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Functional representation of trigeminal nociceptive input in the human periaqueductal gray

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Feb 29, 2024 version files 1.40 GB

Abstract

The periaqueductal gray (PAG) is located in the mesencephalon in the upper part of the brainstem and as part of the descending pain modulation is considered a crucial structure for pain control. Its modulatory effect on painful sensation is often seen as a systemic function affecting the whole body similarly. However, recent animal data suggest some kind of somatotopy in the PAG. This would make the PAG capable of dermatome-specific analgesic function. We electrically stimulated the peripheral dermatomes of the trigemino-cervical complex consisting the three branches of the trigeminal nerve and the greater occipital nerve in sixty-one humans during optimized brainstem fMRI. We provide evidence for a fine-grained and highly specific somatotopic representation of nociceptive input in the PAG in humans and a descending functional connectivity between the individual representations of the peripheral nerves in the PAG and the brainstem nuclei of these nerves. Our data suggest that the downstream antinociceptive properties of the PAG may be rather specific down to the level of individual dermatomes. This study was preregistered at clinicaltrials.gov: NTC03999060 and primary outcomes already published elsewhere.