title: V1 connections reveal a series of elongated higher visual areas in the California ground squirrel, Otospermophilus beecheyi.
abstract: For studies of visual cortex organization, mouse is becoming an increasingly more often used model. In addition to its genetic tractability, the relatively small area of cortical surface devoted to visual processing simplifies efforts in relating the structure of visual cortex to visual function. However, the nature of this compact organization can make some comparisons to the much larger non-human primate visual cortex difficult. The squirrel, as a highly visual rodent offers a useful means for better understanding how mouse and monkey cortical organization compares. More in line with primates than their nocturnal rodent cousin, squirrels rely much more on sight and have evolved a larger expanse of cortex devoted to visual processing. To reveal the detailed organization of visual cortex in squirrels, we injected a highly sensitive monosynaptic retrograde tracer (glycoprotein deleted rabies virus) into several locations of primary visual cortex (V1) in California ground squirrels. The resulting pattern of connectivity revealed an organizational scheme in the squirrel that retains some of the basic features of the mouse visual cortex along the medial and posterior borders of V1, but unlike mouse has an elaborate and extensive pattern laterally that is more similar to the early visual cortex organization found in monkeys. In this way, we show that the squirrel can serve as a useful model for comparison to both mouse and primate visual systems, and may help facilitate comparisons between these two very different yet widely used animal models of visual processing.
authors.affiliation: Department of Anatomy & Neurobiology, School of Medicine, University of California, Irvine, California.|Department of Cognitive Neuroscience, Donders Inst. for Brain, Cognition & Behaviour, Radboud University Medical Centre Nijmegen, Nijmegen, The Netherlands.
authors.forename: Moritz
authors.initials: M
authors.lastname: Negwer
authors.affiliation: Department of Anatomy & Neurobiology, School of Medicine, University of California, Irvine, California.|Department of Honeybee Protection and Biosafety, Institute of Agricultural Research, Chinese Academy of Agricultural Sciences, Haidian District, Beijing, P.R. China.
authors.forename: Yong-Jun
authors.initials: YJ
authors.lastname: Liu
authors.affiliation: Department of Cognitive Neuroscience, Donders Inst. for Brain, Cognition & Behaviour, Radboud University Medical Centre Nijmegen, Nijmegen, The Netherlands.
authors.forename: Dirk
authors.initials: D
authors.lastname: Schubert
authors.affiliation: Department of Anatomy & Neurobiology, School of Medicine, University of California, Irvine, California.
authors.forename: David C
authors.identifier: http://orcid.org/0000-0002-4367-5636
authors.initials: DC
authors.lastname: Lyon
mesh_terms: D000818:Animals; D005260:Female; D007091:Image Processing, Computer-Assisted; D021621:Imaging, Three-Dimensional; D008297:Male; D012589:Sciuridae / Q000033:anatomy & histology*; D014793:Visual Cortex / Q000033:anatomy & histology*; D014795:Visual Pathways / Q000033:anatomy & histology*
keywords: V3; cortical organization; primate; retrograde tracing; rodent; visual cortex