The neurocognitive mechanisms of spelling

Spelling (producing a word's constituent letters) constitutes a “puzzle” in that, although it is an evolutionarily recent skill whose neural circuits cannot have been specifically designed by the human genome, it is neurally instantiated in a remarkably consistent network of left hemisphere brain areas across individuals and scripts. In this article, we review the neural substrates of spelling in the context of the “neural recycling hypothesis,” which hypothesizes that recently invented skills such as spelling “recycle” evolutionarily older circuits that have suitable computational properties and brain connectivity. Specifically, for each brain area that plays a key role in spelling, we discuss how the “new” orthographic function of that area relates to its evolutionarily older function. Although work is required to more precisely identify the neural substrates that support spelling and to better characterize the computations they carry out, the neuronal recycling hypothesis provides a useful framework for understanding many of the issues that have been raised in investigations of the neurocognitive bases of literacy.