Neural repetition suppression reflects fulfilled perceptual expectations.

Summerfield C, Trittschuh EH, Monti JM, Mesulam MM, Egner T.
Nat Neurosci. 2008 Aug 1.

Stimulus-evoked neural activity is attenuated on stimulus repetition (repetition suppression), a phenomenon that is attributed to largely automatic processes in sensory neurons. By manipulating the likelihood of stimulus repetition, we found that repetition suppression in the human brain was reduced when stimulus repetitions were improbable (and thus, unexpected). Our data suggest that repetition suppression reflects a relative reduction in top-down perceptual 'prediction error' when processing an expected, compared with an unexpected, stimulus.

PMID: 18677308

Full text: http://www.nature.com/neuro/journal/vaop/ncurrent/full/nn.2163.html