Abstract
How does the brain assess the potential “interest” of a visual scene? Our research is aimed at understanding the neural basis of the motivational system underlying visual information acquisition that maximizes the intake of novel, but interpretable information. As a way of investigating this system, we have been measuring subjects' preferences for a variety of full color scenes and the effects of repeated exposure on their preference ratings. Previously, we reported that visual preference declines with repeated presentation for a wide variety of scenes of different initial preferences (OPAM, 2001). Our working hypothesis is that the gradient of enkephalin receptors in the ventral visual pathway (sparse in V1, dense in IT; Lewis et al., 1981) mediates visual and cognitive pleasure, producing a preference for those scenes that richly activate new associations in the anterior regions of the ventral visual stream. Competitive learning in these latter stages would result in less neural/enkephalin activity as a stimulus is repeated (see Miller et al., 1993), and thus reduce preference. In this study, we use event-related fMRI to investigate the changes in neural activity associated with initial scene preference and the decrease in preference over repeated exposure. Subjects were asked to view a set of 60 images presented for one second separated by a variable ISI. Each image was shown a total of five times over the course of the experiment. Using preference ratings collected from another set of subjects outside the magnet, we grouped the scenes into high, medium, and low preference sets. We observed differential activity in occipitotemporal regions of the cortex associated with both preference level and exposure. We discuss these results in the context of whether visual preference is computed locally, and how this signal might be used to guide selective attention to areas of the visual world which contain novel, but interpretable information.