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Abstract:
Visual receptive fields have dynamic properties and it has been reported that receptive field organization can change following chronic visual deprivation. We used 4.7 Tesla functional magnetic resonance imaging (fMRI) to study the visual cortex of two healthy adult macaque monkeys, and two monkeys with binocular central retinal lesions. FMRI experiments were performed under light remifentanyl induced anesthesia (Logothetis et al. Nat. Neurosci. 1999). Standard moving horizontal/vertical bar stimuli and expanding ring stimuli were presented to the subjects and the population receptive field (pRF) method (Dumoulin and Wandell, Neuroimage 2008) was used to measure retinotopic maps and pRF sizes in early visual areas. In general, there is good agreement between maps obtained by fMRI and previous results obtained by anatomical and physiological methods. FMRI pRF sizes and electrophysiology measurements in healthy animals show similar trends. For the monkeys with a photocoagulation induced retinal lesion, a former study has shown that the fMRI defined lesion projection zone (LPZ) border in V1 did not shift following the lesion (Smirnakis et al. Nature 2005). We reanalyzed these data using pRF methods and suggest that pRF size in the non-deafferented V1 showed little, if any, change on average. However, voxels inside the LPZ of areas V2/V3 do show visual modulation over time following the lesion, suggesting that area V2/V3 has more capacity for plasticity than area V1. Further investigation using fMRI and standard electrophysiology methods is in progress.
