Visceral sensitivity has also been evaluated using sensory-evoked potentials, the responses evoked by gut stimuli can be recorded at different levels of the afferent pathways using cortical evoked potentials and magnetoencephalography. The problem with these techniques is that it cannot be ascertained as to whether the responses that are recorded relate to perception or to reflex pathways. New imaging techniques, such as positron emission tomography, single-photon emission computer tomography, and functional magnetic resonance imaging use different tracers to detect focal changes in brain blood flow and metabolic activity in response to different stimuli. These techniques provide images of the brain regions activated by visceral stimulation, but their application is limited by their restricted availability. A detailed description of these techniques is provided in Chapter 11.
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