Perception of social stimuli in mania: an fMRI study

Brain functional changes across mood states in bipolar disorder: from a large-scale network perspective

BACKGROUND

Exploring the neural basis related to different mood states is a critical issue for understanding the pathophysiology underlying mood switching in bipolar disorder (BD), but research has been scarce and inconsistent.

METHODS

Resting-state functional magnetic resonance imaging data were acquired from 162 patients with BD: 33 (hypo)manic, 64 euthymic, and 65 depressive, and 80 healthy controls (HCs). The differences of large-scale brain network functional connectivity (FC) between the four groups were compared and correlated with clinical characteristics. To validate the generalizability of our findings, we recruited a small longitudinal independent sample of BD patients (n = 11). In addition, we examined topological nodal properties across four groups as exploratory analysis.

RESULTS

A specific strengthened pattern of network FC, predominantly involving the default mode network (DMN), was observed in (hypo)manic patients when compared with HCs and bipolar patients in other mood states. Longitudinal observation revealed an increase in several network FCs in patients during (hypo)manic episode. Both samples evidenced an increase in the FC between the DMN and ventral attention network, and between the DMN and limbic network (LN) related to (hypo)mania. The altered network connections were correlated with mania severity and positive affect. Bipolar depressive patients exhibited decreased FC within the LN compared with HCs. The exploratory analysis also revealed an increase in degree in (hypo)manic patients.

CONCLUSIONS

Our findings identify a distributed pattern of large-scale network disturbances in the unique context of (hypo)mania and thus provide new evidence for our understanding of the neural mechanism of BD.

Altered empathy-related resting-state functional connectivity in patients with bipolar disorder

Empathy is the ability to generate emotional responses (i.e., cognitive empathy) and to make cognitive inferences (i.e., affective empathy) to other people's emotions. Empirical evidence suggests that patients with bipolar disorder (BD) exhibit impairment in cognitive empathy, but findings on affective empathy are inconsistent. Few studies have examined the neural mechanisms of cognitive and affective empathy in patients with BD. In this study, we examined the empathy-related resting-state functional connectivity (rsFC) in BD patients. Thirty-seven patients with BD and 42 healthy controls completed the self-report Questionnaires of Cognitive and Affective Empathy (QCAE), the Yoni behavioural task, and resting-sate fMRI brain scans. Group comparison of empathic ability was conducted. The interactions between group and empathic ability on seed-based whole brain rsFC were examined. BD patients scored lower on the Online Simulation subscale of the QCAE and showed positive correlations between cognitive empathy and the rsFC of the dorsal Medial Prefrontal Cortex (dmPFC) with the lingual gyrus. The correlations between cognitive empathy and the rsFC of the temporal-parietal junction (TPJ) with the fusiform gyrus, the cerebellum and the parahippocampus were weaker in BD patients than that in healthy controls. These findings highlight the underlying neural mechanisms of empathy impairments in BD patients.

Functional connectivity during affective mentalizing in criminal offenders with psychotic disorders: Associations with clinical symptoms

Psychotic disorders are associated with neurobehavioral impairments in mental state attribution (mentalizing). These impairments are most severe in psychotic patients with elevated symptom levels, particularly negative and cognitive symptoms. There have been few studies of functional connectivity related to mentalizing in psychotic disorders and associations with symptoms. We conducted a functional MRI study of affective mentalizing in individuals with psychotic disorders and varying symptom levels (positive, negative, cognitive). Participants were drawn from an adjudicated inpatient forensic psychiatric population (criminal offenders). Functional MRI scans were acquired using a 32-channel ultra-fast multiband imaging sequence. Mentalizing task performance and functional connectivity were assessed in psychotic criminal offenders (n = 46) and nonpsychotic offenders (n = 41). Temporal coherent brain networks were estimated with group independent component analysis (ICA). Relative to nonpsychotic offenders, psychotic offenders showed impaired task performance and reduced activation in a component comprising the dorsomedial prefrontal cortex, superior temporal gyrus, and ventrolateral prefrontal cortex. Positive and cognitive symptoms were inversely correlated with component activity and task performance. The results are discussed with reference to potential mechanisms underlying impaired social cognition in psychotic disorders and across symptom types.

Decreased medial prefrontal cortex activation during self-referential processing in bipolar mania

BACKGROUND

Patients with bipolar disorder in mania exhibit symptoms pointing towards altered self-referential processing, such as decreased self-focus, flight of ideas and high distractibility. In depression, the opposite pattern of symptoms has been connected to increased activation of medial prefrontal cortex (mPFC) during self-referential processing. In this study, we hypothesized that (1) patients with mania will exhibit decreased activation in the mPFC during self-referential processing and (2) will be more alexithymic and that levels of alexithymia will correlate negatively with mPFC activation.

METHODS

The neural response to standardized pictures was compared in 14 patients with bipolar I disorder in mania to 14 healthy controls using blood oxygen level dependent contrast magnetic resonance imaging. Participants were asked to indicate with button press during the scanning session for each picture whether the pictures personally related to them or not. Toronto alexithymia scale (TAS) scores were recorded from all participants.

RESULTS

In the group analysis, patients with mania exhibited decreased activation in a predefined region of interest in the mPFC during self-referential processing compared to healthy controls. Patients with mania showed significantly higher levels of alexithymia, attributable to difficulties in identifying and describing emotions. Activation in the mPFC correlated negatively with levels of alexithymia.

LIMITATIONS

Results presented here should be replicated in a larger group, potentially including unmedicated patients.

CONCLUSIONS

The finding of decreased mPFC activation during self-referential processing in mania may reflect decreased self-focus and high distractibility. Support for this view comes from the negative correlation between higher alexithymia scores and decreased mPFC activation. These findings represent an opposite clinical and neuroimaging pattern to findings in depression.