Spatial exogenous attention impacts recovery in cortically blind fields

Abstract

Cortical blindness (CB), vision loss resulting from damage to the primary visual cortex or its immediate afferents, can be partially alleviated through visual perceptual training1. However, learning does not transfer deeper within the blind field2,3. Given that exogenous spatial attention (ESA) enables perceptual learning4 and facilitates transfer5, here, we sought to reduce the spatial specificity of training by manipulating ESA. Chronic CB subjects trained on left-right, global direction integration just inside the blind field. In Flash training (n=3), a pre-cue (5-deg disc, 15Hz flicker, 200ms duration) appeared 7-deg deeper in the blind field. In Exposure training (n=3), an identical stimulus appeared simultaneously, 7-deg deeper in the blind field. Pre-cues (1-deg discs, 15Hz flicker, 200ms duration) appeared above both stimuli. For all conditions, blind-field pre-training performance approximated chance. Both ESA training conditions improved performance at trained locations, but Normalized Direction Range (NDR) thresholds following Flash training (57±16%) were poorer than after both Exposure training (35±5%), and single stimulus training without pre-cues (27±9%); the last two groups did not differ (p>.1). None of the three groups exhibited learning at the deeper locations. Thus, the Flash pre-cue reduced training efficacy in the blind field, possibly by withdrawing attentional resources from the training location into a location where no stimulus was presented. Our findings show that directing ESA deep in the blind field attracts attention automatically and hinders performance if no relevant task information is presented at that location, revealing that exogenous attention exerts its effects even in the blind field.