Mapping visual symbols onto spoken language along the ventral visual stream

Description: Reading involves transforming arbitrary visual symbols into sounds and meanings. This study interrogated the neural representations in ventral occipital-temporal cortex (vOT) that support this abstraction process. 24 adults learned to read two sets of 24 novel words that shared phonemes and semantic categories but were written in different artificial orthographies. Following two-weeks of training, participants read the trained words whilst neural activity was measured with fMRI. Representational similarity analysis on item-pairs from the same orthography revealed that right vOT was sensitive to basic visual similarity whereas left vOT coded for letter identity, and that mid- vOT showed greater invariance abstraction across letter position whereas than posterior vOT did not. Further along the left vOT processing stream in mid-to-anterior vOT, item-pairs that shared sounds or meanings, but which were represented by different orthographies (and hence had no visual similarity), had similar neural patterns. These results reveal a hierarchical, posterior-to-anterior gradient in vOT regions, in which representations are transformed from positionlocation-specific to positionlocation invariant, and from visual representations to representations that transmit information about the phonological and semantic attributes of printed words. This demonstrates the critical role of the vOT processing stream in abstracting linguistic information from written word forms.

Related article: http://doi.org/10.1073/pnas.1818575116