« Early Neural Postnatal Development The early postnatal years are marked by a rapid maturation of cognitive, social, and behavioral abilities as infants ...» Document abstract
$2.95
3 word format
Language : english
psychology
research papers
date published
13/11/2007
review : not yet assessed
level : Advanced
requested 0 times
SummaryThe early postnatal years are marked by a rapid maturation of cognitive, social, and behavioral abilities as infants progress from helplessness to autonomy, and children and adolescents develop more sophisticated ways of thinking. The information and abilities acquired by infants, children, and adolescents are staggering. The impact that these early years have on personality development and behavior is profound, longlasting, and at times, refractory to treatment interventions. The consequences of physical or emotional childhood trauma are seen in every psychiatric practice. For such dramatic cognitive, behavioral, and emotional changes, there must be an underlying neurobiological substrate. Neuroscience is exploring the structural and functional foundations of normal postnatal maturation and how it is impacted by the environment.
Table of Contents- Postnatal Cortical Maturation The number of cortical synapses changes dramatically in early postnatal life.
- Many neuronal types alter their shape postnatally, corresponding to altered synaptic connections.
- Environmental Effects on Cortical Connections During early life the cortex is fine-tuning its connections dependent on patterns of neural activity caused by environmental input.
- If kittens are deprived of visual input altogether, compensatory changes are seen in the visual areas
- Early environmental manipulations may also impact higher cognitive functioning.
- Critical Periods for Cognition and Emotion The importance of critical periods does not apply solely to visual and language cortices.
- Behavioral studies in monkeys have shown that early childhood experience can have a profound impact on adult adaptation, especially in the context of social stress.
- In humans, there is evidence that early environmental stimulation, even before preschool, improves learning with an effect that lasts for years.
« to normal brain development and postnatal plasticity are occur in late adolescence or early adulthood Neural Prenatal Development The wonder of development is ...» Document abstract
$6.95
7 word format
Language : english
psychology
research papers
date published
13/11/2007
review : not yet assessed
level : Advanced
requested 0 times
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?
« somatosensory cortex are achieved by postnatal day 21. to the integrative power of neural networks neuropeptides and receptors in early development and adulthood ...» Document abstract
$9.95
11 word format
Language : english
biology
research papers
date published
26/11/2007
review : not yet assessed
level : Advanced
requested 1 times
SummaryNeuropeptide receptors have undergone the same process of discovery and characterization that receptors for other neurotransmitters have enjoyed. The process begins with the pharmacological characterization of the receptor's physicochemical binding properties by assessing the affinity of various metabolically derived and synthetic peptide fragments, and the native molecule, for the receptor binding site found in membrane preparations. Peptide receptor locations are mapped with radioactive or fluorescent tags that are inserted into peptide molecules, which often contain substituted amino acids at the most vulnerable peptidase cleavage sites. Previously, once the peptide receptor was characterized pharmacologically, it was usually purified from some relatively enriched biological tissue source or brain region by affinity column chromatography. After it had been purified, binding parameters and activity were recharacterized for the reconstituted purified receptor protein and structural information obtained by X-ray crystallography. This process was closely followed in the purification of the neurotensin-neuromedin N receptor.
Table of Contents- The neurotensin receptor was first characterized by photoaffinity labeling and cross-linking of radioiodinated ligands, which resulted in two labeled subunits of about 49 Kd and 51 Kd from rat brain synaptosomes.
- The much more powerful tools of molecular biology have been utilized more recently.
- Neuropeptide receptors have been associated with just about every type of second messenger signal transduction system that has been identified.
- Peptides are degraded to smaller fragments, and eventually to single amino acids, by specific enzymes termed peptidases.
- The metabolism of TRH has been investigated fairly completely, principally because of the limited number of fragments that can be generated from a tripeptide.
- The peptides involved in neuroendocrine regulation have cell bodies residing in the hypothalamus that receive feedback from all levels of the endocrine axes.
- Regional differences in CRF receptor regulation by corticosterone have also been reported, which have been shown to partly result from differential glycosylation of the CRF receptor.
- Alzheimer's Disease Dementia of the Alzheimer's Type represents up to two thirds of the demented population encountered in clinical practice, and over half of the nursing home beds in the United States are currently occupied by such patients.
- The CRF-containing interneurons of the cortex are also consistently depleted in Alzheimer's disease. As with SRIF, subcortical areas containing CRF neurons may be spared, but unlike SRIF, CRF receptors are increased in number (up-regulated) with no change in affinity.
- Corticotropin-Releasing Factor After a search spanning nearly three decades, CRF was isolated and characterized in 1981 as a 41-amino acid peptide.
- A series of studies have demonstrated significant elevations of CRF concentrations in the CSF of drug-free patients with major depression or following suicide.
- Like many other neuropeptide transmitters, central administration of SRIF produces a variety of behavioral and physiological effects.
- Decreased neurotensin concentrations in CSF have been reported in several populations of patients with schizophrenia when compared to controls or patients with other psychiatric disorders.
1
knowledge network
Sort by
Subject :
Type :
Extension :
Language :
Size :