  Schizophrenia, a mental disorder that is characterized by abnormal social
behavior and failure to distinguish one's own thoughts and ideas from reality,
has been associated with structural abnormalities in the architecture of
functional brain networks. Using various methods from network analysis, we
examine the effect of two classical therapeutic antipsychotics --- Aripiprazole
and Sulpiride --- on the structure of functional brain networks of healthy
controls and patients who have been diagnosed with schizophrenia. We compare
the community structures of functional brain networks of different individuals
using mesoscopic response functions, which measure how community structure
changes across different scales of a network. We are able to do a reasonably
good job of distinguishing patients from controls, and we are most successful
at this task on people who have been treated with Aripiprazole. We demonstrate
that this increased separation between patients and controls is related only to
a change in the control group, as the functional brain networks of the patient
group appear to be predominantly unaffected by this drug. This suggests that
Aripiprazole has a significant and measurable effect on community structure in
healthy individuals but not in individuals who are diagnosed with
schizophrenia. In contrast, we find for individuals are given the drug
Sulpiride that it is more difficult to separate the networks of patients from
those of controls. Overall, we observe differences in the effects of the drugs
(and a placebo) on community structure in patients and controls and also that
this effect differs across groups. We thereby demonstrate that different types
of antipsychotic drugs selectively affect mesoscale structures of brain
networks, providing support that mesoscale structures such as communities are
meaningful functional units in the brain.
