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Decreased task‐evoked functional connectivity in the descending pain modulatory network in Alzheimer’s disease
Author(s) -
Atalla Sebastian W.,
Iversen Larkin,
Moss Karen,
Wright Kathy,
Monroe Todd B.
Publication year - 2020
Publication title -
alzheimer's and dementia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.713
H-Index - 118
eISSN - 1552-5279
pISSN - 1552-5260
DOI - 10.1002/alz.046571
Subject(s) - insula , anterior cingulate cortex , psychology , medicine , alzheimer's disease , disease , audiology , neuroscience , cognition
Background People with Alzheimer’s disease (AD) may suffer from alterations in the descending pain modulatory network (DPMN). Adults with AD receive fewer analgesic pain medications and report pain less frequently than healthy controls. This study examines possible alterations in task‐evoked functional connectivity (TEFC) in response to thermal pain in several structures comprising the DPMN. We hypothesize that adults with AD will demonstrate decreased TEFC between DPMN regions. Method The sample consisted of 61 adults, 31 people with Alzheimer’s disease (AD; M age = 77) and 30 healthy controls (HC; M age = 73). The groups did not differ on socioeconomic status, current or average pain, or state or trait anxiety scores. Age and depression scores differed between groups and were controlled. Participants completed 4 pseudorandomized fMRI sessions using a passive thermal pain induction task consisting of warmth, mild pain, and moderate pain temperature thresholds. Regions of interest were selected a priori : bilateral primary somatosensory cortex (S1), bilateral anterior insula (aINS), bilateral posterior insula (pINS), anterior cingulate cortex (ACC), and the periaqueductal gray (PAG). Psychophysiological interactions (PPI) analysis was completed using CONN v18.b. Motion correction was performed using Artifact Detection Tools and fMRI sessions for which greater than 20% of the timeseries exceeded 2 mm normalized motion were excluded from the analysis. Age and AD‐related differences in cerebral tissue volume were controlled. Contrasts for this analysis were chosen to be mild pain > warmth and moderate pain > warmth to subtract innocuous stimulus from noxious stimuli. Result Compared to healthy controls, adults with AD exhibited decreased TEFC between the R S1 and L S1 for mild pain > warmth (T = ‐2.03, p = 0.047), and decreased TEFC between the PAG and ACC for moderate pain > warmth (T = ‐2.18, p = 0.033). Conclusion Findings suggest that in people with AD, decreased connectivity between left and right S1 may indicate altered sensory processing of neural input. Evidence of decreased connectivity between the PAG and ACC in adults with AD may indicate an inability to modulate endogenous opioid systems within the brain and may lead to increased suffering from pain.