Spatial Working Memory Deficits Represent a Core Challenge for Rehabilitating Neglect

Abstract

Left neglect following right hemisphere injury is a debilitating disorder that has proven extremely difficult to rehabilitate. Traditional models of neglect have focused on impaired spatial attention as the core deficit and as such, most rehabilitation methods have tried to improve attentional processes. However, many of these techniques (e.g., visual scanning training, caloric stimulation, neck muscle vibration) produce only short-lived effects, or are too uncomfortable to use as a routine treatment. More recently, many investigators have begun examining the beneficial effects of prism adaptation for the treatment of neglect. Although prism adaptation has been shown to have some beneficial effects on both overt and covert spatial attention, it does not reliably alter many of the perceptual biases evident in neglect. One of the challenges of neglect rehabilitation may lie in the heterogeneous nature of the deficits. Most notably, a number of researchers have shown that neglect patients present with severe deficits in spatial working memory (SWM) in addition to their attentional impairments. Given that SWM can be seen as a foundational cognitive mechanism, critical for a wide range of other functions, any deficit in SWM memory will undoubtedly have severe consequences. In the current review we examine the evidence for SWM deficits in neglect and propose that it constitutes a core component of the syndrome. We present preliminary data which suggest that at least one current rehabilitation method (prism adaptation) has no effect on SWM deficits in neglect. Finally, we end by reviewing recent work that examines the effectiveness of SWM training and how SWM training may prove to be a useful avenue for future rehabilitative efforts in patients with neglect.

Prism adaptation treatment to address spatial neglect in an intensive rehabilitation program: A randomized pilot and feasibility trial

“…Moreover, patients in the BIR Program received 30-minute daily computer-assisted cognitive training on RehaCom (Hasomed, Magdeburg, Germany) and CogniPlus (Schuhfried, Moedling, Austria) platforms. These cognitive training sessions were designed to target the core cognitive deficits in domains such as spatial attention and spatial working memory through computerized optokinetic stimulation [ 62 ] or training for spatial working memory (for discussion of association between spatial neglect and spatial working memory, see [ 65 ]). In addition, twice daily physiotherapy sessions in the BIR Program usually involved limb activation (with the help of physiotherapist and/or robotic systems) which was found to reduce spatial neglect even when performed passively [ 66 ].…”

Modulation of visual attention by prismatic adaptation

“…For visuo-spatial working memory, tested with a delayed match-to sample design, it yielded a bilateral decrease in activation (Crottaz-Herbette et al, 2014) within regions known to be specifically involved in this task (Ackerman and Courtney, 2012;Awh et al, 1995;Chang et al, 2007;Courtney et al, 1998;Crottaz-Herbette et al, 2004;Sala and Courtney, 2007). This is of interest, because the spatial working memory network was shown to be coextensive with the dorsal attentional network, which sustains voluntary attentional orienting LaBar et al, 1999) and is often impaired in neglect (Husain et al, 2001;Striemer et al, 2013). Comparing fMRI activation patterns yielded by a target detection task before and after a single brief session of prismatic adaptation in 15 neglect patients highlighted a very similar PA-related modulation (Fig.…”

Neural Markers Associated with the Temporal Deployment of Attention: A Systematic Review of Non-motor Psychophysical Measures Post-stroke

“…This is especially important when attempting to understand everyday functional deficits post-stroke, where the difficulties faced by neglect patients in representing their environment, for example, are due to poor spatiotemporal representations. The universality between the deployment of attention over a time course, and in space, may very well-explain why attentional deployment becomes gradually prolonged from non-neglected to neglected space (Di Pellegrino et al, 1998 ; Hillstrom et al, 2004 ), as well as why spatial working memory deficits are known to have a temporal component (i.e., due to the inability to keep track of spatial information over the course of time; Ferber and Danckert, 2006 ; Striemer et al, 2013 ). In fact, it could be the case that the temporal deployment of attention is an underlying factor that drives neglect behavior, such that when deployment speed becomes slow, it reaches a threshold where spatial symptoms of neglect begin to manifest.…”