The visual what for area: words and pictures in the left fusiform gyrus.

摘要

An area in the left fusiform gyrus labelled the Visual Word Form Area (VWFA) is claimed to be especially, or even selectively, responsive to words. We explored how stimulus type and task demands affect activity in this area by conducting a PET experiment where words and pictures were presented in two conditions that differed in demands on shape processing: colour decision and categorization. The subjects also performed an object decision task with pictures only. The imaging data revealed a main effect of stimulus type: rCBF was higher during word compared with picture processing. When compared individually for colour decision and categorization, the difference between words and pictures was only significant during colour decision, although a trend was present during categorization also. rCBF in the VWFA was highest during the object decision task, where only pictures were presented. Our findings indicate that the putative VWFA is activated more by written words than pictures, but only under certain circumstances. As demands on shape processing increase, the difference in activation between words and pictures decreases and can even be abolished. We suggest that activation in the VWFA could reflect shape configuration-the integration of shape elements into elaborate shape descriptions corresponding to whole objects or words. This process may be required to different degrees for pictures and words depending on task demands.