Cerebral activation during visual stimulation of mirrored hand movements in normal subjects and stroke patients

by Maddalena Brunetti

Institution: Freie Universität Berlin
Department: FB Erziehungswissenschaft und Psychologie
Degree: PhD
Year: 2015
Record ID: 1107376
Full text PDF: http://edocs.fu-berlin.de/diss/receive/FUDISS_thesis_000000099288


Stroke is the second leading cause of death worldwide and one of the leading causes for disability at advanced age. In about one third of the patients, stroke causes hemiplegia, complete paralysis of the upper limb. Low rates of complete recovery even after intensive rehabilitation procedures are probably due to the lack of appropriate therapy strategies for hemiplegic patients. The aim of the present thesis was to examine the underlying neuronal mechanisms of mirror therapy (MT) that creates a mirror illusion by placing a mirror in the mid-sagittal plane in front of the sitting patient, so that the patient sees the reflection of the movements of the non-affected limb as if they were movements from the affected one. Another therapy procedure implementing visual input in motor recovery is Video Therapy (VT) that is based on mere observation of a third person’s movements. It was hypothesized that the mirror neuron system (MNS) and the primary motor cortex (M1) might not be directly modulated by the mirror illusion, in contrast to precuneus (PC) and the primary somatosensory cortex (S1). PC plays a crucial role during the on-line control of hand movements and is part of a crucial node of the fronto-parietal network for planning and execution of visuo-motor tasks. S1 is known to be involved in motor learning and recovery. Moreover, it was suggested that VT and MT elicit different activation patterns. Beyond that, an exploratory examination was conducted to determine if the lateralized precuneal activation observed in normal subjects might be likewise observable in stroke patients or if it differs on a single-subject level or due to pathological factors. Finally, on the basis of the results of healthy controls, it was hypothesized that the lateralized precuneal activation due to the mirror illusion might be a determining factor to classify MT responders and non-responders. The methods of choice were functional near-infrared-spectroscopy (fNIRS) as well as functional magnetic resonance imaging (fMRI). Different activation patterns underlying MT and VT were found. While MT elicits lateralized precuneal activation always contralateral to the observed hand, this was not found during VT. Furthermore, the results demonstrate dissociated lateralization patterns on different ROIs: Activity in M1 is lateralized opposite to the moving hand and in PC opposite to the visually perceived hand, independent of each other. For S1 lateralization changed from ipsilateral to symmetrical, for the left hand only. Moreover, it is confirmed that the mirror illusion does not modulate the MNS. Beyond that, lateralized precuneal activation due to mirror illusion is similarly observed in stroke patients and seems to be a potential candidate for determination of MT efficacy additionally to motor functional base level of the affected hand. It is concluded that MT operates by inverting the interhemispheric imbalance in favor of the affected hemisphere across PC. Thereby, PC seems to be an intermediary structure that receives and processes the…