Recent neuroimaging studies implicate the medial temporal lobe (MTL) in nociception and pain modulation. Here, we aim to identify which subregions of the MTL are involved in human pain and to test its connectivity in a cohort of chronic low-back pain patients (CBP). We conducted 2 coordinate-based meta-analyses to determine which regions within the MTL showed consistent spatial patterns of functional activation (1) in response to experimental pain in healthy participants and (2) in chronic pain compared with healthy participants. We followed PRISMA guidelines and performed activation likelihood estimate (ALE) meta-analyses. The first meta-analysis revealed consistent activation in the right anterior hippocampus (right antHC), parahippocampal gyrus, and amygdala. The second meta-analysis revealed consistently less activation in patients' right antHC, compared with healthy participants. We then conducted a seed-to-voxel resting state functional connectivity of the right antHC seed with the rest of the brain in 77 CBP and 79 age-matched healthy participants. We found that CBP had significantly weaker antHC functional connectivity to the medial prefrontal cortex compared with healthy participants. Taken together, these data indicate that the antHC has abnormally lower activity in chronic pain and reduced connectivity to the medial prefrontal cortex in CBP. Future studies should investigate the specific role of the antHC in the development and management of chronic pain.
Medial temporal lobe activity is investigated in meta-analyses of experimental and chronic pain. Abnormal hippocampal connectivity is found in chronic low-back pain patients.
aFaculty of Dentistry, University of Toronto, Toronto, ON, Canada
bSystems Neuroscience Division, Krembil Research Institute, University Health Network, Toronto, ON, Canada
cUniversity of Toronto Centre for the Study of Pain, University of Toronto, Toronto, ON, Canada
dCenter for Neuroscience, University of California at Davis, Davis, CA, United States
eDepartment of Psychology, University of Toronto, Toronto, ON, Canada
fDepartment of Neural and Pain Sciences, School of Dentistry, University of Maryland Baltimore, Baltimore, MD, United States
gCenter to Advance Chronic Pain Research, University of Maryland Baltimore, Baltimore, MD, United States
hDepartment of Dentistry, Mount Sinai Hospital, Toronto, ON, Canada
Corresponding author. Address: Faculty of Dentistry, University of Toronto, Room 543, 124 Edward St, Toronto, ON M5G 1G6, Canada. Tel.: 416-864-8235. E-mail address: firstname.lastname@example.org (M. Moayedi).
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Received January 22, 2018
Received in revised form January 23, 2019
Accepted February 01, 2019