National Antivisection Society
2004-05 Brain Research - Central nervous system processing of human gut sensation
Lord Dowding Fund scientists have developed a brain imaging technique to non-invasively record nerve cell activity in the human brain without the limitations encountered with previous techniques. The technique is known as Synthetic Aperture Magnetometry (SAM) and has been developed by a collaboration between Dr Qasim Aziz of Hope Hospital, Salford and Dr Paul Furlong of Aston University.
It is known that when nerves in the brain are activated in response to an external stimulus, they generate electromagnetic signals. Cortical evoked potentials (CEP) are the electrical component of these signals and their size can be recorded by simple electrodes placed on the scalp. The magnetic component of the signals can be recorded using Magnetoencephalography (MEG) which identifies the location of the signals within the brain. The introduction of SAM means that not only can the region of brain responsible for the signals be identified, but the depth of the signals within the brain can also be measured. Previously, it was only possible to perform this depth measurement via invasive brain surgery.
Dr Aziz and colleagues are using these techniques to investigate functional gut disorders (FGD) such as irritable bowel syndrome and non-cardiac chest pain. FGDs affect between 10 and 20% of the UK population, with pain being the most commonly occurring symptom. A stimulus in the gut which would usually be non-painful is often perceived as painful by a FGD patient. This condition is known as visceral hypersensitivity and may be due to either hypersensitive nerves within the gut or abnormal processing of gut sensory information by the brain. For example, it has long been recognised that stress, depression and anxiety affect gut function.
Due to the inaccessibility of human gut organs and the lack of substitute models to study human gut pain, virtually all previous research on gut pain and hypersensitivity has been carried out on animals, mainly opossums, rats and primates. However, Dr Aziz’s group has developed the first human model for gut pain hypersensitivity. With LDF support this model has been further validated by providing the first electrophysiological evidence that sensitisation of nerves in the intestines can be studied in humans. Dr Aziz and colleagues have identified the brain regions that process oesophageal pain, i.e. pain experienced in the canal which transports ingested food from the throat to the stomach. Additionally, it has been demonstrated that with SAM it is possible to identify the region of the brain involved in swallowing, an area of research that has previously involved experiments using cats, sheep and primates.
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