ABSTRACT

Different parts of the brain perform different, relatively self-contained functions. In many cases, this functional modularity is undoubtedly innately predetermined, but in other cases it seems likely that experience plays a significant role. We review evidence for experience-dependent neural modularity in three domains: reading, writing, and arithmetic. These skills are recent developments on an evolutionary time scale, they are not shared with nonhuman species, and they do not develop in humans without explicit, systematic instruction. It is therefore unlikely that their neural organization is innate. Nevertheless, findings from case studies of neurological patients and, more recently, from neuroimaging experiments suggest that the brains of educated adults do include neural modules dedicated to these functions.

READING, WRITING, AND ARITHMETIC IN THE BRAIN: NEURAL SPECIALIZATION FOR ACQUIRED FUNCTIONS

One of the central tenets of modern cognitive neuroscience is that the cortical architecture underlying cognition is organized into anatomically segregated subsystems (modules) that perform different functions. Most of the evidence for a modular organization comes from work with patients who are brain damaged. Focal brain lesions occasionally produce impairments that seem to affect a single behavioral function (e.g., color processing, visual object recognition, motor control on one side of the body) without significantly affecting others. A natural (although not always valid) interpretation of such dissociations is that the impaired function depends on a neural subsystem or module that is anatomically segregated from other functions and that is therefore vulnerable to selective damage.