Motor imagery ability in stroke patients: the relationship between implicit and explicit motor imagery measures

Sjoerd De Vries,Hanneke Oosterveld,Wya Feenstra,Bert Otten,Anne M Boonstra,Marga Tepper

doi:10.3389/fnhum.2013.00790

Abstract

There is little consensus on how motor imagery ability should be measured in stroke patients. In particular it is unclear how two methods tapping different aspects of the motor imagery process relate to each other. The aim of this study was to investigate the relationship between implicit and explicit motor imagery ability by comparing performance of stroke patients and controls on a motor imagery questionnaire and a hand laterality judgment task (HLJT). Sixteen ischemic stroke patients (36 ± 13 weeks post-stroke) and 16 controls, matched by age (51 ± 10 years), gender (7 females) and handedness (3 left-handed), performed a HLJT and completed a motor imagery questionnaire. Our study shows that neither in the healthy controls nor in patients, a correlation is found between the HLJT and the motor imagery questionnaire. Although the patient group scored significantly lower than the control group on the visual motor imagery component (U = 60; p = 0.010) and the kinesthetic motor imagery component (U = 63.5; p = 0.015) of the questionnaire, there were no significant differences between patients and controls on accuracy scores of the HLJT. Analyses of the reaction time profiles of patients and controls showed that patient were still able to use an implicit motor imagery strategy in the HLJT task. Our results show that after stroke performance on tests that measure two different aspects of motor imagery ability, e.g., implicit and explicit motor imagery, can be differently affected. These results articulate the complex relation phenomenological experience and the different components of motor imagery have and caution the use of one tool as an instrument for use in screening, selecting and monitoring stroke patients in rehabilitation settings.

Highlights

The ability to imagine or simulate experiences is one of the most extraordinary capabilities of our mind
The present study addresses a specific question relating to measuring motor imagery ability in stroke patients, namely the question of how measures of implicit and explicit motor imagery relate to each other
DIFFERENCES IN IMAGERY ABILITY BETWEEN PATIENTS AND CONTROLS Patient group vs. control group Table 1 shows the results on the questionnaire and hand laterality judgment task (HLJT) for the group of patients and the group of controls

Summary

Introduction

The ability to imagine or simulate experiences is one of the most extraordinary capabilities of our mind. The use and explanation of the term motor imagery has led to substantial confusion about what the exact definition of motor, kinesthetic and visual imagery is and how these different perspectives are used by participants in practice. Considerable confusion arose whether internal kinesthetic imagery should be dissociated from internal visual imagery (see Hardy, 1997; Roberts et al, 2008 for a discussion). Several researcher have concluded, independently, that the kinesthetic and first person internal perspective are best measured with a separate subscale in self-report questionnaires, reflecting a consensus on a more differentiated approach to measuring motor imagery ability (Roberts et al, 2008; Williams et al, 2012)

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