SAT阅读资料:Dopaminergic mind hypothesis

　　SAT阅读资料:Dopaminergic mind hypothesis

　　The dopaminergic mind hypothesis seeks to explain the differences between modern humans and their hominid relatives by focusing on changes in dopamine. It theorizes that increased levels of dopamine were part of a general physiological adaptation due to an increased consumption of meat around two million years ago in Homo habilis, and later enhanced by changes in diet and other environmental and social factors beginning approximately 80,000 years ago. Under this theory, the high-dopamine personality is characterized by high intelligence, a sense of personal destiny, a religious/cosmic preoccupation, an obsession with achieving goals and conquests, an emotional detachment that in many cases leads to ruthlessness, and a risk-taking mentality. High levels of dopamine are proposed to underlie increased psychological disorders in industrialized societies. According to this hypothesis, a dopaminergic society is an extremely goal-oriented, fast-paced, and even manic society, given that dopamine is known to increase activity levels, speed up our internal clocks and create a preference for novel over unchanging environments. In the same way that high-dopamine individuals lack empathy and exhibit a more masculine behavioral style, dopaminergic societies are typified by more conquest, competition, and aggression than nurturance and communality. Although behavioral evidence and some indirect anatomical evidence support a dopaminergic expansion in humans, there is still no direct evidence that dopamine levels are markedly higher in humans relative to other apes. However, recent discoveries about the sea-side settlements of early man may provide evidence of dietary changes consistent with this hypothesis.

　　Dopamine is a catecholamine neurotransmitter present in a wide variety of animals, including both vertebrates and invertebrates. In the brain, this phenethylamine functions as a neurotransmitter, activating the five types of dopamine receptorsD1, D2, D3, D4, and D5and their variants. Dopamine is produced in several areas of the brain, including the substantia nigra and the ventral tegmental area. Dopamine is also a neurohormone released by the hypothalamus. Its main function as a hormone is to inhibit the release of prolactin from the anterior lobe of the pituitary.

　　Dopamine is available as an intravenous medication acting on the sympathetic nervous system, producing effects such as increased heart rate and blood pressure. However, because dopamine cannot cross the blood-brain barrier, dopamine given as a drug does not directly affect the central nervous system. To increase the amount of dopamine in the brains of patients with diseases such as Parkinsons disease and dopa-responsive dystonia, L-DOPA, which is the precursor of dopamine, can be given because it can cross the blood-brain barrier.