Brain Waves Reveal Why People in Mania Struggle to Read Other Minds

One of the most disorienting features of a manic episode is not the racing thoughts or the boundless energy, but the way social interactions seem to go quietly wrong. People experiencing mania often misjudge what others are thinking, overestimate how much others share their enthusiasm, and stumble through conversations that once came easily. Psychologists call the underlying capacity theory of mind: the ability to infer the beliefs, intentions, and perspectives of other people. A new study published in BMC Psychiatry by researchers at the Affiliated Mental Health Center and Hangzhou Seventh People’s Hospital, part of the Zhejiang University School of Medicine, now offers a rare glimpse into what happens in the brain, millisecond by millisecond, when this capacity falters during mania.

The research team, led by corresponding author Jianfei Shi, set out to answer a question that has lingered in the literature on bipolar disorder for years. Impairments in theory of mind have been documented across mood states in bipolar disorder, and they appear to deepen during manic episodes. What has remained murky is the neurophysiological sequence behind those impairments, particularly the timing between two stages of mental-state reasoning: an earlier, posterior stage thought to handle perspective-related processing, and a later, frontal stage involved in selecting among perspectives and managing the conflicts that arise when another person’s viewpoint clashes with one’s own. Behavior alone cannot separate these stages; only a technique with fine temporal resolution can.

That technique is electroencephalography, or EEG, which records electrical activity at the scalp with millisecond precision. From the continuous EEG signal, researchers can extract event-related potentials, stereotyped waves of brain activity time-locked to specific events in a task. In this study, nineteen patients who met ICD-10 diagnostic criteria for a bipolar manic episode and twenty-four healthy controls completed a rapid theory of mind judgment task while their brain activity was recorded. The design was deliberately fast-paced, forcing participants to compute and apply mental-state inferences under time pressure, which is closer to the demands of real social life than the leisurely judgments used in many earlier studies.

The behavioral results confirmed what clinicians observe at the bedside. Compared with healthy controls, the patients with bipolar disorder showed reduced accuracy and prolonged reaction times across all conditions of the task. In other words, they were both slower and less accurate when asked to reason about another person’s perspective, a double deficit that suggests the difficulty is not simply a matter of hesitation or caution but of genuinely impaired computation. Notably, the patients’ manic symptoms were subthreshold at the time of assessment according to established cutoffs on the Young Mania Rating Scale, meaning the participants were not in an acute, severe episode, yet the social-cognitive differences were still measurable.

The electrophysiological findings are where the study makes its most distinctive contribution. The researchers focused on two components. The first, dubbed TP450, spans roughly 325 to 525 milliseconds after a stimulus and is associated with posterior perspective-related processing, drawing on regions toward the back and side of the brain, including areas near the temporoparietal junction that have long been implicated in reasoning about other minds. The second, the late frontal slow wave, or LFSW, spans roughly 600 to 800 milliseconds and is treated as a marker of later frontal processing during perspective selection and conflict management, engaging the prefrontal systems that govern control and decision-making.

When the two groups were compared, a clear dissociation emerged. The patients showed significantly attenuated TP450 amplitudes at right parietal electrode sites, specifically at the P4 position, consistent with altered processing in the posterior network that assembles perspective-related information in the first place. They also exhibited reduced LFSW amplitudes at left frontal sites, at electrode F3, consistent with altered recruitment of the later frontal machinery that selects among perspectives and resolves conflicts between them. The deficit, in other words, was not confined to a single stage. Both the early assembly of social information and the later executive application of that information appeared to be blunted in the patient group.

This two-stage picture matters because it helps distinguish between two broad hypotheses about social-cognitive impairment in bipolar disorder. One possibility is that patients fail at the representational level: they cannot build an adequate model of another person’s mental state. The other is that the model is built adequately but then applied poorly, especially when the patient’s own perspective competes with the other person’s. The concurrent reduction of both the TP450 and the LFSW in this sample suggests that the application phase of theory of mind, not merely the representational phase, is compromised, and that the temporal handoff between posterior and frontal systems may be a key point of failure. The authors frame this as preliminary evidence for differences in posterior perspective-related processing and subsequent frontal processing during theory of mind application.

The methodological care behind these conclusions is worth appreciating. The study was approved by the Ethics Committee of Hangzhou Seventh People’s Hospital and conducted in accordance with the Declaration of Helsinki, with written informed consent obtained from all participants or their legal guardians. It was registered in the National Medical Research Registration and Filing Information System of China. Standard EEG preprocessing practices, including independent component analysis, were applied to clean the data, and neuropsychological measures such as the digit span test and verbal fluency test were used to characterize the participants’ broader cognitive profiles. The work was partly supported by the Construction Fund of Key Medical Disciplines of Hangzhou.

At the same time, the researchers are candid about the limits of what they can claim. The patient sample comprised only nineteen individuals, a small clinical cohort by any standard, and the manic symptoms were subthreshold rather than severe at the time of testing. The authors explicitly state that the findings require replication in larger, independent samples before they can be generalized to the broader population of people with bipolar disorder. Small ERP studies are vulnerable to sampling variability, and effect sizes at individual electrode sites can shift between cohorts. The results should therefore be read as a well-controlled first signal rather than a settled answer, a signal that nonetheless points in a theoretically coherent direction.

If the findings do replicate, the implications could extend well beyond the laboratory. Theory of mind deficits are strongly linked to real-world functioning in bipolar disorder, influencing relationship stability, occupational performance, and the ability to recognize when one’s own judgment is drifting. A temporal marker such as the TP450 or the LFSW could eventually serve as an objective index of social-cognitive state, potentially helping clinicians track recovery across mood episodes or evaluate whether an intervention is restoring not just mood but the neural machinery of social understanding. The study also adds bipolar disorder to the growing list of conditions, from autism to schizophrenia, in which the fine-grained choreography of perspective taking can now be watched in real time, one electrical oscillation at a time.

Subject of Research: Neural mechanisms of theory of mind application deficits in bipolar mania measured with event-related potentials

Article Title: Neural mechanisms underlying theory of mind application deficits in bipolar mania: an event-related potential study

Article References: Zhou, J., Zhou, X., Zhang, K., Wang, C., Li, X., & Shi, J. (2026). Neural mechanisms underlying theory of mind application deficits in bipolar mania: an event-related potential study. BMC Psychiatry. https://doi.org/10.1186/s12888-026-08652-3

Image Credits: AI Generated

DOI: 10.1186/s12888-026-08652-3

Keywords: bipolar disorder, mania, theory of mind, event-related potentials, EEG, TP450, late frontal slow wave, perspective taking, social cognition, temporoparietal junction, prefrontal cortex, BMC Psychiatry