Abstract
Neuroimaging studies have shown that when subjects view written words, there is activation in the fusiform gyrus, more on the left than on the right, in an area called the ‘visual word form area’ (VWFA). In patients, lesions of the left medial occipitotemporal cortex are associated with alexia, whereas lesions of the right medial occipitotemporal cortex are found in some prosopagnosic patients, some of whom also have problems identifying handwriting. These observations suggest that encoding handwriting from written material may occur in the right fusiform cortex, whereas encoding word forms may occur in the left fusiform cortex. To test these hypotheses, we performed an fMRI adaptation experiment in 11 subjects. Functional localizers, one using a contrast between faces and objects and another using a contrast between English and Korean words identified the right fusiform face area (FFA) and the bilateral VWFA respectively. The adaptation run was a block-design consisting of three different experimental conditions; one containing different words in different handwriting, a second containing the same word in different handwriting, and a third containing different words in the same handwriting. Contrary to expectations, we found a significant adaptation for handwriting (p[[lt]].021) but not for word identity in the left VWFA, and a trend to adaptation for handwriting (p[[lt]].065) but not word identity in the right VWFA. No significant adaptation effects were found in the right FFA. These findings raise questions about whether the VWFA encodes word forms invariant of the script in which they are written. Rather than this invariance, they show a sensitivity of the VWFA to script form that is independent of word form.
This work was supported by operating grants from CIHR (MOP-77615) and NIMH (1R01 MH069898). CJF was supported by a CIHR Doctoral Research Award and a Michael Smith Foundation for Health Research Senior Graduate Studentship. GI was supported by the Alzheimer Society of Canada and the Michael Smith Foundation for Health Research. JJSB was supported by a Canada Research Chair and a Senior Scholarship from the Michael Smith Foundation for Health Research.