Novel Cognitive Functions Arise at the Convergence of Macroscale Gradients.

Functions in higher-order brain regions are the source of extensive debate. Past trends have been to describe the brain in terms of a set of functional modules, especially posterior cortical areas, but a new emerging paradigm focuses on interactions between neighboring representations. In this review, we synthesize emerging evidence that a variety of novel functions in the higher-order brain regions are due to convergence. Convergence of macroscale gradients brings feature-rich representations into close proximity, presenting an opportunity for novel functions to arise. Using the TPJ as an example, we demonstrate that convergent areas have three properties, they: (1) are at the peak of the processing hierarchy, (2) combine the most abstracted representations, and (3) are equidistant from other convergent areas. As information moves from primary sensory cortices to higher-order brain regions, it becomes abstracted and hierarchical. Eventually, these processing gradients converge at a point equally and maximally distant from their sensory origins. This convergence, which produces multifaceted cognitive functions, such as mentalizing another person's thoughts or projecting into a future space, parallels evolutionary and developmental characteristics of such regions, resulting in new cognitive and affective faculties.