Evolution Of The Neocortex Sources Abstract ✓ Solved

Evolution of the Neocortex Sources Abstract The evolution o

The evolution of the neocortex is widespread across many species. There is little modern research done to investigate how much the neocortex differs in terms of size, shape, and number of neurons between other species and humans. Some studies focus on how the gyrated human neocortex evolved, through a lineage of neural stem and transit-amplifying cells that grew to form the outer subventricular zone. Other studies focus on aspects of the evolution of the neocortex that make humans novel.

The neocortex is the part of the brain that involves sight and hearing in mammals. It is the most recently evolved part of the cortex and is an important component in terms of higher-level cognitive functioning. The origin of the neocortex can be traced to reptiles that emerged during the Carboniferous Period, where it first appeared as a uniform six-layered sheet made of radially deployed neurons in early small mammals, descended from reptiles during the Triassic/Jurassic transition periods.

How the Neocortex Evolved

Mammals had small forebrains with little neocortex, which primarily involved the olfactory bulb and olfactory cortex. In terms of sensory perception, the anterior and lateral somatosensory cortices didn't change as much as the motor cortex in early primates. Early primates also had a region of granular frontal cortex with sensory inputs and connections with dorsal and ventral premotor areas. This led to the enlargement and subdivision of frontal motor regions in early primates.

Genetic Differences Between Humans and Other Species

The increases in size and complexity of the cerebral cortex have culminated in the modern human, which separated from the mouse line between 90 and 100 million years ago and from Old World monkeys. Using evolutionary developmental biology (EVO-DEVO), researchers have found that in developing monkey and human neocortex, cells with similar morphology to radial glia, but not necessarily spanning ventricle to pia, are found outside of the ventricular zone. Early primates had acquired several features of neocortex that are now distinguishing characteristics of modern primates, including a new array of visual areas that are modified from those widely shared with other mammals.

The primary and secondary visual areas, V1 and V2, exist in nearly all mammals, but these areas have specialized features in primates. A feature of cortical development in all mammalian species is that none of its constituent neurons is generated within the cortex itself; they are generated in the transient proliferative embryonic zones (ventricular zone, subventricular zone) situated near the surface of the cerebral lateral ventricles. After their last cell division, these neurons acquire their proper areal and laminar positions through long-distance radial and tangential migration across the intermediate zone.

Insights from EVO-DEVO

EVO-DEVO helps us gain insights into the evolution of the neocortex by comparing how our genes are similar to and different from those of other species. It examines how novel features may have emerged due to gene mutations, which, if inherited, were propagated during evolution by natural selection. To grasp how cortical evolution occurs at the cellular level, researchers must compare the differential gene expression and developmental events during embryonic development across living mammals.

Formation of New Molecular Pathways

Several features of cortical development differ from the development of other organs and even from other parts of the brain. The cerebral cortex, a cellular sheet composed of projection (or pyramidal) and local circuit neurons (or interneurons), is deployed in horizontal layers and intersected by vertical (or radial) columns that are interconnected in the vertical dimension. This structure exhibits variability in each area, depending on their function. The significant variability is pronounced in the large and convoluted human neocortex, which features more than 50 distinct cytoarchitectonic areas described over a century ago.

The neocortex is also characterized by an "inside-out gradient of neurogenesis." As research suggests, the dramatic increase in neuron number in the evolution of the human cerebral neocortex is linked to an increase in subventricular neurogenic divisions. Understanding the mechanisms regulating large brain size will depend on a detailed description of cellular behaviors, signaling pathways, and gene expression patterns.

Conclusion

Using the principles of evolutionary developmental biology (evo-devo), the evolution of the neocortex can be further explored. This examination delves into how its expansion has benefited the human race over time. The evolution of large and complex cognitive capabilities in humans can be traced through various molecular and genetic developments that distinguish our neocortex from that of other species. By continuing to investigate these fundamental aspects, we can better understand the unique advancements in human cognition that arise from our distinctive neocortical structure.

References

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