A Randomised Controlled Study of Early vs. Late, and Unisensory vs. Multisensory Rehabilitation for Stroke Patients With Perceptual and Cognitive Impairments.

Stroke is one of the major causes of death worldwide, second only to coronary disease, and it is the leading cause of disability with patients needing long hospitalisation and long-term community care (Mackay, Mensah, Mendin, & Greenlund, 2004). Stroke patients with perceptual and cognitive impairments such as unilateral neglect are of particular concern as they have among the worst prognostic outcomes (Di Monaco et al., 2011; Narasimhalu et al., 2011). Unilateral neglect, commonly observed after brain damage of the right posterior parietal cortex, is most often associated with reduced awareness of visual or auditory stimuli presented to the contralesional (left) side of space (Humphreys & Riddoch, 2001), particularly in the presence of competing stimuli on the ipsilesional (right) side (i.e., extinction) (Humphreys, Romani, Olson, Riddoch, & Duncan, 1994). This can manifest as a failure to cancel lines on one side of a page ('neglect'). In milder cases the patient can detect a single stimulus on the contralesional side but fails to detect the same item when another item is presented simultaneously on the ipsilesional side ('extinction'). Currently there is no consensus about optimal training strategies to alleviate neglect and extinction, therefore, it remains important to attempt to develop new procedures that are effective in the medium to long-term, that generalise outside the clinic and that are clinically applicable.

Multisensory integration is a potentially important vehicle for neurorehabilitation because it is known to generate large facilitative effects on information processing across a wide range of individuals. For example, motor reaction times (RTs) are significantly faster (Barutchu, Crewther, & Crewther, 2009; Barutchu, Freestone, Innes-Brown, Crewther, & Crewther, 2013), and perceptual sensitivities (Stein, London, Wilkinson, & Price, 1996), working memory and learning (e.g., Shams & Seitz, 2008), are enhanced in response to spatially and temporally synchronous multisensory stimuli when compared with stimuli presented in a single sensory modality. In addition, multisensory integration can be used to compensate for unisensory decline in the elderly by restoring motor function to levels generally observed in younger adults (e.g., Laurienti, Burdette, Maldjian, & Wallace, 2006). Critically, recent evidence suggests that some stroke patients in general may benefit from early post-stroke rehabilitation (Bai et al., 2012), and that some stroke patients with heminopia can benefit from multisensory integration (e.g., Passamonti, Bertini, & Ladavas, 2009). These studies have also demonstrated that multisensory rehabilitation strategies can have long lasting effects up to 1 year after initial training, and that improvements can generalize to other daily activities, such as reading. However, it is unknown whether these findings can be generalized to other types of perceptual and cognitive impairments. This study will be the first to investigate the combined long-term effects of multisensory signals and establish when is it more effective to intervene during the acute or chronic stage of the disorder.

The aim of this project is to develop a novel approach to the remediation of neglect and extinction by comparing multisensory integration with unisensory integration, and determining whether it is best to intervene during the acute or chronic stage of the disorder. In addition, the project will investigate the neural underpinning of functional recovery in neglect patients, using fMRI.

The specific aims of this research project are:

• To assess if perception can be improved in stroke patients with unilateral neglect/extinction as a result of multi- or uni-sensory integration, how well training effects generalize to other tasks and their longevity when the rehabilitation is delivered in the acute stage vs. the chronic stage of the disorder.
• To evaluate, using functional magnetic resonance imaging (fMRI), adaptive changes and plasticity in brain networks following multisensory learning in patients with neglect/extinction, so that an understanding is gained of the neural mechanisms linked to functional recovery in neglect/extinction patients.