Psych 9 - Development of the Nervous System (219-239)...

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Development of the Nervous System (219-239) Section on Columnar Organization of Primary Visual Cortex - Receptive fields of the visual cortex neurons are attributable to the flow of signals from neurons with simpler receptive fields to those with more complex fields. Primary visual cortex neurons are grouped in functional vertical columns. The response of a visual cortex neuron depends not only on the stimuli in its receptive field, but on the larger scene in which these stimuli are embedded. This plasticity, or ability to adapt to change, which has been largely ignored, appears to be a fundamental property of visual cortex function. Phases of Neurodevelopment - The brain is a plastic, changeable, living organ that continually changes in response to its genetic programs and environment. Neuro-development begins with a single fertilized egg cell and ends with a functional adult brain. The amazing nature of neurodevelopment, the important role of experience in neurodevelopment, and the dire consequences of neurodevelopment errors are all emphasized. Genie’s severe childhood deprivation left her scarred; clearly experience plays a major role in the processes of neurodevelopment. - Zygote is a single cell formed by the amalgamation of an ovum and a sperm. The zygote divides to form two daughter cells., and the division continues until a mature organism is produced. Cells must differentiate; some must become muscle cells, some must become multipolar neurons, some must become glial cells, and so on. Cells must make their way to appropriate sites and align themselves with the cells around them to form particular structures. Cells must establish appropriate functional relations with other cells. This occurs in five phases, induction of the neural plate, neural proliferation, migration and aggregation, axon growth and synapse formation, and neuron death and synapse rearrangement. - Three weeks after conception, the tissue that is destined to develop into the human nervous system becomes recognizable as the neural plate, a small patch of ectodermal tissue on the dorsal surface of the developing embryo. The ectoderm is the outermost of the three layers of embryonic cells ectoderm, mesoderm, and endoderm. The development of the neural plate is induced by chemical signals from an area of the underlying mesoderm layer, an area that is consequently referred to as an organizer. Tissue taken from the dorsal mesoderm of one embryo (donor) and implanted beneath the ventral ectoderm of another embryo (host) induces the development of an extra neural plate on the central surface of the host. The search for the particular substances that are released by the organizer and induce the development of the neural plate is in full swing. -At the time that the neural plate becomes visible an important change occurs. The earliest cells of the human
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This note was uploaded on 02/09/2012 for the course PSYCH 2220 taught by Professor Culham during the Spring '11 term at UWO.

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Psych 9 - Development of the Nervous System (219-239)...

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