Neuroimaging Studies of Primary Dysmenorrhea.

Primary dysmenorrhea (PDM), cyclic menstrual pain in the absence of pelvic anomalies, is one of the most common gynecological disorders in reproductive females. Classified as chronic pelvic pain syndrome, PDM encompasses recurrent spontaneous painful ("on") and pain-free ("off") states and is thus a good clinical model to study state- and trait-related changes of pain in the brain. In this chapter, we summarize state-of-the-art neuroimaging studies of primary dysmenorrhea from phenotype and endophenotype to genotype facets. Structural and functional brain alterations associated with primary dysmenorrhea are discussed.

Encoding of menstrual pain experience with theta oscillations in women with primary dysmenorrhea.

Theta oscillation (4-7 Hz) is well documented for its association with neural processes of memory. Pronounced increase of theta activity is commonly observed in patients with chronic neurogenic pain. However, its association with encoding of pain experience in patients with chronic pain is still unclear. The goal of the present study is to investigate the theta encoding of sensory and emotional information of long-term menstrual pain in women with primary dysmenorrhea (PDM). Forty-six young women with PDM and 46 age-matched control subjects underwent resting-state magnetoencephalography study during menstrual and periovulatory phases. Our results revealed increased theta activity in brain regions of pain processing in women with PDM, including the right parahippocampal gyrus, right posterior insula, and left anterior/middle cingulate gyrus during the menstrual phase and the left anterior insula and the left middle/inferior temporal gyrus during the periovulatory phase. The correlations between theta activity and the psychological measures pertaining to pain experience (depression, state anxiety, and pain rating index) implicate the role of theta oscillations in emotional and sensory processing of pain. The present study provides evidence for the role of theta oscillations in encoding the immediate and sustained effects of pain experience in young women with PDM.

Distinct neuronal oscillatory responses between patients with bipolar and unipolar disorders: a magnetoencephalographic study.

BACKGROUND: Bipolar disorder (BD) and major depressive disorder (MDD) have distinct pathophysiologies but similar depressive appearances. The present study aimed at the differentiation of the brain responses between BD and MDD patients. We hypothesized that different affective disorder patients may have distinct patterns of oscillatory cortical activities in response to negative emotional stimuli. METHODS: Twenty BD patients, twenty MDD patients, and twenty age- and gender-matched healthy normal subjects were recruited. We adopted an implicit emotional task with facial image stimuli. The acquired event-related magnetoencephalographic signals were processed by the time-frequency analysis and beamformer-based source imaging techniques followed by statistical inference. RESULTS: We found that there were gamma oscillation decreases in the frontal regions of both BD and MDD patients, gamma oscillation increases in the bilateral temporal regions of MDD, and alpha-beta rhythm increases in BD patients. Relative to the cortical activation in the control group, the BD patients displayed more widely increased oscillatory activities over the fronto-parieto-occipital regions than MDD patients. CONCLUSIONS: Our results demonstrate the distinct neuropathological patterns of emotional responses in BD and MDD patients. The findings suggest that the dysfunction of emotion regulation in BD may result from the increased sensitivity to emotionally salient information, implicating the potential cause of the emotion lability. The present study also suggests that the implicit emotional task is an effective approach to differentiate bipolar from unipolar disorders and their distinct neuropathological patterns to emotional stimuli may provide objective and quantitative measures for potential diagnostic significance.