I’m Only Paralysed In Your Eyes - the Clinico-anatomical Heterogeneity of Post-stroke Anosognosia and its Treatment
Speaker: Dr Aikaterini Fotopoulou, Institute of Psychiatry
15TH MARCH 2012
Background. According to the ‘embodied cognition’ approach in psychology and cognitive neuroscience, several facets of cognition, including self-awareness, are causally related to the physical body. The embodied self includes the body’s physical properties as the ‘object’ of my awareness (the ‘Me’) and the body as a ‘subjective’ knower and agent capable of initiating action in the world (the “I”). Related notions are the concepts of body ownership (‘I am the subject of a movement’, or that ‘I am experiencing a certain sensation like touch’) and of body agency (‘I am the cause or author of a movement and its consequences in the world’). Despite vast progress in understanding the psychological and neural basis of the bodily self in recent studies with healthy participants, neurological disorders of the bodily self remain uniquely valuable sources of insight. In particular, when right hemisphere stroke causes paralysis, striking delusions concerning the paralysed limbs may also occur. The study of ‘anosognosia for hemiplegia’ (AHP; the apparent unawareness of paralysis) and somatoparaphrenia (the belief that one's limbs belong to someone else) can provide unique insight into the mechanisms and experience of action awareness and body ownership, respectively
Methods. Unfortunately, experimental investigations of such phenomena are scarce. I will present single-case and group studies using novel bedside, experimental approaches and lesion mapping to reveal the neuroanatomical basis of the sensorimotor, cognitive and emotional mechanisms mediating these counterintuitive syndromes. I will place emphasis on the following questions (1) Does faulty motor intention or faulty sensory feedback influence action awareness? (2) Do 1st and 3rd person visual perspectives on the body dissociate? (3) Does implicit and explicit awareness dissociate? Methods include creating visual illusions of movement via realistic rubber-hands and providing sensorimotor feedback via video recordings and mirror-viewing
Results and Discussion. The results suggest that implicit awareness may be linked with the generation of motor intentions, as mediated by intact premotor brain regions. These forward signals may have a profound influence on the on-line representation of one’s actions. Other lesions in cortical and subcortical areas, e.g. insula, basal ganglia, parietal cortex and the limbic system may be linked with explicit unawareness. Body ownership is differentially influenced by 1st and 3rd perspectives on the body and the latter can be used as simple, non-invasive and cheap psychophysical manipulations that can cause unprecedented symptom reversal in post-stroke symptoms previously considered intractable. This work offers potential for a major emphasis change in clinical treatment of higher-order deficits following stroke. I will discuss the potential transition from behavioral adaptation and psychological adjustment to targeted cognitive and behavioural training capable of leading to structural and functional reorganisation and `plasticity'.
Dr Aikaterini Fotopoulou was a Senior Lecturer in Cognitive Neuroscience and Neuropsychology at King’s College. She now heads the Katlab at UCL.