The Crossed Projection to the Striatum in Two Species of Monkey and in Humans: Behavioral and Evolutionary Significance.
The corpus callosum establishes the anatomical continuity between the 2 hemispheres and coordinates their activity. Using histological tracing, single axon reconstructions, and diffusion tractography, we describe a callosal projection to n caudatus and putamen in monkeys and humans. In both species, the origin of this projection is more restricted than that of the ipsilateral projection. In monkeys, it consists of thin axons (0.4-0.6 µm), appropriate for spatial and temporal dispersion of subliminal inputs. For prefrontal cortex, contralateral minus ipsilateral delays to striatum calculated from axon diameters and conduction distance are <2 ms in the monkey and, by extrapolation, <4 ms in humans. This delay corresponds to the performance in Poffenberger's paradigm, a classical attempt to estimate central conduction delays, with a neuropsychological task. In both species, callosal cortico-striatal projections originate from prefrontal, premotor, and motor areas. In humans, we discovered a new projection originating from superior parietal lobule, supramarginal, and superior temporal gyrus, regions engaged in language processing. This projection crosses in the isthmus the lesion of which was reported to dissociate syntax and prosody. The projection might originate from an overproduction of callosal projections in development, differentially pruned depending on species.
Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden.|Brain and Mind Institute, EPFL, Lausanne, Switzerland.
Giorgio M
GM
Innocenti
Danish Research Centre for Magnetic Resonance, Centre for Functional and Diagnostic Imaging and Research, Copenhagen University Hospital Hvidovre, Copenhagen, Denmark.|Department of Applied Mathematics and Computer Science, Technical University of Denmark, Kongens Lyngby, Denmark.
Tim B
TB
Dyrby
Danish Research Centre for Magnetic Resonance, Centre for Functional and Diagnostic Imaging and Research, Copenhagen University Hospital Hvidovre, Copenhagen, Denmark.
Kasper Winther
KW
Andersen
Department of Medicine, Faculty of Sciences, Fribourg Cognition Center, University of Fribourg, Fribourg, Switzerland.
Eric M
EM
Rouiller
Department of Physiology and Pharmacology, University of Rome SAPIENZA, Rome, Italy.|Department of Anatomy, Histology, Forensic Medicine and Orthopedics, University of Rome SAPIENZA, Rome, Italy.
Roberto
R
Caminiti
D000328:Adult; D000818:Animals; D005075:Biological Evolution; D001931:Brain Mapping; D003337:Corpus Callosum / Q000033:anatomy & histology* / Q000000981:diagnostic imaging; D003342:Corpus Striatum / Q000033:anatomy & histology* / Q000000981:diagnostic imaging; D056324:Diffusion Tensor Imaging; D007839:Functional Laterality / Q000502:physiology; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008251:Macaca; D008297:Male; D009413:Nerve Fibers, Myelinated / Q000502:physiology; D009434:Neural Pathways / Q000000981:diagnostic imaging / Q000502:physiology*; D013045:Species Specificity; D055815:Young Adult
axons; conduction delays; corpus callosum; diffusion tractography; language