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Marijuana's damage to short-term memory seems to occur because THC alters the way in which information is processed by the hippocampus, a brain area responsible for memory formation. Laboratory rats treated with THC displayed the same reduced ability to perform tasks requiring short-term memory as other rats showed after nerve cells in their hippocampus were destroyed.
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Heyser, C.J.; Hampson, R.E.; and Deadwyler, S.A. Effects of delta-9-tetrahydrocannabinol on delayed match to sample performance in rats: Alterations in short-term memory associated with changes in task-specific firing of hippocampal cells. Journal of Pharmacology & Experimental Therapeutics 264(1):294-307, 1993.
Acute, reversible actions are not damage: "However, unlike the effects of hippocampal lesions or neurotoxic damage, the effects of delta-9-THC were completely reversible within 24 hr of injection." It later went on to state "...this effect could serve as the basis for the well characterized short-term memory and other cognitive deficits reported in humans after smoking marijuana," popularly known as being high.
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As people age, they normally lose neurons in the hippocampus, which decreases their ability to remember events. Chronic THC exposure may hasten the age-related loss of hippocampal neurons. In one series of studies, rats exposed to THC every day for 8 months (approximately 30 percent of their lifespan), when examined at 11 to 12 months of age, showed nerve cell loss equivalent to that of unexposed animals twice their age.
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Landfield, P.W.; Cadwallader, L.B.; and Vinsant, S. Quantitative changes in hippocampal structure following long exposure to delta-9-tetrahydrocannabinol: Possible mediation of glucocorticoid systems. Brain Res 443(1-2):47-62, 1988.
"However, the animals appeared to be only minimally affected behaviorally by the doses used (highest dose: 8 mg/kg) and no effects of THC were observed on several ultrastructural variables, including synaptic density." What are the implications? How is this supposed to justify prohibition?
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Heishman SJ, et al. Comparative effects of alcoho...[PMID:9264076]
Sullivan JM Molecular Neurobiology Laboratory: Cellular and molecular mechanisms underlying learning and memory impairments produced by cannabinoids.
Misner DL: Mechanism of cannabinoid effects on long-term potentiation and depression in hippocampal CA1 neurons.
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Explain the implications of these and their findings in regards to safety and prohibition.