Localizing sadness activation within the subgenual cingulate in individuals: a novel functional MRI paradigm for detecting individual differences in the neural circuitry underlying depression.

Variations in frontal lobe (FL) functional anatomy, especially the subgenual cingulate gyrus (SGC) suggest that mapping on an individual rather than group level may give greater insight regarding dysregulation of the neural circuitry involved in depression, as well as potentially provide more specific or individualized treatment plans for depressed patients. We designed a functional MRI task capable of imaging FL activity in individuals, including the SGC region, using a transient sadness paradigm. We sought to develop a method that may better detect individual differences of FL subregions related to sadness, since this region has been implicated to show dysregulation in depression. The task was based on a block design that also accommodates individual differences in responsivity to a sadness induction paradigm. Individual differences from nine non-depressed healthy volunteers were analyzed. We also performed functional connectivity analyses to further characterize our findings to the networks associated with the SGC in each individual. The study was designed to account for individual variation rather than using a true experimental design; therefore, no control group was necessary. As expected, due to inter-individual variability, the specific site of SGC activation during sadness varied across individuals. Activation was also observed in other brain regions consistent with other studies of induced sadness and depression. Patterns of functional connectivity to the SGC also highlighted neural circuits known to subserve sadness and depression. This task promises to more precisely localize a given individual's functional organization of the brain circuitry underlying sadness, and potentially depression, in an efficient, standardized way. This task could potentially aid in providing individualized targets in the treatment of depression.