... 7 (1995) 151-156 False recovery from auditory hemineglect produced by source misattribution o... more ... 7 (1995) 151-156 False recovery from auditory hemineglect produced by source misattribution of auditory ... by vision, thereby creating a compelling illusion, the so-called 'ventriloquist' effect [30 ... Procedure The tests for visual neglect (BIT; [47]) and auditory neglect were conducted ...
The impact of damage to different regions and functional systems of the brain on visual working m... more The impact of damage to different regions and functional systems of the brain on visual working memory (WM) is far from understood. Here we examined how impaired object naming due to brain damage affects object identity and location information in working memory. Ten first-event stroke patients with aphasia performed a "delayed estimation" task that examines memory of object location separately from memory of object identity, using a continuous reporting scale. Following a delay of 4 s, objects that could not be named by the aphasic patients were localized more precisely than objects that could be named. The results are interpreted with reference to classic models separating phonological from visuospatial working memory, and with reference to the "verbal overshadowing" effect that is typically associated with long-term memory.
Neglect behavior of experimental animals with unilateral posterior cortical lesions improves with... more Neglect behavior of experimental animals with unilateral posterior cortical lesions improves with the placement of a second lesion in the contralesional superior colliculus or in the intercollicular commissure. Given that the retinotectal fibers are mainly crossed, it has been speculated that ipsilesional eye patching, by depriving the contralesional superior colliculus of its main facilitatory visual input, might achieve similar results, and thus be used as a remediation maneuver in patients with neglect. From six patients with severe persistent neglect, only one showed an unequivocal beneficial effect from ipsilesional eye patching. We discuss the factors which possibly underlie success and failure with this procedure, and the place for it in neglect rehabilitation.
bioRxiv (Cold Spring Harbor Laboratory), Apr 25, 2023
Humans, more than all other species, skillfully flex and extend their fingers to perform delicate... more Humans, more than all other species, skillfully flex and extend their fingers to perform delicate motor tasks. This unique dexterous ability is a product of the complex anatomical properties of the human hand and the neural mechanisms that control it. Yet, the neural basis that underlies human dexterous hand movement remains unclear. Here we characterized individuation (fine control) and strength (gross control) during flexion and extension finger movements, isolated the peripheral passive mechanical coupling component from the central neuromuscular activity involved in dexterity and then applied voxel-based lesion mapping in first-event sub-acute stroke patients to investigate the causal link between the neural substrates and the behavioral aspects of finger dexterity. We found substantial differences in dexterous behavior, favoring finger flexion over extension. These differences were not caused by peripheral factors but were rather driven by central origins. Lesion-symptom mapping identified a critical brain region for finger individuation within the primary sensory-motor cortex (M1, S1), the premotor cortex (PMC), and the corticospinal (CST) fibers that descend from them. Although there was a great deal of overlap between individuated flexion and extension, we were able to identify distinct areas within this region that were associated exclusively with finger flexion. This flexionbiased differential premotor and motor cortical organization was associated with the finger individuation component, but not with finger strength. Conversely, lesion mapping revealed slight extension-biases in finger strength within descending tracts of M1. From these results we propose a model that summarizes the distinctions between individuation and strength and between finger movement in flexion and extension, revealed in human manual dexterity. .
Objective: To assess the effect of ischemic infarctions affecting the basal ganglia (BG) region o... more Objective: To assess the effect of ischemic infarctions affecting the basal ganglia (BG) region on a series of procedural learning tasks. Background: The basal ganglia hypothesis of procedural learning is a matter of debate. As most of the relevant research so far is based on examination of patients suffering from Parkinson disease, this inconsistency might reflect either lesion heterogeneity existing in this pathologic group or the heterogeneity of the procedural learning tasks. Method: Twelve patients with lesions confined to the right (BGr), 10 to the left (BGl) BG region, and 15 matched controls participated in the study. Three procedural learning tasks were used: Tower of Hanoi Puzzle, Mirror Reading, and Porteus Mazes. Declarative memory and general intelligence were also tested. Results: Verbal declarative memory was impaired in the BGl group. For each procedural learning task, baseline performance and learning rate were analyzed. Tower of Hanoi Puzzle: Baseline performance of the BGl group was impaired compared with the other groups. The BGr group was the only group that did not improve over learning trials. MR: Baseline performance of the BGr group was impaired compared with the other groups. The groups' learning rate did not differ significantly. Porteus Mazes: Baseline performance of both patient groups was impaired compared with that of the control group. Learning rate over repetitive trials of the same maze was impaired in the BGr group. However, the transfer of procedural learning to a newly exposed maze was impaired in the BGl group. Conclusions: First, right and left basal ganglia play different roles in different procedural learning tasks. Second, procedural learning is not a unitary capacity subserved by any single neural mechanism.
Annals of physical and rehabilitation medicine, Jul 1, 2018
Conclusion Swiss ball trunk exercise can obviously improve the trunk control, functional balance ... more Conclusion Swiss ball trunk exercise can obviously improve the trunk control, functional balance and walking of stroke patients in the early stages of recovery. Keywords Stroke; Trunk exercise; Swiss ball Disclosure of interest The authors declare that they have no competing interest.
Understanding the impact of variation in lesion topography on the expression of functional impair... more Understanding the impact of variation in lesion topography on the expression of functional impairments following stroke is important, as it may pave the way to modeling structure–function relations in statistical terms while pointing to constraints for adaptive remapping and functional recovery. Multi‐perturbation Shapley‐value analysis (MSA) is a relatively novel game‐theoretical approach for multivariate lesion‐symptom mapping. In this methodological paper, we provide a comprehensive explanation of MSA. We use synthetic data to assess the method's accuracy and perform parameter optimization. We then demonstrate its application using a cohort of 107 first‐event subacute stroke patients, assessed for upper limb (UL) motor impairment (Fugl‐Meyer Assessment scale). Under the conditions tested, MSA could correctly detect simulated ground‐truth lesion‐symptom relationships with a sensitivity of 75% and specificity of ~90%. For real behavioral data, MSA disclosed a strong hemispheric effect in the relative contribution of specific regions‐of‐interest (ROIs): poststroke UL motor function was mostly contributed by damage to ROIs associated with movement planning (supplementary motor cortex and superior frontal gyrus) following left‐hemispheric damage (LHD) and by ROIs associated with movement execution (primary motor and somatosensory cortices and the ventral brainstem) following right‐hemispheric damage (RHD). Residual UL motor ability following LHD was found to depend on a wider array of brain structures compared to the residual motor ability of RHD patients. The results demonstrate that MSA can provide a unique insight into the relative importance of different hubs in neural networks, which is difficult to obtain using standard univariate methods.
International physical medicine & rehabilitation journal, Jun 5, 2018
Objective: Phasic alerting (PA) is a theory-motivated treatment approach for unilateral spatial n... more Objective: Phasic alerting (PA) is a theory-motivated treatment approach for unilateral spatial neglect (USN). It aims to improve the non-spatial attentional components of the syndrome. The objective of this pilot study was to examine the potential benefit of a novel therapeutic approach, combining PA with Visual Spatial Training for individuals with USN. Method: This pilot study, was conducted with 18 USN stroke patients allocated quasi-randomly to one of 3 groups (each 6 participants): experimental (receiving computerized Visual spatial Training combined with PA), 'spatial' control (receiving similar Visual spatial Training without PA), and 'non-spatial' control (receiving a similar amount of non-spatial cognitive treatment). Treatment comprised of 10 daily 30-minute sessions. Assessments of USN and function were made at 3 points in time: before and after the intervention period and after 5 weeks. Results: The experimental group showed more than 50% amelioration in distinct measures of neglect during the treatment period. In contrast, the control groups did not show this trend during that period. All groups showed improvement at the follow-up period. However, in most tests the experimental group performed better with moderate effect size values in major USN tests. Conclusion: Visual spatial training combined with PA shows promising results in producing amelioration in USN reflected both in measures of USN and ADLs.
Visual extinction is a common, poorly understood, consequence of unilateral cerebral damage, wher... more Visual extinction is a common, poorly understood, consequence of unilateral cerebral damage, where a patient fails to detect one of Ž. two simultaneously presented stimuli the one more contralateral to the lesion , despite the fact that each stimulus is correctly detected when presented in isolation. The phenomenon implies a failure of shifting attention from an attended object to an unattended one. We show here that pair detection is improved in conditions where the two stimuli presented to the two halves of the visual field are proximal, co-oriented and co-axial. It is further shown that stimulus properties producing reduced extinction correlate with the selectivity pattern of spatial lateral interactions observed in the primary visual cortex. We suggest that neuronal activity in early stages of cortical visual processing encodes, using long-range lateral interactions, an image description in which visual objects are already segmented and marked. Segmentation seems to function properly even in the presence of significant destruction of the parietal cortex leading to extinction.
■ Patients with unilateral spatial neglect (USN) often show impaired performance in spatial worki... more ■ Patients with unilateral spatial neglect (USN) often show impaired performance in spatial working memory tasks, apart from the difficulty retrieving "left-sided" spatial data from long-term memory, shown in the "piazza effect" by Bisiach and colleagues. This studyʼs aim was to compare the effect of the spatial position of a visual object on immediate and delayed memory performance in USN patients. Specifically, immediate verbal recall performance, tested using a simultaneous presentation of four visual objects in four quadrants, was compared with memory in a later-provided recognition task, in which objects were individually shown at the screen center. Unlike healthy controls, USN patients showed a left-side disadvantage and a vertical bias in the immediate free recall task (69% vs. 42% recall for right-and left-sided objects, respectively). In the recognition task, the patients correctly recognized half of "old" items, and their correct rejection rate was 95.5%. Importantly, when the analysis focused on previously recalled items (in the immediate task), no statistically significant difference was found in the delayed recognition of objects according to their original quadrant of presentation. Furthermore, USN patients were able to recollect the correct original location of the recognized objects in 60% of the cases, well beyond chance level. This suggests that the memory trace formed in these cases was not only semantic but also contained a visuospatial tag. Finally, successful recognition of objects missed in recall trials points to formation of memory traces for neglected contralesional objects, which may become accessible to retrieval processes in explicit memory. ■
Neurorehabilitation and Neural Repair, Jul 17, 2019
Background. Persons with stroke (PwS) are at increased risk of falls, especially toward the paret... more Background. Persons with stroke (PwS) are at increased risk of falls, especially toward the paretic side, increasing the probability of a hip fracture. The ability to recover from unexpected loss of balance is a critical factor in fall prevention. Objectives. We aimed to compare reactive balance capacity and step kinematics between PwS and healthy controls. Methods. Thirty subacute PwS and 15 healthy controls were exposed to forward, backward, right, and left unannounced surface translations in 6 increasing intensities while standing. Single step threshold, multiple step threshold, and fall threshold (ie, perturbation intensity leading to a fall into harness system) were recorded as well as reactive step initiation time, step length, and step velocity. Results. Twenty-five PwS fell into harness system during the experiment while healthy controls did not fall. Fourteen out of 31 falls occurred in response to surface translations toward the nonparetic side, that is, falling toward the paretic side. Compared with healthy controls, PwS demonstrated significantly lower fall threshold and multiple step threshold in response to forward, backward, and lateral surface translations. Impairments were more pronounced in response to forward surface translation and toward the nonparetic side (ie, loss of balance toward the paretic side). A trend toward significant shorter step length in response to lateral surface translations was found in PwS compared with healthy controls. Conclusions. Findings highlight the importance of assessing reactive balance capacity in response to perturbations in different directions and intensities in addition to the routine assessment in PwS.
Several recent functional neuroimaging studies have reported robust bilateral activation (L > R) ... more Several recent functional neuroimaging studies have reported robust bilateral activation (L > R) in lateral posterior parietal cortex and precuneus during recognition memory retrieval tasks. It has not yet been determined what cognitive processes are represented by those activations. In order to examine whether parietal lobe-based processes are necessary for basic episodic recognition abilities, we tested a group of 17 first-incident CVA patients whose cortical damage included (but was not limited to) extensive unilateral posterior parietal lesions. These patients performed a series of tasks that yielded parietal activations in previous fMRI studies: yes/no recognition judgments on visual words and on colored object pictures and identifiable environmental sounds. We found that patients with left hemisphere lesions were not impaired compared to controls in any of the tasks. Patients with right hemisphere lesions were not significantly impaired in memory for visual words, but were impaired in recognition of object pictures and sounds. Two lesion-behavior analyses-area-based correlations and voxel-based lesion symptom mapping (VLSM)-indicate that these impairments resulted from extra-parietal damage, specifically to frontal and lateral temporal areas. These findings suggest that extensive parietal damage does not impair recognition performance. We suggest that parietal activations recorded during recognition memory tasks might reflect peri-retrieval processes, such as the storage of retrieved memoranda in a working memory buffer for further cognitive processing.
Hemiparesis and spasticity are common co-occurring manifestations of hemispheric stroke. The rela... more Hemiparesis and spasticity are common co-occurring manifestations of hemispheric stroke. The relationship between impaired precision and force in voluntary movement (hemiparesis) and the increment in muscle tone that stems from dysregulated activity of the stretch reflex (spasticity) is far from clear. Here we aimed to elucidate whether variation in lesion topography affects hemiparesis and spasticity in a similar or dissimilar manner. Voxel-based lesion-symptom mapping (VLSM) was used to assess the impact of lesion topography on (a) upper limb paresis, as reflected by the Fugl-Meyer Assessment scale for the upper limb and (b) elbow flexor spasticity, as reflected by the Tonic Stretch Reflex Threshold, in 41 patients with first-ever stroke. Hemiparesis and spasticity were affected by damage to peri-Sylvian cortical and subcortical regions and the putamen. Hemiparesis (but not spasticity) was affected by damage to the corticospinal tract at corona-radiata and capsular levels, and by damage to white-matter association tracts and additional regions in the temporal cortex and pallidum. VLSM conjunction analysis showed only a minor overlap of brain voxels where the existence of damage affected both hemiparesis and spasticity, suggesting that control of voluntary movement and regulation of muscle tone at rest involve largely separate parts of the motor network. Stroke is a leading cause of adult long-term motor disability 1 , where the key symptomatology consists of contralesional hemiparesis and spasticity. More than 80% of hospitalized subjects with stroke present some degree of hemiparesis, with upper limb (UL) involvement seen in about 75% 2. Spasticity accompanies paresis at different rates (4-43%) in different time periods post stroke 3,4. Hemiparesis and spasticity may lead to dependence in activities of daily living and reduced quality of life 5,6. By 'hemiparesis' we refer in this article to pathological active movement comprised of reduced muscle strength and impaired movement control (precision and speed of voluntary movement) in the side of the body contralateral to the side of the stroke. The term 'spasticity' is used here as defined by James Lance, to denote velocitydependent increment in muscle resistance to passive stretching, emerging from hyperexcitability of the stretch reflex arc 7. We have specified in this way the usage of the terms 'hemiparesis' and 'spasticity' in order to avoid confusion, as both terms are used in the clinical neurology and neuroscience literature in various ways, especially in discussions of components of the 'pyramidal' or 'upper motor neuron' syndrome and their underlying pathophysiology
This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
The effect of lateralized cerebral damage on free recall of items and recall of spatial location.... more The effect of lateralized cerebral damage on free recall of items and recall of spatial location. under intentional and incidental learning conditions, was investigated. Eleven right braindamaged (RBD) patients. IO left brain-damaged (LBD) patients, 14 young and I I elderly normal controls. participated in this study. The overall performance of the control groups was better than that of the patient groups. For all groups, free recall was better under mtentional than under incidental learning condition. On recall of spatial location the learning condition had a differentral effect on the groups. The RBD group performed better than the LBD group under intentional learning condition. while the reverse was found under incidental learning condition. The youngcontrol group showed an advantage over the elderly-control group under intentional but not under inctdental learning condition. The results are discussed in regard to diffcrcnt approaches to the distinction between automatic and effortful memory processes and their lateralization in the cerebral hemispheres.
BACKGROUND: Autonomic disturbances are a common phenomenon in patients' post-stroke, characterize... more BACKGROUND: Autonomic disturbances are a common phenomenon in patients' post-stroke, characterized by hypo function of the para-sympathetic and/or overactive sympathetic system. The impact of autonomic disturbances on physical therapy tasks during the rehabilitation period has not yet been assessed. OBJECTIVE: To describe the response of the cardiac autonomic nervous system during different tasks, among patients and age-matched healthy controls. METHODS: 19 patients in the subacute phase post first-ever ischemic stroke, and 16 controls. The Polar advanced heart rate monitor (RS800CX) was used to record RR intervals at rest, during paced breathing exercise, while performing different types of muscle contractions, and during single and dual task conditions. RESULTS: RR intervals and heart-rate variability (HRV) parameters were significantly lower among patients post stroke, both at rest and during most of the activities tested. Among the control group a significant autonomic adaptation was seen in the form of reduced RR intervals and HRV during muscle contraction and a significant increase in these parameters during slow breathing, no significant changes were observed among patients post stroke. CONCLUSION: Patients post-stroke experience hyper sympathetic function at rest and less adaptive cardiac autonomic control during different activities, which all may have an impact on rehabilitation outcomes.
Working memory (WM) is known to be impaired in patients with stroke experiencing unilateral spati... more Working memory (WM) is known to be impaired in patients with stroke experiencing unilateral spatial neglect (USN). Here, we examined in a systematic manner three WM components: memory of object identity, memory of object location, and binding between object identity and location. Moreover, we used two different retention intervals to isolate maintenance from other mnemonic and perceptual processes. Fourteen USN first-event stroke patients with right-hemisphere damage were tested in two different WM experiments using long and short retention intervals and an analog response scale. Patients exhibited more identification errors for items displayed on the contralesional side. Localization errors were also more prominent in the contralesional side, especially after a long retention interval. These localization errors were often a result of swap errors, that is, erroneous localizations of correctly identified contralesional objects in correctly memorized locations of ipsilesional objects. We conclude that a key WM deficit in USN is a lateralized impairment in binding between the identity of an object and its spatial tag.
... 7 (1995) 151-156 False recovery from auditory hemineglect produced by source misattribution o... more ... 7 (1995) 151-156 False recovery from auditory hemineglect produced by source misattribution of auditory ... by vision, thereby creating a compelling illusion, the so-called 'ventriloquist' effect [30 ... Procedure The tests for visual neglect (BIT; [47]) and auditory neglect were conducted ...
The impact of damage to different regions and functional systems of the brain on visual working m... more The impact of damage to different regions and functional systems of the brain on visual working memory (WM) is far from understood. Here we examined how impaired object naming due to brain damage affects object identity and location information in working memory. Ten first-event stroke patients with aphasia performed a "delayed estimation" task that examines memory of object location separately from memory of object identity, using a continuous reporting scale. Following a delay of 4 s, objects that could not be named by the aphasic patients were localized more precisely than objects that could be named. The results are interpreted with reference to classic models separating phonological from visuospatial working memory, and with reference to the "verbal overshadowing" effect that is typically associated with long-term memory.
Neglect behavior of experimental animals with unilateral posterior cortical lesions improves with... more Neglect behavior of experimental animals with unilateral posterior cortical lesions improves with the placement of a second lesion in the contralesional superior colliculus or in the intercollicular commissure. Given that the retinotectal fibers are mainly crossed, it has been speculated that ipsilesional eye patching, by depriving the contralesional superior colliculus of its main facilitatory visual input, might achieve similar results, and thus be used as a remediation maneuver in patients with neglect. From six patients with severe persistent neglect, only one showed an unequivocal beneficial effect from ipsilesional eye patching. We discuss the factors which possibly underlie success and failure with this procedure, and the place for it in neglect rehabilitation.
bioRxiv (Cold Spring Harbor Laboratory), Apr 25, 2023
Humans, more than all other species, skillfully flex and extend their fingers to perform delicate... more Humans, more than all other species, skillfully flex and extend their fingers to perform delicate motor tasks. This unique dexterous ability is a product of the complex anatomical properties of the human hand and the neural mechanisms that control it. Yet, the neural basis that underlies human dexterous hand movement remains unclear. Here we characterized individuation (fine control) and strength (gross control) during flexion and extension finger movements, isolated the peripheral passive mechanical coupling component from the central neuromuscular activity involved in dexterity and then applied voxel-based lesion mapping in first-event sub-acute stroke patients to investigate the causal link between the neural substrates and the behavioral aspects of finger dexterity. We found substantial differences in dexterous behavior, favoring finger flexion over extension. These differences were not caused by peripheral factors but were rather driven by central origins. Lesion-symptom mapping identified a critical brain region for finger individuation within the primary sensory-motor cortex (M1, S1), the premotor cortex (PMC), and the corticospinal (CST) fibers that descend from them. Although there was a great deal of overlap between individuated flexion and extension, we were able to identify distinct areas within this region that were associated exclusively with finger flexion. This flexionbiased differential premotor and motor cortical organization was associated with the finger individuation component, but not with finger strength. Conversely, lesion mapping revealed slight extension-biases in finger strength within descending tracts of M1. From these results we propose a model that summarizes the distinctions between individuation and strength and between finger movement in flexion and extension, revealed in human manual dexterity. .
Objective: To assess the effect of ischemic infarctions affecting the basal ganglia (BG) region o... more Objective: To assess the effect of ischemic infarctions affecting the basal ganglia (BG) region on a series of procedural learning tasks. Background: The basal ganglia hypothesis of procedural learning is a matter of debate. As most of the relevant research so far is based on examination of patients suffering from Parkinson disease, this inconsistency might reflect either lesion heterogeneity existing in this pathologic group or the heterogeneity of the procedural learning tasks. Method: Twelve patients with lesions confined to the right (BGr), 10 to the left (BGl) BG region, and 15 matched controls participated in the study. Three procedural learning tasks were used: Tower of Hanoi Puzzle, Mirror Reading, and Porteus Mazes. Declarative memory and general intelligence were also tested. Results: Verbal declarative memory was impaired in the BGl group. For each procedural learning task, baseline performance and learning rate were analyzed. Tower of Hanoi Puzzle: Baseline performance of the BGl group was impaired compared with the other groups. The BGr group was the only group that did not improve over learning trials. MR: Baseline performance of the BGr group was impaired compared with the other groups. The groups' learning rate did not differ significantly. Porteus Mazes: Baseline performance of both patient groups was impaired compared with that of the control group. Learning rate over repetitive trials of the same maze was impaired in the BGr group. However, the transfer of procedural learning to a newly exposed maze was impaired in the BGl group. Conclusions: First, right and left basal ganglia play different roles in different procedural learning tasks. Second, procedural learning is not a unitary capacity subserved by any single neural mechanism.
Annals of physical and rehabilitation medicine, Jul 1, 2018
Conclusion Swiss ball trunk exercise can obviously improve the trunk control, functional balance ... more Conclusion Swiss ball trunk exercise can obviously improve the trunk control, functional balance and walking of stroke patients in the early stages of recovery. Keywords Stroke; Trunk exercise; Swiss ball Disclosure of interest The authors declare that they have no competing interest.
Understanding the impact of variation in lesion topography on the expression of functional impair... more Understanding the impact of variation in lesion topography on the expression of functional impairments following stroke is important, as it may pave the way to modeling structure–function relations in statistical terms while pointing to constraints for adaptive remapping and functional recovery. Multi‐perturbation Shapley‐value analysis (MSA) is a relatively novel game‐theoretical approach for multivariate lesion‐symptom mapping. In this methodological paper, we provide a comprehensive explanation of MSA. We use synthetic data to assess the method's accuracy and perform parameter optimization. We then demonstrate its application using a cohort of 107 first‐event subacute stroke patients, assessed for upper limb (UL) motor impairment (Fugl‐Meyer Assessment scale). Under the conditions tested, MSA could correctly detect simulated ground‐truth lesion‐symptom relationships with a sensitivity of 75% and specificity of ~90%. For real behavioral data, MSA disclosed a strong hemispheric effect in the relative contribution of specific regions‐of‐interest (ROIs): poststroke UL motor function was mostly contributed by damage to ROIs associated with movement planning (supplementary motor cortex and superior frontal gyrus) following left‐hemispheric damage (LHD) and by ROIs associated with movement execution (primary motor and somatosensory cortices and the ventral brainstem) following right‐hemispheric damage (RHD). Residual UL motor ability following LHD was found to depend on a wider array of brain structures compared to the residual motor ability of RHD patients. The results demonstrate that MSA can provide a unique insight into the relative importance of different hubs in neural networks, which is difficult to obtain using standard univariate methods.
International physical medicine & rehabilitation journal, Jun 5, 2018
Objective: Phasic alerting (PA) is a theory-motivated treatment approach for unilateral spatial n... more Objective: Phasic alerting (PA) is a theory-motivated treatment approach for unilateral spatial neglect (USN). It aims to improve the non-spatial attentional components of the syndrome. The objective of this pilot study was to examine the potential benefit of a novel therapeutic approach, combining PA with Visual Spatial Training for individuals with USN. Method: This pilot study, was conducted with 18 USN stroke patients allocated quasi-randomly to one of 3 groups (each 6 participants): experimental (receiving computerized Visual spatial Training combined with PA), 'spatial' control (receiving similar Visual spatial Training without PA), and 'non-spatial' control (receiving a similar amount of non-spatial cognitive treatment). Treatment comprised of 10 daily 30-minute sessions. Assessments of USN and function were made at 3 points in time: before and after the intervention period and after 5 weeks. Results: The experimental group showed more than 50% amelioration in distinct measures of neglect during the treatment period. In contrast, the control groups did not show this trend during that period. All groups showed improvement at the follow-up period. However, in most tests the experimental group performed better with moderate effect size values in major USN tests. Conclusion: Visual spatial training combined with PA shows promising results in producing amelioration in USN reflected both in measures of USN and ADLs.
Visual extinction is a common, poorly understood, consequence of unilateral cerebral damage, wher... more Visual extinction is a common, poorly understood, consequence of unilateral cerebral damage, where a patient fails to detect one of Ž. two simultaneously presented stimuli the one more contralateral to the lesion , despite the fact that each stimulus is correctly detected when presented in isolation. The phenomenon implies a failure of shifting attention from an attended object to an unattended one. We show here that pair detection is improved in conditions where the two stimuli presented to the two halves of the visual field are proximal, co-oriented and co-axial. It is further shown that stimulus properties producing reduced extinction correlate with the selectivity pattern of spatial lateral interactions observed in the primary visual cortex. We suggest that neuronal activity in early stages of cortical visual processing encodes, using long-range lateral interactions, an image description in which visual objects are already segmented and marked. Segmentation seems to function properly even in the presence of significant destruction of the parietal cortex leading to extinction.
■ Patients with unilateral spatial neglect (USN) often show impaired performance in spatial worki... more ■ Patients with unilateral spatial neglect (USN) often show impaired performance in spatial working memory tasks, apart from the difficulty retrieving "left-sided" spatial data from long-term memory, shown in the "piazza effect" by Bisiach and colleagues. This studyʼs aim was to compare the effect of the spatial position of a visual object on immediate and delayed memory performance in USN patients. Specifically, immediate verbal recall performance, tested using a simultaneous presentation of four visual objects in four quadrants, was compared with memory in a later-provided recognition task, in which objects were individually shown at the screen center. Unlike healthy controls, USN patients showed a left-side disadvantage and a vertical bias in the immediate free recall task (69% vs. 42% recall for right-and left-sided objects, respectively). In the recognition task, the patients correctly recognized half of "old" items, and their correct rejection rate was 95.5%. Importantly, when the analysis focused on previously recalled items (in the immediate task), no statistically significant difference was found in the delayed recognition of objects according to their original quadrant of presentation. Furthermore, USN patients were able to recollect the correct original location of the recognized objects in 60% of the cases, well beyond chance level. This suggests that the memory trace formed in these cases was not only semantic but also contained a visuospatial tag. Finally, successful recognition of objects missed in recall trials points to formation of memory traces for neglected contralesional objects, which may become accessible to retrieval processes in explicit memory. ■
Neurorehabilitation and Neural Repair, Jul 17, 2019
Background. Persons with stroke (PwS) are at increased risk of falls, especially toward the paret... more Background. Persons with stroke (PwS) are at increased risk of falls, especially toward the paretic side, increasing the probability of a hip fracture. The ability to recover from unexpected loss of balance is a critical factor in fall prevention. Objectives. We aimed to compare reactive balance capacity and step kinematics between PwS and healthy controls. Methods. Thirty subacute PwS and 15 healthy controls were exposed to forward, backward, right, and left unannounced surface translations in 6 increasing intensities while standing. Single step threshold, multiple step threshold, and fall threshold (ie, perturbation intensity leading to a fall into harness system) were recorded as well as reactive step initiation time, step length, and step velocity. Results. Twenty-five PwS fell into harness system during the experiment while healthy controls did not fall. Fourteen out of 31 falls occurred in response to surface translations toward the nonparetic side, that is, falling toward the paretic side. Compared with healthy controls, PwS demonstrated significantly lower fall threshold and multiple step threshold in response to forward, backward, and lateral surface translations. Impairments were more pronounced in response to forward surface translation and toward the nonparetic side (ie, loss of balance toward the paretic side). A trend toward significant shorter step length in response to lateral surface translations was found in PwS compared with healthy controls. Conclusions. Findings highlight the importance of assessing reactive balance capacity in response to perturbations in different directions and intensities in addition to the routine assessment in PwS.
Several recent functional neuroimaging studies have reported robust bilateral activation (L > R) ... more Several recent functional neuroimaging studies have reported robust bilateral activation (L > R) in lateral posterior parietal cortex and precuneus during recognition memory retrieval tasks. It has not yet been determined what cognitive processes are represented by those activations. In order to examine whether parietal lobe-based processes are necessary for basic episodic recognition abilities, we tested a group of 17 first-incident CVA patients whose cortical damage included (but was not limited to) extensive unilateral posterior parietal lesions. These patients performed a series of tasks that yielded parietal activations in previous fMRI studies: yes/no recognition judgments on visual words and on colored object pictures and identifiable environmental sounds. We found that patients with left hemisphere lesions were not impaired compared to controls in any of the tasks. Patients with right hemisphere lesions were not significantly impaired in memory for visual words, but were impaired in recognition of object pictures and sounds. Two lesion-behavior analyses-area-based correlations and voxel-based lesion symptom mapping (VLSM)-indicate that these impairments resulted from extra-parietal damage, specifically to frontal and lateral temporal areas. These findings suggest that extensive parietal damage does not impair recognition performance. We suggest that parietal activations recorded during recognition memory tasks might reflect peri-retrieval processes, such as the storage of retrieved memoranda in a working memory buffer for further cognitive processing.
Hemiparesis and spasticity are common co-occurring manifestations of hemispheric stroke. The rela... more Hemiparesis and spasticity are common co-occurring manifestations of hemispheric stroke. The relationship between impaired precision and force in voluntary movement (hemiparesis) and the increment in muscle tone that stems from dysregulated activity of the stretch reflex (spasticity) is far from clear. Here we aimed to elucidate whether variation in lesion topography affects hemiparesis and spasticity in a similar or dissimilar manner. Voxel-based lesion-symptom mapping (VLSM) was used to assess the impact of lesion topography on (a) upper limb paresis, as reflected by the Fugl-Meyer Assessment scale for the upper limb and (b) elbow flexor spasticity, as reflected by the Tonic Stretch Reflex Threshold, in 41 patients with first-ever stroke. Hemiparesis and spasticity were affected by damage to peri-Sylvian cortical and subcortical regions and the putamen. Hemiparesis (but not spasticity) was affected by damage to the corticospinal tract at corona-radiata and capsular levels, and by damage to white-matter association tracts and additional regions in the temporal cortex and pallidum. VLSM conjunction analysis showed only a minor overlap of brain voxels where the existence of damage affected both hemiparesis and spasticity, suggesting that control of voluntary movement and regulation of muscle tone at rest involve largely separate parts of the motor network. Stroke is a leading cause of adult long-term motor disability 1 , where the key symptomatology consists of contralesional hemiparesis and spasticity. More than 80% of hospitalized subjects with stroke present some degree of hemiparesis, with upper limb (UL) involvement seen in about 75% 2. Spasticity accompanies paresis at different rates (4-43%) in different time periods post stroke 3,4. Hemiparesis and spasticity may lead to dependence in activities of daily living and reduced quality of life 5,6. By 'hemiparesis' we refer in this article to pathological active movement comprised of reduced muscle strength and impaired movement control (precision and speed of voluntary movement) in the side of the body contralateral to the side of the stroke. The term 'spasticity' is used here as defined by James Lance, to denote velocitydependent increment in muscle resistance to passive stretching, emerging from hyperexcitability of the stretch reflex arc 7. We have specified in this way the usage of the terms 'hemiparesis' and 'spasticity' in order to avoid confusion, as both terms are used in the clinical neurology and neuroscience literature in various ways, especially in discussions of components of the 'pyramidal' or 'upper motor neuron' syndrome and their underlying pathophysiology
This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
The effect of lateralized cerebral damage on free recall of items and recall of spatial location.... more The effect of lateralized cerebral damage on free recall of items and recall of spatial location. under intentional and incidental learning conditions, was investigated. Eleven right braindamaged (RBD) patients. IO left brain-damaged (LBD) patients, 14 young and I I elderly normal controls. participated in this study. The overall performance of the control groups was better than that of the patient groups. For all groups, free recall was better under mtentional than under incidental learning condition. On recall of spatial location the learning condition had a differentral effect on the groups. The RBD group performed better than the LBD group under intentional learning condition. while the reverse was found under incidental learning condition. The youngcontrol group showed an advantage over the elderly-control group under intentional but not under inctdental learning condition. The results are discussed in regard to diffcrcnt approaches to the distinction between automatic and effortful memory processes and their lateralization in the cerebral hemispheres.
BACKGROUND: Autonomic disturbances are a common phenomenon in patients' post-stroke, characterize... more BACKGROUND: Autonomic disturbances are a common phenomenon in patients' post-stroke, characterized by hypo function of the para-sympathetic and/or overactive sympathetic system. The impact of autonomic disturbances on physical therapy tasks during the rehabilitation period has not yet been assessed. OBJECTIVE: To describe the response of the cardiac autonomic nervous system during different tasks, among patients and age-matched healthy controls. METHODS: 19 patients in the subacute phase post first-ever ischemic stroke, and 16 controls. The Polar advanced heart rate monitor (RS800CX) was used to record RR intervals at rest, during paced breathing exercise, while performing different types of muscle contractions, and during single and dual task conditions. RESULTS: RR intervals and heart-rate variability (HRV) parameters were significantly lower among patients post stroke, both at rest and during most of the activities tested. Among the control group a significant autonomic adaptation was seen in the form of reduced RR intervals and HRV during muscle contraction and a significant increase in these parameters during slow breathing, no significant changes were observed among patients post stroke. CONCLUSION: Patients post-stroke experience hyper sympathetic function at rest and less adaptive cardiac autonomic control during different activities, which all may have an impact on rehabilitation outcomes.
Working memory (WM) is known to be impaired in patients with stroke experiencing unilateral spati... more Working memory (WM) is known to be impaired in patients with stroke experiencing unilateral spatial neglect (USN). Here, we examined in a systematic manner three WM components: memory of object identity, memory of object location, and binding between object identity and location. Moreover, we used two different retention intervals to isolate maintenance from other mnemonic and perceptual processes. Fourteen USN first-event stroke patients with right-hemisphere damage were tested in two different WM experiments using long and short retention intervals and an analog response scale. Patients exhibited more identification errors for items displayed on the contralesional side. Localization errors were also more prominent in the contralesional side, especially after a long retention interval. These localization errors were often a result of swap errors, that is, erroneous localizations of correctly identified contralesional objects in correctly memorized locations of ipsilesional objects. We conclude that a key WM deficit in USN is a lateralized impairment in binding between the identity of an object and its spatial tag.
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