11th annual Cognitive Neuroscience Society (CNS) meeting
SAN FRANCISCO
APRIL 18 - 20, 2004
When two dissimilar images are presented to corresponding regions of each eye, one image suppresses the other one from visual awareness. Binocular-suppression has little effect on the build-up of several visual-after effects (tilt aftereffect, translational motion aftereffect, grating adaptation). Thus, invisible stimuli can penetrate some level of cortical visual processing. However, the global motion aftereffect is reduced in magnitude by rivalry suppression. Here, we used configural adaptation to images of human faces to investigate whether high-level aftereffects are suppressed by rivalry. Human fMRI and monkey electrophysiological studies demonstrate that rivalry modulates activity in cortical areas involved in processing faces and objects, although there is evidence from human fMRI that perceptually invisible images still can affect those areas. Participants were trained to identify four individuals. Different identity strengths were created by morphing the original stimuli with an average face. We demonstrated that four seconds of adaptation in the non-dominant eye significantly shifts the psychometric function. Suppression was induced during adaptation by presenting a moving pattern to the dominant eye. Observers monitored the visibility of the face by holding a key down. When the adapting face was perceptually suppressed for less than 3 seconds, the aftereffect was comparable in magnitude to the control condition. However, when the adaptor was invisible for more than 3 seconds, there was no shift in the psychometric function (p<0.01). This indicates that the neural mechanisms underlying configural adaptation to faces depend, at least in part, on perceptual awareness.
http://www.klab.caltech.edu/~farshadm/cns2004/