Updated scalp heuristics for localizing the dorsolateral prefrontal cortex based on convergent evidence of lesion and brain stimulation studies in depression

Abstract

BackgroundRepetitive transcranial magnetic stimulation (rTMS) is entering wider use as a therapeutic intervention for many psychiatric illnesses. The efficacy of this therapeutic intervention may depend on accurately localizing target brain regions. Recent work investigating whole-brain maps of circuits associated with depression and its successful treatment has identified foci of interest within the dorsolateral prefrontal cortex (DLPFC). ObjectiveTo create an updated scalp heuristic for localizing the DLPFC based on convergent evidence of lesion and brain stimulation studies in depression. MethodsUsing the standard MNI ICBM152 anatomical template, we localized the scalp sites at minimum Euclidean distance from target MNI coordinates and performed nasion-inion, tragus-tragus, and head-circumference measurements on the anatomical template. We then derived equations to localize these scalp sites. ResultsThe derived equations to calculate the arc length X and Y for these new targets are as follows: [Y=((NI+TrTr)/2)×0.3167 ; X=HC×0.1359] for the left anterior DLPFC[ Y=((NI+TrTr)/2)×0.2884; X=HC×0.1352] for the right anterior DLPFC[ Y=((NI+TrTr)/2)×0.2480; X=HC×0.1847] for the left posterior DLPFC[ Y=((NI+TrTr)/2)×0.2316 ; X=HC×0.1968] for the right posterior DLPFC ConclusionsThis heuristic may help localize DLPFC targets identified in previous lesion-/stimulation-mapping work. A spreadsheet calculation tool is offered to support use of this heuristic.