A novel hypothesis for the original functionality of the Visual Word Form Area: Processing shape sequences

Abstract

There is ongoing debate about what characteristics of left ventral occipitotemporal cortex drive development of the Visual Word Form Area (VWFA). We offer a new hypothesis. A summary of occipitotemporal organization indicates that the VWFA falls in a cortical region supporting action analysis, rather than object recognition. We discuss evidence that letters are serially processed in a top-down manner during the initial years of reading acquisition, and propose that this sequential activation of letter representations causes the VWFA to develop in motion-sensitive cortex specialized for processing of non-biological shape sequences. Supporting this hypothesis, a new fMRI analysis identifies a left-lateralized region that responds more strongly to dynamic motion of objects than humans; this region's location (-48, -55, -8) falls almost exactly at the canonical VWFA coordinates (-45, -57, -12).

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

“…It responds more strongly to dynamic motion of hands or scissors than static hands or scissors (Costantini et al, 2005). In the left hemisphere only, this region responds more strongly to dynamic motion of actual objects than humans (Whitney et al, 2019).…”

“…A priori, one would expect visual word recognition to be carried out via the object-recognition system. Surprisingly, the VWFA is not located in the cortical region specialized for recognition of inanimate static objects; rather, the VWFA forms in an area that processes the motion of objects undergoing changes in shape (dynamic motion) (Whitney, Ross, Zhou, & Strother, 2019). Why would this be?…”

“…Dynamic object motion is analyzed as a temporal sequence of shapes, and letter processing is obviously serial in early reading acquisition. Therefore, the shape-sequence area is recruited to encode and recognize letter sequences (Whitney et al, 2019).…”

“…We propose that inability to narrow visual attention to individual letters precludes the sequential activation of occipitotemporal letter representations which normally drives VWFA development. Before presenting this account of dyslexia, we review Whitney et al (2019) in more detail, and summarize ongoing experimental research.…”