Biomedical subjects

P D'Erme

Publications and source records attributed to P D'Erme.

8 recordsLinked to original sources

PubMed1998

Perception and action in hemispatial neglect.

Hemispatial neglect is a neurological disorder which entails a spatial bias that penalizes events occurring in the hemispace contralateral to a brain lesion. Mechanisms operating upon various stages ranging from perception to action have been invoked to explain neglect. The present study explores the contribution of a defective programming of arm movements towards the neglected hemispace to neglect behaviour. Two reaction time tasks -- a "perceptual" task and a "motor" task -- were performed by right brain-damaged (RBD) patients with left hemispatial neglect, RBD patients without signs of neglect and control subjects. The perceptual task consisted of lateralized visual stimuli and central motor responses, whereas the motor task consisted of visual stimuli presented on the vertical midline and hand responses to be produced in either hemispace. Neglect patients showed a rightward bias on the perceptual task, but only two RBD patients (showing no signs of severe neglect) were consistently slowed in producing leftward motor responses. Different reference frames may thus be used in perceptual tasks and tasks involving arm movements. We conclude that hemispatial neglect commonly results from attentional impairments operating upon a visual perceptual frame of reference; additional deficits appear to be necessary to produce a directional motor disorder.

Adult↗

PubMed1994

The relationship between visuospatial and representational neglect.

Using a quantitative measure, we analyzed the relationship between visuospatial and representational neglect in right- and left-brain-damaged patients and found signs of representational neglect only in right-brain-damaged patients. Although representational neglect was always associated with visuospatial neglect, suggesting that the two forms share a common underlying mechanism, the most frequent finding in right-brain--damaged patients was that of visuospatial neglect in isolation. A strong influence of the phenomenon of attentional attraction toward space ipsilateral to the lesion in visuospatial, as opposed to imaginal, tasks can account for this finding.

Attention↗

PubMed1992

Early rightwards orienting of attention on simple reaction time performance in patients with left-sided neglect.

A specific disruption in the ability to automatically disengage attention from its previous focus has been hypothesized to account for the extinction phenomenon often observed in the unilateral spatial neglect syndrome. Recent literature, however, also brings out the role played in neglect by an imbalance in the attentional orienting systems, resulting in an early shift of attention towards the side of space ipsilateral to the brain lesion. In the present study we hypothesized that this attentional bias in orienting of attention might be demonstrated in a paradigm of simple reaction time to lateralized visual stimuli by contrasting the presence vs the absence on the computer screen of the square boxes used to facilitate position expectancy. A main prediction was made that patients with neglect would show a significant increase in reaction time to contralateral visual stimuli in the presence of bilateral reference boxes as compared to conditions in which no boxes were displayed. The right-sided box was in fact expected to exert an early attraction on the patient's attention, thus modifying the pattern of reaction times to the proper targets. This prediction was confirmed in right brain-damaged patients with moderate to severe neglect.

Adult↗

PubMed1991

Early orientation of attention toward the half space ipsilateral to the lesion in patients with unilateral brain damage.

Posner has suggested that unilateral spatial neglect could be due to a difficulty in disengaging attention from its current focus to orient it toward the neglected half space. Clinical and experimental data suggest, however, that this disengaging difficulty could be only one aspect of a more complex disturbance also characterized by an early automatic orienting of attention toward the half space ipsilateral to the lesion. To test this hypothesis, two different investigations in unselected groups of patients with right and left brain-damage were carried out. The first investigation, to evaluate forms of lateral orienting of attention severe enough to provoke an overt gaze deviation, consisted of the systematic assessment of the phenomenon of "magnetic gaze attraction". The second investigation, to detect milder forms of automatic orienting of attention, analysed the temporal sequence followed in identifying the pictures represented in an "Overlapping Figures task", to see if patients tended to identify first figures lying in the half space ipsilateral to the lesion. In both investigations results consistently showed: a) that patients with right brain damage tend to orient attention automatically toward the ipsilateral half space more than patients with left brain damage; b) that this tendency is tightly linked to the presence of behavioural manifestations of hemi-neglect. These results are therefore consistent with the hypothesis that hemi-neglect is a multi-component syndrome with an early orienting of attention toward the half space ipsilateral to the lesion as the first of these components.

Analysis of Variance↗

PubMed1989

[Clinical aspects and mechanisms of visual-spatial neglect].

Several interpretations have been advanced to explain the nature of unilateral spatial neglect. According to some authors, unilateral neglect could be due to a sensory deficit or to an oculomotor disorder hampering the patient from completely exploring the half space contralateral to the damaged hemisphere. According to other authors, the unilateral neglect syndrome could result either from a mutilation of the inner representation of the outside space or from a lack of attention for stimuli falling in the half space opposite to the hemispheric locus of lesion. We have wondered whether the relationships between unilateral neglect and hemispheric lateralization could not help to understand the nature of the neglect phenomena. A retrospective analysis of data gathered in neuropsychological literature, and results of an experimental study in which we had contrasted results obtained on an "overlapping figures" task and on a visual search task and a qualitative analysis of neglect phenomena observed in right brain-damaged patients, have led to the following conclusions: a) unilateral neglect is specifically linked to right hemisphere lesions in tasks requiring extraction of information from the central part of the visual field, whereas no difference between right-sided and left-sided lesions is observed on tasks requiring a full exploration of extra-personal space; b) tasks selectively affected in right brain-damaged patients require an automatic orienting of attention toward the more peripheral parts of the stimuli, which could be partly impaired owing to an early orientation of attention toward the right side of the pattern and a subsequent difficulty to detach attention from this early focus to orient it toward parts fo the stimulus lying in the left half space.

Brain Damage, Chronic↗

PubMed1986

Focal brain lesions and intelligence: a study with a new version of Raven's Colored Matrices.

Contrasting results have been obtained in previous investigations, which have used the standard version of Raven's Colored Progressive Matrices for studying the effects of localized brain lesion on visual-spatial intelligence. Some of these discrepancies might be due to the fact that specific factors, such as unilateral spatial neglect, could contribute to decreased performance obtained on Raven's test by patients with focal brain lesions. A new set of Colored Matrices, devised to minimize the influence of unilateral spatial neglect without changing the essential features of the original task, was therefore constructed. The test was administered to 76 normal controls, 74 right brain-damaged patients, 87 aphasics, and 61 nonaphasic left brain-damaged patients, in order to study the effect of laterality of lesions and of language impairment on Raven's scores. The results show that, if the influence of unilateral spatial neglect is minimized and Raven's scores are corrected in reference to age, educational level, and lesion size, then: no significant differences are observed between right and left brain-damaged patients; aphasics score worse than nonaphasic left brain-damaged patients; impairment is greater in patients with Wernicke's and Global aphasia (i.e., in patients with severe language comprehension disorders) than in patients classified as Broca's, Anomic, or Conduction aphasia; impairment is greater in patients with semantic-lexical discrimination errors than in patients free from semantic-lexical comprehension disorders.

Aphasia↗

PubMed1986

Mechanisms of unilateral spatial neglect in relation to laterality of cerebral lesions.

An Overlapping Figures test, considered as appropriate to study focusing of attention on small but complex stimuli falling in the central parts of visual field and a Searching for Animals test, designed to study the exploration of large parts of extrapersonal space, were administered to 38 controls, and 90 right and 82 left brain-damaged patients. The investigation was designed to test the hypothesis that the extent of space to be explored may have a different influence on unilateral spatial neglect of right and left brain-damaged patients. Both right and left brain-damaged patients showed an asymmetric exploration of space on the Searching for Animals test, making more omissions on the side contralateral to the damaged hemisphere than on the ipsilateral one. On the Overlapping Figures test, however, only right brain-damaged patients showed a clear tendency to omit figures lying on the left side of the composite pattern. This finding suggests that inability to extract visual information from one side of the stimuli during single eye fixations may be the most characteristic feature of unilateral spatial neglect resulting from right hemisphere lesions.

Attention↗

PubMed1985

Are drawing errors different in right-sided and left-sided constructional apraxics?

The drawings of 70 control subjects, 95 right and 118 left brain-damaged patients (BDP) were evaluated by two independent judges having no knowledge of the literature on constructional apraxia, who were requested to give both a quantitative and a qualitative evaluation of each drawing. Scoring made it possible to classify the BDP as affected or not affected by constructional apraxia. Qualitative errors were classified in two groups: (A) "executive" errors: increased number of right angles, structural simplification of the models and omission of details and (B) "visualspatial" errors: inattention to lateral elements or omission of one half of the figures, errors in spatial relations and diagonal orientation of the drawings. Contrary to expectations, no clear qualitative difference was observed between the drawing errors of right and left BDP. The types of errors most frequently observed in constructional apraxics were very similar, irrespective of lesion side, and consisted in difficulty in reproducing the spatial relations between the various parts of the models and in a tendency to oversimplify the most difficult designs. The only type of error which differentiated right apraxics from left apraxics was omission of lines or of whole figures on the half space contralateral to the damaged hemisphere, but this type of error could not be responsible for right-sided constructional apraxia, since judges had been instructed to base their assessment only on the parts of the models actually reproduced by the patients without scoring as errors manifestations of neglect. These results do not support the hypothesis that two different mechanisms, "executive", and "visual-spatial", underlie constructive disabilities of left and right brain-damaged patients.

Adult↗