Our aim was to examine how a scotoma (blind area) caused by glaucoma affects the response of the visual cortex that normally receives input from this region, specifically during stimulation of the adjacent visual field. Using fMRI, patients were tested monocularly with 16 s blocks of radially oriented alternating checkerboards placed (i) within the scotoma; (ii) at the edges of the scotoma; and (iii) across the scotoma, as well as equivalent locations in the other hemifield. The ‘good eye’ viewing condition acted as an ideal control: the difference between activation through good and affected eyes is an index of the degree of recruitment. As expected, presenting a stimulus to the blind scotoma region resulted in less activation than stimulating the analogous location in the good eye. However, presenting stimuli either from the fovea to the edge of the scotoma, or extending across the scotoma, resulted in significantly greater activation in the cortex representing the blind region than equivalent stimulation in the ‘good’ eye. These results suggest the visual cortex that loses normal input due to glaucoma ‘extrapolates’ from information presented around the scotoma. This may be the neural correlate of the ‘filling in’ that prevents awareness of the scotoma.
|Number of pages||1|
|Issue number||1 supplement|
|Publication status||Published - 2011|