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Ahrens, J.

Publications and source records attributed to Ahrens, J..

2 recordsLinked to original sources

Distributed neurophysiological dynamics link perception, action, and language in schizophrenia

Schizophrenia is characterized by disturbances in both perception and expression that profoundly impair social functioning, yet these domains are typically studied in isolation. Predictive processing theories suggest that such symptoms may arise from abnormal updating of internal models, but the neural mechanisms linking perceptual and expressive dysfunction remain unclear. Using magnetoencephalography during multisensory perception and motor tasks, we tested whether beta-band activity (15-30 Hz), a neural signal implicated in predictive control, provides a shared substrate across domains. Compared to healthy individuals, patients with schizophrenia showed attenuated event-related modulation of beta activity, including weaker beta suppression during sensory processing and delayed or reduced post-movement beta rebound. These abnormalities were associated with a widened audiovisual temporal binding window, indicating atypical multisensory integration. Multivariate analyses further revealed that reduced beta modulation across sensory and motor systems covaried with impoverished semantic diversity, simplified syntactic structure in natural speech, and greater clinical symptom burden. Notably, beta abnormalities emerged as distributed latent patterns spanning sensory, motor, and frontotemporal regions. Together, these findings identify diminished event-related beta modulation as a common neural signature linking disrupted multisensory integration, action monitoring, and language organization in schizophrenia. We situate perceptual and expressive impairments within a unified framework of predictive dysfunction and advance a mechanistically grounded account that highlights beta dynamics as a promising target for future mechanistic and translational studies in psychosis. Significance StatementSchizophrenia disrupts both how people perceive the world and how they express their thoughts, yet these symptoms are usually studied separately. Using magnetoencephalography during multisensory and motor tasks, we identify a shared neural mechanism linking these domains: reduced event-related modulation of beta-band (15-30 Hz) activity, a signal implicated in predictive control. Compared to healthy individuals, patients showed diminished beta changes during sensory processing and movement completion, suggesting reduced flexibility in updating internal models. Importantly, this neural pattern covaried with abnormal audiovisual binding, disorganized natural speech, and greater clinical severity. These findings reveal distributed beta modulation as a cross-domain neural marker of predictive dysfunction, offering a unified framework for understanding perceptual and expressive disturbances in schizophrenia.

neuroscience↗

Converging effects of cannabis and psychosis on the dopamine system: A longitudinal neuromelanin-sensitive MRI study in cannabis use disorder and first episode schizophrenia.

ImportanceDespite evidence that individuals who use cannabis early in life are at elevated risk of psychosis and that the neurotransmitter dopamine has a role in both conditions, the mechanism linking the two conditions remains unclear. ObjectiveTo use neuromelanin-sensitive MRI (neuromelanin-MRI), a practical, proxy measure of dopamine function, to assess whether a common alteration in the dopamine system may be implicated in cannabis use and psychosis and whether this alteration can be observed in cannabis users whether or not they have a diagnosis of first-episode schizophrenia. Design, Setting, and ParticipantsThis longitudinal observational study recruited participants from 2019 to 2023 from an early intervention service for psychosis in London, Ontario, Canada. The sample consisted of 25 participants with cannabis use disorder (CUD) and 36 participants without CUD (nCUD), of which 28 had first-episode schizophrenia (FES). One-year follow-up was completed for 12 CUD and 25 nCUD participants. Main Outcomes and MeasuresNeuromelanin-MRI contrast within the substantia nigra (SN) and within a subregion previously linked to psychosis severity (a priori psychosis region of interest) and diagnoses of schizophrenia-spectrum disorder and cannabis use disorder derived from the Structured Clinical Interview for DSM-5. Linear mixed effects analyses were performed relating neuromelanin-MRI contrast to clinical measures. ResultsWe found that CUD was associated with elevated neuromelanin-MRI signal in a cluster of ventral SN voxels (387 of 2060 SN voxels, pcorrected=0.027, permutation test). Furthermore, CUD was associated with elevated neuromelanin-MRI signal in an SN subregion previously documented to have elevated signal in relation to untreated psychotic symptoms (t92 =2.12, p=0.037). In contrast, FES was not associated with a significant alteration in neuromelanin-MRI signal (241 SN voxels had elevated signal, pcorrected=0.094). Conclusions and RelevanceThese findings suggest that elevated dopamine function in a critical SN subregion may contribute to the risk of psychosis in people with CUD. Thus, cannabis affects the long-suspected final common pathway for the clinical expression of psychotic symptoms. Imaging the dopamine system with neuromelanin-MRI may index long-term dopamine turnover. Key PointsO_ST_ABSQuestionC_ST_ABSIs the same midbrain dopamine pathway impacted by cannabis as in psychosis? FindingsCannabis use disorder participants had elevated neuromelanin-MRI signal in a cluster of ventral substantia nigra voxels and in a subregion previously documented to have elevated signal in relation to untreated psychotic symptoms. MeaningIncreased dopamine functioning in the ventral substantia nigra may contribute to the risk of psychosis in people with cannabis use disorders.

neuroscience↗