The object advantage can be eliminated under equiluminant conditions.
A key phenomenon supporting the existence of object-based attention is the object advantage, in which responses are faster for within-object, relative to equidistant between-object, shifts of attention. The origins of this effect have been variously ascribed to low-level "bottom-up" sensory processing and to a cognitive "top-down" strategy of within-object attention prioritization. The degree to which the object advantage depends on lower-level sensory processing was examined by differentially stimulating the magnocellular (M) and parvocellular (P) retino-geniculo-cortical visual pathways by using equiluminant and nonequiluminant conditions. We found that the object advantage can be eliminated when M activity is reduced using psychophysically equiluminant stimuli. This novel result in normal observers suggests that the origin of the object advantage is found in lower-level sensory processing rather than a general cognitive process, which should not be so sensitive to differential activation of the bottom-up P and M pathways. Eliminating the object advantage while maintaining a spatial-cueing advantage with reduced M activity suggests that the notion of independent M-driven spatial attention and P-driven object attention requires revision.
Department of Psychology, University of Georgia, Athens, GA, 30602-3013, USA, jmbrown@uga.edu.
James M
JM
Brown
Benjamin A
BA
Guenther
Shruti
S
Narang
Aisha P
AP
Siddiqui
Nicholas C
NC
Foley
D001288:Attention / Q000502:physiology*; D065839:Edinger-Westphal Nucleus / Q000502:physiology; D006801:Humans; D008029:Lighting; D065838:Oculomotor Nuclear Complex / Q000502:physiology; D010364:Pattern Recognition, Visual / Q000502:physiology*; D011601:Psychophysics; D011930:Reaction Time / Q000502:physiology*; D012160:Retina / Q000502:physiology; D014795:Visual Pathways / Q000502:physiology