Differential influence of habitual third-person vision of a body part on mental rotation of images of hands and feet.

Left/right judgement (LRJ) tasks involve determining the laterality of presented hand or feet images. Allocentric images (third-person perspective; 3PP) take longer to identify than egocentric images (first-person perspective; 1PP), supporting that implicit motor imagery (IMI)-mentally manoeuvring one's body to match the shown posture-is used. While numerous cognitive processes are involved during LRJs, it remains unclear whether features of the individual (e.g., visual exposure, experience, task-dependent use) influence the type of recognition strategy used during LRJs (IMI versus non-IMI). To investigate whether an individual's routine visual exposure to hands/feet in 3PP disrupts the typical perspective-reaction time (RT) relationship in LRJs, hand therapists, podiatrists, and healthy controls completed online LRJ tasks of hand and feet images. A group-specific reduction in RT for only allocentric images would represent a switch to non-IMI strategies. The results show that routine visual exposure to feet in 3PP (podiatrists) results in quicker RTs only for allocentric images of feet, suggesting a switch from IMI to non-IMI (e.g., visual object-based recognition) strategies. In contrast, routine visual exposure to hands in 3PP (hand therapists) does not alter RT for allocentric images, suggesting maintenance of IMI. However, hand therapists have quicker RTs (vs other groups) for egocentric hand images, supporting enhanced sensorimotor processing for the hand, consistent with task-dependent use (precise hand use). Higher accuracy in health professionals (vs control) on both tasks supports enhanced body schema. Combined, this suggests that 3PP visual exposure to body parts and task-dependent use contribute to LRJ performance/recognition strategy.

The development of a shoulder specific left/right judgement task: Validity & reliability.

BACKGROUND: Disruption of cortically-held working body schema has been associated with a variety of pain conditions. A motor imagery technique - the left right judgement task (LRJT) - has been used as an indirect assessment of the integrity of the working body schema. To date there is no LRJT specifically designed to investigate the body schema of persons with shoulder pain. OBJECTIVES: To develop a shoulder specific LRJT and assess its validity and reliability. DESIGN: Cross-sectional repeated measures. METHODS: Shoulder images were developed representing the shoulder in a variety of postures of graded complexity/awkwardness and degree of rotation. These images were digitally mirrored to represent both left and right shoulders. Participants viewed the images on a computer and determined whether images were of a left or right shoulder. RESULTS: 1413 participants were recruited worldwide and performed the shoulder LRJT (laterality judgement). Mean response time (SD) for the task was 1738(741) ms. Mean accuracy (SD) was 93.5(9.2)%. Chronbach's Alpha for shoulder image response times was 0.95. Participants were fastest responding to images of simple postures and slowest to images corresponding to the more awkward postures (mean difference 520 ms, 95%CI 469-570 ms). Participants were fastest responding to the least rotated images and slowest responding to inverted images, (mean difference 981 ms, 95%CI 919-1043 ms). CONCLUSIONS: The shoulder specific LRJT proved to be highly reliable. Response times increased with complexity and rotation of images, implying a motor imagery strategy was used to complete the task, validating the task as a measure of shoulder joint implicit motor imagery. Abnormal performance cut-offs for age were reported. This result will enable further research examining the relationship between shoulder pain and body schema.

Left/right neck rotation judgments are affected by age, gender, handedness and image rotation.

Understanding motor imagery of the hands and feet has led to promising new treatments for neurological and chronic pain disorders. We aimed to extend this line of research to the neck with a view to developing the definitive platform study upon which clinical and experimental studies can be based. In a cross-sectional experiment with a convenience sample, volunteers were shown 40 photographs of a model with their head turned to the left or right. Images were presented in random order and orientation. Participants judged the direction of neck rotation. They also completed a left/right hand judgment task. 1361 pain-free participants volunteered. Mean ± standard deviation response time (RT) for making left/right judgments of neck rotation was 1.621 ± 0.501 s. Median accuracy was 92.5%. RT was related to age, gender, and handedness (p < 0.001). That is, RT increased with age, was greater in females than in males and was greater in left-handers than in right-handers. Accuracy reduced with age (p < 0.001), but was unaffected by gender or handedness. Judgments were more accurate when images showed a neck rotated to the right than when they showed a neck rotated to the left (p < 0.001). The magnitude of image rotation affected both response time and accuracy (p < 0.001). In general, the performance parameters established for left/right limb judgments also apply for left/right neck rotation judgments. The current work establishes the definitive normative values against which clinical and experimental groups can be compared and reveals unpredicted effects of the direction neck rotation and the orientation of the image.