Abstract
The degree to which neural responses in visual cortex vary as a function of stimulus category is a longstanding topic of vision science. The possibility of word-selective processing in visual cortex is supported by the results of numerous behavioral and fMRI studies, many of which suggest left-lateralized visual processing of word stimuli. In the current study, we hypothesized that left-lateralized word-selective visual processing would be reflected in the results of population receptive field (pRF) modeling. We used fMRI to measure pRF properties in occipitotemporal cortex (OT) in response to words and non-word control stimuli to determine whether or not pRF properties differ between the two hemispheres. We also varied the format in which these stimuli were viewed, either individually or in the context of sentences displayed within a sweeping bar aperture. We found that left OT showed greater word-selective fMRI responses than right OT in the pRF estimation experiments, as well as in corresponding independent fMRI localizer experiments that allowed us to identify word-selective subregions of OT. More voxels in left OT showed pRFs for word than non-word stimuli. Additionally, word-selective subregions of left OT showed greater foveal bias for word stimuli as compared to non-word stimuli. This indicates a correspondence between pRF properties and word-selective visual processing. In contrast, no difference in pRFs was found between word and non-word stimuli in right OT. Word-selective left OT showed evidence of larger visual field coverage than word-selective right OT, which indicates left lateralization of pRFs. Lastly, we observed a greater number of word-selective voxels in left OT and larger coverage for the single word view experiment. These results provide new evidence for stimulus specific brain responses in the OT using pRF modeling, and support the idea that left-lateralized word-selective visual processing can be studied effectively using pRF estimation.
Acknowledgement: Research reported here was supported by the National Institute of General Medical Sciences (P20 GM103650)