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Biomedical subjects

J R Stevens

Publications and source records attributed to J R Stevens.

At least 91 records · Page 5Linked to original sources
PubMed1983

Pathophysiology of schizophrenia.

There is still another type of convulsive movement, involving the muscles of the eye and speech, which is both characteristic and of frequent occurrence in dementia praecox. Some of these movements correspond exactly to the movements of expression; wrinkling of the eyebrow, distortion of the mouth, rolling the eyes, and those other facial movements which are characterized as grimacing. These movements remind one of choreic movements and are quite independent of the ideas and feelings. They may be associated with the smacking of the lips, clucking the tongue, sudden grunting, sniffing, and coughing. Furthermore, in the lips we observe very rapid rhythmical movements. More often there exists a peculiar choreiform movement of the mouth which may be described as an athetoid ataxia.

Antibodies, Viral↗
PubMed1982

Loss of eye movements abolishes light entrainment of circadian mesolimbic catecholamine excitability: a function for REM?

Light entrainment of the circadian rhythm of mesolimbic dopamine excitability, measured by the amphetamine-induced locomotor response, and the circadian feeding rhythm was abolished following section of the extraocular muscles of the rat. Endogenous (free-running) circadian rhythms were preserved. The results are consistent with electrophysiologic evidence that the rapid eye movements during paradoxical sleep transmit light-modulated electrical potentials to regions of the brain that influence circadian rhythms and dopamine release.

Animals↗
PubMed1982

Neuropathology of schizophrenia.

Histologic sections were made from selected regions of the brains of 25 schizophrenic patients aged 21 to 54 years (mean, 43.5 years) who died during their hospitalization at St Elizabeths Hospital, Washington, DC. These sections were compared with similarly prepared sections from the same brain regions of 28 nonschizophrenic patients of similar age, who were hospitalized and died at the same hospital during the same period, and with sections from 20 age-matched, nonpsychiatric patients who died in a general hospital. Although few differences were apparent in material from schizophrenic and nonpsychiatric cases in sections stained for cellular structures, myelin, or axis cylinders, Holzer's stain for glial fibrils demonstrated increased fibrillary gliosis that affected principally the periventricular structures of the diencephalon, the periaqueductal region of the mesencephalon, or the basal forebrain in three fourths of the brains from schizophrenic subjects. Hypothalamus, midbrain tegmentum, and substantia innominata were most often affected. The nature and distribution of the findings suggest previous or low-grade inflammation. Review of the clinical history and course of each case allows some correlations to be made between clinical signs and histopathologic data.

Adult↗
PubMed1982

Telemetered EEG in schizophrenia: spectral analysis during abnormal behaviour episodes.

In an attempt to detect electroencephalographic (EEG) changes associated with characteristic clinical signs and symptoms of schizophrenia, power spectra were derived from scalp EEGs of schizophrenic patients recorded by telemetry during free behaviour on their psychiatric wards. Power spectra from EEG epochs coincident with psychomotor blocking, stereotyped automatism or hallucinations were compared with spectra derived during periods of relatively normal behaviour, during performance of specific tasks and spectra from control subjects. Ramp spectra, characterised by a smooth decline in power from lowest to highest frequencies, previously found in conjunction with subcortical spike activity of epilepsy were not found in any control subject, but appeared in spectra from schizophrenic patients during catatonic episodes, hallucinatory periods and visual checking. Schizophrenic patients also had more slow activity and less alpha activity in their EEGs than normal control subjects.

Adult↗
PubMed1979

Telemetered EEG-EOG during psychotic behaviors of schizophrenia.

In an effort to establish correlations between abnormal behaviors characteristic of schizophrenia and simultaneous cerebral electrical activity, EEGs and electro-oculograms (EOGs) were continuously recorded for 2 to 24 hours by radiotelemetry from 40 patients with schizophrenia and 12 normal control subjects. Trained observers recorded specific behavior patterns permitting visual and computer analysis of EEG during hallucinations, stereotypy, catatonia, psychomotor blocking, and other characteristic manifestations of schizophrenia. Electroencephalographic abnormalities consisting of focal slow or spike activity over either temporal region were found in nearly half of the patients so recorded. In contrast to the EEG during ictal episodes of epilepsy, the abnormal wave forms of schizophrenic patients seldom coincided with episodes of blocking, stereotypy, or other abnormal behaviors. Increased extraocular activity or blinking were recorded in a majority of patients, but were not consistently associated with the abnormal behavior or perceptual events.

Adult↗
PubMed1979

Ontogeny of spontaneous blinking and of habituation of the blink reflex.

Habituation of the blink reflex to glabellar percussion was examined in 164 infants and children from ages 2 days to 18 years and in 18 adults aged 18 to 50 years. Spontaneous blink rates were measured in 269 children and 179 adults. The mean number of glabellar taps required for habituation of the blink reflex increased from 2.7 (SD 1.2) at 0 to 2 months of age to a peak of 13.3 (SD 5.6) at age 3 to 4, remained at more than 10 until age 6, after which a rapid decline occurred, reaching the adult level of 2 to 5 blinks to habituation at age 12 years. The mean rate of spontaneous blinking was less than 2 per minute in early infancy and increased steadily during childhood up to age 14 or 15. The inverse relationship of spontaneous blink rate and number of blink reflexes to habituation in early childhood and in disorders of dopamine transmission suggests that spontaneous blink rate and habituation of the blink reflex reflect maturation and integrity of dopaminergic circuits in the brain.

Adolescent↗
PubMed1978

Disturbances of ocular movements and blinking in schizophrenia.

Neurological examination and electroencephalograms and electro-oculograms, recorded by telemetry, from unmedicated patients with acute and chronic schizophrenia demonstrate a number of abnormalities of extraocular movement including staring, abnormal blink rate, absent glabellar reflex, and increase in horizontal eye movements. As potential clues to the pathophysiology of schizophrenia, these disturbances are analysed in relation to anatomical substrate and dopamine modulation of ocular movement, rapid eye movement sleep, and the neurological disorders in which similar disturbances of ocular movement occur.

Adolescent↗
PubMed1978

Eye blink and schizophrenia: psychosis or tardive dyskinesia?

The author found abnormalities of ocular movement including abnormal blink rate and blink reflex to glabellar tap in 34 of 44 medication-free schizophrenic patients. It is not clear whether these signs represent part of the pathology of schizophrenia or result from withdrawal of neuroleptic treatment.

Dyskinesia, Drug-Induced↗
PubMed1978

Kindling of the mesolimbic dopamine system: animal model of psychosis.

In order to examine the behavioral and physiologic consequences of chronic activation of the mesolimbic dopamine system, the nucleus of origin in the ventral tegmental area was stimulated electrically for 2 seconds daily through chronically implanted intracranial electrodes in cats at the same point where instillation of the GABA blocking agent bicuculline induced a characteristic fear, staring, searching, and withdrawal response. None of the animals developed sustained after-discharge or seizures following daily stimulation for 2 months. Progressive fearfulness, hiding, loss of social behavior, and EEG spike or slow activity in the ipsilateral nucleus accumbens developed in three of six intact animals. Two cats with prior 6-hydroxydopamine lesions of catecholamine pathways did not develop behavioral change in response to local bicuculline or daily electrical stimulation of the ventral tegmental area but demonstrated pronounced after-discharge or EEG spike propagation during the kindling procedure.

Animals↗
PubMed1977

The EEG spike: signal of information transmission?

Enhanced neuronal excitability or coherence, leading to a rapid-bursting mode of unit discharge or to synchronous polarization, underlies the electroencephalographic spike. The propensity for EEG spike activity to occur in relation to events that require absolute command of neural circuitry suggests that the EEG spike represents a mode of discharge of underlying neural elements which is employed for communication of imperative messages. Normal when confined to certain axial nuclei of the brain during sleep or during photic or sexual excitation, compensatory in response to deafferentation or hypoxia, this powerful transmission mode must have certain advantages to have persisted throughout evolutionary history.

Adolescent↗
PubMed1976

Computer analysis of the telemetered EEG in the study of epilepsy and schizophrenia.

Computation of power spectra from averaged brief epochs of spike free scalp EEG coincident with the subcortical spike has revealed a distinctive spectral configuration characterized by smooth monotonic decline in power from lowest to highest frequencies. Nine out of 10 patients with epilepsy display similar patterns preceeding long latency responses to a verbal motor reaction time task. Although subcortical spike activity has been recorded from the parasental region of patients with schizophrenia by several investigators half of our patients with schizophrenia displayed a different pattern which resembles a "white noise" spectrum during the delayed reaction time of incorrect response trials. Power spectra derived from 24-hour telemetered scalp EEGs from patients with epilepsy and schizophrenia are also sharply differentiated by similar criteria. These non-invasive methods for analysis of the scalp EEG in relation to careful and controlled behaviour observations may give useful information regarding subcortical activity when intracranial electrodes cannot be utilized.

Adult↗