The human neocortex participates in a wide range of tasks, yet superficially appears to adhere to a relatively uniform six-layered architecture throughout its extent. For that reason, much research has been devoted to characterizing a single “canonical” cortical computation, repeated massively throughout the cortex, with differences between areas presumed to arise from their inputs and outputs rather than from “intrinsic” properties. There is as yet no consensus, however, about what such a canonical computation might be, little evidence that uniform systems can capture abstract and symbolic computation (e.g., language) and little contact between proposals for a single canonical circuit and complexities such as differential gene expression across cortex, or the diversity of neurons and synapse types. Here, we evaluate and synthesize diverse evidence for a different way of thinking about neocortical architecture, which we believe to be more compatible with evolutionary and developmental biology, as well as with the inherent diversity of cortical functions. In this conception, the cortex is composed of an array of reconfigurable computational blocks, each capable of performing a variety of distinct operations, and possibly evolved through duplication and divergence. The computation performed by each block depends on its internal configuration. Area-specific specialization arises as a function of differing configurations of the local logic blocks, area-specific long-range axonal projection patterns and area-specific properties of the input. This view provides a possible framework for integrating detailed knowledge of cortical microcircuitry with computational characterizations. With Adam Marblestone, MIT and Tom Dean, Google
Gary Marcus, Professor of Psychology at NYU and Visiting Cognitive Scientist at the Allen Institute for Brain Science, is the author of four books including the NYTimes Bestseller, Guitar Zero. He writes frequently for The New Yorker, Wall Street Journal, and The New York Times, and is co-editor of the forthcoming book, The Future of the Brain: Essays By The World’s Leading Neuroscientists. His research on language, evolution, computation and cognitive development has been published widely, in leading journals such as Science and Nature.