Cerebellar-Prefrontal Network Connectivity and Negative Symptoms in Schizophrenia

TLDR

Psychiatric neuroimaging is hampered by reliance on correlational data, making it difficult to determine whether negative symptoms in schizophrenia are causal, compensatory, or epiphenomenal, and these symptoms remain largely treatment‑resistant. The study first identified a dorsolateral prefrontal cortex–cerebellum functional connectivity network linked to negative symptoms using resting‑state fMRI in 44 patients, then tested its modulation by applying five days of twice‑daily transcranial magnetic stimulation to the cerebellar midline in 11 patients. TMS‑induced restoration of the cerebellar–dorsolateral prefrontal network significantly reduced negative symptoms, establishing a causal link between connectivity breakdown and symptom severity and supporting a novel network‑based therapeutic target.

Abstract

The interpretability of results in psychiatric neuroimaging is significantly limited by an overreliance on correlational relationships. Purely correlational studies cannot alone determine whether behavior-imaging relationships are causal to illness, functionally compensatory processes, or purely epiphenomena. Negative symptoms (e.g., anhedonia, amotivation, and expressive deficits) are refractory to current medications and are among the foremost causes of disability in schizophrenia. The authors used a two-step approach in identifying and then empirically testing a brain network model of schizophrenia symptoms.In the first cohort (N=44), a data-driven resting-state functional connectivity analysis was used to identify a network with connectivity that corresponds to negative symptom severity. In the second cohort (N=11), this network connectivity was modulated with 5 days of twice-daily transcranial magnetic stimulation (TMS) to the cerebellar midline.A breakdown of connectivity in a specific dorsolateral prefrontal cortex-to-cerebellum network directly corresponded to negative symptom severity. Restoration of network connectivity with TMS corresponded to amelioration of negative symptoms, showing a statistically significant strong relationship of negative symptom change in response to functional connectivity change.These results demonstrate that a connectivity breakdown between the cerebellum and the right dorsolateral prefrontal cortex is associated with negative symptom severity and that correction of this breakdown ameliorates negative symptom severity, supporting a novel network hypothesis for medication-refractory negative symptoms and suggesting that network manipulation may establish causal relationships between network markers and clinical phenomena.