Investigating changes in the premotor cortex-derived frontal-striatal-thalamic subcircuit in attenuated psychosis syndrome.

Frontal-striatal-thalamic circuit impairment is presumed to underlie schizophrenia. Individuals with attenuated psychosis syndrome (APS) show longitudinal volume reduction of the putamen in the striatum, which has a neural connection with the premotor cortex through the frontal-striatal-thalamic subcircuit. However, comprehensive investigations into the biological changes in the frontal-striatal-thalamic subcircuit originating from the premotor cortex in APS are lacking. We investigated differences in fractional anisotropy (FA) values between the striatum and premotor cortex (ST-PREM) and between the thalamus and premotor cortex (T-PREM) in individuals with APS and healthy controls, using a novel method TractSeg. Our study comprised 36 individuals with APS and 38 healthy controls. There was a significant difference between the control and APS groups in the right T-PREM (odds ratio = 1.76, p = 0.02). Other factors, such as age, sex, other values of FA, and antipsychotic medication, were not associated with differences between groups. However, while FA value reduction of ST-PREM and T-PREM in schizophrenia has been previously reported, in the present study on APS, the alteration of the FA value was limited to T-PREM in APS. This finding suggests that ST-PREM impairment is not predominant in APS but emerges in schizophrenia. Impairment of the neural network originating from the premotor cortex can lead to catatonia and aberrant mirror neuron networks that are presumed to provoke various psychotic symptoms of schizophrenia. Our findings highlight the potential role of changes in a segment of the frontal-thalamic pathway derived from the premotor cortex as a biological basis of APS.