Redundant target effects in the hemianopic field of patients with primary visual cortex lesions

Poster Session F - Tuesday, April 16, 2024, 8:00 – 10:00 am EDT, Sheraton Hall ABC

Jessica Smith¹, Kel-Li Chen¹, Ayat Karim¹, Bradford Mahon¹; ¹Carnegie Mellon University

The redundant target effect (RTE) refers to the observation that simple response times are faster when two targets are presented simultaneously than when a single target is presented. Previous studies have demonstrated an RTE for a variety of visual stimuli (e.g., dots, words, faces), but it is unknown how simple response times may be modulated for images of different categories, and how potential category modulations interact with visual field location. The systems involved in processing different categories can have dissociable retinotopic or laterality biases (e.g., faces lateralized to the right hemisphere, tools to the left hemisphere). We present an RTE study using images from visual categories known to differentially involve dissociable brain regions and pathways: including neutral and fearful faces, animals, tools, and low, medium and high spatial frequency sinusoidal gratings. All stimuli were contrast normalized, matched for overall luminance, and presented against an isoluminant background. We tested a sample of healthy neurotypical controls and an individual presenting with right homonymous hemianopia after a focal stroke affecting left striate cortex. For all participants, RTE magnitudes varied by image category and across the visual field, suggesting that even in a simple detection task there are dissociable forms of processing for different classes of visual inputs. The presence of an RTE when redundant stimuli were presented in the blind field of the individual with hemianopia suggests that simple detection for some types of visual images can be processed in the absence of an experience of seeing.

Topic Area: PERCEPTION & ACTION: Vision