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Biomedical subjects

Y Rossetti

Publications and source records attributed to Y Rossetti.

At least 19 recordsLinked to original sources
PubMed2007

Prism adaptation to optical deviation alleviates pathologic pain.

BACKGROUND: The human visual and somatosensory systems are interdependent. Using a visual subjective body-midline (SM) judgment task, we previously confirmed that pathologic pain and deafferentation can modify visuospatial perception, indicating that altered somatosensory experience can modify visual perception. Conversely, in the present study we investigated whether a change in visual experience can modify perception of pathologic pain. METHODS: We used prism adaptation (PA) to modify subjects' visual experience. Five patients with complex regional pain syndrome (CRPS) adapted to wedge prisms, producing a 20-degree visual displacement toward the unaffected side. Further, we used several types of prisms in a longitudinal single-case study. Wearing prismatic goggles, the subjects performed a target-pointing task once a day for 2 weeks. We evaluated pain intensity and visual SM judgment to measure the adaptive aftereffects at three time points: before PA (pre-test), immediately after the first PA exposure (IA-test), and after a 14-day sequence of PA exposure (post-test). RESULTS: PA toward the unaffected side alleviated pathologic pain and other CRPS pathologic features, when measured at post-test. None of the IA-test results showed an analgesic effect. In the longitudinal study, sham PA and 5-degree PA did not produce any effects, and PA toward the affected side actually exacerbated the subjective pain. CONCLUSIONS: Our findings suggest that vision can influence pathologic pain, and preliminarily suggest that prism adaptation has a direction-specific and reproducible effect on not only pathologic pain but also other CRPS pathologic features. Thus, prism adaptation may be a viable cognitive treatment for CRPS.

Adaptation, Physiological↗
PubMed2006

Left size distortion (hyperschematia) after right brain damage.

OBJECTIVE: To quantitate a size distortion involving the side of space contralateral to the lesion (contralesional) in two right-brain-damaged patients. METHODS: We studied two right-brain-damaged patients with lesions sparing the occipital lobe and a mild left neglect on target cancellation or line bisection. The lesions involved the temporoparietal region (Patient 1) and the basal ganglia and the insula (Patients 1 and 2). Patients were given drawing tasks and tasks requiring perceptual and visuomotor judgments of horizontal extent. RESULTS: In drawing objects such as a daisy both from memory and by copying, patients exhibited a disproportionate enlargement of the left-hand side of objects and added more left-sided petals to the drawn daisy. This pathologic behavior persisted when the patients were blindfolded and was likely to reflect a perceptual, rather than premotor, size distortion. In a task requiring the perceptual matching of two rectangles, patients underestimated the left-sided stimulus. In a visuomotor task requiring the reproduction of the horizontal extent of a segment, patients exhibited a hyperextension, when a leftward movement was required. CONCLUSIONS: We showed a disordered representation of extrapersonal space, possibly involving a contralesional relaxation of the spatial medium. The deficit does not arise at the level of retinotopic coordinate frames and is independent of unilateral spatial neglect.

Basal Ganglia↗
PubMed2006

Functional anatomy of the therapeutic effects of prism adaptation on left neglect.

OBJECTIVE: To investigate the anatomic substrates underlying the beneficial effect of prism adaptation in five patients with persistent left neglect following right stroke. METHODS: In a functional imaging PET study, we used a covariation analysis to examine linear changes of regional cerebral blood flow over sessions as a function of left neglect improvement. RESULTS: The network of significant brain regions associated with improvement of left neglect performance produced by prism adaptation involved the right cerebellum, the left thalamus, the left temporo-occipital cortex, the left medial temporal cortex, and the right posterior parietal cortex. CONCLUSION: Our results suggest that the realignment of visuomotor coordinates is processed by the cerebellum and that low level sensorimotor adaptation actively modulates cerebral areas, albeit now relying on intact cerebellocerebral connections. Hence, our data support the hypothesis that the beneficial effect of prism adaptation on the clinical presentation of left neglect derives from modulation of cortical regions implicated in spatial cognition.

Adaptation, Physiological↗
PubMed2006

No double-dissociation between optic ataxia and visual agnosia: multiple sub-streams for multiple visuo-manual integrations.

The current dominant view of the visual system is marked by the functional and anatomical dissociation between a ventral stream specialised for perception and a dorsal stream specialised for action. The "double-dissociation" between visual agnosia (VA), a deficit of visual recognition, and optic ataxia (OA), a deficit of visuo-manual guidance, considered as consecutive to ventral and dorsal damage, respectively, has provided the main argument for this dichotomic view. In the first part of this paper, we show that the currently available empirical data do not suffice to support a double-dissociation between OA and VA. In the second part, we review evidence coming from human neuropsychology and monkey data, which cast further doubts on the validity of a simple double-dissociation between perception and action because they argue for a far more complex organisation with multiple parallel visual-to-motor connections: 1. A dorso-dorsal pathway (involving the most dorsal part of the parietal and pre-motor cortices): for immediate visuo-motor control--with OA as typical disturbance. The latest research about OA is reviewed, showing how these patients exhibit deficits restricted to the most direct and fast visuo-motor transformations. We also propose that mild mirror ataxia, consisting of misreaching errors when the controlesional hand is guided to a visual goal though a mirror, could correspond to OA with an isolated "hand effect". 2. A ventral stream-prefrontal pathway (connections from the ventral visual stream to pre-frontal areas, by-passing the parietal areas): for "mediate" control (involving spatial or temporal transpositions [Rossetti, Y., & Pisella, L. (2003). Mediate responses as direct evidence for intention: Neuropsychology of Not to-, Not now- and Not there-tasks. In S. Johnson (Ed.), Cognitive Neuroscience perspectives on the problem of intentional action (pp. 67-105). MIT Press.])--with VA as typical disturbance. Preserved visuo-manual guidance in patients with VA is restricted to immediate goal-directed guidance, they exhibit deficits for delayed or pantomimed actions. 3. A ventro-dorsal pathway (involving the more ventral part of the parietal lobe and the pre-motor and pre-frontal areas): for complex planning and programming relying on high representational levels with a more bilateral organisation or an hemispheric lateralisation--with mirror apraxia, limb apraxia and spatial neglect as representatives. Mirror apraxia is a deficit that affects both hands after unilateral inferior parietal lesion with the patients reaching systematically and repeatedly toward the virtual image in the mirror. Limb apraxia is localized on a more advanced conceptual level of object-related actions and results from deficient integrative, computational and "working memory" capacities of the left inferior parietal lobule. A component of spatial working memory has recently been revealed also in spatial neglect consecutive to lesion involving the network of the right inferior parietal lobule and the right frontal areas. We conclude by pointing to the differential temporal constraints and integrative capabilities of these parallel visuo-motor pathways as keys to interpret the neuropsychological deficits.

Agnosia↗
PubMed2006

Prism adaptation improves spatial dysgraphia following right brain damage.

Visuo-manual adaptation to prisms produces a long-lasting improvement of visuo-spatial neglect. Improvement is also observed in tasks that do not involve visuo-manual component and that can all be consider to rely on a rightward (ipsilesional) orienting bias. Here, we report positive effects of prism adaptation on spatial dysgraphia, in a neglect patient following right brain damage. A long-lasting improvement concerned the right-page preference reflecting the ipsilesional bias but also the sloping lines and the broken lines reflecting visuo-constructive disorders in handwriting. Moreover, a transient improvement was also evidenced for the graphic errors. 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 useful tool in the theoretical attempt to identify the underlying 'core' mechanisms of the neglect syndrome.

Adaptation, Physiological↗
PubMed2005

Two waves of a long-lasting aftereffect of prism adaptation measured over 7 days.

Prism adaptation is a useful paradigm to study the integration and reorganization of various sensory modalities involved in sensory-motor tasks. By prolonging the prismatic aftereffect and well-timed observation, we aimed to dissociate the components and mechanisms involved in human prism adaptation by their differential decay and development time courses. Here, we show that a single session of prism adaptation training, combining small increments of prism strength below the subjects' awareness threshold, during a pointing task with a free walk session with total prism exposure duration of 75 min, generated a surprisingly long-lasting aftereffect. The aftereffect was measured by the magnitude of the proprioceptive shift (assessed by straight-ahead pointing in the dark) for 7 days. An aftereffect was observed, which lasted for more than 6 days, by a single prism adaptation session. The aftereffect did not decay gradually. Unlike previous descriptions, the aftereffect showed two separate time-courses of decay and increase. After a significant initial decay within 6 h, the aftereffect increased again from 1 day up to 3 days. The novel decay and delayed development profile of this adaptation aftereffect suggests two separate underlying neural mechanisms with different time scales. Our experimental paradigms promise to reveal directly the temporal characteristics of early versus late long-term neural plasticity in complex human adaptive behavior.

Adaptation, Physiological↗
PubMed2005

Ipsidirectional impairment of prism adaptation after unilateral lesion of anterior cerebellum.

In a patient with damage of the left cerebellar cortex (SCA territory), the authors tested four combinations of exposure to optical shift (leftward prisms, right hand; rightward prisms, right hand; leftward prisms, left (ataxic) hand; rightward prisms, left (ataxic) hand). He adapted to rightward but not leftward prisms, independent of which hand was used during exposure. This suggests a role of anterior cerebellar cortex in the computation or compensation of ipsidirectional visual error.

Adaptation, Physiological↗
PubMed2005

[Assessment of disability and quality of life in patients with cognitive disorders].

OBJECTIVE: To identify disability, handicap and quality of life questionnaires available for patients with cognitive impairment. MATERIALS AND METHODS: We systematically reviewed the literature in Medline using the keywords assessment, evaluation, deficiency, disability, disadvantage, handicap, quality of life, scale, index, questionnaire, ICIDH-1, and ICIDH-2, combined with the cognitive deficits dysexecutive syndrome, memory deficits, attention deficits, neglect, apraxia, aphasia, agnosia and mood disorders. We focused on validated scales and distinguished scales dedicated to assess disability, handicap and quality of life. RESULTS: At the level of disability, global and specific scales are available. Specific scales exist for dysexecutive syndrome, memory deficits, attention deficits, unilateral neglect, aphasia and mood disorders. French adaptations of foreign language tests and original tests developed in French have been validated in these areas. No specific tool is available for isolated apraxia or agnosia. Generic scales and pathology-specific scales (for stroke, traumatic brain injury, and multiple sclerosis) are available for quality of life. For aphasia, specific tools are available for incapacity handicap and quality of life. CONCLUSION: Previous results show the impact of the ICIDH-1 framework on functional outcome assessment of cognitive impairments. This approach is often limited by the lack of theoretical background and by the difficulty to assess the involvement of environment and anosognosia.

Cognition Disorders↗
PubMed2005

Optic ataxia errors depend on remapped, not viewed, target location.

Optic ataxia is a disorder associated with posterior parietal lobe lesions, in which visually guided reaching errors typically occur for peripheral targets. It has been assumed that these errors are related to a faulty sensorimotor transformation of inputs from the 'ataxic visual field'. However, we show here that the errors observed in the contralesional field in optic ataxia depend on a dynamic gaze-centered internal representation of reach space.

Adult↗
PubMed2005

Visually guided reaching: bilateral posterior parietal lesions cause a switch from fast visuomotor to slow cognitive control.

The visually guided reaching of two patients with bilateral optic ataxia was explored in two experiments. In Experiment 1 simple delayed pointing was compared with immediate pointing. In the immediate pointing task both variable and constant errors increased with target eccentricity. In contrast to the performance of control subjects and contrary to their own beliefs, the patients both showed improved accuracy in the delay condition. This improvement was manifest as a reduction in both pointing variability and in the constant angular error towards the point of fixation. Both angular errors and their improvement with the delay were proportional to target eccentricity. Experiment 2 used a task in which the target was pre-viewed 5s prior to its re-exposure for pointing ('delayed real pointing'). On some trials a conflict was introduced between the present and previous visual information by changing the target's location during the delay. In contrast to control subjects, who ignored the pre-viewed location and aimed directly at the current target, both patients with optic ataxia initiated their movements towards the previously viewed target location. Evidently they relied on off-line information in preference to on-line visual information. In addition, the patients often failed to detect the changes in target location. One of the patients sometimes even guessed incorrectly that the target had changed its location, and her movement trajectory was then more affected by her false belief than by the target's actual location. These findings confirm that posterior parietal lesions severely disrupt direct visuomotor transformations, and suggest that the residual performance is mediated indirectly by expectations or beliefs about target position.

Acoustic Stimulation↗
PubMed2004

Preserved prism adaptation in bilateral optic ataxia: strategic versus adaptive reaction to prisms.

To date the anatomical substrate(s) of prism adaptation remain(s) particularly debated, with two main candidates emerging from the literature: the posterior parietal cortex (PPC) and the cerebellum. The functional processes involved in the acquisition of the adaptive aftereffects also remain largely unknown. The main result shown here is that a patient with a bilateral optic ataxia can adapt to an optical deviation, which allows us to make a step forward on these two issues. First, it demonstrates that the corresponding part of the PPC is not a necessary substrate for prism adaptation. Second, since this patient exhibits deficit for fast visuo-motor guidance, it provides direct evidence for a dissociation between on-line visuo-motor control and visuo-motor plasticity. Since the intermanual transfer rate of adaptation is larger in this patient than in control subjects, the PPC may still have an influence on adaptation under normal conditions. We propose a model of the relative contribution of the PPC and the cerebellum during prism exposure, associating these two structures with the two interacting behavioural components of prism adaptation described by previous psychophysical experiments: the strategic component would be linked to the PPC and the adaptive component to the cerebellum. In this model, the strategic component enters in conflict with the development and the generalisation of the adaptive aftereffects. This idea is compatible with the fact that a lesion of the PPC increases the transfer rate and the generalisation of the adaptation, as is also observed in unilateral neglect.

Adaptation, Physiological↗
PubMed2004

Sensorimotor effects on central space representation: prism adaptation influences haptic and visual representations in normal subjects.

Prism adaptation improves visual and haptic manifestations of left neglect, and can induce a small but reliable simulation of left visual neglect in normal individuals. Here, we present two experiments in which the effects of prism adaptation on the representation of space were explored. In Experiment 1, normal subjects were required to locate the centre of a haptically explored circle, before and after adaptation to leftward displacing prisms. In Experiment 2, a visual circle centring task was used. In both tasks, prism adaptation induced a significant rightward shift of performance. In addition, in both experiments, three classical measures of visuo-manual adaptation were taken: the visual shift, the proprioceptive shift and the total shift. The effects found on the haptic and visual tasks did not correlate with any of these measures. This suggests that the effects of prism adaptation on the circle centring tasks did not depend directly on the sensorimotor consequences of the adaptation. These results imply that prism adaptation can affect noetic levels of space representation in normal subjects, supporting the hypothesis that this low-level sensorimotor intervention can exert a bottom-up structuring influence on higher levels of cognitive integration.

Adaptation, Psychological↗
PubMed2004

Does action make the link between number and space representation? Visuo-manual adaptation improves number bisection in unilateral neglect.

If the visual world is artificially shifted by only 10 degrees, people initially experience difficulty in directing their actions toward visual goals, but then rapidly compensate the visual distortion. The consequence of such adaptation can be measured as visual and proprioceptive aftereffects, as well as by performance on pointing tasks without visual feedback. Recent work has shown that more cognitive deficits can be improved following prism adaptation in patients with unilateral neglect. Here we show that a short visuo-manual adaptation to prisms improves performance on a mental number-bisection task recently shown to be impaired in unilateral neglect. The association previously found between space and number representation (the mental number line) may thus be grounded in common action principles. Our results suggest that visuo-motor plasticity functionally links parietal areas involved in space and number representation.

Brain Ischemia↗
PubMed2003

Visuo-motor control of the ipsilateral hand: evidence from right brain-damaged patients.

We investigated the extent to which the right hemisphere is involved in the control of the ipsilateral hand by analysing the kinematics of right-hand prehension in right brain-damaged (RBD) patients. We required patients to grasp one of five possible objects, equally-sized and distributed over a 40 degrees wide workspace. With the purpose of investigating the right hemisphere contribution to the on-line visuo-motor control, we also assessed patients' ability to correct their movement "in-flight", in response to a sudden change of object position. Patients' performance was compared to that of aged-matched controls. A Younger group of healthy subjects, matching the population classically tested on double-step paradigms, was also evaluated to fully assess whether patients' kinematics could be partially due to normal ageing. As a further aim, the possible influence of hemispatial neglect was evaluated by comparing the performances of right brain-damaged patients with and without neglect. In normal subjects, the results confirmed and extended the notion of (a). positional tuning of grip formation, and (b). fast reactions following a change in object position. In addition, subtle effects of ageing on visuo-motor behaviour were shown by less efficient movement correction in the Elderly group. Patients executing reach-to-grasp actions into the left contralesional hemispace were selectively affected in both temporal and spatial aspects of movements. While their performances were relatively well preserved in the right hemispace, patients did not show positional tuning of grip formation, nor fast corrections of their movements when acting in the left hemispace. Interestingly, similar deficits were found irrespective of the presence of neglect. These results show that the right hemisphere contributes to the processing of visuo-motor information that is necessary for executing actions with the ipsilateral hand in the contralateral space.

Adult↗
PubMed2003

Vision for spatial perception and vision for action: a dissociation between the left-right and near-far dimensions.

Neuropsychological and psychophysical studies have suggested that two distinct visual sub-systems are responsible for perception and action. One of the main psychophysical arguments for this is based on visual illusion such as the Induced Roelofs Effect (IRE), where the location of a visual target presented with an off-centre frame is misperceived when evaluated verbally, but not with a reaching response. This dissociated effect suggests the existence of two independent representations of visual space devoted, respectively, to categorisation and to egocentric localisation of reachable objects. These "cognitive" and "sensorimotor" representations have been assumed to be produced through specific anatomical pathways stemming from the primary visual cortex (respectively, the ventral and dorsal streams). To account for the dissociation found with the IRE, it has been suggested that only the cognitive system is sensitive to contextual information. However this view has been challenged by recent psychophysical studies demonstrating the influence of environmental cues on distance perception and the guiding of movement. In the present study, the IRE is re-evaluated but the near-far and right-left dimensions were dissociated. In agreement with previous findings, our results showed that the IRE in the right-left dimension gives rise to a perceptual misperception of target position with no effect on motor performance. Conversely, when the IRE was induced in the near-far dimension a misperception of the target position affected both perceptual and motor responses. This dissociation indicates that the spatial constraints of the task, and not only the nature of the response, interfere with sensitivity to contextual information leading to visual illusions. It is thus likely that the action system (imputed to the dorsal stream) can be sensitive to contextual information, at least when depth processing is emphasised.

Adult↗
PubMed2003

Delayed reaching and grasping in patients with optic ataxia.

A series of experiments documenting the reaching and grasping of two patients with optic ataxia is presented. We compare their immediate responses with their behavior when required to delay for a few seconds before responding. When the delayed response is 'pantomimed', i.e. made in the absence of the target object, their performance typically improves. This pattern was predicted from a two-visual-systems model in which the cortical dorsal stream mediates normal visually guided actions while the ventral stream deals with visual information that has to be held in memory. We further found that when a 'preview' task was used in which the patients could use memorized information to guide a response to a still-present target object, they did so in preference to using the visual information facing them.

Adult↗
PubMed2003

Pointing errors in immediate and delayed conditions in unilateral optic ataxia.

The present paper provides an analysis of the pointing errors of a patient with unilateral optic ataxia (O.K.) following right hemispheric damage, revealing the type of errors related tothe use of the contralesional hand and/or to the reaching of targets located in the contralesional visual field. In addition, comparison between immediate and delayed pantomime pointing allow testing of whether pointing deficits of this patient are specific to real-time visuo-motor control and, subsequently, whether delay could improve his pointing performance. The results show different patterns in the four hand-field combinations. The following conclusion can be drawn from the results of the delayed condition. In the case of patient O. K., the delay reduced the pointing variability for both hands in the left visual field but not in the right visual field. However, the pointing biases did not improve accordingly. As in healthy subjects, target locations tended to be coded in memory with a bias directed toward the fixation point. These results are discussed and contrasted with respect to those previously obtained in the literature in patients with bilateral optic ataxia.

Adult↗