Schizophrenia (SZ) is a complex disorder characterized by a range of behavioral and
cognitive symptoms as well as structural and functional alterations in multiple cortical
and subcortical structures. SZ is associated with reduced functional network connectivity
involving core regions such as the anterior cingulate cortex (ACC) and the thalamus.
However, little is known whether effective coupling, the directed influence of one
structure over the other, is altered during rest in the ACC-thalamus network.We collected
resting-state fMRI and diffusion-weighted MRI data from 18 patients and 20 healthy
controls. We analyzed fronto-thalamic effective connectivity using dynamic causal
modeling for cross-spectral densities in a network consisting of the ACC and the left
and right medio-dorsal thalamic regions. We studied structural connectivity using
fractional anisotropy (FA).We found decreased coupling strength from the right thalamus
to the ACC and from the right thalamus to the left thalamus, as well as increased
inhibitory intrinsic connectivity in the right thalamus in patients relative to controls.
ACC-to-left thalamus coupling strength correlated with the Positive and Negative Syndrome
Scale (PANSS) total positive syndrome score and with delusion score. Whole-brain structural
analysis revealed several tracts with reduced FA in patients, with a maximum decrease
in white matter tracts containing fronto-thalamic and cingulo-thalamic fibers.We found
altered effective and structural connectivity within the ACC-thalamus network in SZ.
Our results indicate that ACC-thalamus network activity at rest is characterized by
reduced thalamus-to-ACC coupling. We suggest that positive symptoms may arise as a
consequence of compensatory measures to imbalanced fronto-thalamic coupling.
