Skip to main content

Currently Skimming:

8 Synaptogenesis and Development of Pyramidal Neuron Dendritic Morphology in the Chimpanzee Neocortex Resembles Humans--Serena Bianchi, Cheryl D. Stimpson, Tetyana Duka, Michael D. Larsen, William G. M. Janssen, Zachary Collins, Amy L. Bauernfeind, Steven J. Schapiro, Wallace B. Baze, Mark J. McArthur, William D. Hopkins, Derek E. Wildman, Leonard Lipovich, Christopher W. Kuzawa, Bob Jacobs, Patrick R. Hof, and Chet C. Sherwood
Pages 135-152

The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.


From page 135...
... In macaque monkeys, cortical synaptogenesis peaks during early infancy and developmental changes in synapse den sity and dendritic spines occur synchronously across cortical regions. Thus, relatively prolonged synapse and neuronal maturation in humans might contribute to enhancement of social learning during development and transmission of cultural practices, including language.
From page 136...
... To address this question, we used immunohistochemis try, electron microscopy, and Golgi staining to characterize synaptic den sity and dendritic morphology of pyramidal neurons in primary somato sensory (area 3b) , primary motor (area 4)
From page 137...
... . In humans, however, dendritic arbors of prefrontal cortex pyramidal neurons reach adult-like morphological complexity and spine density later in development than dendritic arbors in sensory and motor cortices (Travis et al., 2005)
From page 138...
... . We predicted that, if chimpanzee cortical development is more similar to humans than to macaques, synaptogenesis and maturation of dendritic arbors of pyramidal neurons would be extended into the juvenile period, and show a more prolonged trajectory in the prefrontal cortex relative to other regions.
From page 139...
... This model confirmed a significant cubic polynomial regression based only on age, and showed a better Akaike information criterion value than a model including the cubic polynomial based on both age and a term for cortical region differences. The model with differences by cortical region did not fit significantly better according to a likelihood ratio test; P values were 0.55 and 0.48 for either an unstructured or a compound symmetry model, respectively.
From page 140...
... Cortex Overall Regression Region Intercept Age Age2 Age3 r2 Root MSE P Value Area 3b 94.3 −11.5 −56.5 48.7 0.26 33.6 0.22 Area 4 100.5 −25.6 66.2*
From page 141...
... . Results from EM synapse density counts showed a pronounced developmental increase in the prefrontal cortex, which can be attributed mostly to postnatal changes in the density of excitatory asymmetric synapse subtypes.
From page 142...
... Results indicated significant regional differences in the dendritic structure of pyramidal neurons across areas of the infant chimpanzee neocortex (n = 4, 0- to 24-month-old) , as assessed by six measures of morphological complexity, including cell body size: F12, 144 = 1.86, P = 0.04; total dendritic length (TDL)
From page 143...
...   148 ± 78   166 ± 101   169 ± 84   401 ± 203 DSD (μm)  0.16 ± 0.04  0.17 ± 0.07   0.19 ± 0.04   0.33 ± 0.22 NOTE: TDL, total dendritic length; MSL, mean segment length; DSC, dendritic segment count; DSN, dendritic spine number; DSD, dendritic spine density.
From page 144...
... (Scale bar, 100 μm.) Below the tracing, closeup photomicrographs depict dendritic shafts of pyramidal neurons in (B)
From page 145...
... [NOTE: Figure can be viewed in color in the PDF version of this volume on the National Academies Press website, www.nap.edu/catalog.php? record_ id18573.]
From page 146...
... . Our current analyses demonstrate that similar to humans, synaptic proliferation in chimpanzees is prolonged through the mid-juvenile period, and development of pyramidal neurons in the prefrontal cortex is delayed relative to other cortical areas.
From page 147...
... , synapse density, glial cell numbers, and other factors. Delayed Dendritic Growth in the Prefrontal Cortex In addition to synaptogenesis, we examined regional changes in the development of dendritic branching of pyramidal neurons.
From page 148...
... Although the present study focused on the rostral prefrontal cortex to be consistent with previous research in adult chimpanzees and humans, it is possible that delayed maturation of pyramidal neurons also characterizes association cortices in other frontal, parietal, and temporal regions. Despite sharing these neurodevelopmental similarities, it is important to note that cognitive ontogeny in chimpanzees differs from humans in several respects.
From page 149...
... These results suggest that several key features of human brain ontogeny for enhanced developmental plasticity emerged before the divergence of the chimpanzee and human lineages. In addition to these shared similarities of early postnatal development, later phases of human neocortical maturation appear to be more evolutionarily modified and distinct from chimpanzees, involving prolonged myelination that continues into early adulthood (Miller et al., 2012)
From page 150...
... at 37°C in an oven for 30 min. Sections were rinsed and immersed in a solution of 0.75 percent hydrogen peroxide in 75 percent methanol to eliminate endogenous peroxidase activity, then incubated in the primary antiserum diluted in PBS with 2 percent normal goat serum and 0.1 percent Triton X-100 for ~24 hours on a rotator at 4°C.
From page 151...
... Sampling fields were chosen by using the random sampling method and the number of synapses per unit volume was calculated through the following formula: NV = NA/d, where NV is the number of synapses per unit volume, NA is the number of synaptic junctions per unit area of an electron micrograph, and d is the mean length of densities associated with the synaptic junctions (Colonnier and Beaulieu, 1985)
From page 152...
... However, because apical dendrites were often incomplete because of sectioning, quantitative comparisons of dendritic length and spine number across cortical regions were limited to basilar dendrites. All tracings were performed blind to the regions of interest by C.D.S.


This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More information on Chapter Skim is available.