Cognitive assessment to optimize prediction of functional outcome in subacute hip fracture: a short-term prospective study.

BACKGROUND: Cognitive impairment is a long-known negative prognostic factor after hip fracture. Cognition is usually screened by a single easy-to-administer bedside tool, but recent studies have shown that screening tests may be not enough to rule out cognitive impairment with an unfavorable prognostic role. Unfortunately, data on outcome prediction by further cognitive assessments is sparse. AIM: We focused on patients with subacute hip fracture defined cognitively intact or mildly impaired on the screening evaluation performed by the Short Portable Mental Status Questionnaire (SPMSQ). We hypothesized that each of 3 further cognitive tests could independently predict activities of daily living, with optimal prediction of function obtained by performing all three the tests. DESIGN: Short-term prospective study. SETTING: Rehabilitation ward. POPULATION: Inpatients with subacute hip-fracture. METHODS: Three cognitive tests were performed on admission to rehabilitation in the patients who made ≤4 errors on the SPMSQ: Montreal Cognitive Assessment (MoCA), Rey Auditory Verbal Learning Test (RAVLT, immediate and delayed recall) and Frontal Assessment Battery (FAB). We assessed activities of daily living by the Barthel index. Successful rehabilitation was defined with a Barthel Index Score ≥85. RESULTS: Each of the three cognitive tests assessed before rehabilitation significantly predicted the Barthel index scores measured at the end of the rehabilitation course in our sample of 280 inpatients. However, only the MoCA score retained its significant predictive role when the scores from the three tests were included together as independent variables in a multiple regression model, with adjustments for a panel of potential confounders (P=0.007). The adjusted odds ratio to achieve successful rehabilitation for a seven-point change in MoCA score was 1.98 (CI 95% from 1.02 to 3.83; P=0.042). CONCLUSIONS: Contrary to our hypothesis, MoCA but not RAVLT and FAB retained the prognostic role when the scores from the three tests were evaluated together as potential predictors of functional ability in activities of daily living. CLINICAL REHABILITATION IMPACT: In the presence of a normal (or mildly altered) score on the SPMSQ in subacute hip fracture, MoCA scores improve prediction of activities of daily living and should be routinely performed.

Effects of prism adaptation and visual scanning training on perceptual and response bias in unilateral spatial neglect.

In some patients with unilateral spatial neglect, symptoms reflect impaired lateralized spatial attention and representation (perceptual bias) whereas in others the inability to respond to stimuli located in contralesional space (response bias). Here, we investigated whether prismatic adaptation (PA) and visual scanning training (VST) differentially affect perceptual and response bias and whether rehabilitation outcome depends on the type of bias underlying symptoms. Two groups of neglect patients in the subacute phase were evaluated before, immediately after, and two weeks following 10 days of PA (n = 9) or VST (n = 9). Standard neuropsychological tests (i.e., Behavioural Inattentional Test, Diller cancellation test, and Line Bisection test) were administered to assess neglect symptoms, while the Landmark task was used to disentangle perceptual and response biases. Performance on the Landmark task revealed that PA was more effective in improving the perceptual bias, while VST mainly modulated the response bias. Neuropsychological tests performance suggested that VST is better suited to modulate neglect in patients with response bias, while PA may be effective in patients with both types of bias. These findings may offer novel insights into the efficacy of PA and VST in the rehabilitation of perceptual and response biases in patients with neglect.

A screening test is not enough to define the prognostic role of cognitive impairment after hip fracture: a short-term prospective study.

BACKGROUND: Cognitive impairment assessed by easy-to-administer tests successfully predicts function after hip fracture, whereas the prognostic role of additional cognitive evaluations is largely unknown. AIMS: To investigate the capability of further assessments to discriminate cognitive impairment with prognostic relevance in hip-fracture women defined cognitively intact or mildly impaired on the Short Portable Mental Status Questionnaire (SPMSQ). METHODS: We prospectively investigated women with subacute hip fracture admitted to our rehabilitation facility. The women who made ≤4 errors on the SPMSQ were further assessed by 4 tests: Montreal Cognitive Assessment, Rey Auditory Verbal Learning Test (immediate and delayed recall) and Frontal Assessment Battery. Activities of daily living (ADL) were measured by the Barthel index. Successful rehabilitation was defined with a Barthel index score ≥85. RESULTS: Data from 127 women were available. Each of the 4 cognitive tests assessed at admission significantly predicted the Barthel index scores measured at discharge. The predictive role persisted after multiple adjustments. For a change in cognitive scores corresponding to the difference between 25° and 75° percentiles in their distribution in the sample, the adjusted odds ratio to achieve successful rehabilitation roughly ranged from 2 to 4, depending on which cognitive test was adopted. DISCUSSION: The women with subacute hip fracture defined cognitively intact or mildly impaired on the SPMSQ could have cognitive impairment revealed by further examination, with prognostic disadvantages in ADL. CONCLUSIONS: Assessing cognition by the SPMSQ seems not enough to exclude the presence of cognitive impairment with relevant prognostic disadvantage in hip-fracture women.

Bodily self-recognition in patients with pathological embodiment.

The ability to discriminate between one's own and others' body parts can be lost after brain damage, as in patients who misidentify someone else's hand as their own (pathological embodiment). Surprisingly, these patients do not use visual information to discriminate between the own and the alien hand. We asked whether this impaired visual discrimination emerges only in the ecological evaluation when the pathological embodiment is triggered by the physical alien hand (the examiner's one) or whether it emerges also when hand images are displayed on a screen. Forty right brain-damaged patients, with (E+ = 20) and without (E- = 20) pathological embodiment, and 24 healthy controls underwent two tasks in which stimuli depicting self and other hands was adopted. In the Implicit task, where participants judged which of two images matched a central target, the self-advantage (better performance with Self than Other stimuli) selectively emerges in controls, but not in patients. Moreover, E+ patients show a significantly lower performance with respect to both controls and E- patients, whereas E- patients were comparable to controls. In the Explicit task, where participants judged which stimuli belonged to themselves, both E- and E+ patients performed worst when compared to controls, but only E+ patients hyper-attributed others' hand to themselves (i.e., false alarms) as observed during the ecological evaluation. The VLSM revealed that SLF damage was significantly associated with the tendency of committing false alarm errors. We demonstrate that, in E+ patients, the ability to visually recognize the own body is lost, at both implicit and explicit level.

Reach planning with someone else's hand.

To investigate the relationship between the sense of body ownership and motor control, we capitalized on a rare bizarre disorder wherein another person's hand is misattributed to their own body, i.e., a pathological form of embodiment (E+). Importantly, despite E+ is usually associated with motor deficits, we had the opportunity to test two E+ patients with spared motor function, thus able to perform a reaching task. Crucially, these patients had proprioceptive deafferentation, allowing us to purely isolate the embodiment-dependent effect from proprioception-dependent ones that are usually associated in experimental manipulations of body ownership in healthy participants. Previous evidence suggests that the reaching movement vector is attracted towards an embodied hand during the rubber hand illusion (RHI). However, these results are confounded by the spared proprioception, whose modulation alone could explain the effects on reach planning. The neuropsychological approach employed here provides unambiguous evidence about the role of body ownership in reach planning. Indeed, three brain-damaged patients with proprioceptive deafferentation, two E+ and a well-matched control patient without pathological embodiment (E-), and 10 age-matched healthy controls underwent a reaching task wherein they had to reach for a target from a fixed starting point, while an alien hand (the co-experimenter's) was placed on the table. Irrespective of proprioception, damaged in all patients, only in E+ patients reaching errors were significantly more shifted consistently with the pathological belief, i.e., as if they planned movements from the position of the alien (embodied) hand, as compared to controls. Furthermore, with an additional experiment on healthy participants, we demonstrated that reaching errors observed during the RHI correlate with the changes in ownership. In conclusion, our neuropsychological approach suggests that when planning a reach, we do so from where our owned hand is and not from its physical location.

Monochannel Preference in Autism Spectrum Conditions Revealed by a Non-Visual Variant of Rubber Hand Illusion.

Individuals with autism spectrum conditions (ASC) are less susceptible to multisensory delusions, such as rubber hand illusion (RHI). Here, we investigate whether a monochannel variant of RHI is more effective in inducing an illusory feeling of ownership in ASC. To this aim, we exploit a non-visual variant of the RHI that, excluding vision, leverages only on the somatosensory channel. While the visual-tactile RHI does not alter the perceived hand position in ASC individuals, the tacto-tactile RHI effectively modulates proprioception to a similar extent as that found in typical development individuals. These findings suggest a more effective integration of multiple inputs originating from the same sensory channel in ASC, revealing a monochannel preference in this population.

Virtual Reality for Motor and Cognitive Rehabilitation From Clinic to Home: A Pilot Feasibility and Efficacy Study for Persons With Chronic Stroke.

Aims: Continuity of care is an important issue in healthcare for persons after stroke. The present multi-center pilot study investigates the feasibility and efficiency of an innovative approach, the Human Empowerment Aging and Disability (HEAD), for digital-health motor and cognitive rehabilitation. The approach is explored within an in-clinic context (ClinicHEAD) and in continuity of care (HomeHEAD) for persons after chronic stroke. Methods: Thirty-four outpatients with chronic stroke (mean age 55 years, SD 13.7) participated. The HEAD VR protocol was administered in two consecutive phases: Phase I in clinic (ClinicHEAD) consisting of 4 weeks of 12 supervised HEAD rehabilitation sessions (45-min), including motor, cognitive and dual task for all participants; Phase II at home (HomeHEAD) consisted of 60 sessions of the same VR activities, 5 times/week for 3 months. All participants in the ClinicHEAD were allocated (ratio 1:2) to continue with tele-monitored home rehabilitation (HH, N = 11) or to follow usual care (UC, N = 23). Blind evaluation was carried out at baseline, after ClinicHEAD, after 3 months of HomeHEAD and at 3 months Follow-up. Primary outcomes were functional mobility [2-min Walking Test (2MWT)] and cognition [Montreal Cognitive Assessment (MoCA)]. Feasibility and acceptance were assessed with adherence to treatment and the System Usability Satisfaction. Within group analyses were done with dependent samples t-tests, and between groups HomeHEAD comparisons were carried out on change scores with independent samples t-test (p = 0.05, two tailed). Results: The HEAD protocol was feasible with good adherence both in the ClinicHEAD phase (92%) and HomeHEAD (89%) phase, along with good perceived system satisfaction. ClinicHEAD resulted in a significant increase in functional mobility (2MWT, p = 0.02) and cognition (MoCA, p = 0.003) and most secondary outcome variables. At 3 months follow up of HomeHEAD the HH_group showed a further significantly greater maintenance of functional mobility with respect to UC_group (p = 0.04). Conclusion: The HEAD VR protocol was feasible in clinical and at home tele-rehabilitation for persons in the chronic phase after stroke. In clinic the approach was effective in augmenting motor and cognitive abilities and at home it was effective in longterm maintenance of functional mobility, indicating its usefulness in continuity of care. Clinical Trial Registration: ClinicalTrials.gov, NCT03025126.

Drawing lines and circles in Parkinson's Disease: The lateralized symptoms interfere with the movements of the unaffected hand.

INTRODUCTION: Evidence about altered bimanual coordination has been reported in Parkinson's Disease. However, no previous study has explored such an alteration quantifying the interference effect that the trajectory of each hand might impose on the other one. Thus, in the present research, we applied the traditional Circles-Lines Coupling Task, which allowed assessing the motor coordination of the two hands, in the context of Parkinson's Disease. METHODS: Thirty-six individuals affected by Parkinson's Disease were consecutively recruited and assigned to two groups according to their symptoms' lateralization. Moreover, eighteen age-matched healthy controls participated in the study. We capitalized on the Circles-Lines Coupling Task, in which the performance during incongruent movements (drawing lines with one hand and circles with the other hand) was compared with the performance during congruent movements (drawing lines with both hands). A bimanual coupling index was computed to compare the interference effect of each hand on the other one. RESULTS: In healthy controls, the bimanual coupling index did not differ between the two hands. Crucially, in both groups of individuals affected by Parkinson's Disease, the less affected hand showed a significantly higher bimanual coupling index, due to the abnormal interference exerted by the most affected one, than vice versa. CONCLUSIONS: Our results highlighted an altered spatial bimanual coupling in Parkinson's disease, depending on the symptoms' lateralization. We offered different explanations of our results according to the theoretical frameworks about the mechanisms subserving bimanual coordination.

Effects of an Innovative Telerehabilitation Intervention for People With Parkinson's Disease on Quality of Life, Motor, and Non-motor Abilities.

Parkinson's disease (PD) often leads to multifactorial motor and non-motor disabilities with resultant social restrictions. Continuity of care in this pathology, including a tailored home rehabilitation, is crucial to improve or maintain the quality of life for patients. The aim of this multicenter study was to test in a pilot sample of PD patients the efficiency and efficacy of the Human Empowerment Aging and Disability (HEAD) program. The virtual reality HEAD program was administered in two consecutive phases: (1) in clinic (ClinicHEAD, 12 45-minutes sessions, 3 sessions/week); (2) at home (HomeHEAD, 60 45-minutes sessions, 5 sessions/week). Thirty-one PD outpatients were enrolled [mean age (SD) = 66.84 (9.13)]. All patients performed ClinicHEAD, and after allocation (ratio 1:2) were assigned to the HomeHEAD or the Usual Care (UC) group. Motor, cognitive and behavioral outcome measures were assessed at enrollment (T0), at hospital discharge (T1), at 4 (T2) and 7 (T3) months after baseline. After ClinicHEAD (T1 vs. T0 comparison) a significant (p < 0.05) improvement in functional mobility, balance, upper limb mobility, global cognitive function, memory, quality of life and psychological well-being was observed. After the HomeHEAD intervention there was an additional enhancement for upper limb mobility. At T3 follow-up, the UC group that did not continue the HEAD program at home showed a worsening with respect to the HomeHEAD group in balance and functional mobility. Furthermore, in the HomeHEAD group, a positive association was observed between adherence, mental and physical health (SF-12). A trend was also registered between adherence and positive affect. The digital health patient-tailored rehabilitation program resulted in improving motor and non-motor abilities and quality of life in clinical setting, enhancing the motor function in telerehabilitation at home, and maintaining the non-motor abilities and quality of life at follow-up. In the near future, people with PD can be supported also at home with individualized rehabilitation strategies for a better quality of life and wellbeing along with lower costs for society.

The anatomo-clinical picture of the pathological embodiment over someone else's body part after stroke.

Recently, a monothematic delusion of body ownership due to brain damage (i.e., the embodiment of someone else's body part within the patient's sensorimotor system) has been extensively investigated. Here we aimed at defining in-depth the clinical features and the neural correlates of the delusion. Ninety-six stroke patients in a sub-acute or chronic phase of the illness were assessed with a full ad-hoc protocol to evaluate the embodiment of an alien arm under different conditions. A sub-group of seventy-five hemiplegic patients was also evaluated for the embodiment of the movements of the alien arm. Fifty-five patients were studied to identify the neural bases of the delusion by means of voxel-based lesion-symptom mapping approach. Our results show that, in forty percent of the whole sample, simply viewing the alien arm triggered the delusion, but only if it was a real human arm and that was seen from a 1st person perspective in an anatomically-correct position. In the hemiplegic sub-group, the presence of the embodiment of the alien arm was always accompanied by the embodiment of its passive and active movements. Furthermore, the delusion was significantly associated to primary proprioceptive deficits and to damages of the corona radiata and the superior longitudinal fasciculus. To conclude, we show that the pathological embodiment of an alien arm is well-characterized by recurrent and specific features and might be explained as a disconnection deficit, mainly involving white matter tracts. The proposed exhaustive protocol can be successfully employed to assess stroke-induced disorders of body awareness, unveiling even their more undetectable or covert clinical forms.

A Multidimensional Virtual Reality Neurorehabilitation Approach to Improve Functional Memory: Who Is the Ideal Candidate?

Aims: We aimed to identify the significant predictors of ecological memory amelioration after the Human Empowerment Aging and Disability (HEAD) rehabilitation program, a multidimensional treatment for chronic neurological diseases. Materials and Methods: Ninety-three patients with Parkinson disease (n = 29), multiple sclerosis (n = 26), and stroke (n = 38) underwent a multidimensional rehabilitation. We focused on changes after treatment on ecological memory (outcome measure) evaluated by Rivermead Behavioral Memory Test, Third Edition (RBMT-3). Minimal clinically important difference (MCID) after treatment were calculated for RBMT-3. The change score on RBMT-3 was categorized in positive effect, stabilization, or no effect of the treatment. Random forest classification identified who significantly benefited from treatment against who did not in terms of ecological memory functioning. Accordingly, logistic regression models were created to identify the best predictors of the treatment effect. A predicted probability value was derived, and the profile of the ideal candidate of HEAD protocol was shown by combining different ranks of significant predictors in a 3 × 3 matrix for each pair of predictors. Results: A significant number of cases reported positive effect of the treatment on ecological memory, with an amelioration over the MCID or a stabilization. The random forest analysis highlighted a discrete accuracy of prediction (>0.60) for all the variables considered at baseline for identifying participants who significantly benefited and who did not from the treatment. Significant logistic regression model (Wald method) showed a predictive role of Montreal Cognitive Assessment (MoCA; p = 0.007), 2-Minute Walk Test (2MWT; p = 0.038), and RBMT-3 (p < 0.001) at baseline on HEAD treatment effect. Finally, we observed a high probability of success in people with higher residual cognitive functioning (MoCA; odds ratio = 1.306) or functional mobility (2MWT; odds ratio = 1.013). Discussion: The HEAD program is a rehabilitation with effects on multiple domains, including ecological memory. Residual level of cognitive and/or motor functioning is a significant predictor of the treatment success. These findings confirm the intrinsic relationship subsisting between motor and cognitive functions and suggest the beneficial effects of physical activity on cognitive functions and vice versa.

Efficiency and Patient-Reported Outcome Measures From Clinic to Home: The Human Empowerment Aging and Disability Program for Digital-Health Rehabilitation.

Background: The recent exponential growth of Digital Health (DH) in the healthcare system provides a crucial transformation in healthcare, answering to alarming threats related to the increasing number of Chronic Neurological Diseases (CNDs). New long-term integrated DH-care approaches, including rehabilitation, are warranted to address these concerns. Methods: The Human Empowerment Aging and Disability (HEAD) rehabilitation program, a new long-term integrated care including DH-care system, was evaluated in terms of efficiency and patient-reported outcome measures (PROMs) in 107 CND patients (30 with Parkinson's Disease, PD; 32 with Multiple Sclerosis, MS; 45 with stroke in chronic stage). All participants followed 1-month of HEAD rehabilitation in clinic (ClinicHEAD: 12 sessions, 3/week), then 1:3 patient was consecutively allocated to 3-months telerehabilitation at home (HomeHEAD: 60 sessions, 5/week). Efficiency (i.e., adherence, usability, and acceptability) and PROMs (i.e., perceived functioning in real-world) were analyzed. Results: The rate of adherence to HEAD treatment in clinic (≥90%) and at home (77%) was high. Usability of HEAD system was judged as good (System Usability Scale, median 70.00) in clinic and even more at home (median 80.00). Similarly, administering the Technology Acceptance Model 3 questionnaire we found high scores both in clinic/at home (Usefulness, mean 5.39 ± 1.41 SD/mean 5.33 ± 1.29 SD; Ease of use, mean 5.55 ± 1.05 SD/ mean 5.45 ± 1.17 SD, External Control, mean 4.94 ± 1.17 SD/mean 5.07 ± 1.01 SD, Relevance, mean 5.68 ± 1.29 SD/mean 5.70 ± 1.13 SD and Enjoyment, mean 5.70 ± 1.40 SD/mean 6.01 ± 1.08 SD). After ClinicHEAD, participation and autonomy in daily routine was maintained or even ameliorated (PD and stroke > MS). Whereas, increased functionality and participation in the MS group was found only after HomeHEAD intervention. Discussion: Our results suggest that a tele-health-based approach is both feasible and efficient in providing rehabilitation care to CNDs from clinic to home. Increasing and maintaining participation as well as autonomy in daily routine are promising findings that open up scenarios for the continuity of care at home through DH-care for CNDs.

Numerical Activities of Daily Living - Financial (NADL-F): A tool for the assessment of financial capacities ‡.

Financial capacity is the ability to manage one's own finances according to self-interests. Failure in financial decisions and lack of independence when dealing with money can affect people's quality of life and are associated with neuropsychological deficits or clinical conditions such as mild cognitive impairment or Alzheimer's disease. Despite the importance of evaluating financial capacity in the assessment of patients with neuropsychological and psychiatric disorders, only a few tools have been developed. In the present article, the authors introduce the Numerical Activities of Daily Living - Financial (NADL-F) test, a new test to assess financial capacity in clinical populations. The NADL-F is relatively short, yet it encompasses the most common activities involving financial capacities. The NADL-F proved to have satisfactory psychometric properties and overall good validity for measuring financial abilities. Associations with performance on basic neuropsychological tests were investigated, in particular focusing on mathematical abilities as cognitive correlates of financial capacity. Results indicate that the NADL-F could be a useful tool to guide treatments for the enhancement of financial capacities. By sharing all materials and procedures, the authors hope to promote the development of further versions of the NADL-F in different languages, taking into account the necessary adjustments related to different socio-cultural contexts.

Defending the Body Without Sensing the Body Position: Physiological Evidence in a Brain-Damaged Patient With a Proprioceptive Deficit.

The ability to know where our body parts are located in space (proprioception) is fundamental for both successfully interacting with the external world and monitoring potential threats. In this case-control study, we investigated whether the absence of proprioceptive signals may affect physiological defensive responses. To this aim, a right brain-damaged patient with a left upper-limb proprioceptive deficit (P+ patient) and age-matched healthy controls, underwent the recording of the Hand-Blink Reflex (HBR). This defensive response, elicited by electrical stimulation of the median nerve and recorded from the orbicularis oculi, is modulated by the hand position: it is enhanced when the threatened hand is near to the face, inside the defensive peripersonal-space (DPPS). According to the classical neuropsychological perspective, we used P+ patient as a model to investigate the role of proprioception in HBR modulation, by manipulating the congruity/incongruity between the intended and actual positions of the stimulated hand. P+ patient, with his eyes closed, had to voluntarily place his left hand either far from or near to his face and to relieve the arm's weight over a supporting device. Then, in congruent conditions, the hand was stimulated in the actual (intended) position. In incongruent conditions, the patient's hand was moved by the examiner from the intended to the opposite (not-intended) position and then stimulated. We observed an inverse response pattern between congruent and incongruent conditions. In congruent conditions, P+ patient showed an HBR enhancement in near compared to far position, comparable to that found in healthy controls. This suggests that, even in absence of proprioceptive and visual information, the HBR modulation was still present. Conversely, in incongruent conditions, P+ patient showed a greater HBR magnitude for far position (when the hand was actually far, but the patient intended it to be near) than for near position (when the hand was actually near, but the patient intended it to be far). This result suggests that proprioceptive signals are not necessary for HBR modulation to occur. It relies more on the intended than on the actual position of the hand. The role of motor intention and planning in shaping the DPPS is discussed.

Feeling touch on the own hand restores the capacity to visually discriminate it from someone else' hand: Pathological embodiment receding in brain-damaged patients.

The sense of body ownership, i.e., the belief that a specific body part belongs to us, can be selectively impaired in brain-damaged patients. Recently, a pathological form of embodiment has been described in patients who, when the examiner's hand is located in a body-congruent position, systematically claim that it is their own hand (E+ patients). This paradoxical behavior suggests that, in these patients, the altered sense of body ownership also affects their capacity of visually discriminating the body-identity details of the own and the alien hand, even when both hands are clearly visible on the table. Here, we investigated whether, in E+ patients with spared tactile sensibility, a coherent body ownership could be restored by introducing a multisensory conflict between what the patients feel on the own hand and what they see on the alien hand. To this aim, we asked the patients to rate their sense of body ownership over the alien hand, either after segregated tactile stimulations of the own hand (out of view) and of the alien hand (visible) or after synchronous and asynchronous tactile stimulations of both hands, as in the rubber hand illusion set-up. Our results show that, when the tactile sensation perceived on the patient's own hand was in conflict with visual stimuli observed on the examiner's hand, E+ patients noticed the conflict and spontaneously described visual details of the (visible) examiner's hand (e.g., the fingers length, the nails shape, the skin color…), to conclude that it was not their own hand. These data represent the first evidence that, in E+ patients, an incongruent visual-tactile stimulation of the own and of the alien hand reduces, at least transitorily, the delusional body ownership over the alien hand, by restoring the access to the perceptual self-identity system, where visual body identity details are stored.

Are movements necessary for the sense of body ownership? Evidence from the rubber hand illusion in pure hemiplegic patients.

A question still debated within cognitive neuroscience is whether signals present during actions significantly contribute to the emergence of human's body ownership. In the present study, we aimed at answer this question by means of a neuropsychological approach. We administered the classical rubber hand illusion paradigm to a group of healthy participants and to a group of neurological patients affected by a complete left upper limb hemiplegia, but without any propriceptive/tactile deficits. The illusion strength was measured both subjectively (i.e., by a self-report questionnaire) and behaviorally (i.e., the location of one's own hand is shifted towards the rubber hand). We aimed at examining whether, and to which extent, an enduring absence of movements related signals affects body ownership. Our results showed that patients displayed, respect to healthy participants, stronger illusory effects when the left (affected) hand was stimulated and no effects when the right (unaffected) hand was stimulated. In other words, hemiplegics had a weaker/more flexible sense of body ownership for the affected hand, but an enhanced/more rigid one for the healthy hand. Possible interpretations of such asymmetrical distribution of body ownership, as well as limits of our results, are discussed. Broadly speaking, our findings suggest that the alteration of the normal flow of signals present during movements impacts on human's body ownership. This in turn, means that movements have a role per se in developing and maintaining a coherent body ownership.

When your arm becomes mine: pathological embodiment of alien limbs using tools modulates own body representation.

Previous evidence has shown that active tool-use can reshape one's own body schema, extend peripersonal space and modulate the representation of related body parts. Here we investigate the effect of tool-use training on length representation of the contralesional forearm in brain-damaged hemiplegic patients who manifested a pathological embodiment of other people body parts. Four patients and 20 aged-matched healthy-controls were asked to estimate the mid-point of their contralesional forearm before and after 15 min of tool-use training (i.e. retrieving targets with a garbage plier). In the case of patients, training was always performed by the examiner's (alien) arm acting in two different positions, aligned (where the pathological embodiment occurs; E+ condition) or misaligned (where the pathological embodiment does not occur; E- condition) relative to the patients' shoulder. Healthy controls performed tool-use training either with their own arm (action condition) or observing the examiner's arm performing the task (observation condition), handling (observation with-tool condition) or not (observation without-tool condition) a similar tool. Crucially, in the E+ condition, when patients were convinced to perform the tool-use training with their own paralyzed arm, a significant overestimation effect was found (as in the Action condition with normal subjects): patients mislocated their forearm midpoint more proximally to the hand in the post- than in the pre-training phase. Conversely, in the E- condition, they did not show any overestimation effect, similarly to healthy subjects in the observation condition (neither in the with-tool nor in the without-tool condition significant overestimation effects were found). These findings show the existence of a tight link between spatial, motor and bodily representations and provide strong evidence that a pathological sense of body ownership can extend to intentional motor processes and modulate the sensory map of action-related body parts.

Drawing perseveration in neglect: effects of target density.

In cancellation tasks, patients with unilateral spatial neglect typically fail to mark targets within the side of the sheet contralateral to the side of the lesion (contralesional). Moreover, they can show a perseverative behaviour, which consists in repeatedly cancelling stimuli, mainly in the side of the display ipsilateral to the side of the lesion (ipsilesional). We investigated in 13 right-brain-damaged patients with left spatial neglect and perseverative behaviour whether and how different densities of horizontal targets modulated omission and perseverative errors. We found that the density of targets modulated the patients' distribution of neglect (area of omission), but not its extent, as indexed by the percentage of omissions. Specifically, the area of omissions tightened when target density increased leftwards. On the other hand, target density did not affect the distribution of perseverative behaviour (area of perseveration), as well as its extent, as indexed by the percentage of perseverations. Correlation analyses showed that both the extent and the distribution of omissions were positively correlated to clinical measures of spatial neglect. Conversely, perseverations did not show such a correlation. These findings support the view that two different pathological mechanisms might be involved in left spatial neglect and in ipsilesional perseverative behaviour.