description of neurogenesis

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Let's talk about neurogenesis. Neurogenesis (birth of neurons) is the process by which neurons are created. It is a very new concept that neurogenesis occurs post birth. Adult neurogenesis is a recent example of a long-held scientific theory being overturned, with the phenomenon only recently being largely accepted by the scientific community. Early neuroanatomists, considered the nervous system fixed and incapable of regeneration. This concept of being fixed lasted for about 100 years. It was only in about 2000 that it became plainly evident that it does occur throughout life and w/o it the person begins to degenerate. Neurogenesis is important to learning and memory. the following paragraph is directly

from Wilkepedia: Adult born neurons appear to have a role in the regulation of stress. Malberg et al. (2000) [8] and Manev et al. (2001) [9] have linked neurogenesis to the beneficial actions of

certain antidepressants, suggesting a connection between decreased hippocampal neu rogenesis and depression. In a subsequent paper, Santarelli et al. (2003) [10] demonstrated that the behavioural effects of antidepressants in mice did not occur when neurogenesis was prevented with x-irradiation techniques. In fact, adult-born neurons are more excitable than older neurons due to a differential expression of GABA receptors. A plausible model therefore is that these neurons augment the role of the hippocampus in the negative feedback mechanism of the HPA-axis (physiolo gical stress) and perhaps in inhibiting the amygdala (the region of brain responsible for fearful responses to stimuli). This is consistent with numerous findings linking stress-relieving activities (learning, exposure to a new yet benign environment, and exercise) to increased levels of neurogenesis, as well as the observation that animals exposed to physiological stress (cortisol) or psychological

stress (e.g. isolation) show markedly decreased levels of adult-born neurons. Very recent papers have linked together learning and memory with depression, and have suggested that neurogenesis may promote neuroplasticity. For instance, Castren (2005) [11] has proposed that our mood may be regulated, at a base level, by plasticity, and thus not chemistry; for instance, the effects of antidepressant treatment are only secondary to this. The mechanism by which it occurs is not yet understood but some things are known. The mechanism probably uses neural stem cells and neurotophic factors (eg. BDNF - brain derived neurotrophic factor). It probably does not use neurotransmittors however they are involved in synaptic plasticity and the firing of nerves. These concepts are very important to everyone's well-being not just those with DS. This is a good start.

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