Abstract
People prefer some perceptual inputs to others, an effect readily manifested in visual fixations during free viewing. This preference may be based on the activity of a gradient of -opiate receptors (ligand = endomorphin) that, surprisingly, is found in the ventral cortical pathway for visual recognition. This gradient, discovered in the macaque, is sparse in V1 and increases in density through V2, V4, TEO, IT, and the parahippocampal cortex. The magnitude of endomorphin activity would determine perceptual and cognitive preference, resulting in a preference for patterns that are both richly interpretable (because they activate many associations in the opiate rich anterior regions of the ventral pathway) and novel. Repetition of a scene would result in less activity because of competitive interactions. Event related fMRI activity was recorded during the viewing of 1 s presentations of scenes that varied in their rated preference. The scenes were repeated 5 times over the course of the experiment. Highly preferred scenes produced greater BOLD activity than less preferred scenes in more anterior areas of the ventral pathway, such as the parahippocampal cortex, consistent with the endomorphin hypothesis. Both rated preference and parahippocampal activity consistently declined with repetition, further supporting the link between preference and endomorphin activity. The activity in more posterior areas was not closely associated with preference. For example, area LO showed no systematic modulation by preference nor a consistent decline in activity with repetition.