« Neural Prenatal Development The wonder of development is that a structure as complex as the human brain originates from a flat sheet of embryologic ectoderm. ...» Document abstract
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Language : english
psychology
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date published
13/11/2007
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SummaryThe wonder of development is that a structure as complex as the human brain originates from a flat sheet of embryologic ectoderm. The final, formed brain shows remarkable order in its predictable cortical layering, its diversity of cortical areas, and the numerous networks linking specific cortical areas and subcortical structures. To have cells choosing to become a certain neuronal type, attaining the correct laminar position, finding the correct target, and expressing the correct neurotransmitters at first seems overwhelmingly difficult. However, the final, breathtakingly complex set of connections in the human brain depends on a series of much simpler decisions as neurons become progressively more restricted in the choices they make. These decisions require the subtle interplay of genetic and environmental factors; much has been learned at a molecular level about these processes. At first glance this information seems most relevant to mental retardation or autistic disorder, in which abnormal brain development results in lifelong disability. However, even schizophrenia is believed to originate in subtle aberrant brain development, and understanding it requires an understanding of its etiology.
Table of Contents
- Neurogenesis and Neural Identity The cerebral cortex possesses an orderly six-layered array of neuronal and glial cell types; layer I is the most superficial layer closest to the meninges, layer VI lies deeper, closest to white matter.
- The first postmitotic neurons leave the neuroepithelium and accumulate beneath the pial surface to form the preplate.
- The microenvironment may also provide other information about a neuron's fate, such as what kind of cortex to become.
- Neuronal Migration Once neurons are born in the ventricular zone, they migrate past earlier born neurons to assume their final laminar position.
- The leading edge of the axon, the growth cone, has an array of molecules on its surface.
- Cell Death Once cortical neurons are created and assume their connections, there is a period of naturally occurring cell death (apoptosis) in widespread areas.
- Implications for Psychiatry What happens when the developmental plan goes awry?
- Such subtle developmental anomalies are being discovered in many animal species.
- One dysfunctional neural network in schizophrenia links the association cortices of the frontal, parietal, and temporal lobes and the limbic cortex and subcortical structures.
- Postmortem morphometric studies of brains from patients with schizophrenia are consistent with in vivo imaging studies.
- A neuron-specific stain for nicotinamide-adenine dinucleotide phosphate-diaphorase (NADPH-d) has been used to study brains from patients with schizophrenia.
- Molecules crucial to normal brain development and postnatal plasticity are being investigated in schizophrenia.
- If abnormal brain development causes schizophrenia, why does onset of symptoms occur in late adolescence or early adulthood?
« in utero directly cause development of hyperactivity? in mesolimbic and visuospatial neural circuits elicited 1982), Behavioral effects of prenatal exposure to ...» Document abstract
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Language : english
biology
presentation
date published
19/02/2008
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SummaryThe goal of this paper is to evaluate the significance of the co-morbidity of nicotine abuse in adolescents afflicted with ADHD (Attention-Deficit Hyperactivity Disorder). Due to the nature of the disorder and its possible underlying pathophysiology of dopaminergic dysfunction, the use of nicotine can be implicated as a form of self-medication. I will provide evidence of the co-morbidity and early onset of nicotine dependence and prevalence of smoking habit in adolescents with ADHD. Furthermore, I will discuss prenatal exposure to nicotine and its behavioral consequences, followed by an analysis of the pharmacology of nicotine and proposed circuitry of ADHD. Nicotine use in ADHD adolescents can no longer be attributed to mainstream “peer pressure". There are reinforcing effects provided by nicotine that parallel stimulant medication used to treat the disorder.
Table of Contents
- Introduction.
- Background.
- ADHD and the Smoking Epidemic.
- Prenatal Exposure.
- Neurobiological support.
- Pliszka etal (1996) Multistage Hypothesis of ADHD.
- Self-Medication Hypothesis.
- Conclusion.
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