fMRI pain activation in the periaqueductal gray in healthy volunteers during the cold pressor test.
The periaqueductal gray (PAG), a brain area belonging to the descending pain modulatory system, plays a crucial role in pain perception. Little information is available on the relationship between PAG activation and perceived pain intensity. In this study, we acquired functional magnetic resonance imaging (fMRI) scans from the PAG during the cold pressor test, a model for tonic pain, in 12 healthy volunteers. fMRI data were acquired with a 12-channel head-coil and a 3-Tesla scanner and analyzed with Statistical Parametric Mapping (SPM8) software. During the cold pressor test, fMRI showed significant activation clusters in pain-related brain areas: bilateral middle and superior frontal gyrus, anterior cingulate cortex and thalamus, left insula, right inferior frontal gyrus, left inferior temporal gyrus and in the bilateral PAG (cluster level corrected threshold p<0.05). PAG activation correlated directly with the pain threshold and inversely with the participant's perceived pain intensity (cluster level corrected threshold (p<0.05). The cold pressor test consistently activated the PAG as well as other pain-related areas in the brain. Our study, showing that the greater the PAG activation the higher the pain threshold and the weaker the pain intensity perceived, highlights the key role of the PAG in inhibiting the pain afferent pathway function. Our findings might be useful for neuroimaging studies investigating PAG activation in patients with chronic idiopathic pain conditions possibly related to dysfunction in the descending pain modulatory system.
Department of Neurology and Psychiatry, University Sapienza, Rome, Italy.
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La Cesa
Department of Neurology and Psychiatry, University Sapienza, Rome, Italy.
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Tinelli
Medical Physics Section, Department of Biomedicine and Prevention, University of Rome "Tor Vergata", Rome, Italy; Department of Radiology, Athinoula A. Martinos Center for Biomedical Imaging, Boston, MA 02219, USA; Harvard Medical School, Boston, MA 02115, USA.
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Toschi
Department of Neurology and Psychiatry, University Sapienza, Rome, Italy.
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Di Stefano
Department of Neurology and Psychiatry, University Sapienza, Rome, Italy.
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Collorone
Department of Neurology and Psychiatry, University Sapienza, Rome, Italy.
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Aceti
Department of Neurology and Psychiatry, University Sapienza, Rome, Italy.
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Francia
Department of Neurology and Psychiatry, University Sapienza, Rome, Italy.
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Cruccu
Department of Neurology and Psychiatry, University Sapienza, Rome, Italy.
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Truini
Department of Neurology and Psychiatry, University Sapienza, Rome, Italy. Electronic address: francesca.caramia@uniroma1.it.
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Caramia
D000328:Adult; D001931:Brain Mapping / Q000379:methods*; D003080:Cold Temperature; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D009415:Nerve Net / Q000502:physiology*; D058748:Pain Perception / Q000502:physiology*; D010487:Periaqueductal Gray / Q000502:physiology*; D012016:Reference Values; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
Cold pressor test; Descending modulatory system; Fibromyalgia; Periacqueductal gray; fMRI