Sometimes very simple tasks are more complicated than we imagine. An example is the Left Right Judgement Task (LRJT). In this task individuals are shown images of body parts and they must decide if the image is of the left or right side of the body (or if it is turned to the left or right for the low back and neck). Often individuals with Musculoskeletal Disorders (MSD) demonstrate differences in performance in this task compared to persons without MSD . Why do individuals with MSD perform differently on this task? The LRJT is a cognitive task involving no overt movement and therefore the answer must lie somewhere in the brain.
Imaging studies of the LRJT demonstrate that the task is associated with activation of areas within the brain involved in integration of sensory information, motor planning and execution, as well as areas involved in cognitive processes [2-4]. This activation in areas of the brain is similar to when we actually perform the movement suggesting that making the judgement involves implicitly imagining moving our body into the same position as we see in the image. Even the primary motor cortex appears to be involved in the task as Transcranial Magnetic Stimulation of the motor regions of the brain affects LRJT performance [5, 6].
Differences in performance on the LRJT are often attributed to changes in the Body Schema, attentional bias, and/or cognitive processing . However, the imaging studies suggest that changes in any of the areas activated while performing the task may be implicated in changes in performance of the LRJT task. Indeed, people with MSD also demonstrate changes in sensory and motor performance as well as changes in cognitive function . There is evidence that activity in forebrain areas involved in emotional responses are also associated with pain and MSD . Thus, when we find differences in LRJT performance between individuals with and without MSD, these differences may also be related to any of the brain areas activated while performing the task including changes in cognitive and motor functions and areas involved in emotional responses related to pain and the injury/condition.
We performed two experiments involving the mental rotation task in persons with MSD of the wrist and hand (i.e arthritis of the thumb, fractures, tendinitis, De Quervain’s tenosynovitis …) [10, 11]. In the first experiment we were interested in determining the relationship between mental rotation task and motor performance, pain related measures and disability . We found that mental rotation task performance in participants with wrist/hand pain was decreased both for accuracy and reaction time. We found no association between the LRJT performance and pain severity, symptom duration or self reported disability. The LRJT was correlated with motor performance in the healthy control participants but not those with wrist/hand pain. Surprisingly, we did find that LRJT performance accuracy was positively correlated and reaction time was negatively correlated with a measure of affective distress. That is, higher levels of affective distress were associated with better performance. The major limitation of this study is that it only involved 15 participants in each group.
We have recently completed a study involving the mental rotation task in a larger sample of participants with heterogeneous wrist/hand pain . In this second study we measured cognitive function (concentration and motor imagery ability), motor (grip strength and dexterity), sensory (tactile acuity, pressure pain thresholds), proprioception (joint position sense), pain and pain related psychosocial aspects, and self reported disability. We found that a sizable portion of LRJT performance for the hands and the feet were explained by the cognitive factors, attention and motor imagery ability. In the affected hand only, accuracy in the mental rotation task was further explained by the addition of four other factors: tactile acuity, motor function, pain medication taken on the day of the evaluation, and participation in general activities. Poorer sensory and motor function were related to poorer mental rotation task accuracy.
These studies suggest that the LRJT is not simply a function of the Body Schema but is a complex mental task that is related to psychological factors such as distress and clinical measures of sensory, cognitive, and motor processes. Improvement in performance in this task and improvement in outcome measures associated with LRJT may be the result of changes in areas in the CNS implicated in these functions, all of which have been shown to be associated with pain and MSD. It is possible that the performance of the LRJT helps to improve cognitive processes, emotional regulation related to movements that may be painful, the integration of sensorimotor information, and/or the Body Schema. It is even possible that the LRJT helps to improve sensory and motor function that has been associated with mental processes such as motor imagery [12, 13].
We need further study to help decipher these processes associated with the LRJT and LRJT improvement and how these relate to the clinical measures of function/disability. This information will help us to better target those individuals with MSD who are good candidates for these cognitive driven exercises in addition to conventional rehabilitation treatments to help improve function and decrease pain and hopefully develop more efficacious treatments .
About René Pelletier
René is an osteopath who returned to do a PhD after more than 20 years of clinical practice. He has recently completed his PhD in Rehabilitation Science at the University of Montreal. His PhD research involved the study of neurophysiological changes associated with musculoskeletal injuries and conditions of the wrist/hand and how these were related to clinical measures of pain (pain intensity, symptom duration), psychosocial factors related to pain (i.e. life control, affective distress, pain interference …), self reported disability, and measures of sensory and motor function. He would like to continue to investigate how cognitive and emotional processes interact with sensory and motor areas of the brain in persons with and without musculoskeletal conditions and injuries. Secondly how these processes are related to clinical measures of motor and sensory function as well as disability.
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 Tomasino, B. and M. Gremese, Effects of Stimulus Type and Strategy on Mental Rotation Network: An Activation Likelihood Estimation Meta-Analysis. Front Hum Neurosci, 2015. 9: p. 693.
 Cohen, M.S., et al., Changes in cortical activity during mental rotation A mapping study using functional MRI. Brain, 1996. 119(1): p. 89-100.
 Ganis, G., et al., Transcranial magnetic stimulation of primary motor cortex affects mental rotation. Cereb Cortex, 2000. 10(2): p. 175-80.
 Hyde, C., et al., Primary Motor Cortex Excitability Is Modulated During the Mental Simulation of Hand Movement. Journal of the International Neuropsychological Society, 2017. 23(2): p. 185-193.
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 Pelletier, R., J. Higgins, and D. Bourbonnais, Laterality recognition of images, motor performance, and aspects related to pain in participants with and without wrist/hand disorders: An observational cross-sectional study. Musculoskeletal Science and Practice, 2018. 35: p. 18-24.
Pelletier, R., et al., Left Right Judgement Task and Sensory, Motor, and Cognitive Assessment in Participants with Wrist/Hand Pain. Rehabilitation Research and Practice, 2018. 2018.
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