Reversed Frontotemporal Connectivity During Emotional Face Processing in Remitted Depression

BackgroundVulnerability to relapse persists after remission of an acute episode of major depressive disorder. This has been attributed to abnormal biases in the processing of emotional stimuli in limbic circuits. However, neuroimaging studies have not so far revealed consistent evidence of abnormal responses to emotional stimuli in limbic structures, such as the amygdala, in remitted depression. This suggests the problem might lie in the integrated functioning of emotion processing circuits.MethodsWe recruited 22 unmedicated patients in remission from major depressive disorder (rMDD) and 21 age-matched healthy control subjects. Functional magnetic resonance imaging was performed during a face emotion processing task. Dynamic causal modeling was used with Bayesian model selection to determine the most likely brain networks and valence-specific modulation of connectivity in healthy control subjects and rMDD.ResultsIn healthy volunteers, sad faces modulated bi-directional connections between amygdala and orbitofrontal cortex and between fusiform gyrus and orbitofrontal cortex. Happy faces modulated unidirectional connections from fusiform gyrus to orbitofrontal cortex. In rMDD, the opposite pattern was observed, with evidence of happy faces modulating bidirectional frontotemporal connections and sad faces modulating unidirectional fusiform–orbitofrontal connections.ConclusionsParticipants with rMDD have abnormal modulation of frontotemporal effective connectivity in response to happy and sad face emotions, despite normal activations within each region. Specifically, processing of mood incongruent happy information was associated with a more richly modulated frontotemporal brain network, whereas mood congruent sad information was associated with less network modulation. This supports a hypothesis of dysfunction within cortico–limbic connections in individuals vulnerable to depression

Diminished Neural and Cognitive Responses to Facial Expressions of Disgust in Patients with Psoriasis: A Functional Magnetic Resonance Imaging Study

Psoriasis produces significant psychosocial disability; however, little is understood about the neurocognitive mechanisms that mediate the adverse consequences of the social stigma associated with visible skin lesions, such as disgusted facial expressions of others. Both the feeling of disgust and the observation of disgust in others are known to activate the insula cortex. We investigated whether the social impact of psoriasis is associated with altered cognitive processing of disgust using (i) a covert recognition of faces task conducted using functional magnetic resonance imaging (fMRI) and (ii) the facial expression recognition task (FERT), a decision-making task, conducted outside the scanner to assess the ability to recognize overtly different intensities of disgust. Thirteen right-handed male patients with psoriasis and 13 age-matched male controls were included. In the fMRI study, psoriasis patients had significantly (P<0.005) smaller signal responses to disgusted faces in the bilateral insular cortex compared with healthy controls. These data were corroborated by FERT, in that patients were less able than controls to identify all intensities of disgust tested. We hypothesize that patients with psoriasis, in this case male patients, develop a coping mechanism to protect them from stressful emotional responses by blocking the processing of disgusted facial expressions

Mirtazapine antagonises the subjective, hormonal and neuronal effects of m-chlorophenylpiperazine (mCPP) infusion: A pharmacological-challenge fMRI (phMRI) study

Aberrant signalling through central 5-HT2C receptor pathways has been implicated in various psychiatric disorders but this has not been amenable to experimental investigation in the absence of a valid in-vivo biomarker of functional 5-HT2C neurotransmission. One approach is drug-challenge pharmaco-magnetic resonance imaging (phMRI). We have previously shown that intravenous administration of the 5-HT2C agonist m-chlorophenylpiperazine (mCPP) elicits increases in blood oxygenation dependent signal (BOLD) in regions consistent with the distribution of 5-HT2C receptors. In the current study we determined whether BOLD signal responses to mCPP could be blocked by pre-treatment with a 5-HT2C antagonist. Healthy male volunteers received oral mirtazapine, 5-HT2/5-HT3 receptor antagonist, or placebo 90 min prior to intravenous mCPP challenge phMRI. BOLD signal increases following mCPP infusion occurred in areas known to be rich in 5-HT2C receptors such as the substantia nigra, hypothalamus, pallidum and amygdala. These responses were attenuated by mirtazapine pre-treatment. The results suggest that mCPP-challenge phMRI produces reliable patterns of response that are mediated by 5-HT2C receptors; these responses may therefore be useful in-vivo measures of 5-HT2C function in psychiatric disorders. -------------------------------------------------------------------------------