyses demonstrated asymmetries of alpha activity during these tasks, and in this paper we describe sequential changes of alpha asymmetry associated with playing Pong. Alpha power was stable in the left hemisphere but decreased in the right hemisphere during each rally, returning to symmetry during inter-rally intervals. Theta activity increased bilaterally in most of the tasks and differed from the alpha patterns in several respects. The second experiment demonstrated the usefulness of video games for assessing sex and age differences in visuospatial capacities'--male performance was better than female and performance was inversely related to age.

Aging↗
PubMed1984

Hemispheric lateralization of event-related potentials in a cued reaction-time task.

Subjects were tested in a cued reaction-time task wherein warning stimuli (S1) of 5-letter words or dot patterns inter-mixed across trials were briefly presented. After 2 sec a second stimulus (S2) of th same category as the S1 appeared and the subject pressed a key with the left or right hand. The right key was pressed if S2 was a synonym of S1 or if the second dot pattern was the same as the first. The left key was pressed for antonyms or different patterns. It was predicted that CNVs would be larger over the left than right hemisphere on word trials and vice-versa on pattern trials in accordance with speculations concerning hemispheric specialization. The CNV was lateralized as expected, most prominently on pattern trials. In addition a negative transient evoked by S2, and a late negative post-imperative slow wave were similarly lateralized. P300 waves were very large and largest to the S2 when it differed from S1. Factor analysis confirmed these results and indicated, in addition, that P300 was larger in the hemisphere least relevant to the task.

Adult↗
PubMed1983

Hemispheric asymmetries in a signal detection task.

Reaction time and signal detection performance were measured during a 78-min. vigilance task. 12 right-handed male subjects served in two experimental sessions. Subjects focused on a central fixation point and responded to signals presented at unpredictable times in one of three locations: 2.5 degrees to right of central fixation, central, and 2.5 degrees to the left of center. Subjects decided whether to press a response key with either the left or right hand with each presentation. Over-all vigilance performance (signal detections and response time) was similar for left and right visual-field presentations. Evidence from reaction times indicated that responses controlled by the left hemisphere were faster to a verbal stimulus (T) while reactions controlled by the right hemisphere were faster to an apparent non-verbal stimulus, an inverted T.

Adult↗
PubMed1978

Differential hemispheric activation during complex visuomotor performance.

Bilateral EEGs were recorded from central, temporal and parietal scalp locations from seven male and seven female human subjects (Ss) while they were engaged in verbal and non-verbal tasks. Alpha power was higher in the right hemisphere when Ss listened to verbal material being read to them; the reverse was true when Ss performed in an imaginative block rotation task. Compared with intergame rest periods, alpha power was suppressed in the right hemisphere when Ss either watched or played Pong (TV tennis). Watching Pong was as effective in producing in producing alpha asymmetry as playing the game in the parietal region, but motor involvement enhanced asymmetry at central and temporal leads. Performance was non-linearly related to asymmetry, first increasing and then decreasing as asymmetry increased.

Adult↗
PubMed1978

EEG asymmetry in educationally handicapped children.

Bilaterally homologous parietal and temporal EEGs were recorded from two groups of educationally handicapped children while the subjects (Ss) rested with eyes open or closed or performed in simple tasks designed to differentially activate the two hemispheres (reading by Ss, reading to Ss, draw a picture). A 'dyslexic' but not dysphasic group showed a reversal of theta asymmetry from eyes closed to eyes open (L less than R to L greater than R). This difference between groups was reflected most at the parietal placement. Theta in the parietal lead changed in accordance with expectations from reading to drawing (reduction of the R/L ratio), but that pattern did not occur at the temporal lead in 'dyslexics'. A discriminant analysis on theta power correctly classified 20 of the 22 children.

Adolescent↗
PubMed1978

Neuroelectric measures of lateral specialization in relation to performance.

Four experiments were undertaken to study EEG asymmetry in relation to cognitive specialization of the hemispheres of the human brain and in relation to the proficiency of behavioral performance. Individual differences in the functional significance of alpha lateralization were noted, but there were, within subjects, consistent indications of lateral specialization and of the influence of alpha asymmetry on reaction time. Simultaneous demands for both input processing and motor output control by a given hemisphere caused a decrement in reaction time performance. The decrement appeared to involve impaired perceptual processing, as indicated by factor analysis of the evoked potential. A factor identified as P300 was least represented in the wave forms associated with conditions leading to long reaction times.

Alpha Rhythm↗