Introducing left/right judgement tasks (LRJTs) into clinical practice and using them in the management of individuals with chronic pain is, I think, something to celebrate and a success story for translational research. Seminal work on the mental rotation of objects almost 50 years ago (Shepard & Metzler, 1971) led the way for the subsequent discovery that when presented with an image showing a disembodied hand or foot and asked to judge its laterality, rather than imagining the image rotating, we imagine our own hand or foot moving to the position of the one depicted in order to make our judgment (Cooper & Shepard, 1975; Parsons, 1987; Sekiyama, 1982). In the 21st Century, this established ability of LRJTs to elicit implicit motor imagery has been embraced by clinicians as a therapeutic tool, the noigroup leading the charge with practical guidance for clinicians (Moseley et al., 2012) as well as online tools making these useful tasks accessible to large numbers of clinicians and patients (http://www.noigroup.com/en/Product/BTRAPP). I applaud the work of this group, both for facilitating this accessibility and consequently for drawing current research into a clinical setting in a practical and beneficial way. However, I do have concerns about some aspects of LRJT use and have raised these recently (Punt, 2017). Here, I focus on two specific issues where I think current practice requires attention.
(i) Detailed performance data is critical for the demonstration of motor imagery
The ability of LRJTs to elicit motor imagery is critical to their use in therapy. While hundreds of studies have demonstrated this ability for hand and foot-based LRJTs, these tasks can also be performed without using motor imagery. Confidence that the tasks are eliciting motor imagery can be provided in multiple ways but the most persuasive of these comes from the biomechanical constraints that are reflected in response time (RT) data when individuals perform the task. Research has supported the principle of exact match confirmation for hand-based LRJTs which holds that when presented with an image of a hand, one imagines one’s own corresponding limb moving from its current position to the one depicted. This confirmation process not only means that RTs are slower for images where performing this movement would require a longer trajectory, but they are also slower for images that would require more awkward movements regardless of the length of the trajectory (Parsons, 1994). The data presented in Figure 1 are from my lab but reflect established findings in mental rotation (imagery) research. See how RTs for awkward vs. natural images are different when individuals perform motor imagery (left). The task can also be performed using other strategies (e.g. visual imagery) as seen on the right. We have reported a case of a patient with complex regional pain syndrome who selects to perform the task without performing motor imagery because of related pain (King et al., 2015). If participants are using non-motor strategies, LRJTs are unlikely to be helpful clinically. In order to establish which strategies participants are using it is important to have access to data relating to images where biomechanical constraints vary.
[Figure 1]
(ii) Has some practice developed in the absence of underpinning science?
The rehabilitation field has extended the use of LRJTs to include tasks which involve other parts of the body (e.g. back, neck, shoulder, knee; see http://www.noigroup.com/en/Product/BTRAPP). These are very different tasks to those presenting a hand or a foot. Typically, they involve presenting a whole body or a body segment showing some kind of asymmetry or lateral deviation (e.g. an outstretched arm for a shoulder-based LRJT; see figure 2, left image). Additionally, the whole image may also be oriented around one of the body’s axes (middle and right images). The assumption with such tasks is that individuals imagine moving the lateralised part of their body to the position shown in order to make their judgment, thus eliciting motor imagery with related therapeutic benefits. However, the evidence contradicts this assumption. If these tasks did elicit the simulation of lateralised movements, then RTs should be slower for images requiring larger movements (e.g. Figure 2, middle image) than smaller movement (e.g. right image). This is not the case. University of Birmingham PhD student Latifah Alazmi recently led a study demonstrating this absence of biomechanical constraint effects for trunk-based LRJTs (Alazmi et al., 2018). The study provides the clearest indication to date that these tasks do not elicit motor imagery and questions their therapeutic value.
Ultimately I’m enthusiastic about LRJTs and pleased to see their introduction into clinical practice. However, research relating to their clinical utility is in its infancy and in order for these tasks to remain credible and useful, it is important that their development is prudent and informed by established findings from other fields (e.g. cognitive psychology, neuroscience). If not, these potentially powerful tools may be considered spurious and fail to realise the promise they offer.
About David Punt
A late starter in the world of research, David Punt is a physiotherapist working in the field of stroke rehabilitation. An interest in the neglect syndrome following stroke led him to undertake a PhD in experimental psychology, focusing on neglect-related movement problems. Since then, his research has continued to steer a course between rehabilitation and experimental psychology, with an evergrowing interest in how we determine left from right! David is currently a senior lecturer (associate professor) at the University of Birmingham in the UK.
References
Alazmi, L., Gadsby, G.E., Heneghan, N.R., & Punt, T.D. (2018). Do trunk-based left/right judgment tasks elicit motor imagery? Musculoskeletal Science and Practice, 35, 55-60.
Cooper, L.A., & Shepard, R.N. (1975). Mental transformations in the identification of left and right hands. Journal of Experimental Psychology: Human Perception and Performance, 104(1), 48-56.
King, R., Johnson, M.I., Ryan, C.G., Robinson, V., Martin, D.J., & Punt, T.D. (2015). My foot? Motor imagery-evoked pain, alternative strategies and implications for laterality recognition tasks. Pain Medicine, 16(3), 555-557.
Moseley, G.L., Butler, D.S., Beames, T.B., & Giles, T.J. (2012). The Graded Motor Imagery Handbook. Adelaide: Noigroup Publications.
Parsons, L.M. (1987). Imagined spatial transformations of one’s hands and feet. Cognitive Psychology, 19(2), 178-241.
Parsons, L.M. (1994). Temporal and kinematic properties of motor behavior reflected in mentally simulated action. Journal of Experimental Psychology: Human Perception and Performance, 20(4), 709-730.
Punt, T.D. (2017). Re: The development of a shoulder specific left/right judgement task: Validity & reliability. Musculoskeletal Science and Practice, 30, e87.
Sekiyama, K. (1982). Kinesthetic aspects of mental representations in the identification of left and right hands. Perception and Psychophysics, 32(2), 89-95.
Shepard, R.N., & Metzler, J. (1971). Mental rotation of three-dimensional objects. Science, 171(3972), 701-703.