Reductions in regional theta power and fronto-parietal theta-gamma phase-amplitude coupling during gaze processing in bipolar disorder

Impaired social cognition is common in bipolar disorder (BD) and predicts poor functional outcomes. A critical determinant of social cognition is the ability to discriminate others' gaze direction, and its alteration may contribute to functional impairment in BD. However, the neural mechanisms underlying gaze processing in BD are unclear. Because neural oscillations are crucial neurobiological mechanisms supporting cognition, we aimed to understand their role in gaze processing in BD. Using electroencephalography (EEG) data recorded during a gaze discrimination task for 38 BD and 34 controls (HC), we examined: theta and gamma power over bilateral posterior and midline anterior locations associated with early face processing and higher-level cognitive processing, and theta-gamma phase-amplitude coupling (PAC) between locations. Compared to HC, BD showed reduced midline-anterior and left-posterior theta power, and diminished bottom-up/top-down theta-gamma PAC between anterior/posterior sites. Reduced theta power and theta-gamma PAC related to slower response times. These findings suggest that altered theta oscillations and anterior-posterior cross-frequency coupling between areas associated with higher-level cognition and early face processing may underlie impaired gaze processing in BD. This is a crucial step towards translational research that may inform novel social cognitive interventions (e.g., neuromodulation to target specific oscillatory dynamics) to improve functioning in BD.

Deficits of social cognition in bipolar disorder: Systematic review and meta-analysis

BACKGROUND

The association between impaired social cognition and bipolar disorder (BD) is well established. However, to our knowledge, there has not been a recent systematic review that characterizes disparate dimensions of social cognition in BD. Herein, this systematic review and meta-analysis aimed to synthesize the literature on core aspects of social cognition (i.e., Theory of Mind, emotion recognition, and social judgment) to identify potential areas of impairment.

METHODS

Online databases (i.e., PubMed, Cochrane Libraries, PsycINFO) and Google Scholar were searched from inception to May 2021. Studies with populations ages ≥16 with DSM-IV or DSM-5 defined BD (I or II) either in a euthymic or symptomatic state were included. The risk of bias was measured using the ROBINS-1 tool, and the quality of the sources was evaluated using GRADE criteria. The results of the studies were quantitatively measured by synthesizing Hedge's g effect sizes through a random effects meta-analytic approach.

RESULTS

A total of 29 studies were included in the final review (i.e., 12 studies on the Theory of Mind, 11 on emotion recognition, and 6 on social judgment). Overall, results demonstrated social cognition to be moderately impaired in individuals with BD (d = 0.59). The individual domains ranged in effect size (0.38 < d < 0.70), providing evidence for variation in impairment within social cognition.

DISCUSSION

Individuals with BD exhibit clinically significant deficits in social cognition during euthymic and symptomatic states. Social cognition impairments in individuals with BD are an important therapeutic target for treatment discovery and development.

Direct Gaze Holds Attention, but Not in Individuals with Obsessive-Compulsive Disorder

The attentional response to eye-gaze stimuli is still largely unexplored in individuals with obsessive-compulsive disorder (OCD). Here, we focused on an attentional phenomenon according to which a direct-gaze face can hold attention in a perceiver. Individuals with OCD and a group of matched healthy controls were asked to discriminate, through a speeded manual response, a peripheral target. Meanwhile, a task-irrelevant face displaying either direct gaze (in the eye-contact condition) or averted gaze (in the no-eye-contact condition) was also presented at the centre of the screen. Overall, the latencies were slower for faces with direct gaze than for faces with averted gaze; however, this difference was reliable in the healthy control group but not in the OCD group. This suggests the presence of an unusual attentional response to direct gaze in this clinical population.

Social attention across borders: A cross-cultural investigation of gaze cueing elicited by same- and other-ethnicity faces

The gaze-cueing effect is a robust phenomenon which illustrates how attention can be shaped by social factors. In four experiments, the present study explored the interaction between the ethnic membership of the participant and that of the face providing the gaze cue. Firstly, we aimed to further investigate the differential impact of White, Black, and Asian faces on the gaze-cueing effect in White individuals. Secondly, we aimed to explore, for the first time, the impact of faces belonging to different ethnicities on gaze cueing in Chinese participants. The results allowed to rule out alternative accounts and showed that White participants exhibit a gaze-cueing effect for White and Asian faces, but not for Black faces, consistent with previous studies. As regards Chinese participants, the overall findings suggested a stronger gaze-cueing effect for White faces than for Asian faces. The results are discussed with reference to differences in the perceived social status of the various groups, pointing to the need of taking into account different cultural contexts.

Impaired social cognition in bipolar disorder: A meta-analysis of Theory of Mind in euthymic patients

OBJECTIVE

To conduct a meta-analysis of Theory of Mind studies exclusively in euthymic patients with bipolar disorder.

METHOD

After the exclusion of studies evaluating symptomatic patients during acute episodes, we performed a meta-analysis including a total of 30 studies, comparing 1294 euthymic bipolar disorder patients and 1116 healthy controls.

RESULTS

Patients with bipolar disorder presented a significant impairment in Theory of Mind performance when compared to controls (Hedge's g = -0.589, 95% confidence interval: -0.764 to -0.414, Z = -6.594, p < 0.001). When compared to controls, Theory of Mind was impaired in patients with both bipolar disorder I (Hedge's g = -0.663, 95% confidence interval: -0.954 to -0.372, Z = -4.462, p < 0.001) and bipolar disorder II (Hedge's g = -1.165, 95% confidence interval: -1.915 to -0.415, Z = -3.044, p = 0.002). Theory of Mind impairments were also significantly more severe in verbal tasks (Hedge's g = -1.077, 95% confidence interval: -1.610 to -0.544, Z = -3.961 p < 0.001) than visual tasks (Hedge's g =-0.614, 95% confidence interval: -0.844 to -0.384, Z = -5.231, p < 0.001) when compared to controls.

CONCLUSION

The results obtained confirm that Theory of Mind is impaired in remitted bipolar disorder patients, being a potential endophenotype for bipolar disorder. Moreover, we found higher deficits in verbal Theory of Mind, compared with visual Theory of Mind. Since most studies were cross-sectional, there is a need for longitudinal studies to evaluate whether the deficits detected in Theory of Mind are progressive over the course of the illness.