(This is known as the reciprocal interaction/activation-synthesis model).
This model proposed that reciprocally interacting chemicals secreted in an elementary part of the brain that has nothing to do with complex mental functioning were responsible for the creation of dream images.
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Intraperitoneal or oral administration of high doses of 5-HT precursor (5-HTP) causes a marked increase in corticosterone secretion in rodents, whereas the effects of oral 5-HTP on HPA-axis hormone secretion in humans are somewhat more variable in studies using lower doses of the racemic mixture (, ) and/or enteric coated tablets (52). There is now evidence that 200 mg 5-HTP, in nonenteric coated tablets, reliably stimulates HPA-axis hormones and prolactin secretion in normal humans, and that 5-HTP-induced activation of both HPA-axis and prolactin secretion are probably related to 5-HT mechanisms (52). Significantly higher 5-HTP (, : 200 mg; : 125 to 200 mg) -induced cortisol responses were observed in major depressed subjects than in normal controls or minor depressed subjects (38, 54). The use of 5-HTP as a 5-HT probe was challenged, because administration of very high doses of 5-HTP in rodents may lead to 5-HT synthesis in central catecholaminergic neurons and may increase synthesis of catecholamines (73). The dose of 5-HTP used in human studies, however, is much lower than that needed to increase catecholamine turnover in animal studies. Because 5-HT postsynaptic receptors are probably down-regulated in major depression, the above findings may be explained either by supersensitive 5-HT or 5-HT receptors. Since several types of studies (reviewed here) indicate increased 5-HT receptor binding or disorders in 5-HT–related behaviors in major depression or suicide, whereas there is no specific evidence as yet for 5-HT receptor supersensitivity in depression, it may be suggested that the results of the studies with 5-HTP as challenger are compatible with up-regulation or supersensitivity of 5-HT postsynaptic receptors (52).
ACTIVATION-SYNTHESIS HYPOTHESIS - Psychology …
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The last review of these hypotheses in this series (51) concluded that the available data on the role of 5-HT in major depression favored the hypothesis that a deficiency in brain serotonergic activity increases vulnerability to major depression. This review (51) summarized the following evidence: (a) Disorders in serotonergic activity could contribute to many of the symptoms of major depression, for example, mood, appetite, sleep, activity, suicide, sexual, and cognitive dysfunction. (b) Interference with 5-HT synthesis or storage may induce depression in some vulnerable individuals. (c) Abnormalities in serotonergic activity in depression could occur at one or more of several levels, for example, diminished availability of tryptophan (TRP), the precursor of 5-HT, impaired 5-HT synthesis, release, reuptake, or metabolism, or 5-HT postsynaptic receptor abnormalities. (d) Finally, antidepressant drugs may act, in part, by enhancing central serotonergic activity.
Activation-Synthesis Hypothesis of ..
In concluding this overview of findings on dream content inside and outside the sleep laboratory, it should be noted that the coherence, consistency, and continuity of most dream content revealed in virtually every study is not what would be expected on the basis of Freudian, Jungian, or activation-synthesis theory. In fact, these studies contradict every specific hypothesis that was put forth by Freud in The Interpretation of Dreams (1900), as shown in detailed critiques of the theory and its current main proponent, Mark Solms (Domhoff, 2003b, pp. 136-143; 2004). In the case of Jungian theory, the finding of continuity between dreams and waking concerns is in direct contradiction to its claim that dreaming has a "compensatory" function (according to this key Jungian tenet, dreams purportedly reveal the underdeveloped aspects of the psyche that are not expressed in waking life) (Jung, 1974). As for activation-synthesis theory, it is most severely challenged at the content level by the realistic and coherent nature of dream content revealed in both laboratory studies and studies of lengthy dream journals that stretch over decades.
What is the activation-synthesis theory
This neural network encompasses the limbic, paralimbic, and association cortices, with little or no role for the dorsolateral prefrontal cortex, sensorimotor cortex, or primary visual cortex. Thus, the association cortices, paralimbic structures, and limbic structures may operate as a closed loop to generate the process of dreaming. On the one hand, this subsystem is cut off from the primary sensory cortices that provide information about the external world, and on the other from the prefrontal cortices that integrate incoming sensory information with memory and emotion in the process of decision-making. This model implies that an unconstrained and freewheeling conceptual system can operate when there is sufficient brain activation. At the same time, it is clear from the nature of dream content that the neural network for dreaming contains enough cognitive processing areas, such as the medial frontal cortex and anterior cingulate cortex, to produce coherent dramatizations that often reflect the dreamer's conceptions and concerns in waking life. (For a detailed account that brings together the early neuropsychological and brain imaging studies, go to my , which fits with more recent findings except on a few details.)