title: Comparative diffusion tractography of corticostriatal motor pathways reveals differences between humans and macaques.
abstract: The primate corticobasal ganglia circuits are understood to be segregated into parallel anatomically and functionally distinct loops. Anatomical and physiological studies in macaque monkeys are summarized as showing that an oculomotor loop begins with projections from the frontal eye fields (FEF) to the caudate nucleus, and a motor loop begins with projections from the primary motor cortex (M1) to the putamen. However, recent functional and structural neuroimaging studies of the human corticostriatal system report evidence inconsistent with this organization. To obtain conclusive evidence, we directly compared the pattern of connectivity between cortical motor areas and the striatum in humans and macaques in vivo using probabilistic diffusion tractography. In macaques we found that FEF is connected with the head of the caudate and anterior putamen, and M1 is connected with more posterior sections of the caudate and putamen, corroborating neuroanatomical tract tracing findings. However, in humans FEF and M1 are connected to largely overlapping portions of posterior putamen and only a small portion of the caudate. These results demonstrate that the corticobasal connectivity for the oculomotor and primary motor loop is not entirely segregated for primates at a macroscopic level and that the description of the anatomical connectivity of corticostriatal motor systems in humans does not parallel that of macaques, perhaps because of an expansion of prefrontal projections to striatum in humans.
authors.affiliation: Brain Center Rudolf Magnus, Department of Psychiatry, University Medical Centre, Utrecht, The Netherlands; b.neggers@umcutrecht.nl.
authors.forename: S F W
authors.initials: SF
authors.lastname: Neggers
authors.affiliation: Department of Psychology, Vanderbilt Vision Research Center, Center for Integrative and Cognitive Neuroscience, Vanderbilt University, Nashville, Tennessee; and Donders Institute for Brain, Cognition and Behaviour, Radboud University, Nijmegen, The Netherlands.
authors.forename: B B
authors.initials: BB
authors.lastname: Zandbelt
authors.affiliation: Department of Psychology, Vanderbilt Vision Research Center, Center for Integrative and Cognitive Neuroscience, Vanderbilt University, Nashville, Tennessee; and.
authors.forename: M S
authors.initials: MS
authors.lastname: Schall
authors.affiliation: Department of Psychology, Vanderbilt Vision Research Center, Center for Integrative and Cognitive Neuroscience, Vanderbilt University, Nashville, Tennessee; and.
authors.forename: J D
authors.initials: JD
authors.lastname: Schall
mesh_terms: D000328:Adult; D000818:Animals; D001931:Brain Mapping / Q000379:methods*; D002540:Cerebral Cortex / Q000502:physiology*; D003342:Corpus Striatum / Q000502:physiology*; D056324:Diffusion Tensor Imaging / Q000379:methods*; D004525:Efferent Pathways / Q000502:physiology*; D005260:Female; D006801:Humans; D008255:Macaca radiata; D008297:Male; D013045:Species Specificity; D055815:Young Adult
keywords: DTI; comparative anatomy; human; macaque; oculomotor