Uncovering specific changes in network wiring underlying the primate cerebrotype.
Regular scaling of brain networks during evolution has been proposed to be the major process leading to enlarged brains. Alternative views, however, suggest that deviations from regular scaling were crucial to the evolution of the primate brain and the emergence of different cerebrotypes. Here, we examined the scaling within the major link between the cerebellum and the cerebral cortex by studying the deep cerebellar nuclei (DCN). We compared the major axonal and dendritic wiring in the DCN of rodents and monkeys in search of regular scaling. We were able to confirm regular scaling within the density of neurons, the general dendritic length per neuron and the Purkinje cell axon length. However, we also observed specific modification of the scaling rules within the primates' largest and phylogenetically newest DCN, the dentate nucleus (LN/dentate). Our analysis shows a deviation from regular scaling in the predicted dendritic length per neuron in the LN/dentate. This reduction in the dendritic length is also associated with a smaller dendritic region-of-influence of these neurons. We also detected specific changes in the dendritic diameter distribution, supporting the theory that there is a shift in the neuronal population of the LN/dentate towards neurons that exhibit spatially restricted, clustered branching trees. The smaller dendritic fields would enable a larger number of network modules to be accommodated in the primate LN/dentate and would provide an explanation for the unique folded structure of the primate LN/dentate. Our results show that, in some brain regions, connectivity maximization (i.e., an increase of dendritic fields) is not the sole optimum and that increases in the number of network modules may be important for the emergence of a divergent primate cerebrotype.
Department of Cognitive Neurology, HIH for Clinical Brain Research, Otfried-Müller-Str. 27, 72076, Tübingen, Germany.
Salah
S
Hamodeh
Department of Cognitive Neurology, HIH for Clinical Brain Research, Otfried-Müller-Str. 27, 72076, Tübingen, Germany.
Ayse
A
Bozkurt
Department of Cognitive Neurology, HIH for Clinical Brain Research, Otfried-Müller-Str. 27, 72076, Tübingen, Germany.
Haian
H
Mao
Department of Cognitive Neurology, HIH for Clinical Brain Research, Otfried-Müller-Str. 27, 72076, Tübingen, Germany. fahad.sultan@umu.se.|Department of Integrative Medical Biology, Umeå University, Linnéus väg 9, 901 87, Umeå, Sweden. fahad.sultan@umu.se.
Fahad
http://orcid.org/0000-0001-9194-9905
F
Sultan
D000123:Acetyltransferases / Q000378:metabolism; D000704:Analysis of Variance; D000818:Animals; D001369:Axons / Q000378:metabolism; D001931:Brain Mapping; D002529:Cerebellar Nuclei / Q000166:cytology* / Q000502:physiology; D002540:Cerebral Cortex / Q000502:physiology*; D003712:Dendrites / Q000378:metabolism; D008253:Macaca mulatta; D008297:Male; D009419:Nerve Tissue Proteins / Q000378:metabolism; D009434:Neural Pathways / Q000166:cytology* / Q000502:physiology; D009457:Neuroglia / Q000166:cytology / Q000378:metabolism; D009474:Neurons / Q000166:cytology / Q000502:physiology*; D066330:Printing, Three-Dimensional; D051381:Rats; D013045:Species Specificity
D009419:Nerve Tissue Proteins; C091104:Purkinje cell protein L7; D000123:Acetyltransferases; C071107:microtubule-associated protein acetyltransferase
3D reconstructions; Cerebellar nuclei; Comparative neuroanatomy; Dentate nucleus; Motor systems; Purkinje cells; Quantitative immunohistochemistry