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Robert Hess, Benjamin Thompson, Xingfeng Li, Bruce Hansen; The mapping of spatial frequency across amblyopic visual cortex. Journal of Vision 2009;9(8):1056. doi: https://doi.org/10.1167/9.8.1056.
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Aims: Human amblyopes exhibit spatial frequency-specific behavioural deficits and we sought to understand how spatial frequency is represented in the amblyopic cortex and what aspects of processing might be disrupted.
Methods: MR images were acquired on a 1.5T Siemens scanner using a TR of 3sec. We used a phase-encoded design with a sinusoidal checkerboard stimulus (8Hz; 80% contrast; 20° field) that cycled from high to low spatial frequency (0.5–6c/d) and vice versa. Here we compare the phase responses as a function of stimulus spatial frequency.
Results: Following on from the approach of Sasaki et al, (2001 Nat. Acad Sci USA, 98, 2077) in normals, we found a similar mapping of spatial frequency across the amblyopic cortex, going from higher spatial frequencies more centrally, to lower spatial frequencies more peripherally. However, while there is a similar relationship between preferred spatial frequency for the amblyopic and normal eye, the spatial frequency map is less regular for the amblyopic input, reflecting the fact that fewer voxels exhibit a clear spatial frequency preference.
Conclusions: Spatial frequency is mapped in a qualitatively similar way for the normal and fellow amblyopic eye, although voxels exhibit less spatial frequency preference for the amblyopic eye input. This can be modeled as a broader spatial frequency tuning of individual cortical cells receiving input from the amblyopic eye.
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