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David Bressler, Michael Silver; The effects of spatial attention and population receptive field size estimation on fMRI topographic mapping signals. Journal of Vision 2008;8(6):803. doi: 10.1167/8.6.803.
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© ARVO (1962-2015); The Authors (2016-present)
Classical phase-encoded fMRI mapping with rotating wedge and contracting/expanding ring stimuli is a useful method for identifying the visual field layout and boundaries of visual cortical areas in the human brain. However, recent analytical and methodological advances allow more precise and extensive mapping of topographic visual cortical areas. A new fMRI analysis technique (Dumoulin and Wandell, 2008) computes a receptive field size and visual space location for a given voxel based on the aggregate neural responses within that voxel. Also, a phase-encoded mapping task that employs covert visual spatial attention has revealed additional topographic areas in the intraparietal sulcus that were not identifiable using passive viewing alone (Silver et al., 2005). Measurement of population receptive fields results in greater spatial precision of retinotopic maps than standard phase-encoded mapping analysis (Dumoulin and Wandell, 2008). In addition, we have found that a task requiring sustained attention to a periodic stimulus results in larger and more reliable topographic mapping signals in a number of occipital and parietal cortical areas compared to either stimulus-based or attention mapping alone. A combination of these techniques, employing sustained attention to a high-contrast visual stimulus while measuring precise spatial tuning of neuronal populations, should enhance both SNR and spatial precision of fMRI visual field maps of topographic visual areas. This combined approach will also allow us to assess the effects of visual spatial attention on population receptive field sizes for all visual field locations across a number of visual cortical areas.
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