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Biomedical subjects

E Bisiach

Publications and source records attributed to E Bisiach.

52 records · Page 3Linked to original sources
PubMed1979

Unilateral neglect, representational schema and consciousness.

Right brain-damaged patients with unilateral neglect were asked to detect differences within pairs of patterns moving left- or rightward behind a narrow vertical slit. It was seen that differences occurring on the left side of the mentally reconstructed images were less easily detected; therefore it is suggested that a representational disorder plays a primary role in unilateral neglect. In the light of these findings, it is possible to take into consideration some implications of unilateral neglect for theories of conscious brain activity.

Aged↗
PubMed1978

Unilateral neglect of representational space.

Two patients showing left unilateral neglect were asked to describe imagined perspectives of familiar surroundings. Left-sided details were largely omitted in the descriptions. Some theoretical implications of the occurrence of unilateral neglect in representational space are briefly considered.

Aged↗
PubMed1977

Decision in ambiguity: hemispheric dominance or interaction?

Fifty-eight subjects were shown tachistoscopically grey rectangles, at the centre of the field of vision. The rectangles extended equally to the left and right of the visual fixation point, and were presented under four background conditions: all white, all black, white in the left half of the field and black in the right half, black in the left and white in the right half. "Chimerical" backgrounds were assumed to create an interhemispheric ambiguity in the perception of the greyness of the stimuli as a consequence of opposed brightness contrasts. The reported birghtness was therefore expected to reflect a hemispheric dominance or an interhemispheric averaging of information. The results of the experiment supported the second hypothesis.

Discrimination, Psychological↗
PubMed1976

Cerebral dominance and visual similarity judgements.

Visual similarity judgements among rectangles varying in form and area were investigated in control subjects and in patients with lesions confined to either cerebral hemisphere. While an overweighing of form with respect to area was found in both control subjects and right brain-damaged, left brain-damaged patients equally weighted the two relevant dimensions. Beyond revealing differential processing rules related to the side of the injury in the brain, the findings lend themselves to some speculation about cerebral dominance.

Brain Damage, Chronic↗
PubMed1976

Halving a horizontal segment: a study on hemisphere-damaged patients with cerebral focal lesions.

The aim of this study was to point out a hemisphere asymmetry in focal brain-damaged patients and a hand asymmetry in normals on halving binocularly a horizontal line. 50 left hemisphere and 53 right hemisphere patients (both subdivided by presence/absence of visual field defect) and 50 controls (divided by the hand they used to carry out the task) were employed. 4 differently long segments made up the test material and the error scores with respect to the geometric midpoint were worked out by means of parametric statistical procedures. It turned out that: (i) healthy subjects committed a mean leftward displacement, regardless of the hand they used. All the same, only the halving error committed by the right hand is significant keeping as reference the geometric midpoint of the segment; (ii) left and right hemisphere-damaged patients committed halving errors, that are opposite in direction, leftward for the former and rightward for the latter; (iii) the behaviour of right patients with visual field defects is the only to be significantly different from that of the corresponding controls. Our findings point to prevailing importance of the right hemisphere mainly of its posterior areas, in the halving task.

Brain Damage, Chronic↗
PubMed1975

Focal hemisphere and visuoperceptual categorization.

Visuoperceptual categorization was investigated in patients with unilateral brain damage by a task in which meaningless shapes had to be classified with reference to a number of prototype patterns. Right brain-damaged subjects with visual field defect turned out to have a narrower categorization span. As this outcome seems to be scarcely consonant with a lower level disorder of visual processing, a major competence of the right hemisphere is suggested for visuoperceptual categorization.

Brain Mapping↗
PubMedDate not supplied

Dissociation of ophthalmokinetic and melokinetic attention in unilateral neglect.

A line cancellation task was performed by 36 right brain-damaged patients with unilateral neglect under four different conditions: normal and mirror-reversed view, with and without cueing. Two types of unilateral neglect were distinguished by directing ophthalmo- and melokinetic components of visuomanual scanning to opposite sides of the stimulus array. In ophthalmokinetic neglect, contralesional visual scanning of the stimulus array was defective, while manual scanning was unimpaired. The converse was true of melokinetic neglect. Ophthalmokinetic neglect was predominantly associated with posterior brain damage, while melokinetic neglect was predominantly associated with frontal or subcortical brain damage. In a few instances, cueing visuomanual scanning toward the neglected side of the stimulus array converted ophthalmokinetic into melokinetic neglect, and vice versa. The results are held to be indicative of two components of space representation and to provide further evidence of response-driven modulation of perceptual awareness.

Adult↗