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Biomedical subjects

M Regard

Publications and source records attributed to M Regard.

At least 55 records · Page 3Linked to original sources
PubMed1992

Frontal lobe function in amyotrophic lateral sclerosis: a neuropsychologic and positron emission tomography study.

In this study the regional cerebral glucose utilization and the neuropsychological performance of patients with amyotrophic lateral sclerosis (ALS) was investigated. Special attention was given to neuropsychological tests thought to mirror frontal lobe dysfunction. The regional cerebral glucose utilization was studied in 18 patients using high-resolution positron emission tomography. Clinically all patients displayed upper and lower motor neurone signs. In ALS patients glucose metabolism was significantly reduced in the frontal and in the entire cortex compared with controls; no changes were seen in the cerebellum. Comprehensive neuropsychological assessment of ALS patients compared to a pair matched control group revealed mild frontal dysfunction which in part significantly correlated with reduced glucose metabolism in the cortex and subcortical structures. We conclude that in patients with ALS, glucose consumption is decreased in parts of the brain other than the motor cortex accompanied by mild neuropsychological deficits based on the tests employed in this study.

Adult↗
PubMed1991

[Dementia: classification, diagnosis--in search of treatable causes].

There are so many possible etiologies of dementia that its evaluation must be well directed. The neuropsychological examination permits the diagnosis of dementia and allows for a classification of a dementia as 'cortical' dementia, i.e. with aphasic, apraxic or agnosic disturbances, or 'subcortical' dementia, which is mainly characterized by psychomotor retardation. Virtually all treatable dementias present as 'subcortical' dementia. The search for a cause of a dementia includes the clinical setup and a number of additional examinations, which may reveal causes that were not suspected on clinical grounds. In this paper we propose a classification of dementias based on the distinctions 'cortical/subcortical dementia' and 'somatic neurological examination normal/abnormal'. Furthermore, we suggest an array of additional examinations which in our view should be performed in any case of dementia.

Aged↗
PubMed1991

Balint's syndrome in subacute HIV encephalitis.

A 45 year old patient with AIDS is described in whom Balint's syndrome developed over several days without other higher cognitive defects. Radiological findings were typical of subacute HIV encephalitis involving mainly the white matter of the occipital lobes with extension into the parietal and temporal lobe on the left side and into the temporal lobe on the right side. While the patient could usually recognise only one single component within her visual field, her performance in reading much improved if she was allowed to observe the examiner writing. This finding is attributed to well preserved movement perception in our patient, which may have helped her in directing her visual attention. The preservation of movement perception despite damage to the lateral temporo-occipital area may be due to the distinct pathology of subacute HIV encephalitis, which leaves the cortex and adjacent subcortical white matter virtually intact and therefore allows information transfer between primary visual areas in the occipital lobe and movement specific areas in the lateral temporo-occipital area through U-fibres.

AIDS Dementia Complex↗
PubMed1991

Cognitive changes at high altitude in healthy climbers and in climbers developing acute mountain sickness.

We report the cognitive functions of 17 non-acclimatized mountaineers who ascended from low lands to an altitude of 4,559 m in 24 h and were studied there within 6 h. We found that this rapid ascent to high altitude had small, but differential effects upon cognitive performance depending upon the later development of acute mountain sickness (AMS). Subjects who developed AMS within a 24-48-h stay at high altitude were mildly impaired in short term memory, but improved in conceptual tasks, while subjects who remained healthy had a better short term memory performance but no improvement in cognitive flexibility. Possible explanations for these unexpected effects of high altitude are discussed.

Adult↗
PubMed1990

[The right cerebral hemisphere].

An attempt is made to delineate typical clinical syndromes in the light of four selected patients with lesions in different regions of the right hemisphere. For higher cortical functions of the right hemisphere, as in the rest of the central nervous system, the locus of the lesion is critical for the nature of the deficit. Comparisons of damage to homologous areas in the contralateral left hemisphere with those in the right suggest that the functions of the right hemisphere are not subordinate to those of the left but are complementary and work in coordination with dominant hemisphere functions. In addition to dominance for spatial functions, the tasks of the right hemisphere are to recognize, evaluate, and react to non-verbal signals such as emotions, facial expressions, gestures and intentional modulation of speech. Impairment of these functions after right hemisphere damage shows that such compromised behaviors can frequently lead to serious social consequences.

Affective Symptoms↗
PubMed1990

Neuropsychological studies of auditory-visual fusion illusions. Four case studies and their implications.

A heard speech sound which is not the same as the synchronized speech sound can sometimes give rise to an illusory phonological percept. Typically, a heard /ba/ combines with a seen /ga/ to give the impression that /da/ has been heard (McGurk, H. and MacDonald, J. Nature Lond. 264, 746-748, 1976). We report the susceptibility to this illusion of four individuals with localized brain lesions affecting perceptual function. We compare their performance to that of ten control subjects and relate these findings to the efficiency of processing seen and heard speech in separate and combined modalities. The pattern of performance strongly suggests LH specialization for the phonological integration of seen and heard speech. The putative site of such integration can be effectively isolated from unilateral and from bilateral inputs and may be driven by either modality.

Adult↗
PubMed1990

Sensitivity to eye gaze in prosopagnosic patients and monkeys with superior temporal sulcus ablation.

Accuracy at perceiving frontal eye gaze was studied in monkeys and human subjects using a forced-choice detection task on paired photographs of a single human face. Monkeys learned the task readily, but after bilateral removal of the banks and floor of the superior temporal sulcus (STS) they failed to perform the task efficiently. This result is consistent with the conclusion, based on recordings from single cells in awake, behaving monkeys [Perret et al., Physiological Aspects of Clinical Neuro-ophthalmology, Chapman & Hall, London, 1988] that this region of the temporal lobe is important for coding information about eye-gaze of a confronting animal. Human subjects were given identical stimuli in a task where they were asked to detect "the face that is looking straight at you". Human performance is sensitive to the degree of angular deviation from the frontal gaze position, being poorest at small angular deviations from 0 degrees. This was also true of monkeys viewing these stimuli, pre- and post-operatively. Compared with normal controls, two humans prosopagnosics were impaired at this task. However the extent of impairment was different in the two patients. These findings are related to earlier reports (including those for patients with right-hemisphere damage without prosopagnosia), to normal performance with upright and inverted face photographs, and to notions of independent subsystems in face processing.

Adult↗
PubMed1990

Bitemporal hypoperfusion in transient global amnesia: 99m-Tc-HM-PAO SPECT and neuropsychological findings during and after an attack.

We report a patient who was evaluated neuropsychologically and with single photon emission computed tomography (SPECT) during and after an episode of transient global amnesia. During the attack, there was patchy retrograde amnesia and an inability to learn both verbal and non-verbal material. SPECT showed severe bitemporal hypoperfusion. Serial neuro-psychological testing documented a rapid recovery of recognition, but delayed recovery in reproduction of learned information. Recovery of spontaneous verbal and figural fluency was even further delayed. Follow up SPECT examination showed a recovered cerebral perfusion. This case supports the hypothesis that TGA is associated with transient hypoperfusion of bilateral medial-temporal brain structures and suggests an additional involvement of structures responsible for drive and initiation.

Aged↗
PubMed1989

Shift of functional cerebral asymmetry during the menstrual cycle.

This study investigated whether for females, who are said to be less strongly lateralized for cognitive functions than men, hemispheric superiority might depend on the phase of the menstrual cycle. The results show that while asymmetry in lexical decisions did not change throughout the menstrual cycle, asymmetry in face perception decreased linearly from a large right hemisphere superiority during menstruation to a small left hemisphere superiority during the premenstrual phase. This is seen as being relevant not only for the discussion of sex differences in cerebral asymmetry but also for the concept of cerebral organization in general.

Adult↗
PubMed1989

Persistent cognitive impairment in climbers after repeated exposure to extreme altitude.

We performed neuropsychological testing in eight world class climbers who had reached summits higher than 8,500 meters without supplementary oxygen. Five had mildly impaired concentration, short-term memory, and ability to shift concepts and control errors. There were no defects in perception or other cognitive activities. The pattern of impairment suggests malfunctioning of bifronto-temporo-limbic structures. Repeated extreme-altitude exposure can cause mild but persistent cognitive impairment.

Adult↗
PubMed1988

[Hemianopsia and agnosia].

Hemianopsia and agnosia, the coexistence of a disorder of perception and a disorder of recognition, is exemplified by two patients chosen for their clinical similarity. These two patients each had a stroke, one of the left and the other of the right posterior cerebral artery, resulting right and left hemianopsia respectively. Primary visual functions such as visual acuity and contrast sensitivity were intact. The differences were only apparent as regards the severity of the agnostic disorders. The patient with the lesion on the left failed to recognize stylized drawings, was alexic, could not lipread and was color anomic, but could easily identify handwriting, faces, and voices. The patient with the right posterior lesion could not recognize handwriting, was prosopagnosic and topographagnosic, but had no difficulty in reading, lipreading, or in recognizing stylized drawings. The apparent double dissociation of function demonstrates the presence of two different visual processing mechanisms which are very probably peculiar to the visual system of the left hemisphere in the one case and to that of the right hemisphere in the other. The authors' findings suggest that the two cerebral hemispheres differ fundamentally in the way they process visual information.

Agnosia↗
PubMed1988

Prosopagnosia and agnosia for noncanonical views. An autopsied case.

It has been postulated that for prosopagnosia to occur, bilateral lesions of the central visual system are usually necessary. All but 1 of the 10 previously documented cases that came to autopsy showed this pattern. However, the long survival period after the onset of prosopagnosia in most of these patients limits the value of the autopsy findings for clinicopathological correlation. A patient is presented who died 10 days after she had developed prosopagnosia, topographagnosia and an agnosia for real objects seen from noncanonical views. These clinical symptoms corresponded directly to the autopsy finding of a recent large occipitotemporal ischaemic infarct in the territory of the right posterior cerebral artery. An additional right frontal infarct and a cortical microinfarct in a deep left lateral parieto-occipital sulcus were both old lesions and had passed unnoticed clinically. This first report of a direct clinicopathological correlation between a fresh right posterior lesion and prosopagnosia demonstrates that bilateral involvement of the visual system is not a prerequisite for prosopagnosia.

Aged↗
PubMed1987

Schizophrenia--an emotional hypersensitivity of the right cerebral hemisphere.

While modern neuropsychological and electrophysiological studies claim a functional disturbance of the left hemisphere (LH) in schizophrenia, historical clinical and anatomical work rather points to the right hemisphere (RH) as the main site of psychosis. In the light of an interhemispheric functional balance of inhibition and release, LH-dysfunction in schizophrenia could be interpreted as a consequence of an overactive and inhibiting RH. Since the RH is especially activated by emotional stimuli, and exaggerated distractability and sensitivity to emotional stimuli are hallmarks of schizophrenia, we compared the emotional irritability of the RH and LH in 35 acute schizophrenics and 22 matched controls. Using tachistoscopic half-field presentation we found in acute schizophrenics a selective impairment of RH-function with simultaneous improvement of LH-performance induced by emotional distractors. We therefore suggest that a right hemispheric dysfunction and hypersensitivity to emotional material plays an essential catalytic role in acute schizophrenia.

Acute Disease↗
PubMed1986

Face recognition and lipreading. A neurological dissociation.

Two cases with medial occipitotemporal ischaemic infarction in the territory of the posterior cerebral artery are discussed; neither was aphasic. The patient with the right-sided lesion is prosopagnosic and topographagnosic and is impaired at recognizing or classifying facial expressive gestures but can lipread speech efficiently. The other patient, with only a left-sided lesion, shows no deficits in face recognition nor in the classification of faces in terms of nonverbal messages, but is alexic and impaired at lipreading. It is argued that processing faces for verbal information (lipreading) and processing faces for nonverbal information (face recognition and interpretation of emotive and gestural messages) are functionally dissociated in the human brain. Theoretical interpretations of prosopagnosia that stress a perceptual component to all types of face recognition failure may therefore be misleading, for similar stimulus processing mechanisms are likely to be required to identify a speech sound from a face as to identify a nonverbal gesture of the mouth. Only the associative properties of the task differ.

Aged↗
PubMed1985

Functional inhibition and release: unilateral tachistoscopic performance and stereoelectroencephalographic activity in a case with left limbic status epilepticus.

During prolonged nonconvulsive unilateral left limbic status epilepticus, a natural model of functional hemispheric inhibition, we performed two tachistoscopic experiments, a lexical decision task associated with a RVF (left hemisphere) superiority and a facial matching task associated with a LVF (right hemisphere) superiority. We found that epileptic activity in the left hemisphere, especially rhythmic high-frequency "tonic" discharges, inhibited performance on the lexical task but not on the facial matching task. This suggests that only cognitive activity in the discharging hemisphere is inhibited. Strikingly, the best performance of the right hemisphere was obtained while the left hemisphere was most inhibited, suggesting a functional balance of inhibition and release.

Adult↗