Submitted on October 5, 2006
Accepted on March 26, 2007
Reproducibility of Human Brain Activity Evoked by Oesophageal Stimulation Using Functional Magnetic Resonance Imaging
Steven John Coen1*, Lloyd J Gregory2, Lidia Yágüez3, Edson Amaro Jnr1, Mick J Brammer1, Steven CR Williams1, and Qasim Aziz4
1 Neuroimaging Research Group, Institute of Psychiatry, Kings College London, London,, United Kingdom
2 Translational Imaging Unit, Hope Hospital, University of Manchester, Manchester, United Kingdom
3 Department of Psychology, Institute of Psychiatry, Kings College London, London, United Kingdom
4 Section of GI Sciences, University of Manchester, Manchester, United Kingdom
* To whom correspondence should be addressed. E-mail: s.coen{at}iop.kcl.ac.uk.
Background and aims: Functional magnetic resonance imaging (fMRI) is a popular tool for investigating central processing of visceral pain in healthy and clinical populations. Despite this, the reproducibility of the neural correlates of visceral sensation using fMRI remains unclear. The aim of the present study was to address this issue. Methods: Seven healthy right-handed volunteers participated in the study. Blood oxygen level dependant (BOLD) contrast images were acquired at 1.5Tesla whilst subjects received non-painful and painful phasic balloon distensions ('on-off' block design, 10 stimuli per 'on' period, 0.3 Hz) to the distal oesophagus. This procedure was repeated on two further occasions to investigate reproducibility. Results: Painful stimulation resulted in highly reproducible activation over 3 scanning sessions in the anterior insula, primary somatosensory cortex (SI) and anterior cingulate cortex (ACC). A significant decrease in strength of activation occurred from session 1 to session 3 in the ACC, SI and supplementary motor cortex (SMA) which may be explained by an analogous decrease in pain ratings. Non-painful stimulation activated similar brain regions to painful stimulation, but with greater variability in signal strength and regions of activation between scans. Conclusions: Painful stimulation of the oesophagus produces robust activation in many brain regions. A decrease in subjective perception of pain and brain activity from the first to the final scan, suggest serial brain imaging studies may be affected by habituation. These findings indicate that for brain imaging studies that require serial scanning, development of experimental paradigms that control for the effect of habituation is necessary.
