On top of the brainstem and buried under the cortex, there is a set of more evolutionarily primitive brain structures called the limbic system (e.g., amygdala and hippocampus, as in Figure 2). The limbic system structures are involved in many of our emotions and motivations, particularly those that are related to survival, such as fear, anger, and sexual behavior.
The limbic system is also involved in feelings of pleasure that are related to our survival, such as those experienced from eating and sex. The large limbic system structure, the hippocampus, is also involved in memory.
One of the reasons that drugs of abuse can exert such powerful control over our behavior is that they act directly on the more evolutionarily primitive brainstem and limbic system structures, which can override the cortex in controlling our behavior. In effect, they eliminate the most human part of our brain from its role in controlling our behavior.
Source: NIDA (NIH)1
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Limbic System: A set of forebrain structures common to all mammals that is defined functionally and anatomically. It is implicated in the higher integration of visceral, olfactory, and somatic information as well as homeostatic responses including fundamental survival behaviors (feeding, mating, emotion). For most authors, it includes the Amygdala; Epithalamus; Gyrus Cinguli; hippocampal formation (see Hippocampus); Hypothalamus; Parahippocampal Gyrus; Septal Nuclei; anterior nuclear group of thalamus, and portions of the basal ganglia. (Parent, Carpenter's Human Neuroanatomy, 9th ed, p744; Neuronames, http://rprcsgi.rprc.washington.edu/neuronames/index.html (September 2, 1998)).2
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- Fear: Fear is an emotional reaction to situations of danger or stress. However, unreasonable fear may indicate disorders such as a panic attack (anxiety attack), Panic Disorder, or Anxiety Disorder. Fear
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- Anger: Anger may be a normal behavior if rational, but abnormal anger can indicate a variety of disorders. Certain psychological disorders may exhibit anger and aggressive behavior, as can substance abuse
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- Memory Symptoms: Memory symptoms generally refer to the failure of memory. Mild forms are called forgetfulness or memory loss; more severe types may be blackouts or amnesia. In many cases, the onset
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- Abuse: Abuse is a general term for a variety of medical issues. It may indicate substance abuse, such as alcohol abuse (alcohol intoxication) or illicit drug use. Prescription drug abuse is
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- Source: NIDA (NIH): teens.drugabuse.gov/ teachers/ mind-over-matter/ teachers-guide
- Source: MeSH (U.S. National Library of Medicine)
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