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Biomedical subjects

E Bisiach

Publications and source records attributed to E Bisiach.

At least 37 records · Page 2Linked to original sources
PubMed1994

Challenging current accounts of unilateral neglect.

Two left-neglect patients were asked (i) to bisect a 15 cm line, (ii) to bisect the empty space between the endpoints of a 15 cm virtual line, and (iii) to set the endpoints of a 15 cm virtual line, given its midpoint. With one patient, the subjective midpoint of the virtual line was found to be displaced leftwards with respect to the subjective midpoint of the real line, whereas with the other it was found to be displaced rightwards. However, in condition (iii) both patients significantly underestimated the distance from the centre of the rightmost point of the virtual line while relatively overestimating that from the centre to the left endpoint. This latter result challenges current accounts of unilateral neglect.

Aged↗
PubMed1993

Unilateral neglect in route description.

Route description was investigated in two patients suffering from left unilateral neglect. Both had evident difficulty with left turns. This finding suggests that the topological correspondence between represented environment and representational mechanisms in the brain is not confined to frozen (picture-like) perspectives.

Aged↗
PubMed1991

Remission of somatoparaphrenic delusion through vestibular stimulation.

The effects of vestibular stimulation on somatoparaphrenic delusion were investigated in a patient suffering from a fronto-temporo-parietal infarction located in the right hemisphere. Transitory remission of the patient's delusional belief was consistently observed during unilateral vestibular activation obtained by means of cold-water irrigation of the left (contralesional) ear.

Aged↗
PubMed1990

Break-down of perceptual awareness in unilateral neglect.

Four neglect patients are reported who where unable to detect left-side differences in pairs of drawings though being sometimes influenced by such differences in making preference judgements. In most instances, tracing the silhouette of the drawings did not help patients to find the difference despite the fact that tracing implied crossing the altered detail or following its contour with the fingertip. This finding cannot easily be accommodated by current theories of unilateral neglect.

Aged↗
PubMed1990

Perceptual and premotor factors of unilateral neglect.

Right-brain-damaged patients showing unilateral neglect underwent a specifically devised line-bisection task that allowed uncoupling of the direction of visual attention from that of hand movement. This made it possible to isolate and separately assess perceptual and premotor factors of the disorder. Comparison of experimental and radiologic data suggested that premotor factors were more pronounced in patients with lesions involving the frontal lobes than in patients with lesions confined to postrolandic areas. The technique employed is compatible with bedside examination and provides data useful for standard assessment of neglect symptomatology for both clinical and experimental purposes.

Adult↗
PubMed1989

Influence of response modality on perceptual awareness of contralesional visual stimuli.

Visual extinction on double simultaneous stimulation was investigated in left and right brain-damaged patients in two response conditions: verbal and motor. In right brain-damaged patients contralesional detection was significantly worse when monitored by motor rather than by verbal responses in condition of single as well as of double stimulation. Previous research in normal subjects had shown that the left hemisphere is selectively involved in choice reactions such as those occurring in the motor condition of the present experiment in brain-damaged patients. The results of the latter are interpreted using as a basis the findings of that research and Kinsbourne's hemisphere activation hypothesis concerning unilateral neglect of space.

Analysis of Variance↗
PubMed1988

The role of the left hemisphere in decision-making.

The role of the left hemisphere in decision-making processes in choice reactions to unstructured visual stimuli (Bisiach, Mini, Sterzi and Vallar, 1982) was further investigated in normal right-handed individuals. Subjects were required to provide a motor response to lateralized single dots, abstaining from giving a response when two dots were shown. In the first study, in which the disruptive effects of concurrent articulatory activity were assessed, the decision required integration of information provided to both hemispheres, as the no-go stimulus was constituted by two dots symmetrically positioned, one in each half-field. In the second study, all information relevant to the decision was available to each hemisphere, as the no-go stimulus was represented by two dots in either half-field. Since in both experiments the decision mechanism remained located in the left hemisphere, the following conclusions are drawn: (i) the right hemisphere is unable to fulfil the demands of the present decision-making task, even when either a secondary task interferes with left hemisphere processes or it has direct acces to all the relevant information; this suggests a pattern of absolute hemispheric specialization; (ii) the left hemisphere decision-making process does not rely upon any sort of articulatorily-based "inner speech" component.

Analysis of Variance↗
PubMed1987

Remission of hemineglect and anosognosia during vestibular stimulation.

The effects of vestibular stimulation on extrapersonal and personal neglect and on awareness of disease were investigated in four patients with severe neglect and anosognosia. Neglect phenomena improved in all patients, while an effect on anosognosia was found in two cases. These preliminary findings indicate a possible role of vestibular stimulation on hemispheric activation.

Aged↗
PubMed1986

Unilateral neglect: personal and extra-personal.

Ninety-seven right brain-damaged patients were given two tasks aimed at assessing unilateral neglect in personal and in extra-personal space. The frequency of the two aspects of neglect, as well as their patterns of association with each other and with more elementary neurological disorders are reported and discussed. The results suggest a non-unitary frame of spatial reference for unilateral neglect, which may tentatively be interpreted in terms of a personal vs extra-personal dichotomy.

Animals↗
PubMed1986

Unawareness of disease following lesions of the right hemisphere: anosognosia for hemiplegia and anosognosia for hemianopia.

Unawareness of motor and visual-field defects was investigated in 97 right brain-damaged subjects. Both kinds of anosognosia were found to be double-dissociated from more elementary neurological disorders and from personal and extra-personal neglect. The relationships between anosognosia and unilateral neglect are discussed and allusion is made to the implications concerning the neurological organization of higher control functions.

Adult↗
PubMed1985

Two basic properties of space representation in the brain: evidence from unilateral neglect.

It is argued, on the grounds of earlier findings, that the neural substrate of egocentric space representation has analogue (non-symbolic) topo-topical properties. It is then argued from fresh evidence that space representation appears to be anchored to the sagittal midplane of the trunk and to the line of sight. A tentative reduction of the suggested properties of space representation to the neuro-physiological level is briefly outlined.

Brain↗
PubMed1984

Disorders of perceived auditory lateralization after lesions of the right hemisphere.

The disorders of perceived auditory lateralization after unilateral damage of the cerebral hemispheres were investigated by dichotic presentation of pure tones, lateralization being obtained by interaural intensity differences. Observations were made on 107 unilateral brain-damaged patients and 30 normal subjects who were required to localize the perceived position of fused sound images. The images were generated by dichotic stimuli delivered through headphones and the patients were asked to point the perceived position. A clear-cut hemispheric asymmetry was found. Whereas left brain-damaged patients and right brain-damaged patients without visual field defects were not impaired in this task in comparison with controls, the performance of right brain-damaged patients with visual field defects was defective, with a systematic directional error towards the right side, that is, the side ipsilateral to the damaged hemisphere. The defect of auditory lateralization involved both the half-space contralateral to the lesion and the ipsilateral one. Different hypotheses are discussed in order to explain the present results. It is argued that they cannot easily be interpreted in terms of defective processing of sensory information and the proposal is made that lesions of the right hemisphere may produce a distortion of the internal representation of egocentric space to the right, yielding a systematic error of auditory lateralization are discussed.

Attention↗
PubMed1983

Line bisection and cognitive plasticity of unilateral neglect of space.

Patients with neglect of the left half of space were asked to bisect lines of different lengths. The leftmost points of the represented lines, determined on the basis of the midpoints set by the patients on the objective lines, were the dependent variable. It was thus possible to recognize diverse patterns of behavior which were conceivably averaged away in earlier investigations. In discussing the results, the question is raised of whether unilateral neglect of space may be altered by cognitive processes.

Attention↗
PubMed1982

Hemispheric lateralization of the decisional stage in choice reaction times to visual unstructured stimuli.

Simple manual RTs to lateral visual stimuli were found to be faster in uncrossed than in crossed anatomical conditions. Neither hand nor hemifield effects were found. By contrast significant asymmetries were found in Choice RTs involving both hemispheres, even in uncrossed condition. The field effect was marked when the responding hand was the right but insignificant when the responding hand was the left. The data seem consistent with a model which assumes the location of the decisional structures in the left hemisphere.

Choice Behavior↗
PubMed1979

Recognition of random shapes in unilateral brain damaged patients: a reappraisal.

The performance of unilateral brain-damaged patients on recognition of random shapes was investigated by means of two different experiments. In experiment I interitem similarity and number of response-choice alternatives were varied to evaluate their possible influence on the subjects' performance. In experiment II stimulus exposure time was varied, In both experiments left brain-damaged patients with visual field defect obtained lower scores than control subjects. Right brain-damaged patients with visual field defect obtained scores significantly lower than controls only in the brief exposure condition.

Brain Damage, Chronic↗