For the 2006 meeting of the Cognitive Neuroscience Society

Behavioral and neurophysiological results demonstrate that coexisting stimuli compete for neural representation in the visual cortex. According to the Biased Competition model (Desimone & Duncan, 1995), attention modulates competitive interactions in the visual cortex with top-down signals that specify a stimulus' behavioral relevance. To determine whether this model could be extended to visual short-term memory, we used Sternberg's recognition paradigm and sinusoidal gratings as study and probe items to examine interactions among sequentially presented visual stimuli.

Subjects had to remember the spatial frequency of either one or two distinct study items and determine if the probe item matched a study item (Yotsumoto & Sekuler, in press). On each trial, a brief cue defined the behavioral relevance of one or both study items; this defining cue appeared before, during or after the study items. Subjects successfully deployed temporal attention to include or exclude items of a particular serial position in a study series.

Recognition performance was strongly modulated by the cue, reflecting enhancement of visual and memory processing of the attended item. Attentional modulation varied systematically with the cue's timing. To account for these results, we built an Expanded Biased Competition Model (EBiC), in which separate layers of stimulus selective neurons represent stimulus values in vision and in memory. EBiC, which successfully simulates our behavioral data, provides a quantitative and theoretical account of memory noise's role in competitive interactions within and between vision and memory, and how attention modulates such interactions.

Supported by NIH grants MH068404 and NSF grant SBE-034378.