Neuroanatomical and behavioural factors associated with the effectiveness of two weekly sessions of prism adaptation in the treatment of unilateral neglect

ABSTRACT

Among the different interventions to alleviate the symptoms of unilateral neglect, prism adaptation (PA) appears especially promising. To elucidate the contribution of some neuroanatomical and behavioural factors to PA’s effectiveness, we conducted a study combining neuropsychological and lesion mapping methods on a group of 19 neglect patients who underwent two sessions of PA during one week and assessed their improvement relative to the baseline until the following week (7–8 days later). Correlation analyses revealed a significant positive relationship between the magnitude of the proprioceptive after-effect and the improvement at the follow-up session in two perceptual tasks requiring motor responses. Conversely, no correlation was found between the proprioceptive after-effect and the improvement in a perceptual task with no motor involvement. This finding suggests that patients’ potential to show a prism-related improvement in motor-related tasks might be indicated by the strength of their proprioceptive response (proprioceptive after-effect). As for the neuroanatomical basis of this relationship, subtraction analyses suggested that patients’ improvement in perceptual tasks with high motor involvement might be facilitated by the integrity of temporo-parietal areas and the damage of frontal and subcortical areas.

KEYWORDS:

• Unilateral neglect
• Prism adaptation
• Cancellation tasks
• Landmark task
• Lesion analysis

Acknowledgements

M.G.-H. was supported by grants from the Bavarian Elite Aid Act and the Graduate School of Systemic Neurosciences. This work was funded with financial resources from the former Neuropsychology Clinic of the City Hospital Bogenhausen and the ReHa-Hilfe e.V. The authors are grateful to Professor Masud Husain, Professor Georg Goldenberg, and Professor Stefan Glasauer for their valuable comments and suggestions. Furthermore, the authors would like to thank the patients and their families for their willingness to participate in our study, Dr Jürgen Herzog and Ms Stefanie Tucha from the Schön Klinik Schwabing for providing access to their patients, and Ms Stella Welter for dedication and assistance with data collection.

Disclosure statement

No potential conflict of interest was reported by the authors.

Notes

1 In an attempt to provide statistical evidence for the subtraction data, binary voxel-based lesion-symptom mapping analyses (VLSM) were conducted by means of the Liebermeister test. As for the uncorrected statistical maps (p < .05), the results obtained resembled those of the maximal subtraction lesion overlaps. However, when narrowing the analyses to voxels damaged in at least one patient and applying FDR correction, none of the results remained significant. This could be explained by the small size of the patients’ sample. It has been suggested that a large number of observations (minimum 20) is required to survive multiple comparison correction (Timmann et al., 2009).