title: Neuronal responses to face-like and facial stimuli in the monkey superior colliculus.
abstract: The superficial layers of the superior colliculus (sSC) appear to function as a subcortical visual pathway that bypasses the striate cortex for the rapid processing of coarse facial information. We investigated the responses of neurons in the monkey sSC during a delayed non-matching-to-sample (DNMS) task in which monkeys were required to discriminate among five categories of visual stimuli [photos of faces with different gaze directions, line drawings of faces, face-like patterns (three dark blobs on a bright oval), eye-like patterns, and simple geometric patterns]. Of the 605 sSC neurons recorded, 216 neurons responded to the visual stimuli. Among the stimuli, face-like patterns elicited responses with the shortest latencies. Low-pass filtering of the images did not influence the responses. However, scrambling of the images increased the responses in the late phase, and this was consistent with a feedback influence from upstream areas. A multidimensional scaling (MDS) analysis of the population data indicated that the sSC neurons could separately encode face-like patterns during the first 25-ms period after stimulus onset, and stimulus categorization developed in the next three 25-ms periods. The amount of stimulus information conveyed by the sSC neurons and the number of stimulus-differentiating neurons were consistently higher during the 2nd to 4th 25-ms periods than during the first 25-ms period. These results suggested that population activity of the sSC neurons preferentially filtered face-like patterns with short latencies to allow for the rapid processing of coarse facial information and developed categorization of the stimuli in later phases through feedback from upstream areas.
authors.affiliation: System Emotional Science, Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama Toyama, Japan.
authors.forename: Minh Nui
authors.initials: MN
authors.lastname: Nguyen
authors.affiliation: System Emotional Science, Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama Toyama, Japan.
authors.forename: Jumpei
authors.initials: J
authors.lastname: Matsumoto
authors.affiliation: System Emotional Science, Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama Toyama, Japan.
authors.forename: Etsuro
authors.initials: E
authors.lastname: Hori
authors.affiliation: Primate Center and Laboratory of Neurosciences and Behavior, Department of Physiological Sciences, Institute of Biology, University of Brasília Brasilia, Brazil.
authors.forename: Rafael Souto
authors.initials: RS
authors.lastname: Maior
authors.affiliation: Primate Center and Laboratory of Neurosciences and Behavior, Department of Physiological Sciences, Institute of Biology, University of Brasília Brasilia, Brazil.
authors.forename: Carlos
authors.initials: C
authors.lastname: Tomaz
authors.affiliation: System Emotional Science, Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama Toyama, Japan.
authors.forename: Anh H
authors.initials: AH
authors.lastname: Tran
authors.affiliation: System Emotional Science, Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama Toyama, Japan.
authors.forename: Taketoshi
authors.initials: T
authors.lastname: Ono
authors.affiliation: System Emotional Science, Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama Toyama, Japan.
authors.forename: Hisao
authors.initials: H
authors.lastname: Nishijo
keywords: face; face-like patterns; monkey; subcortical pathway; superior colliculus