Biomedical subjects

P Bartolomeo

Publications and source records attributed to P Bartolomeo.

At least 19 recordsLinked to original sources

PubMed2004

Right spatial neglect after left hemisphere stroke: qualitative and quantitative study.

OBJECTIVES: Comparatively little research has been conducted on right neglect after left brain damage. The authors sought to assess contralateral neglect in subacute left hemisphere stroke patients using a comprehensive test battery validated in a large control group after right hemisphere stroke. METHODS: Seventy-eight left hemisphere stroke patients were assessed. The test battery included a preliminary assessment of anosognosia and visual extinction, a clinical assessment of gaze orientation and personal neglect, and paper-and-pencil tests of spatial neglect in the peripersonal space. Only nonverbal tests were used. RESULTS: Drawing and cancellation tasks revealed neglect in 10 to 13% of patients. The combined battery was more sensitive than any single test alone. A total of 43.5% of patients showed some degree of neglect on at least one measure. Anatomic analyses showed that neglect was more common and severe when the posterior association cortex was damaged. CONCLUSIONS: The frequency of occurrence of right neglect was, as expected, much lower than that reported in a study using the same assessment battery in right brain damage stroke patients. Nevertheless, neglect was found in a substantial proportion of patients at a subacute stage, suggesting that it should be considered in the rehabilitation planning of left brain damage stroke patients.

Awareness↗

PubMed2004

The influence of limb crossing on left tactile extinction.

BACKGROUND: Previous research on patients with left tactile extinction has shown that crossing of hands, so that each hand is on the opposite side of the body midline relative to the other, improves detection of stimuli given to the left hand. OBJECTIVES: To study the influence of the spatial position of limbs on left tactile extinction, and its relations with left visual neglect. METHODS: Normal participants and patients with right cerebral hemisphere damage and left tactile extinction were asked to detect single or double light touch stimuli applied to their cheeks, hands, or knees with their arm and legs either in anatomical or in crossed position, increasing the attentional load of the task. RESULTS: In patients with left extinction, limb crossing caused a deterioration in performance for stimuli applied to right body parts, with only a tendency to an improvement in detection for left body parts (only two of 24 patients showed substantial (>20%) improvement in left extinction after limb crossing). After crossing, left limb detections of double stimuli decreased with increasing degrees of visual neglect. CONCLUSIONS: In conditions of high attentional load, limb crossing may impair tactile detection in most patients with left extinction, and particularly in those showing signs of left visual neglect. These results underline the importance of general attentional capacity in determining tactile extinction. Attentional and somatotopic mechanisms of extinction may assume different weights in different patients.

Aged↗

PubMed2002

Sensitivity of clinical and behavioural tests of spatial neglect after right hemisphere stroke.

OBJECTIVES: The lack of agreement regarding assessment methods is responsible for the variability in the reported rate of occurrence of spatial neglect after stroke. The aim of this study was to assess the sensitivity of different tests of neglect after right hemisphere stroke. METHODS: Two hundred and six subacute right hemisphere stroke patients were given a test battery including a preliminary assessment of anosognosia and of visual extinction, a clinical assessment of gaze orientation and of personal neglect, and paper and pencil tests of spatial neglect in the peripersonal space. Patients were compared with a previously reported control group. A subgroup of patients (n=69) received a behavioural assessment of neglect in daily life situations. RESULTS: The most sensitive paper and pencil measure was the starting point in the cancellation task. The whole battery was more sensitive than any single test alone. About 85% of patients presented some degree of neglect on at least one measure. An important finding was that behavioural assessment of neglect in daily life was more sensitive than any other single measure of neglect. Behavioural neglect was considered as moderate to severe in 36% of cases. A factorial analysis revealed that paper and pencil tests were related to two underlying factors. Dissociations were found between extrapersonal neglect, personal neglect, anosognosia, and extinction. Anatomical analyses showed that neglect was more common and severe when the posterior association cortex was damaged. CONCLUSIONS: The automatic rightward orientation bias is the most sensitive clinical measure of neglect. Behavioural assessment is more sensitive than any single paper and pencil test. The results also support the assumption that neglect is a heterogeneous disorder.

Activities of Daily Living↗

PubMed2001

Retest effects and cognitive decline in longitudinal follow-up of patients with early HD.

OBJECTIVE: To assess the natural progression of cognitive impairment in Huntington's disease (HD) and to reveal factors that may mask this progression. BACKGROUND: Although numerous cross-sectional studies reported cognitive deterioration at different stages of the disease, progressive cognitive deterioration has been, up to now, difficult to demonstrate in neuropsychological longitudinal studies. METHODS: The authors assessed 22 patients in early stages of HD at yearly intervals for 2 to 4 years (average, 31.2 +/- 10 months), using a comprehensive neuropsychological battery based on the Core Assessment Program for Intracerebral Transplantation in Huntington's Disease (CAPIT-HD). RESULTS: The authors observed a significant decline in different cognitive functions over time: these involved primarily attention and executive functions but also involved language comprehension, and visuospatial immediate memory. Episodic memory impairment that was already present at the time of enrollment did not show significant decline. The authors found a significant retest effect at the second assessment in many tasks. CONCLUSION: Many attention and executive tasks adequately assess the progression of the disease at an early stage. For other functions, the overlapping of retest effects and disease progression may confuse the results. High interindividual and intraindividual variability seem to be hallmarks of the disease.

Adult↗

PubMed2001

Modulating the attentional bias in unilateral neglect: the effects of the strategic set.

Left unilateral neglect is a neurological condition characterized by an impairment in orienting and responding to events occurring on the left side. To gain insight into the brain mechanisms of space processing and to provide theoretical foundations for patient rehabilitation, it is important to explore the attentional bias shown by neglect patients in the light of existing models of normal attentional orienting. Three experiments tested the hypothesis that attentional bias in neglect involves primarily exogenous, or stimulus-based, orienting of attention, with relatively preserved endogenous, or voluntary, orienting. Six patients with right hemisphere damage and left unilateral neglect and 18 age-matched participants without brain damage performed a cued reaction time (RT) task to targets which could appear in one of two lateral boxes. Cues consisted of a brief brightening of the contour of one of the boxes. The target followed the cue at 150, 550, or 1000 ms stimulus-onset asynchrony (SOA). In experiment 1, the cues were not informative about the future location of the target, and thus elicited a purely exogenous orienting of attention. Controls showed slowed RTs to the cued locations at SOAs > 150 ms, consistent with the notion of inhibition of return (IOR). Neglect patients had no evidence of IOR for right targets; they showed a disproportionate cost for left targets preceded by right (invalid) cues; this cost was maximal at the shortest SOA, consistent with the idea of a biased exogenous orienting in neglect. In experiment 2, 80% of the cues were valid (i.e., they correctly predicted the location of the impending target), thus inducing an initially exogenous, and later endogenous, attentional shift toward the cued box. Neglect patients showed again a cost for left invalidly cued targets, which this time persisted at SOAs > 150 ms, as if patients' attention had been cued to the right side not only exogenously, but also endogenously, thus rendering more difficult an endogenous reorienting toward the left. In experiment 3, only 20% of the cues were valid, so that the best response strategy was to endogenously orient attention toward the box opposite to the cued one. Controls were able to take advantage of invalid cues to rapidly respond to targets. In this condition, neglect patients were able to nullify their spatial bias; they achieved their fastest RTs to left targets, which were in the range of their RTs to right targets. However, for neglect patients fast responses to left targets occurred only at 1000 ms SOA, while controls were able to redirect their attention to the uncued box already at 550 ms SOA. Altogether, these results suggest that endogenous orienting is relatively spared, if slowed, in unilateral neglect.

Adult↗

PubMed2001

Variability of response times as a marker of diverted attention.

Anderson et al. (Variability not ability: another basis for performance decrements in neglect. Neuropsychologia 2000;38:785-796) have recently reported that variability of response times (RTs) progressively increases from the right to the left side in left neglect patients. Anderson et al. propose that this lack of consistency is an important determinant of patients' behaviour, and may result from a deficit independent of other mechanisms causing neglect. Here we suggest that an increase of variability, and not only of RTs, is to be expected when attention is exogenously biased away from the probed location. Consequently, space-based variability can be interpreted in the framework of existing models of unilateral neglect. According to one such model, a basic impairment in left neglect is a bias toward rightward exogenous orienting of attention. As a result, left targets often fail to rapidly capture patients' attention, thus yielding slow RTs. However, since the probability for a left target attracting attention is low but not null, relatively fast RTs can occur on those rare occasions in which a left target does capture patients' attention. The coexistence of these relatively fast with slow RTs could be at the basis of space-based variability in neglect. Empirical support for our hypothesis comes from the results of a re-analysis for variability of cued RTs obtained in 18 normal individuals and six left neglect patients. Cues were peripheral and non-informative, thus eliciting an exogenous attentional shift. For normal individuals, invalid trials yielded less consistent response times than valid trials at short (150 ms) cue-target interval; for neglect patients, a similar phenomenon occurred for left invalidly-cued targets, thus paralleling the disproportionate cost in RTs typically evoked by this condition in unilateral neglect. We conclude by discussing some possible determinants of gradient-shaped effects and by outlining the implications of space-based variability for current models of unilateral neglect.

Adult↗

PubMed2001

Laterally directed arm movements and right unilateral neglect after left hemisphere damage.

Signs of unilateral neglect for events occurring in one hemispace most often result from right hemisphere lesions. Right unilateral neglect after left hemisphere damage is much rarer, and has received less attention. The present study explores the relationships between right unilateral neglect and asymmetries in producing laterally directed arm movements in the horizontal plane in left brain-damaged (LBD) patients. Participants produced right- or left-directed arm movements with their left arm in response to centrally located visual stimuli. Results showed that LBD patients with signs of right unilateral neglect were consistently slowed when producing arm movements toward the right (neglected) side, as compared to left-directed movements. Taking into account patients with and without signs of neglect, this directional asymmetry positively correlated with a reaction-time measure of perceptual spatial bias. These findings stand in contrast with previous results obtained with the same experimental paradigm in right brain-damaged patients, in whom a consistent slowing of leftward-directed movements was rare and apparently unrelated to the presence and severity of left neglect. These conflicting results are discussed with respect to the hypothesis that different mechanisms may underlie left and right unilateral neglect.

Adult↗

PubMed2001

[Presenting a battery for assessing spatial neglect. Norms and effects of age, educational level, sex, hand and laterality].

The aim of this study was to build up a battery for assessing spatial neglect, then to analyse the norms and potential effects of age, education level, sex, hand used, and laterality. It was also to contribute evaluating the pseudoneglect phenomenon described by Heilman, which consists in a tendency of normal subjects to neglect the right peripersonal space. Tasks selected were presented to important groups of normal subjects, most often larger than 450. The battery comprised of a bell cancellation test, scene copy, clock drawing, two line bisection tasks, identification of overlapping figures, text reading, writing task, and the representational task of the France map. For each of them, different variables were selected, especially investigating the difference between performance in the right and the left hemispaces. This study allowed defining the threshold values (percentiles 5 and 95) for deciding of the pathological character of a patient performance. It also showed that the pseudoneglect phenomenon is more obvious in some tasks such as line bisection, and probably also in the representational task of the France map and writing. His importance and at times his side were influenced by the factors we studied, with between tasks differences, but also by the nature of the task to be performed, and especially his verbal component.

Adult↗

PubMed2000

Motor and cognitive improvements in patients with Huntington's disease after neural transplantation.

BACKGROUND: Huntington's disease is a neurodegenerative disease of genetic origin that mainly affects the striatum. It has severe motor and cognitive consequences and, up to now, no treatment. Motor and cognitive functions can be restored in experimental animal models by means of intrastriatal transplantation of fetal striatal neuroblasts. We explored whether grafts of human fetal striatal tissue could survive and have detectable effects in five patients with mild to moderate Huntington's disease. METHODS: After 2 years of preoperative assessment, patients were grafted with human fetal neuroblasts into the right striatum then, after a year, the left striatum. Final results were assessed 1 year later on the basis of neurological, neuropsychological, neurophysiological, and psychiatric tests. The results obtained were compared with those of a cohort of 22 untreated patients at similar stages of the disease who were followed up in parallel. Repeated magnetic resonance imaging (MRI) and positron emission tomography (PET) scanning with fluorine-18-labelled fluorodeoxyglucose was also done to assess metabolic activity. FINDINGS: The final PET-scan assessment showed increased metabolic activity in various subnuclei of the striatum in three of five patients, contrasting with the progressive decline recorded in the two other patients in the series, as seen in patients with untreated Huntington's disease. Small areas of even higher metabolic activity, coregistering with spherical hyposignals on MRI were also present in the same three patients, suggesting that grafts were functional. Accordingly, motor and cognitive functions were improved or maintained within the normal range, and functional benefits were seen in daily-life activities in these three patients, but not in the other two. INTERPRETATION: Fetal neural allografts could be associated with functional, motor, and cognitive improvements in patients with Huntington's disease.

Brain↗

PubMed2000

Safety and tolerability assessment of intrastriatal neural allografts in five patients with Huntington's disease.

This study describes issues related to the safety and tolerability of fetal striatal neural allografts as assessed in five patients with Huntington's disease. Huntington's disease (HD) is characterized by motor, cognitive, and behavioral disturbances. The latter include psychological disturbances and, as a consequence, we took particular care to analyze behavioral changes, in addition to the usual "safety" follow-up. We conducted multidisciplinary follow-up at least 2 years before and 1 year after grafting. Psychological care extended to close relatives. The grafting procedure itself was altogether safe and uneventful, and there were no apparent clinical deleterious effects for 1 year. The immunosuppressive treatment, however, was complicated by various problems (irregular compliance, errors of handling, side effects). Direct psychological consequences of the transplantation procedure were rare and not worrisome, although mood alteration requiring treatment was observed in one patient. Indirectly, however, the procedure required patients and relatives to accept constraints that tended to complicate familial situations already marred by aggressivity and depression. All patients and close relatives expressed major expectations, in spite of our strong and repeated cautioning. It is clearly important to be aware of these particular conditions since they may eventually translate into psychological difficulties in coping with the long-term clinical outcome of the procedure, if not beneficial. Despite an overall good tolerance, therefore, this follow-up calls for caution regarding the involvement of HD patients in experimental surgical protocols.

Adult↗

PubMed2000

[Right parietal lesions, spatial neglect and egocentric reference].

Using a proprioceptive "straight-ahead" pointing task, we determined the position of the subjective sagittal middle in thirty unselected patients with unilateral vascular lesions in the right hemisphere and twenty-two normal controls. Patients with extensive right parietal damage (n = 16) showed an ipsilesional (rightward) deviation of their egocentric reference, whereas patients with lesions that substantially spared the right parietal lobe (n = 14) showed a contralesional (leftward) deviation. No significant correlation emerged between the position of the egocentric reference and the performance on a neglect battery. These results can help explain some dissociations between left neglect signs and ipsilesional deviation of the egocentric reference, and raise some questions about the links among lesion location, neglect signs and egocentric frame of reference.

Aged↗

PubMed1999

The heparin management test: a new device for monitoring anticoagulation during coronary intervention.

Whole blood coagulation analysers are widely used during percutaneous coronary interventions. The precise degree of anticoagulation in patients is important in this setting. The aim of this investigation was to compare the results obtained with ACT (Hemochron) and HMT, the Heparin Management Test (TAS) in patients undergoing percutaneous coronary interventions. Patients (n = 100) were enrolled prospectively. Each patient received 10,000 units of heparin. At the end of the procedure, the mean ACT was 284+/-31 seconds and the mean HMT was 292+/-33 seconds. The correlation between the two methods was highly significant (r = 0.64, p<0.001). The HMT correlates well with ACT values in patients undergoing percutaneous coronary interventions. Its use in the management of these patients should be considered.

Angina, Unstable↗

PubMed1999

Left unilateral neglect or right hyperattention?

BACKGROUND: Contradictory interpretations of left unilateral neglect suggest that it reflects either decreased attention toward the left or increased attention toward the right. According to the right-hyperattention postulate, increasing severity of neglect should result from an increasingly stronger bias toward the right. Thus, response times to right-sided targets should become progressively faster as neglect increases in severity across patients. The left-hypoattention postulate predicts that as neglect increases, progressively less-attentional resources are deployed in both hemispaces. Thus, response times to right targets should progressively increase with increasing neglect. METHODS: We analyzed the distribution of manual response times to left- and right-sided targets in 24 patients with right hemisphere lesions and varying degrees of left neglect. RESULTS: Not only the responses to left targets but also those to right targets became progressively slower as neglect increased, consistent with the hypoattention account. However, the two regression lines were not parallel. With increasing neglect, responses to left targets increased more steeply than those to right targets did. CONCLUSIONS: A rightward attentional bias is present in patients with left neglect, together with left hypoattention. However, this rightward bias is one of defective, and not enhanced, attention.

Aged↗

PubMed1999

Facilitation instead of inhibition for repeated right-sided events in left neglect.

When two visual events appear consecutively in the same spatial location, our response to the second event is slower than that to the first. This inhibition for repeated events may reflect a bias toward sampling novel locations, a bias useful for exploring the visual space. Patients with right hemisphere damage and left neglect explore asymmetrically a visual scene. They are initially attracted by right-sided items and become stuck to them, being unable to reorient their attention toward the left. Here we show that neglect patients show facilitation instead of inhibition for repeated events on the right, non-neglected side. Patients without neglect showed normal inhibition. Our observation may explain why neglect patients' exploration of space cannot extend beyond a few right-sided objects.

Aged↗

PubMed1999

Egocentric frame of reference: its role in spatial bias after right hemisphere lesions.

The reference shift hypothesis of unilateral neglect holds that spatial bias in left neglect stems from a rightward deviation of patients' egocentric frame of reference (ER). Twenty five unselected right brain-damaged patients participated in a straight-ahead pointing task to assess the position of their ER (Experiment 1). A rightward ER shift emerged only in the subgroup of patients with extensive parietal lesions. In Experiment 2, we found that the position of the ER did not predict the outcome of various visuospatial neglect tests (r = 0.07 to 0.27). In Experiment 3, no significant positive correlation emerged between the ER position and visual (r = 0.26) or tactile (r = -0.48) extinction. Two further experiments examined the relationships between the ER position and patients' performance on a reaction time test of directional motor bias (Experiment 4), and on a test of response times to lateralised visual stimuli (Experiment 5). Results showed that the ER position did not predict the distribution of accuracy scores or response times in either task (Experiment 3: accuracy: r = 0.06; response times: r = 0.16; Experiment 4: accuracy: r = 0.09; response times: r = 0.04). We concluded that the position of the ER plays no crucial role in the behavioural consequences of spatial bias induced by right hemisphere lesions.

Aged↗

PubMed1998

Position of the egocentric reference and directional arm movements in right-brain-damaged patients.

We asked 12 right-brain-damaged patients (6 with left neglect signs and 6 without left neglect signs) to perform a straight ahead pointing task and a visual detection task with lateralized motor response, in order to investigate the relationship between the position of the egocentric reference and response time and accuracy in producing lateralized arm movements. Results showed that there was no correlation between the position of the egocentric reference and neglect signs, nor between the position of the egocentric reference and the latencies to direct a motor response toward either side of space. These findings were interpreted within the context of egocentric hypotheses of neglect. In particular, it was suggested that attentional or intentional neglect signs cannot be considered as a direct consequence of an ipsilesional deviation of the egocentric reference.

Adult↗

PubMed1998

Multiple-domain dissociation between impaired visual perception and preserved mental imagery in a patient with bilateral extrastriate lesions.

A brain-damaged patient is described whose pattern of performance provides insight into both the functional mechanisms and the neural structures involved in visual mental imagery. The patient became severely agnosic, alexic, achromatopsic and prosopagnosic following bilateral brain lesions in the temporo-occipital cortex. However, her mental imagery for the same visual entities that she could not perceive was perfectly preserved. This clear-cut dissociation held across all the major domains of high-level vision: object recognition, reading, colour and face processing. Our findings, together with other reports on domain-specific dissociations and functional brain imaging studies, provide evidence to support the view that visual perception and visual mental imagery are subserved by independent functional mechanisms, which do not share the same cortical implementation. In particular, our results suggest that mental imagery abilities need not be mediated by early visual cortices.

Aged↗

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↗