bioRxiv2019
In schizophrenia, among the most consistent brain changes are both aberrant dopamine function in the dorsal striatum and aberrant intrinsic functional connectivity (iFC) between distinct cortical networks and thalamic nuclei; however, it is unknown whether these changes are pathophysiologically related. Such a relationship is expected because cortico-thalamic-connectivity is modulated by striatal dopamine within topographically distinct, parallel but interacting cortico-basal-ganglia-thalamic circuits. We hypothesized: (1) Within-circuits, aberrant striatal dopamine contributes to aberrant cortico-thalamic-iFC, specifically, associative-striatum dopamine contributes to salience-network-thalamic-iFC, and sensorimotor-striatum dopamine to auditory-sensorimotor-network-thalamic-iFC. (2) Due to between-circuits interactions following an anterior-to-posterior gradient, salience-network-centered-system changes contribute to auditory-sensorimotor-network-centered-system changes. To test these hypotheses, 19 patients with schizophrenia during symptomatic remission of positive symptoms and 19 age- and sex-comparable controls underwent simultaneous fluorodihydroxyphenyl-L-alanine positron emission tomography (18F-DOPA-PET) and resting-state functional magnetic resonance imaging (rs-fMRI). The influx constant kicer based on 18F-DOPA-PET was used to measure dopamine synthesis capacity (DSC), indicating striatal dopamine function; correlation coefficients between rs-fMRI time-series of cortical networks and thalamic regions-of-interest were used to measure iFC. In the salience-network(SAL)-centered-system, patients had reduced associative-striatum-DSC, which correlated positively with SAL-mediodorsal-thalamus-iFC and mediated the reduction of SAL-thalamic-iFC in patients. In the auditory-sensorimotor-network(ASM)-centered-system, patients had reduced sensorimotor-striatum-DSC, which correlated positively with ASM-ventrolateral-thalamus-iFC, but did not mediate increased ASM-thalamic-iFC in patients. Finally, aberrant DSC and iFC of the SAL-centered-system mediated corresponding changes in the ASM-centered-system. Results demonstrate that cortico-thalamic-dysconnectivity links with aberrant striatal dopamine in schizophrenia - in a topographically distinct way, with an anterior-to-posterior gradient, and primary changes in the SAL-centered system.