Scientists identify brain regions associated with auditory hallucinations in borderline personality disorder

Recent research published in Psychiatry Research: Neuroimaging suggests that people with borderline personality disorder who hear voices show distinct structural differences in certain brain regions. These physical brain differences tend to appear in areas involved in language processing, sensory integration, and emotional regulation. The findings provide evidence that hallucinations might arise from partly shared biological mechanisms across different mental health conditions.

Borderline personality disorder, or BPD, is a severe mental health condition characterized by deep difficulties with self-image, unstable relationships, and challenges in managing emotions. Beyond these well-known symptoms, up to half of individuals with this diagnosis also experience psychotic symptoms. Specifically, many of these patients experience auditory verbal hallucinations, which means they hear voices that other people do not hear.

Historically, the scientific focus on auditory hallucinations has centered on schizophrenia. Because of this, the physical brain characteristics linked to hearing voices in borderline personality disorder have remained poorly understood. Scientists wanted to see if specific brain structures differ in people with borderline personality disorder who hear voices compared to those who do not.

“Auditory verbal hallucinations refer to the experience of hearing voices in the absence of an external auditory stimulus. Although they are most commonly associated with schizophrenia, these experiences can also occur in other psychiatric conditions, including borderline personality disorder,” said study author Robert Christian Wolf, deputy director at the Department of General Psychiatry at Heidelberg University Hospital.

“Despite their relatively high prevalence in BPD, the neurobiological basis of these experiences has been studied far less in this population. We wanted to address this gap by examining whether structural brain alterations associated with hallucinations in schizophrenia might also appear in BPD. Understanding this could help clarify whether hallucinations reflect shared neural mechanisms across different mental disorders.”

The researchers conducted a study using magnetic resonance imaging to look at brain structure. They specifically measured gray matter volume, which refers to the dark tissue containing the main body of nerve cells involved in memory and speech. The sample included 76 right-handed female participants, a choice made to minimize the impact of sex-specific biological differences.

The study group was divided into three specific categories based on their clinical evaluations. The sample consisted of 20 patients with borderline personality disorder who currently or previously heard voices. It also included 26 patients with the same diagnosis who had never heard voices, along with 30 healthy control participants with no psychiatric history.

To measure clinical aspects, the researchers used a combination of interviews and self-report questionnaires. They verified psychiatric diagnoses using a standardized clinical interview designed for personality disorders. The specific characteristics of the hallucinations, such as the emotional distress they cause, were measured using the Psychotic Symptom Rating Scales.

The participants then underwent a brain scan using a high-resolution magnetic resonance imaging machine. The scanner captured detailed three-dimensional images of their brain anatomy. The scientists analyzed these images using specialized software to compare the volume of gray matter across the entire brain for all three groups.

When comparing all participants with borderline personality disorder to the healthy control group, the researchers found overall reductions in gray matter volume. These reductions appeared in the frontal and parietal lobes, which help with movement and sensory processing. They also appeared in the cingulate cortex, an area tied to emotion, and the cerebellum, which coordinates physical movement and some cognitive functions.

The comparisons between the two patient groups revealed additional physical differences specific to hallucination symptoms. Patients who experienced auditory hallucinations showed lower gray matter volume in occipital regions of the brain compared to patients who did not hear voices. The occipital lobe sits at the back of the brain and is traditionally associated with visual processing, but it also plays a role in integrating different sensory inputs.

“One notable finding was the involvement of occipital brain regions, which are typically associated with visual processing,” Wolf told PsyPost. “Hallucinations are often studied mainly in relation to auditory and language related brain areas. The presence of structural differences in occipital regions suggests that broader sensory integration processes may also be involved. This supports the view that hallucinations arise from distributed brain networks rather than from a single brain region.”

The researchers also looked closely at a brain area called the inferior frontal gyrus, which contains regions essential for speech production and language processing. They found that patients with borderline personality disorder who heard voices had reduced gray matter in this language center compared to healthy individuals. This suggests a direct physical link between language networks and the experience of hearing internal voices.

Finally, the researchers matched the brain scans of the hallucinating patients with their symptom severity scores. They found that higher distress and symptom severity correlated with lower gray matter volume in several key areas. These areas included regions of the temporal lobe, which processes sound, as well as the frontal lobe, parietal lobe, and cerebellum.

“Our findings suggest that voice hearing experiences in people with BPD are linked to structural differences in several brain regions involved in language processing, sensory integration, and emotional regulation,” Wolf explained. “Some of these patterns overlap with findings from schizophrenia research, supporting the idea that hallucinations may arise from partly shared neural mechanisms across different diagnoses. At the same time, the results also indicate that these experiences likely emerge from complex interactions between cognitive, sensory, and emotional brain systems.”

“The structural differences we observed are subtle and occur at the group level. This means they cannot be used to diagnose an individual person or determine whether someone will experience hallucinations. Instead, the findings contribute to a better understanding of the brain networks that may be involved in these experiences. The practical significance therefore lies primarily in improving scientific knowledge about the mechanisms underlying hallucinations.”

“In the long term, this knowledge could help inform and refine treatment strategies, for example through the optimization of non-invasive neurostimulation approaches such as transcranial magnetic stimulation,” Wolf continued.

While these findings point to overlapping brain patterns between borderline personality disorder and schizophrenia, the scientists caution against misinterpreting the results. It is important to remember that hallucinations in borderline personality disorder are not identical to those in schizophrenia. Factors such as severe trauma exposure, high stress sensitivity, and intense emotional dysregulation likely play a distinct role in how these sensory experiences emerge in borderline personality disorder.

The study also comes with a few limitations that provide context for the findings. The research used a cross-sectional design, meaning it only captured a single snapshot in time. Because of this, the scientists cannot determine how these brain structures might change as the disorder progresses over the years.

“An important next step is to investigate these processes over time and to combine structural imaging with functional neuroimaging approaches that can examine how brain networks interact during internal speech and related cognitive processes,” Wolf told PsyPost. “Longitudinal studies would also help clarify how hallucinations develop and change across the course of the disorder. In the long term, this research may contribute to more targeted therapeutic strategies that address the neural systems involved in these experiences.”

“One important point is that hallucinations should be understood as a transdiagnostic symptom. This means they can occur across different mental health conditions rather than belonging to a single diagnosis. Studying such symptoms across diagnostic boundaries may provide a more precise understanding of the underlying brain mechanisms and may help move psychiatric research toward a more neurobiologically informed mechanistic perspective that focuses on functional domains and related symptoms rather than traditional diagnostic categories.”

The study, “Structural correlates of auditory verbal hallucinations in patients with borderline personality disorder,” was authored by Mert Koc, Marie-Luise Otte, Mike M. Schmitgen, Nadine D. Wolf, Yunus Balcik, Chantal Tech, Yéléna Le Prieult, and Robert C. Wolf.