We had a question via Twitter last week regarding a left/right discrimination finding from Perth physio Jay Tan:
I checked with Jay and he was happy for me to post this question on noijam so that we could discuss it in more than 140 characters.
Jay explained further that the client’s recognise results were slower on the unaffected side compared to norms as well as compared to the painful side.
Lets have a look at what some of the science says
Implicit motor imagery
The Graded Motor Imagery Handbook provides a detailed discussion of the science and understanding of what’s going on in the brain when a person performs an implicit left/right judgement.
You can get a taste of this here, with a series of free GMI Posters.
Here are some key points:
-Implicit motor imagery (left/right judgements)occurs when the person performing the judgement is not aware that they are mentally ‘moving’
-During implicit motor imagery, premotor cells modify primary motor cells without activating them
-Implicit motor imagery is less likely to activate a pain neurotag than explicit motor imagery (the person is aware that they are mentally moving) and mirror therapy.
– Data suggests that a left/right discrimination accuracy of about 80%, a response time of 2 seconds +/- .5 for hands and feet, 1.6 seconds +/- .5 for backs and necks, with equal results left and right, is normal.
Making sense of the results
The Graded Motor Imagery Handbook provides a model for understanding the results of performing an implicit left right judgement based on the most up to date research, trials and brain science.
The interpretation of the results of a left/right judgement test will vary dependent on whether the injury is acute or chronic (shaky territory with those “definitions” I know, but bear with me).
With an acute left hand injury, when faced with the difficult decision of quickly determining if a viewed image of a right hand is a left or a right hand, the safest presumption is that the image is a left hand because this is the injured hand. The left hand is mentally moved, outside of awareness, and an internal check reveals that this is incorrect. The process occurs over – choose right hand, mentally move right hand and check, and this time the result is correct and the process results in a response, that is selecting “right” via the method being used to test laterality.
When a person with an acute left hand injury is faced with deciding whether a viewed image of a left hand is left or right, the same process occurs, but this time the initial presumption is correct.
The initial presumption towards the acutely injured left hand results in a faster response time for left images. That is, in an acute injury situation, the person is faster to recognise images of/relating to their injured side.
In a chronic pain state things are different, in fact, usually opposite. In a chronic pain state, the initial presumption is towards the non-painful side/part. The suggestion is that this is a protective response – it is safest for the person to presume that the image is of their non-painful part/side as they are protecting that part of themselves that is in trouble by not focussing on it.
This results in the person generally being slower to recognise images of/relating to their injured side.
The plot thickens
However, we know that clinically and anecdotally, there are some interesting and different presentations when people in trouble perform left/right judgements.
Experiences outside of the norm challenge us to continue to think and question what might be happening in the brain of a person in trouble; to explore, to experiment and to use clinical reasoning powered up by modern neuroimmune science paradigms.
In answer to your question…
The explanation above might be enough to help answer Jay’s original question, however I want to open it to noijam readers – the superstar clinicians out there using Recognise™ and GMI every day, the noi faculty teaching the future superstar clinicians and anyone else interested in people with tricky pain states and how the brain responds and changes when faced with trouble- you’re all superstars too.
Questions, comments, thoughts and answers all welcome in the comments below.
– Tim Cocks
Tap into the most up to date Graded Motor Imagery Resources with a noigroup course or get your hands on the culmination of 15 years worth of neuroscience research and clinical trials in the Graded Motor Imagery Handbook with chapters covering all three stages of GMI, the science behind them, some pain education essentials and tips on progression and clinical reasoning.