I was reading Valery Legrain’s blog and it caused me to reflect on what sort of daily use I give my working memory. Have I needed to mentally rehearse a phone number while dialling it? No, my phone dials whoever I ask it to. Have I bothered to calculate the amount of change I’m going to get at the checkout because the young assistant looks like they can’t? Well that’s just silly – it’s what a cash register is for. But, these tasks used to be common place and they are excellent examples of using one’s working memory. With smart technology these days, all you need do is get on with life while silicon chips work out the answer.
This could be troublesome if it spells a loss of working memory function. In their paper, Legrain, Crombez et al (2011) reported that mental rehearsal such as occurs during a working memory task, suppressed the ability of a nociceptive stimulus to distract attention. The nifty method they used to test this teased out the contributions of working memory from a general shift in attention load (read Valery’s blog or the paper for a deeper coverage of this); a factor widely acknowledged to influence the amount of cognitive processing allocated to nociceptive stimuli.
Just to recap, subjects participated in two sessions: a) a colour discrimination task and b) a colour matching task. Each task involved two conditions: a response according to the current image or a response according to the previous image (1-back task involving mental rehearsal and working memory). Prior to seeing the image, subjects were given either a tactile (tactile-visual) or a nociceptive (nociceptive-visual) stimulus. They didn’t know which one was coming.
In the current image tasks, subjects responded significantly slower to the nociceptive-visual trials than tactile-visual trials, that is the nociceptive stimulus intruded and disrupted the task. But, when working memory was engaged (the 1-back tasks), there was no significant difference in response time between the two trials. This was a consistent finding, despite decreased attentional load in the first task, and showed that suppression of nociceptive messages was due to the activity of the working memory.
The ability for working memory to suppress nociceptive message processing is an important issue. Firstly it means that there are top down ways of controlling the amount of attention paid to nociceptive stimuli. This could be something to explore further in chronic pain states where the brain may show an over-eagerness to listen to incoming signals of threat (Crombez, Van Damme et al. 2005). Secondly, by reducing the ability for the nociceptive messages to intrude, task oriented brain activities are preserved and further processing that could result in the perception of pain is likely to be reduced.
In the clinic a bit of thought to the sequence and style in which we do things can capitalise on the idea of facilitating working memory to improve task output and decrease nociceptive input. For example, guiding a client’s foot through heel strike to toe off at the same time as asking them to make a mental image of the feeling (not pain-related, but proprioceptive and sensory) of it can be the 1-back task. If we ask them to rehearse that mental image while preparing to produce the same motor pattern by themselves, and then to match the mental image with a physical task, we are achieving our goals. I am tempted to say that repetition may reinforce improvement, so it could be a long session on the floor!
Working memory is your ‘here and now’ memory which means to capitalise on using it we need focus during clinic time. Focus on the goals and tasks and away from the pain. Anyway, it seems it is time the memory worked again, before we forget where to find it!
Carolyn Berryman
Carolyn has been teaching with the Noisters (Neuro Orthopaedic Institute) for the last 10 years and finally got herself into research via a very competitive post-graduate scholarship. Not that she has every stopped studying – she already has a masters in physiotherapy and in pain science – good luck fitting PhD onto the business card! What is Carolyn researching for her PhD? Based at the University of South Australia in Adelaide Carolyn is looking at neurophysiological profiles between chronic pain and PTSD (post traumatic stress disorder) during working memory tasks.
What does Carolyn do day to day? She is under piles of papers doing a systematic review of working memory and cognitive impairment in chronic pain. Carolyn will then be using EEG to evaluate what happens in people with pain. When she is not in the office, she lives on an island 100 kms south of Adelaide (that’s a long commute!) and spends her off-time playing with family, sailing and walking. Here is Carolyn talking more about the research she is doing.
References
Crombez G, Van Damme S, & Eccleston C (2005). Hypervigilance to pain: an experimental and clinical analysis. Pain, 116 (1-2), 4-7 PMID: 15927387
Legrain V, Crombez G, Mouraux A, 2011 Controlling Attention to Nociceptive Stimuli with Working Memory. PLoS ONE 6(6): e20926.doi:10.1371/journal.pone.0020926