Biomedical subjects

Gilles Rode

Publications and source records attributed to Gilles Rode.

11 recordsLinked to original sources

PubMed2006

Visuo-spatial neglect: a systematic review of current interventions and their effectiveness.

Left visuo-spatial neglect is a well-recognized predictor of poor functional outcome following right hemisphere stroke. Over the past 60 years, 18 different methods have been described and evaluated aimed at reducing the effects of this impairment. Although there are some grounds for optimism particularly in terms of short-term impairment-based effects, the range and degree of disability borne by many patients remain high and the clinical effectiveness of the different methods viewed in terms of long-lasting functional improvement (i.e. improvement of disabilities or handicap) is not clear. A systematic review of the available clinically relevant literature, using comparative and stringent levels of evidence, indicates that visual scanning training (VST), trunk rotation (TR) or repeated neck muscle vibrations (NMV) when associated with an extensive training program, mental imagery training, video feedback training and prism adaptation (PA) can be recommended for the rehabilitation of patients with left neglect. More studies however are needed to determine the optimal paradigm of limb activation (LA) eliciting a sustained functional improvement. Sensory stimulations alone and Fresnel prisms do not appear to be functionally relevant. For the other methods, the actual literature is not sufficient to conclude whether or not a long-term functional improvement can be achieved.

Functional Laterality↗

PubMed2006

Prism adaptation in the rehabilitation of patients with visuo-spatial cognitive disorders.

PURPOSE OF REVIEW: The traditional focus of neurorehabilitaion has been on the patients' attention on their deficit, such that they should become aware of their problems and gain intentional control of compensatory strategies (descending approach). We review prism adaptation as one of the approaches that emphasize ascending rather than descending strategies to the rehabilitation of visuo-spatial disorders. The clinical outcome of prism adaptation highlights the need for a theoretical reconsideration of some previous stances to neurological rehabilitation. RECENT FINDINGS: Recent years have given rise to a growing body of experimental studies showing that the descending strategy is not always optimal, especially when higher-level cognition is affected by the patients' condition. Ascending approaches have, for example, used visuo-manual adaptation for the rehabilitation of visuo-spatial deficits. A simple task of pointing to visual targets while wearing prismatic goggles can produce remarkable improvements of various aspects of unilateral neglect. SUMMARY: The neural mechanisms underpinning visuo-manual plasticity can be viewed as a powerful rehabilitation tool that produces straightforward effects not only on visual and motor parameters, but on visuo-spatial, attentional and higher cognitive neurological functions. The use of prism adaptation therapy in neglect and other visuo-spatial disorders has just started to reveal its potential, both at a practical and theoretical level.

Adaptation, Physiological↗

PubMed2006

Neglect and prism adaptation: a new therapeutic tool for spatial cognition disorders.

PURPOSE: A large proportion of right-hemisphere stroke patients show unilateral neglect, a neurological deficit of perception, attention, representation, and/or performing actions within their left-sided space, inducing many functional debilitating effects on everyday life, and responsible for poor functional recovery and ability to benefit from treatment. This spatial cognition disorder affects the orientation of behaviour with a shift of proprioceptive representations toward the lesion side. METHODS: This shift can be reduced after a prism adaptation period to a right lateral displacement of visual field (induced by a simple target-pointing task with base-left wedge prisms). The modification of visuo-motor or sensory-motor correspondences induced by prism adaptation involves improvement of different symptoms of neglect. RESULTS: Classical visuo-motor tests could be improved for at least 2h after adaptation, but also non-motor and non-visual tasks. In addition, cross-modal effects have been described (tactile extinction and dichotic listening), mental imagery tasks (geographic map, number bisection) and even visuo-constructive disorders. These cognitive effects are shown to result from indirect bottom-up effects of the deeper, adaptive realignment component of the reaction to prisms. Lesion studies and functional imaging data evoke a cerebello-cortical network in which each structure plays a specific role and not all structures are crucial for adaptation ability. CONCLUSIONS: These cognitive effects of prism adaptation suggest that prism adaptation does not act specifically on the ipsilesional bias characteristic of unilateral neglect but rehabilitates more generally the visuo-spatial functions attributed to the right cortical hemisphere. These results reinforce the idea that the process of prism adaptation may activate brain functions related to multisensory integration and higher spatial representations and show a generalization at a functional level. Prism adaptation therefore appears as a new powerful therapeutic tool for spatial cognition disorders.

Adaptation, Physiological↗

PubMed2006

Prism adaptation first among equals in alleviating left neglect: a review.

PURPOSE: The current paper was designed to provide a critical overview on the different methods proposed for the rehabilitation of left spatial neglect. METHODS: On the basis of a previous systematic review of the literature, we analyzed all articles available aiming at reducing left spatial neglect which included a long term functional assessment. RESULTS: The aim of most early rehabilitation approaches, such as visuo-scanning training, was to re-orient visual scanning toward the neglected side. This review confirmed the utility of this method for rehabilitation purposes. More recent - theory driven - procedures, also based on a training approach, include limb activation, mental imagery training and video-feedback training. Although there is ground for optimism, the functional effectiveness of these methods still relies on few single-case studies. Newer methods have tried to stimulate automatic orientation of gaze or attention towards neglected space in a bottom-up fashion. Sensory stimulations can remove most of the classical signs of left neglect but their effects are short-lived. Such stimulations are not functionally relevant for rehabilitation except for trunk rotation or repeated neck muscle vibrations if they are associated with an extensive training program. A more promising intervention is prism adaptation given the growing evidence of relatively long-term functional gains from comparatively short term usage. CONCLUSION: Overall, there is now evidence for several clinically relevant long-term benefits in the case of visual scanning training, mental imagery training, video feedback training, neck muscle vibration and trunk rotation if associated with visual scanning training and prism adaptation. However, the amount of evidence is still limited to a small number of relevant published articles and it is mandatory to continue the research in this field. In this review, the possible routes for new rehabilitation procedures are discussed on the basis of the actual knowledge regarding the neuro-cognitive mechanisms underlying the therapeutic effect of prism adaptation.

Adaptation, Physiological↗

PubMed2004

Geographic information has to be spatialized to be neglected: a representational neglect case.

A patient with unilateral neglect had to evoke mentally the map of France in two different conditions. In the first condition, he was asked to build an iconic representation of the map of France and to list all the towns that he could 'see' on this mental image within two minutes. In the second condition, he had to remember and name as many French towns as possible within two minutes, without being instructed to form a mental image. Left representational neglect was observed in the first condition only, i.e., when an iconic representation was required. These findings, which were replicated four months later, suggest a dual mode of coding, retrieval, or both, of geographic information and show that, although topographic, geographic data has to be spatialized to be neglected.

Aged↗

PubMed2003

Simulating unilateral neglect in normals using prism adaptation: implications for theory.

Rightward deviation on line bisection is considered one of the most classic clinical signs of unilateral visual neglect--a cognitive disorder of spatial processing that commonly follows right brain damage. Recently, short-term adaptation to wedge prisms has been shown to significantly reduce neglect on this and other conventional diagnostic tasks. Our previous study has shown that visuomotor adaptation in normals produces a similar pattern of directional bias on a line bisection task. Based on the good working knowledge of how neglect patients perform on different versions of the standard diagnostic task, we showed here that using leftward-deviating prisms in normals, it is possible to produce: (1) a reliable bias on line bisection, (2) a rightward specific deviation, (3) a modulation of rightward deviation, which depends on the relative spatial location of the target lines and (4) a line length effect. A final experiment confirmed that these after-effects are specific to prism adaptation rather than passive prism exposure. Collectively, these findings confirm that adaptation to left-deviating prisms in normals produces a reliable right-sided bias and as shown by a previous visuospatial judgement task, these findings cannot be adequately explained by the symmetric sensori-motor effects of prism adaptation. Taken together with the improvement of spatial neglect shown by right-deviating prisms only, the present study suggests that low level sensori-motor adaptations play a greater role in right hemisphere organisation for spatial cognition than previously thought.

Adaptation, Physiological↗

PubMed2003

Bottom-up transfer of sensory-motor plasticity to recovery of spatial cognition: visuomotor adaptation and spatial neglect.

A large proportion of right-hemisphere stroke patients show hemispatial neglect, a neurological deficit of perception, attention, representation, and/or performing actions within their left-sided space, inducing many functional debilitating effects on everyday life, and responsible for poor functional recovery and ability to benefit from treatment. This spatial cognition disorder affects the orientation of behavior with a shift of proprioceptive representations toward the lesion side. This shift is similar to that produced by psychophysical manipulations as a wedge-prism exposure in normal healthy subjects. In both subjects, one major compensative effect of short-term prism adaptation is a shift of proprioceptive representations, demonstrated by a shift in manual straight-ahead pointing in the dark, in a direction opposite to the visual shift. In neglect patients, prism adaptation involves the shift of proprioceptive representations to the left with a reduction of rightward bias observed in neglect patients in visuo-manual tasks as line-bisection, line-cancellation or copy drawing. Improvement of neglect is also observed in no visuo-manual tasks as mental imagery, auditory extinction or posture. This generalization of prism adaptation effects at different neglect level symptoms suggests that the process of prism adaptation may activate brain functions related to multisensory integration and higher spatial representations. Moreover the positive effects found for both sensorimotor and more cognitive spatial functions lasted for at least two or more hours after prism removal. Unlike reduction of neglect through sensory stimulations, the long-lasting improvement of neglect after prism adaptation suggests the activation of short-term plasticity of brain functions related to coordinate transformations and space representations. Lastly, the duration of these effects could be useful in rehabilitation programs, as suggested by the effects of prism adaptation on disabling neglect symptoms as wheelchair driving, posture or writing.

Adaptation, Physiological↗

PubMed2002

After-effects of visuo-manual adaptation to prisms on body posture in normal subjects.

Postural equilibrium is known to be controlled by sensorimotor reflexes and automatic control loops but also depends on high-level body representation in space, probably implicating the right temporoparietal cortex. Indeed, short-term prism adaptation to a 10 degrees rightward visual shift has been shown to reduce predominant postural imbalance in patients with right hemisphere damage, as it did for neglect symptoms. These effects are likely to be explained by a high level effect of prism adaptation on body and space representation, rather than by a sensorimotor effect. Cognitive after-effects of prism adaptation to a leftward visual shift, suggesting neglect-like symptoms, have also recently been shown in normal subjects on line bisection tasks. In the present study, we investigated the effect of wedge prism adaptation on postural control in normal subjects. Two groups of seven healthy subjects were either adapted to a leftward or a rightward visual shift. Results showed that our procedure induced changes in lateral postural control in normal subjects. Furthermore, this lateral postural after-effect was dependent on direction of prism adaptation. Indeed, only adaptation to a leftward visual shift induced significant rightward postural bias in normal subjects. The rightward postural lateral displacement was negatively correlated with the visual vertical. Both transfer and direction specific effect of visuo-manual adaptation to prisms on postural control suggest that effects of adaptation act more on high-level postural control linked to body representation in space or at least reveal close interaction between sensorimotor plasticity and body representation.

Adolescent↗

PubMed2002

Dissociated long lasting improvements of straight-ahead pointing and line bisection tasks in two hemineglect patients.

In this experiment, we evaluated over a longer time period the previously demonstrated effects of a short prism adaptation on hemispatial neglect. We followed two patients (PE and SA), during a period of 5 days (1 day before and 4 days after the prism adaptation procedure), repeatedly measuring their performances on a straight-ahead pointing task and a line bisection task. We also assessed the comparative temporal evolution of the rightward biased egocentric reference frame (as measured by the straight-ahead demonstration) and a classical neuropsychological symptom of neglect, namely the rightward bias observed on line bisection. Firstly, the results showed that prismatic effect could be maintained for 4 days, on the two tasks (separately straight-ahead for PE, line bisection for SA). This long-term effect implies a very profound action of prism adaptation based on active processes and opens large possibilities for clinical applications. Secondly, no correlation was found between the evolution of the performances on the two tasks, neither for patient PE, nor for patient SA (within-subject double-dissociation). Moreover, a double-dissociation between subjects was demonstrated on long-term effects. A new conception has thus to be found to explain the various symptoms manifested in neglect and more investigations have to be performed in order to establish to what extent they can be considered independent. It can be concluded that elucidating the mechanism through which prism adaptation affects neglect could lead to a better understanding of the neglect syndrome.

Adaptation, Psychological↗

PubMed2002

Bilateral vestibular stimulation does not improve visual hemineglect.

This work compared the effect of unilateral (right and left) and bilateral vestibular stimulation in a right-brain-damaged patient with neglect. Neglect was improved following left caloric vestibular stimulation, and worsened following right vestibular stimulation. On the other hand, no modification of neglect was observed after bilateral vestibular stimulation. These results support the idea that caloric vestibular stimulation may improve neglect through a specific effect; bilateral stimulation making the putative activation bilateral and symmetrical does not affect the lateral bias of neglect.

Aged↗

PubMed1998

Improvement of mental imagery after prism exposure in neglect: a case study.

Previous work has shown that various symptoms of unilateral neglect, including the pathological shift of the subjective midline to the right, may be improved by a short adaptation period to a prismatic shift of the visual field to the right. We report here the improvement of imagined neglect after prism exposure in a patient with a left unilateral neglect. Despite a strong neglect observed for mental images as well as for conventional tests, the mental evocation of left-sided information from an internal image of the map of France map was fully recovered following prism adaptation to the right. This improvement could not be explained by the alteration of visuomotor responses induced by the prism adaptation. Prism adaptation may therefore act not only on sensory-motor levels but also on a higher cognitive level of mental space representation and/or exploration.

Journal Article↗