Mental rotation of hands and objects in ageing and Parkinson's disease: differentiating motor imagery and visuospatial ability.

Motor imagery supports motor learning and performance and has the potential to be a useful strategy for neurorehabilitation. However, motor imagery ability may be impacted by ageing and neurodegeneration, which could limit its therapeutic effectiveness. Motor imagery can be assessed implicitly using a hand laterality task (HLT), whereby laterality judgements are slower for stimuli corresponding to physically more difficult postures, as indicated by a "biomechanical constraint" effect. Performance is also found to differ between back and palm views of the hand, which may differentially recruit visual and sensorimotor processes. Older adults and individuals with Parkinson's disease (PD) have shown altered performance on the HLT; however, the effects of both ageing and PD on laterality judgements for the different hand views (back and palm) have not been directly examined. The present study compared healthy younger, healthy older, and PD groups on the HLT, an object-based mental rotation task, and an explicit motor imagery measure. The older and PD groups were slower than the younger group on the HLT, particularly when judging laterality from the back view, and exhibited increased biomechanical constraint effects for the palm. While response times were generally similar between older and PD groups, the PD group showed reduced accuracy for the back view. Letter rotation was slower and less accurate only in the PD group, while explicit motor imagery ratings did not differ significantly between groups. These results suggest that motor imagery may be slowed but relatively preserved in both typical ageing and neurodegeneration, while a PD-specific impairment in visuospatial processing may influence task performance. The findings have implications for the use of motor imagery in rehabilitation protocols.

Illuminating sex differences in mental rotation using pupillometry.

We use pupillometry to measure sex differences in mental rotation (MR) and to investigate the contentious claim that it is a unique spatial ability marked by male advantage in performance. Across two MR tasks - using Shepard-Metzler style cube figures and images of human hands - we measure reaction time (RT) and sensitivity, d', and supplement these behavioural data with a physiological metric of 'cognitive effort', pupil diameter. Differences in RT and in d' between the sexes are slight for the cubes task, while females are consistently faster than males on the hands task. In contrast, pupillometry reveals striking a sex difference, with males showing significantly lower pupil dilation during the cubes task, suggesting less cognitive effort for comparable behavioural performance. This difference is attenuated during the MR of hands, in line with recent findings that sex differences in spatial abilities dissipate when elements of social perspective taking are introduced. Taxonomy: Attention, Perception.