1. Anatomical connectivity properties as measured by DTI and effective connectivity as measured by TMS/EEG will provide complementary information regarding the timing, the spatial extent, and the white matter interconnections between brain regions.
2. Anatomical connectivity (with DTI) and effective connectivity (with TMS/EEG) can be used to characterize differences in brain connectivity between healthy control subjects and patients with schizophrenia.
1. To develop methods for combining measurements of anatomical connectivity with diffusion tensor imaging (DTI) and effective cortico-cortical connectivity using transcranial magnetostimulation (TMS) with EEG.
2. To apply these methods to the characterization and comparison of cortico-cortical anatomical and effective connectivity patterns in healthy control subjects.
3. To apply these methods to the characterization and comparison of cortico-cortical anatomical and effective connectivity patterns in patients with schizophrenia. The measurements will be compared between schizophrenia patients and controls.
DTI data will be collected on all subjects and maps of the mean diffusivity and diffusion anisotropy will be computed. White matter tractography (WMT) will be used to estimate anatomic patterns of white matter connectivity between cortical regions. Properties of the DTI measures and WMT estimates will be used as metrics of anatomic connectivity. In collaboration with Dr. Giulio Tononi, effective connectivity properties will be measured using the timing and amplitudes of electrical responses by EEG in response to TMS pulses applied to the subject's scalp. The positioning of the TMS coil will be determined by the results of the WMT estimates. Both healthy controls and patients with schizophrenia will be studied. The anatomic connectivity measurements by DT-MRI and the effective connectivity measurements by TMS/EEG will be compared both within subjects and between groups.