The Visual Word Form Area natively processes shape sequences: Implications for developmental dyslexia

Abstract

The Visual Word Form Area (VWFA) is a cortical region that adapts to support fluent word recognition. Surprisingly, the region of ventrolateral occipitotemporal cortex that becomes VWFA is specialized for processing the motion of inanimate objects that change shape. Such motion is neurally analyzed as a temporal sequence of shape 'snapshots'. We have proposed that the VWFA develops in this region because letter representations are serially activated in occipitotemporal cortex during typical reading acquisition. Therefore, the region that analyzes inanimate shape sequences is recruited to recognize letter sequences. We discuss the implications of this account for developmental dyslexia. In particular, inability to focus attention down to a single letter may preclude the serial letter selection that typically drives VWFA formation. Such a deficit would also interfere with acquisition of cortical letter-phoneme connections. Instead, compensated dyslexics employ the ventromedial object-recognition system for whole-word recognition, and the subcortical procedural system for phonological decoding.