title: Encoding of Stimulus Probability in Macaque Inferior Temporal Cortex.
abstract: Optimal perceptual decisions require sensory signals to be combined with prior information about stimulus probability. Although several theories propose that probabilistic information about stimulus occurrence is encoded in sensory cortex, evidence from neuronal recordings has not yet fully supported this view. We recorded activity from single neurons in inferior temporal cortex (IT) while monkeys performed a task that involved discriminating degraded images of faces and fruit. The relative probability of the cue being a face versus a fruit was manipulated by a latent variable that was not revealed to the monkeys and that changed unpredictably over the course of each recording session. In addition to responding to stimulus identity (face or fruit), population responses in IT encoded the long-term stimulus probability of whether a face or a fruit stimulus was more likely to occur. Face-responsive neurons showed reduced firing rates to expected faces, an effect consistent with "expectation suppression," but expected stimuli were decoded from multivariate population signals with greater accuracy. These findings support "predictive coding" theories, whereby neural signals in the mammalian visual system actively encode and update predictions about the local sensory environment.
authors.affiliation: Laboratory of Brain and Cognition, National Institute of Mental Health, 9000 Rockville Pike, Bethesda, MD 20892, USA; Department of Experimental Psychology, University of Oxford, South Parks Road, Oxford OX1 3UD, UK; MRC Cognition and Brain Sciences Unit, 15 Chaucer Road, Cambridge CB2 7EF, UK. Electronic address: andrew.bell@psy.ox.ac.uk.
authors.forename: Andrew H
authors.initials: AH
authors.lastname: Bell
authors.affiliation: Department of Experimental Psychology, University of Oxford, South Parks Road, Oxford OX1 3UD, UK.
authors.forename: Christopher
authors.initials: C
authors.lastname: Summerfield
authors.affiliation: Laboratory of Brain and Cognition, National Institute of Mental Health, 9000 Rockville Pike, Bethesda, MD 20892, USA.
authors.forename: Elyse L
authors.initials: EL
authors.lastname: Morin
authors.affiliation: Laboratory of Brain and Cognition, National Institute of Mental Health, 9000 Rockville Pike, Bethesda, MD 20892, USA.
authors.forename: Nicholas J
authors.initials: NJ
authors.lastname: Malecek
authors.affiliation: Laboratory of Brain and Cognition, National Institute of Mental Health, 9000 Rockville Pike, Bethesda, MD 20892, USA.
authors.forename: Leslie G
authors.initials: LG
authors.lastname: Ungerleider
mesh_terms: D000818:Animals; D008253:Macaca mulatta / Q000502:physiology*; D008297:Male; D010364:Pattern Recognition, Visual; D013702:Temporal Lobe / Q000502:physiology*
keywords: decision making; expectation suppression; monkey; neuron; predictive coding