Intelligence in Nature - Jeremy Narby [93]
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P. 132: MEMORY FOR THE SHORT TERM
Connors (2002) describes research which found âthat a single, isolated neuron, when stimulated briefly, could generate sustained increases in its electrical activity that were graded in intensity and readily reversible. In other words, one such neuron could quickly remember (and forget) numerous bits of informationâ¦Individual neurons are unlikely to go it alone, because memories are distributed across large numbers of neurons. But perhaps intrinsically mnemonic neurons are an essential component of interconnected networks that encode memoriesâ¦. Without short-term memory, cognition itself crumbles. Disorders of working memory have, for instance, been implicated in such devastating, psychiatric diseases as schizophrenia. If a single-neuron mnemonic mechanism does prove relevant to behavior, it will help us to understand working memoryâand its dysfunctionsâat the molecular levelâ (pp. 133â34). The quote in the main text on short-term memory is by Connors (2002, p. 133).
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P. 132: NEW MEMORIES FROM NEW NEURONS
Macklis (2001) describes the research conducted on the brains of adult rats by a team of neuroscientists: âThe authors found that a roughly 80 percent reduction in the number of newborn neurons in the adult hippocampus impaired the hippocampus-dependent trace-conditioning memory, but had no effect on another, hippocampus-independent form of memory. Restoring normal levels of neurogenesis in the hippocampus, after the end of the treatment with MAM (a drug which kills proliferating cells), led to the recovery of trace-conditioning memory. The implication is that the normal level of neurogenesis in the hippocampus of adult rats is required for some types of memory that are related to the timing and temporal order of events. By extension, it seems that the new neurons themselves are involved in forming new memoriesâ(p. 315).
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P. 133: LEARNING AND EXERCISE INCREASE SURVIVAL OF NEW NEURONS
Gage (2003) writes: âOne of the most striking aspects of neurogenesis in the hippocampus is that experience can regulate the rate of cell division, the survival of newborn neurons and their ability to integrate into the existing neural circuitry. Adult mice that are moved from a rather sterile, simple cage to a larger one that has running wheels and toys, for instance, will experience a significant increase in neurogenesisâ¦Exercising mice in a running wheel is sufficient to nearly double the number of dividing cells in the hippocampus, resulting in a robust increase in new neurons. Intriguingly, regular physical activity such as running can also lift depression in humans, perhaps by activating neurogenesisâ¦The links between neurogenesis and increased mental activity and exercise also suggest that people might be able to reduce their risk of neural disease and enhance the natural repair processes in their brains by choosing a mentally challenging and physically active lifeâ (p. 34).
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P. 133: NEURONAL NETWORKS AND HOW THE BRAIN LEARNS
See Fuster (2003, pp. xâxi) and Vaadia (2000, p. 523) for the quotes in main text.
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P. 133: BRAINâS PLASTICITY
See Holloway (2003) regarding string musicians, dyslexic children and paraplegics.
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P. 134: VIEWS OF SELF
Gray (2002) writes: âCognitive science follows Buddhist teachings in viewing the self as a chimera. Our perceptions are fragments, picked out from an unfathomable richnessâbut there is no one doing the selecting. Our selves are themselves fragmentaryâ¦. We labor under an error. We act in the belief that we are all of one piece, but we are able to cope with things only because we are a succession of fragments. We cannot shake off the sense that we are enduring selves, and yet we know not who we areâ (pp. 71â73). Llinás (2001) writes in the same vein: ââIâ has always been the magnificent mystery; I believe, I say, I whatever. But one must understand that there is no such tangible thingâ (p. 127).