Neural correlates of statistical learning in the inferior-temporal cortex of rhesus monkeys

We learn to implicitly extract the statistical regularities in the environment around us, e.g. sequences of stimuli that follow each other (e.g. letters in specific words). In the visual domain, human observers can extract regular sequences of visual stimuli from a continuous stream of visual shapes. The neural correlates of such visual sequence learning are still unclear. Here, we determined whether a neural correlate of short sequences of visual images, presented in a continuous stream, is present in macaque inferior temporal (IT) cortex. Two monkeys passively fixated while a continuous stream of 3 fixed sequences of 5 grayscale images of animals of various species each were presented in a random order. After a passive exposure of two months, we assessed whether the responses of IT neurons showed a correlate of the sequences by introducing deviant stimuli in the fixed standard sets. We compared the multiunit neuronal responses for the deviant stimuli with identical stimuli when presented in the standard, learned sequence. We observed a significant enhancement of the responses to the deviant stimulus and the trailing standard stimuli, when the deviant was either from the same sequence (p <0.05 for each monkey) or from the other two sequences (p