Chunk #36 — 3 Neural Substrates for the Negative Emotional State Associated with Alcoholism — 3.2 Between-System Neuroadaptations that Contribute to Compulsivity Associated with the Dark Side of Alcoholism
Brain neurochemical systems involved in arousal-stress modulation may also be engaged within the neurocircuitry of the brain stress systems in an attempt to overcome the chronic presence of the perturbing drug (alcohol) and to restore normal function despite the presence of drug. The neuroanatomical entity termed the extended amygdala (Heimer and Alheid 1991) may represent a common anatomical substrate integrating brain arousal-stress systems with hedonic processing systems to produce some of the between-system opponent process elaborated above. The extended amygdala is composed of the central nucleus of the amygdala, bed nucleus of the stria terminalis, and a transition zone in the medial (shell) subregion of the nucleus accumbens. Each of these regions has cytoarchitectural and circuitry similarities (Heimer and Alheid 1991). The extended amygdala receives numerous afferents from limbic structures, such as the basolateral amygdala and hippocampus, and sends efferents to the medial part of the ventral pallidum and a large projection to the lateral hypothalamus, thus further defining the specific brain areas that interface classical limbic (emotional) structures with the extrapyramidal motor system (Alheid et al. 1995). The extended
