Visual Perception in the Periphery: The Role of Covert Attention Vectors in the Extraction of Semantic Information

Abstract

Under covert attention, our visual perception deteriorates dramatically as eccentricity increases. This reduction of peripheral visual acuity (PVA) is partially due to the coarse sampling of the retinal ganglion cells towards the periphery, but this property cannot be solely responsible. Other factors, such as character crowding, have been studied, yet the origin of the poor PVA is not entirely understood. This gap motivated us to investigate the PVA by varying the crowding conditions systematically. Under completely crowded conditions (i.e. resembling a full page of text), PVA was observed to be eight times worse than the PVA under uncrowded conditions. By partially crowding the periphery, we obtained PVA values between the fully crowded and uncrowded conditions. On the other hand, crowding the fovea center while leaving the periphery uncrowded improved PVA relative to the uncrowded case. These results support a model for a top-down "covert attention vector" that assists the resulting PVA in a manner analogous to saccadic eye movement for overt attention. We speculate that the attention vector instructs the dorsal pathway to transform the peripheral character to the foveal center. Then, the scale-invariant log-polar retinotopy of the ventral pathway can scale the centered visual input to match the prior memory of the specific character shape.