One of the most basic and general functions of the brain is to detect the occurrence of unexpected and therefore potentially informative events. This function rests on two foundations. First, the brain must extract from ongoing experience information about the transitional statistics of the environment: information about what events tend to follow what other events. Second, it must monitor ongoing experience so as to signal when predictions based on previously experienced transitional statistics are violated. We know that the brain accomplishes these feats but we know little about the underlying neuronal mechanisms. We propose to investigate this problem by studying a phenomenon recently discovered in the primate visual system: prediction suppression. Prediction suppression is induced by allowing a monkey to view repeatedly a display in which images follow each other in fixed sequence. During subsequent viewing, neurons in area TE, a visual area in the temporal lobe, respond weakly to images in the trained sequence but respond strongly to images that appear out of sequence. This phenomenon possesses potential as a test bed for the study of neural mechanisms mediating predictive processes in the brain. The general goal of the proposed project is to answer fundamental outstanding questions about prediction suppression so as to solidify the status of the phenomenon as a model for studying the neural mechanisms of predictive processes. We propose three sets of experiments. In all of them, we will expose monkeys, during a training period, to dynamic displays governed by fixed transitional statistics and then, during a testing period, will monitor neuronal responses to predicted and unpredicted sequences. Experiments in the first series will characterize the conditions required for inducing prediction suppression. Experiments in the second series will characterize the neural processes initiated by presenting a predictive stimulus. Experiments in the third series will determine whether prediction suppression is manifest at visual processing stages before and after the level of area TE.
The proposed experiments will improve our knowledge about the neural mechanisms that underlie object vision and in particular its dependence on past knowledge about the environment. Better understanding of the visual system will improve our ability to diagnose and treat the grave disorders of vision that follow from injury to occipital an temporal lobe cortex in humans.
