What’s on : Lectures

Can you really know someone’s pain?

Lectures
Date
23 Sep 2014
Start time
7:30 PM
Venue
Tempest Anderson Hall
Speaker
Irene Tracey
Can you really know someone's pain?

Event Information

Can you really know someone’s pain?

Irene Tracey, Nuffield Professor of Anaesthetic Science, University of Oxford

The ability to experience pain is old and shared across species. It confers an evolutionary advantage and provides a warning of harm or impending threat. This highly adaptive ‘acute pain’ can unfortunately become maladaptive and chronic that as a consequence brings tremendous suffering. Chronic pain is one of the largest medical health problems in the developed world affecting 1 in 5 adults and costing society hundreds of millions of pounds per annum in care, treatment and days lost from work. Treatment is poor and many sufferers are left with unmanaged pain that significantly reduces their quality of life.

Until recently it has been difficult to obtain reliable objective information regarding the neural underpinnings of this private and subjective pain experience. It is needed as over-reliance on the verbal report and description of pain makes diagnoses and determination of treatment efficacy challenging. With the advent of modern brain imaging tools (generally called functional neuroimaging), such as functional magnetic resonance imaging (FMRI), positron emission tomography (PET), electroencephalography (EEG) and magnetoencephalography (MEG) this has been made feasible. Using such non-invasive brain imaging tools we can now identify what brain regions activate during painful experiences and relate this to an individual’s specific pain experience or measure of pain relief, bringing potential diagnostic value as well as a better neuroscientific understanding of pain perception.

Report

We know our own experience of pain, but infer that of others by observing their behaviour.  Brain imaging techniques such as functional Magnetic Resonance Imaging (fMRI) and  positron emission tomography (PET) make it possible to investigate brain activity during the experience of pain, and to identify the regions of the brain, and the processes involved.  Brain activity can be located with an accuracy of around 1 mm, and studied in real time; precision scarcely conceivable only a few years ago.

In the end, however, the perception of pain is subjective.  Although we have specific pain receptors – nociceptors – in our skin, pain is not simply a matter of a stimulus signalling directly to the brain.  As Hippocrates realised, pain comes from the brain.  External circumstances, mood, prior experience, expectation, and distraction all affect our perception of pain (as they do other forms of perception). Listening to music can affect the perception of pain, gloomy music making a given stimulus appear more painful; and previous sensitisation can result in a light touch being perceived as acutely painful.

It is not easy to devise experiments on pain in humans which are both scientifically valid and ethically acceptable:  the necessary ‘informed consent’ of the subject can distort the prior expectation required by the experiment.  Prof. Tracey described one particular experiment which satisfied both requirements, and clearly demonstrated how perception of pain can be manipulated.  The subject was connected to an intravenous  tube, through which a painkiller could be infused.  Initially, a mildly painful stimulus was applied, and ‘scored’.  The painkiller infusion was then started, unknown to the subject: the level of perceived pain fell slightly.  The subject was then told that the infusion had started: at which point the pain perceived fell sharply; and when told that the painkiller had been withdrawn it rose to the initial level – even though the infusion continued unchanged.

Such research clarifies the mechanisms of pain perception; but also makes it possible to envisage more effective approaches to the management of pain, both chronic and acute.

Peter Hogarth