<qa>  What is the aim of the MT ratio measures?Specific Aim 3: To examine the neurocognitive correlates of frontal and striatal compromise identified using MRS and MT ratio measures in patients with MDD and controls. The associations between NAA and a global cognitive scale and MT ratios from the bilateral dorsolateral white matter and subcortical nuclei and subscales targeted to dorsolateral and striatal cognitive functioning will be examined. 