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Biomedical subjects

R C Gur

Publications and source records attributed to R C Gur.

At least 145 records · Page 8Linked to original sources
PubMed1985

Brain function in psychiatric disorders. III. Regional cerebral blood flow in unmedicated schizophrenics.

Regional cerebral blood flow (rCBF) was measured during resting baseline and the performance of a verbal and a spatial task in 19 unmedicated schizophrenics and 19 matched controls. Abnormalities in rCBF were evident in schizophrenics both for resting and activated measures. Resting flows were higher in the left hemisphere for schizophrenics, supporting the hypothesis of left hemispheric overactivation. This effect was stronger in the more severely disturbed patients. The pattern of rCBF changes during activation with the verbal and spatial tasks was also different in schizophrenics. Laterality of flow changes further supported the hypothesis of left hemispheric overactivation. Furthermore, whereas normals had greater increase in flow for the spatial than the verbal task, schizophrenics showed the reverse pattern. This effect also was more pronounced in the severely disturbed patients. Comparison with an earlier sample of medicated schizophrenics suggested that neuroleptics restore symmetry of resting flows before they produce symptomatic relief. Medication did not affect the abnormalities in pattern of rCBF changes during activation with cognitive tasks.

Adolescent↗
PubMed1985

Voice recognition and the ontological status of self-deception.

Douglas and Gibbins (1983) recently argued that our demonstration that errors in self-other recognition are often instances of self-deception was inadequate. In their study, they found that both self-other and acquaintance-other recognition errors met two of the four criteria we had offered as necessary and sufficient for ascribing self-deception. They presented no evidence that either type of recognition error was not an instance of self-deception. Here we describe the original basis of our demonstration and point out the logical fallacy in Douglas and Gibbins' argument.

Auditory Perception↗
PubMed1984

Brain function in psychiatric disorders. II. Regional cerebral blood flow in medicated unipolar depressives.

Regional cerebral blood flow was measured during resting baseline and the performance of a verbal and a spatial task in 14 medicated depressives and 25 matched controls. Overall resting flows did not differ, nor were there hemispheric or anteroposterior differences between patients and controls for resting flows. Differences between patients and controls were evident during cognitive activity, and the effects were different for male and female patients. Depressed female patients had higher than normal flows in all conditions, whereas depressed male patients had lower than normal resting flows, which increased to normal during cognitive activity. Their anterior flows increased for the verbal task but not for the spatial task.

Adult↗
PubMed1984

Positron emission tomographic studies of perceptual tasks.

Metabolic mapping in conjunction with positron emission tomography was used to examine the response of the human brain to physiological stimuli. Local cerebral glucose consumption was measured by means of the fluorine-18-labeled fluorodeoxyglucose technique. The coefficient of variation of this measurement for various gray matter structures varies from 19.5 to 26.4%. If repeat measurements are made in the same subject using carbon-11-labeled deoxyglucose as the tracer, the coefficient of variation of repeat measurements for these same structures is reduced to between 5.2 and 8.7%. Stimulation of one visual field in normal subjects produced a significant (p less than 0.01) increase in metabolism in the contralateral visual cortex. An auditory stimulus consisting of a tape-recorded factual story presented through earphones to only one ear produced a significant (p less than 0.001) increase in glucose consumption in the contralateral temporal cortex. The effects of vigilance or attention on cerebral metabolism were also examined. There was significantly greater metabolism in the right versus the left inferior parietal region in subjects attending to a visual or auditory task compared with those who were not. Anxiety appeared to produce significantly greater glucose utilization in the right hemisphere compared with the left in those subjects who had a higher level of anxiety during the measurement. Metabolic mapping promises to be a powerful new tool in furthering our understanding of the organization and functioning of the human brain.

Anxiety↗
PubMed1984

Hemispheric control of the writing hand: the effect of callosotomy in a left-hander.

We report a case of a left-hander with left hemispheric language. After callosotomy, he could use the left hand to write only random letters and digits, and he became right-handed for writing. Therefore, writing by left-handers with left hemispheric language dominance may be accomplished by transcallosal transmission of the linguistic content from the left hemisphere to the right.

Adult↗
PubMed1983

Brain function in psychiatric disorders. I. Regional cerebral blood flow in medicated schizophrenics.

We measured regional cerebral blood flow during resting baseline and the performance of verbal and spatial tasks in 15 medicated schizophrenics and 25 matched controls. Patients did not differ from controls in resting flows but showed different blood-flow changes during task performance. Controls replicated earlier findings in normal subjects: flow increased during task performance, and the hemispheric increase was greater in the left for the verbal and in the right for the spatial task. In contrast, patients showed no flow asymmetry for the verbal task and greater left hemispheric increase for the spatial task. The latter finding is consistent with the hypothesis that schizophrenia is associated with left hemispheric overactivation for spatial tasks. In addition, schizophrenic women had unusual flow changes in that their highest flow increase was for the verbal task.

Adult↗
PubMed1983

Hemispheric asymmetries in processing emotional expressions.

Three experiments are reported on visual field asymmetries in the perception of emotional expressions on the face. In experiment I full faces expressing six different emotions were presented unilaterally for exposure durations, allowing the subject to judge whether the facial expression was positive or negative. Right-handed subjects judged all expressions except happiness as more negative when presented in the left visual field (LVF). This effect was smaller for left-handers and was absent in left-handers who use the non-inverted writing posture. In experiment II subjects were presented with happy, sad and "mixed" chimeric faces, projected to each visual field, for durations allowing only the detection of the existence of a face. LVF presentations produced greater differential rating of emotional valence for the three types of stimuli. In experiment III chimeric faces containing happy and sad expressions were presented unilaterally for durations allowing the subject to perceive the existence of two expressions on the face. The subjects were required to decide whether the mood expressed in the face was predominantly negative or positive. RVF presentations resulted in a bias toward positive judgments. These results indicate right hemispheric superiority for the perception and processing of emotional valence and a left hemispheric perceptual bias toward positive aspects of emotional stimuli.

Cerebral Cortex↗
PubMed1983

A cognitive-motor network demonstrated by positron emission tomography.

The rate of local cerebral glucose metabolism was measured in subjects receiving a verbal (n = 4) and a spatial (n = 4) task. The verbal task produced greater metabolism in Wernicke's area relative to the right hemispheric homotopic region, whereas the spatial task produced greater metabolic activity in the right hemispheric homotopic region. Broca's area and its right hemisphere counterpart showed symmetrical activity during the verbal task, but there was a significant asymmetry to the right during the spatial task. Lateralized task effects were also obtained in the frontal eye fields, supporting a hypothesized neural network linking cognitive activity with motor orientation.

Adult↗
PubMed1983

Mutism as a consequence of callosotomy.

Transient mutism has been reported following commissurotomy and callosotomy. The cause for this mutism is unknown. A case of mutism following callosotomy is presented, and the preoperative and postoperative data on neurological, physiological, and psychological functioning are discussed. The data suggest that the mutism is not caused by general intellectual deterioration, cortical lesion, or peripheral damage affecting speech production. The syndrome may result from severing interhemispheric connections in cases where both hemispheres are required for speech production.

Adult↗
PubMed1982

Sex and handedness differences in cerebral blood flow during rest and cognitive activity.

Cognitive activity resulted in increased flow of blood to the cerebral hemispheres. The increase was greater to the left hemisphere for a verbal task and greater to the right hemisphere for a spatial task. The direction and degree of hemispheric flow asymmetry were influenced by sex and handedness, females having a higher rate of blood flow per unit weight of brain, and females and left-handers having a greater percentage of fast-clearing tissue, presumably gray matter.

Adolescent↗
PubMed1982

Hemispheric asymmetry in the expression of positive and negative emotions. Neurologic evidence.

Three retrospective studies were conducted to examine functional brain asymmetry in the regulation of emotion. In the first study, reports of 119 cases were collected of pathological laughing and crying associated with destructive lesions. Pathological laughing was associated with predominantly right-sided damage, whereas pathological crying was associated with predominantly left-sided lesions. In the second study, 19 reports detailing mood following hemispherectomy were collected; right hemispherectomy was associated with euphoric mood change. In the third study, lateralization of epileptic foci was assessed in reports of 91 patients with ictal outbursts of laughing (gelastic epilepsy). Foci were most likely to be predominantly left-sided. The findings are congruent with studies of the effects of unilateral brain insult on mood, and a general model of hemispheric asymmetry in the regulation of emotion is presented.

Adolescent↗
PubMed1982

Positron emission tomography in two cases of childhood epileptic encephalopathy (Lennox-Gastaut syndrome).

Two patients with childhood epileptic encephalopathy were studied by positron emission tomography before and after corpus callosotomy. Preoperatively, both patients showed in the temporal lobe unilateral hypometabolism that is characteristic of interictal epileptic foci. Postoperatively, the first patient had no seizures by the time of scanning, and his temporal lobe metabolism was bilaterally symmetric. Seizure control in the second patient did not improve by the time of scanning, and unilateral temporal hypometabolism persisted. This finding suggests a temporal lobe focus in two patients with Lennox-Gastaut syndrome.

Adult↗
PubMed1980

Differences in the distribution of gray and white matter in human cerebral hemispheres.

The distribution of gray matter in the two cerebral hemispheres was determined by the xenon-133 inhalation method. There was more gray matter relative to white matter in the left hemisphere than in the right, particularly in the frontal and precentral regions. This finding suggests that the organization of the left hemisphere, relative to that of the right, emphasizes processing or transfer within regions, or both, rather than transfer across regions.

Brain↗