Effects of Hand Orientation on Motor Imagery - Event Related Potentials Suggest Kinesthetic Motor Imagery to Solve the Hand Laterality Judgment Task

Abstract

Motor imagery (MI) refers to the process of imagining the execution of a specific motor action without actually producing an overt movement. Two forms of MI have been distinguished: visual MI and kinesthetic MI. To distinguish between these forms of MI we employed an event related potential (ERP) study to measure interference effects induced by hand orientation manipulations in a hand laterality judgement task. We hypothesized that this manipulation should only affect kinesthetic MI but not visual MI. The ERPs elicited by rotated hand stimuli contained the classic rotation related negativity (RRN) with respect to palm view stimuli. We observed that laterally rotated stimuli led to a more marked RRN than medially rotated stimuli. This RRN effect was observed when participants had their hands positioned in either a straight (control) or an inward rotated posture, but not when their hands were positioned in an outward rotated posture. Posture effects on the ERP-RRN have not previously been studied. Apparently, a congruent hand posture (hands positioned in an outward rotated fashion) facilitates the judgement of the otherwise more demanding laterally rotated hand stimuli. These ERP findings support a kinesthetic interpretation of MI involved in solving the hand laterality judgement task. The RRN may be used as a non-invasive marker for kinesthetic MI and seems useful in revealing the covert behavior of MI in e.g. rehabilitation programs.

Children with unilateral cerebral palsy show diminished implicit motor imagery with the affected hand

“…Previous ERP studies have shown that mental rotation is accompanied by a negative-going amplitude modulation of the late-latency ERP components. [10][11][12] This modulation has been referred to as rotation-related negativity (RRN) and has been observed in several mental rotation studies. 10,11 Interestingly, RRN is more pronounced for outward rotated stimuli than for inward rotated stimuli.…”

“…[10][11][12] This modulation has been referred to as rotation-related negativity (RRN) and has been observed in several mental rotation studies. 10,11 Interestingly, RRN is more pronounced for outward rotated stimuli than for inward rotated stimuli. 11,12 These findings suggest that RRN, similar to reaction time, is also modulated by biomechanical constraints.…”

“…10,11 Interestingly, RRN is more pronounced for outward rotated stimuli than for inward rotated stimuli. 11,12 These findings suggest that RRN, similar to reaction time, is also modulated by biomechanical constraints. 11,12 Only a few studies have investigated implicit motor imagery by means of EEG measurements in patient groups.…”

“…6,7 This rotation effect has been repeatedly replicated since. [10][11][12] In recent years, behavioral studies have emerged that scrutinize the motor imagery ability of individuals with CP. [13][14][15] It was concluded that although adolescents with CP are able to engage in mental rotation, the implicit motor imagery capacity seemed to be compromised.…”

“…Extracting eventrelated potentials (ERPs) from the ongoing electroencephalogram (EEG), however, provides an excellent means to directly study the neural responses associated with implicit motor imagery. 11,12 ERP components are typically divided into two types, based on their respective latencies. Components with latencies of up to 100ms are referred to as exogenous components, 16 whereas the endogenous components (>100ms after stimulus onset) are assumed to be determined by cognitive aspects of information processing.…”