Paul M. Jenkinson

Bodily pleasure matters: velocity of touch modulates body ownership during the rubber hand illusion

The sense of body ownership represents a fundamental aspect of our self-consciousness. Influential experimental paradigms, such as the rubber hand illusion (RHI), in which a seen rubber hand is experienced as part of ones body when ones own unseen hand receives congruent tactile stimulation, have extensively examined the role of exteroceptive, multisensory integration on body ownership. However, remarkably, despite the more general current interest in the nature and role of interoception in emotion and consciousness, no study has investigated how the illusion may be affected by interoceptive bodily signals, such as affective touch. Here, we recruited 52 healthy, adult participants and we investigated for the first time, whether applying slow velocity, light tactile stimuli, known to elicit interoceptive feelings of pleasantness, would influence the illusion more than faster, emotionally-neutral, tactile stimuli. We also examined whether seeing another persons hand vs. a rubber hand would reduce the illusion in slow vs. fast stroking conditions, as interoceptive signals are used to represent ones own body from within and it is unclear how they would be integrated with visual signals from another persons hand. We found that slow velocity touch was perceived as more pleasant and it produced higher levels of subjective embodiment during the RHI compared with fast touch. Moreover, this effect applied irrespective of whether the seen hand was a rubber or a confederates hand. These findings provide support for the idea that affective touch, and more generally interoception, may have a unique contribution to the sense of body ownership, and by implication to our embodied psychological “self.”

Unawareness after stroke: A review and practical guide to understanding, assessing, and managing anosognosia for hemiplegia

How should stroke patients with poor motor awareness be managed? This question is important because unawareness (or anosognosia) is related to poor rehabilitation and prognosis. This narrative review provides a guide for clinicians and (applied) academics to understanding, assessing and managing anosognosia. Questions addressed are: What is anosognosia? What causes anosognosia? How can anosognosia be assessed? And how can anosognosia be managed? We suggest that anosognosia is a multifaceted disorder, with diverse neuroanatomical and psychopathological origins. Assessment should measure various aspects of awareness, and management should be multidimensional to address problems with motor function, awareness, and emotional/motivational disturbance.

Body ownership and attention in the mirror: Insights from somatoparaphrenia and the rubber hand illusion

The brain receives and synthesises information about the body from different modalities, coordinates and perspectives, and affords us with a coherent and stable sense of body ownership. We studied this sense in a somatoparaphrenic patient and three control patients, all with unilateral right-hemisphere lesions. We experimentally manipulated the visual perspective (direct- versus mirror-view) and spatial attention (drawn to peripersonal space versus extrapersonal space) in an experiment involving recognising ones own hand. The somatoparaphrenic patient denied limb ownership in all direct view trials, but viewing the hand via a mirror significantly increased ownership. The extent of this increase depended on spatial attention; when attention was drawn to the extrapersonal space (near-the-mirror) the patient showed a near perfect recognition of her arm in the mirror, while when attention was drawn to peripersonal space (near-the-body) the patient recognised her arm in only half the mirror trials. In a supplementary experiment, we used the Rubber Hand Illusion to manipulate the same factors in healthy controls. Ownership of the rubber hand occurred in both direct and mirror view, but shifting attention between peripersonal and extrapersonal space had no effect on rubber-hand ownership. We conclude that the isolation of visual perspectives on the body and the division of attention between two different locations is not sufficient to affect body ownership in healthy individuals and right hemisphere controls. However, in somatoparaphrenia, where first-person body ownership and stimulus-driven attention are impaired by lesions to a right-hemisphere ventral attentional-network, the body can nevertheless be recognised as ones own if perceived in a third-person visual perspective and particularly if top-down, spatial attention is directed away from peripersonal space.

Motor awareness in anosognosia for hemiplegia: experiments at last!

Anosognosia for hemiplegia (AHP) is the apparent inability to acknowledge contralesional paralysis, typically following right-hemisphere lesions. Here, we review studies that regard AHP as a specific deficit of motor awareness and explain its symptoms by employing an established computational model of motor control. These accounts propose that AHP arises from a breakdown in the monitoring of intended and actual movement. First, we critically examine physiological and behavioural experiments, which attempt to provide an account of AHP by verifying the presence or absence of motor intentions. We then review more recent experiments that endeavour to empirically address the hitherto unexplored role of motor intentions and internal representations of movements in AHP patients’ non-veridical (illusory) awareness of movement. Finally, we consider implications of AHP research for clinical practice and the understanding of motor awareness more generally. We conclude that the false experience of movement in AHP may provide insight into what occurs when the mechanism responsible for monitoring and correcting significant discrepancies between predicted and executed actions is impaired. The system seems to continue to operate by deceiving awareness.

Contribution of the left dorsomedial thalamus to recognition memory: a neuropsychological case study.

This study reports a patient with a unilateral left thalamic lesion which was centred on the dorsomedial thalamic nucleus. Cognitive neuropsychological assessment revealed a severe impairment in verbal memory and symptoms of executive dysfunction, in the presence of relatively intact visual and facial recognition, working memory, praxis, language and IQ. Verbal and visual recognition memory were investigated using the remember-know paradigm. The results indicated a profound impairment in recollection-driven verbal recognition memory. These results are discussed in the context of the role of the dorsomedial thalamic nucleus in recognition memory, and functional models of memory.

Anosognosia for hemiplegia as a global deficit in motor awareness: evidence from the non-paralysed limb.

The current study adds to the growing empirical research into the mechanisms underlying unawareness of paralysis following stroke (anosognosia for hemiplegia or AHP) by investigating action awareness for the non-paralysed limb in a single AHP patient. Visual feedback representing patient GGs goal-directed reaching movements was either modified by a computer or left unperturbed. Unlike healthy and brain-damaged controls, GG was unable to detect computer-generated visual perturbations as large as 20°. GG also failed to report awareness of the large on-line corrective movements that he made when compensating (often unsuccessfully) for the visual perturbations. These results suggest that the motor comparators implicated in AHP are functioning, but not at optimum levels. Moreover, because the current findings reveal a deficit in awareness for reaches with the unimpaired limb, it is suggestive of common right hemisphere networks for motor awareness in both limbs and that AHP may be a global deficit in motor awareness as opposed to a specific lack of awareness for a particular motor deficit.

Why are some Parkinson disease patients unaware of their dyskinesias

ObjectiveTo test the hypothesis that anosognosia for dyskinesias in Parkinson disease (PD) results from a failure to detect discrepancies between intended and actual movement. BackgroundPD patients often complain of drug-induced dyskinesias (involuntary movements) less than their carers. This remarkable unawareness is an example of anosognosia (ie, unawareness of deficits associated with an illness). A better understanding of anosognosia for dyskinesias in PD is important to understand the impact of the illness and side effects of treatment. MethodsThe ability to detect a discrepancy between intended movement and visual feedback about actual movement was investigated in 6 PD patients with anosognosia for dyskinesias, 11 nonanosognosic PD controls with dyskinesias, and 22 healthy volunteers, using a mirror to reverse the expected visual consequences of an executed movement. ResultsNonanosognosic PD patients and healthy volunteers rated mirror-reversed movement as significantly stranger than normal movement (P=0.024 and <0.001, respectively), whereas PD patients with anosognosia for dyskinesias did not (P=0.375). ConclusionsThe findings support our proposal, in that PD patients with anosognosia for dyskinesias do not report mirror-reversed movement (in which intentions and visual feedback conflict) as feeling distinct from normal movement.

The affective modulation of motor awareness in anosognosia for hemiplegia: Behavioural and lesion evidence

The possible role of emotion in anosognosia for hemiplegia (i.e., denial of motor deficits contralateral to a brain lesion), has long been debated between psychodynamic and neurocognitive theories. However, there are only a handful of case studies focussing on this topic, and the precise role of emotion in anosognosia for hemiplegia requires empirical investigation. In the present study, we aimed to investigate how negative and positive emotions influence motor awareness in anosognosia. Positive and negative emotions were induced under carefully-controlled experimental conditions in right-hemisphere stroke patients with anosognosia for hemiplegia (n = 11) and controls with clinically normal awareness (n = 10). Only the negative, emotion induction condition resulted in a significant improvement of motor awareness in anosognosic patients compared to controls; the positive emotion induction did not. Using lesion overlay and voxel-based lesion-symptom mapping approaches, we also investigated the brain lesions associated with the diagnosis of anosognosia, as well as with performance on the experimental task. Anatomical areas that are commonly damaged in AHP included the right-hemisphere motor and sensory cortices, the inferior frontal cortex, and the insula. Additionally, the insula, putamen and anterior periventricular white matter were associated with less awareness change following the negative emotion induction. This study suggests that motor unawareness and the observed lack of negative emotions about ones disabilities cannot be adequately explained by either purely motivational or neurocognitive accounts. Instead, we propose an integrative account in which insular and striatal lesions result in weak interoceptive and motivational signals. These deficits lead to faulty inferences about the self, involving a difficulty to personalise new sensorimotor information, and an abnormal adherence to premorbid beliefs about the body.

Polymorphisms of the cannabinoid 1 receptor gene and cognitive impairment in multiple sclerosis

Cognitive impairment occurs in 45—65% of multiple sclerosis (MS) patients. The cannabinoid system may potentially be neuroprotective in MS. We examined the relationship between polymorphisms of the CNR1 gene and neuropsychological outcome in MS using a test and confirmatory sample of patients. One hundred and ninety-four MS patients were assessed over five key areas of neuropsychological function, which are most commonly impaired in MS. The first 97 patients formed the test sample. A further confirmatory sample of 97 patients was used to test association found in the test sample. The schedule included: Wisconsin card sorting test 64 version, Rey auditory verbal learning task immediate and delayed scores, controlled oral word association task, judgement of line orientation and symbol digit modalities task. Three single nucleotide polymorphisms (SNPs) were typed within the CNR1 gene. For the overall neuropsychological assessment score we used a multiple linear regression model with selected covariates to show that subjects with the AA genotype of the SNP RS1049353 were more impaired (mean -2.47, SD 5.75, P = 0.008, Bonferroni corrected P = 0.024) than the other subjects (mean 0.24, SD 4.24). This was not confirmed when the association was retested in the confirmatory sample. No associations were identified between these CNR1 variants and cognitive impairment in MS. Multiple Sclerosis 2008; 14: 177—182. http://msj.sagepub.com

Mentalizing the body: spatial and social cognition in anosognosia for hemiplegia

Patients with anosognosia for hemiplegia after right-hemisphere stroke deny the existence of contralesional motor deficits. Besharati et al. show that such patients are impaired in social cognition tasks requiring 3 rd person perspective-taking. A reduced ability to disengage from the 1 st person perspective may explain the patients’ reduced bodily self-awareness.