Attention-control deficits and their impact upon motor deficits in stroke

Abstract

Background: Motor impairment and attention deficits are common in stroke. Little is known about how a patient’s attentional capacity influences their motor function, motor-learning and recovery. This relationship may present a target for rehabilitation. This thesis aimed to: 1) survey the prevalence of attention deficits following stroke; 2) investigate the relationship between attention deficits and motor performance; 3) assess how the attention and motor profile of patients related to lesion location and disruption of functional brain networks; and 4) to develop and test a practical tool that allows for measurement and rehabilitation of attention-motor deficits in combination.

Methods: Study 1: Anatomically-unselected stroke patients performed the Attention Network Task, a sensitive measure of attention, with performance related to lesion anatomy. Study 2: Stroke patients and controls were tested on a novel visuomotor tracking task, with variable distractors, using a commercially available hand-grip controller. Relationships between motor-tracking performance and distractibility were determined, as were the dependency of these behavioural measures on lesion location and functional network integrity. Study 3: A separate group of subjects performed a visumotor tracking task while functional MRI was obtained. Performance and motor-learning was related to changes in resting-state networks before and after the task. Study 4: A novel portable hand-grip and variant of the visuomotor tracking task were designed and developed for bedside assessment and rehabilitation. The novel system was tested on hemiparetic patients, and its accessibility was compared with existing mobile gaming technologies.

Results: Study 1: A majority of stroke patients showed attention deficits, especially attention-control deficits; even though a far smaller proportion showed attentional-neglect on standard bedside tests. Attention-control impairments were seen equally with lesions to subcortical, premotor and prefrontal cortices. Study 2: Motor performance was closely related to attention-control performance. This was dependent upon lesion location and interference with both attention-control and motor network connectivity. Study 3: The visuomotor task influenced changes in connectivity of visuo-spatial, sensorimotor and cerebellar resting-state networks. These differed between patient and controls, and related to motor-learning. Study 4: A significantly greater proportion of hemiparetic patients – particularly those with a severe motor deficit - could engage with our novel attention-motor trainer than existing technologies.

Conclusions: This work provides evidence that attention deficits frequently accompany stroke and have a significant effect on a patient’s motor ability and recovery potential. Variability in patients’ motor function can be accounted for by lesions that damage both corticospinal and attention-control systems. A novel portable electronic device, designed as part of the PhD, allows for both testing and training of motor stroke patients, for both their motor and related attention deficits.