title: Effect of silhouetting and inversion on view invariance in the monkey inferotemporal cortex.
abstract: We effortlessly recognize objects across changes in viewpoint, but we know relatively little about the features that underlie viewpoint invariance in the brain. Here, we set out to characterize how viewpoint invariance in monkey inferior temporal (IT) neurons is influenced by two image manipulations-silhouetting and inversion. Reducing an object into its silhouette removes internal detail, so this would reveal how much viewpoint invariance depends on the external contours. Inverting an object retains but rearranges features, so this would reveal how much viewpoint invariance depends on the arrangement and orientation of features. Our main findings are1) view invariance is weakened by silhouetting but not by inversion;2) view invariance was stronger in neurons that generalized across silhouetting and inversion;3) neuronal responses to natural objects matched early with that of silhouettes and only later to that of inverted objects, indicative of coarse-to-fine processing; and4) the impact of silhouetting and inversion depended on object structure. Taken together, our results elucidate the underlying features and dynamics of view-invariant object representations in the brain.NEW & NOTEWORTHYWe easily recognize objects across changes in viewpoint, but the underlying features are unknown. Here, we show that view invariance in the monkey inferotemporal cortex is driven mainly by external object contours and is not specialized for object orientation. We also find that the responses to natural objects match with that of their silhouettes early in the response, and with inverted versions later in the response-indicative of a coarse-to-fine processing sequence in the brain.
authors.affiliation: Centre for Neuroscience, Indian Institute of Science, Bangalore, India.
authors.forename: N Apurva
authors.identifier: 0000-0003-2191-797X
authors.initials: NA
authors.lastname: Ratan Murty
authors.affiliation: Centre for Neuroscience, Indian Institute of Science, Bangalore, India sparun@cns.iisc.ernet.in.
authors.forename: S P
authors.identifier: 0000-0001-9602-5066
authors.initials: SP
authors.lastname: Arun
mesh_terms: D000200:Action Potentials; D000818:Animals; D005556:Form Perception / Q000502:physiology*; D000882:Haplorhini; D008839:Microelectrodes; D009474:Neurons / Q000502:physiology*; D010364:Pattern Recognition, Visual / Q000502:physiology*; D010775:Photic Stimulation / Q000379:methods; D013702:Temporal Lobe / Q000502:physiology*; D014793:Visual Cortex / Q000502:physiology
keywords: invariance; object recognition; shape coding; viewpoint