Causal evidence for frontal cortex organization for perceptual decision making

Significance The frontal cortex has long been understood as the seat of higher level cognition. Recent research, however, highlights its role in modulating perception. Here, we present a theoretical framework for frontal involvement in perceptual decision making and test it with the causal technique of transcranial magnetic stimulation. We find that progressively rostral regions of frontal cortex are involved in the control of progressively later stages of perceptual decision making. These causal findings are further corroborated by functional MRI and simulations of a dynamic model of decision making. Our results point to a critical role of the frontal cortex in the control of perceptual processes and reveal its intrinsic organization in support of modulating perception. Although recent research has shown that the frontal cortex has a critical role in perceptual decision making, an overarching theory of frontal functional organization for perception has yet to emerge. Perceptual decision making is temporally organized such that it requires the processes of selection, criterion setting, and evaluation. We hypothesized that exploring this temporal structure would reveal a large-scale frontal organization for perception. A causal intervention with transcranial magnetic stimulation revealed clear specialization along the rostrocaudal axis such that the control of successive stages of perceptual decision making was selectively affected by perturbation of successively rostral areas. Simulations with a dynamic model of decision making suggested distinct computational contributions of each region. Finally, the emergent frontal gradient was further corroborated by functional MRI. These causal results provide an organizational principle for the role of frontal cortex in the control of perceptual decision making and suggest specific mechanistic contributions for its different subregions.