D. Phil., School of Anatomical Sciences, Faculty of Health Sciences, University of the Witwatersrand, 2011 / Whether the neuropil is a static, optimally wired entity, whose components must be
balanced in a certain way, is an open question. Are the proportions of the components
of the neuropil consistent across different mammalian cortices, especially in primates
where the cerebral cortex is complexly organized? This question is interesting
because the actual biological underpinnings of complex behaviours and intelligence in
big-brained primates remain enigmatic and why they seem qualitatively different from
other animals in terms of their cognitive abilities. Understanding changes that may
have occurred in the brain, especially at the level of neuropil organization, during the
evolution in primates is important to our growing understanding of the intellectual
abilities and behaviours exhibited by members of this group. The current series of
quantitative studies was aimed at investigating variations in the proportionality of the
“wire fraction” in three primate species, the olive baboon (Papio anubis), vervet
monkey (Cercopithecus aethiops) and the common chimpanzee (Pan troglodytes), in
a range of higher and lower order cortical areas, using a newly developed method that
involves standard and immunohistochemical staining techniques to reveal and
quantify the various profiles of the fine structures of the cerebral cortex. The results of
these studies demonstrate clear layer differences in the wire fraction of the cerebral
cortex, and for the most part, consistency in the neuropil wire fraction of the same
layer across areas of the cerebral cortex within and between individuals of the same
species; however, differences in the wire fraction of the neuropil were associated with
changes in brain size. It is apparent that the neuropil is not static, as wiring
“optimality” changes with layers and brain size and this has functional implications
regarding neuronal processing and behavioural outcomes. The adaptive rationale
adopted by evolutionary psychology studies to explain behaviours may be erroneous,
as adaptation does not always explain sufficiently the emergence of complex
behaviours related to brain size increases, especially in primates.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:wits/oai:wiredspace.wits.ac.za:10539/10671 |
| Date | 31 October 2011 |
| Creators | Jillani, Ngalla Edward |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | application/pdf |
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