Science29 Sep 2010 03:01 am
The amygdala, an almond-sized and -shaped brain structure, has long been linked with a person’s mental and emotional state. But thanks to scientific advances, researchers have recently grasped how important this 1-inch-long structure really is. Associated with a range of mental conditions from normalcy to depression to even autism, the amygdala has become the focal point of numerous research projects.
The amygdala sits in the brain’s medial temporal lobe, a few inches from either ear. Coursing through the amygdala are nerves connecting it to a number of important brain centers, including the neocortex and visual cortex. “More and more we’re beginning to believe, and the evidence is pointing to the idea, that it’s the circuits that are important, not just the structure per se,” says Ned Kalin, professor of psychiatry, University of Wisconsin-Madison. “And in this particular case the circuitry between the frontal cortical regions of the brain may be critical in regulating emotion and in guiding emotion-related behaviors.”
The existence of the amygdala was first formally recognized in the early 19th century. The name, derived from the Greek, was meant to denote the almond-like shape of this region in the medial temporal lobe. Much debate has since ensued, and continues today, about how the amygdala should be subdivided. Also controversial is how the subdivisions relate to other major regions of the brain.
One long-standing idea is that the amygdala consists of an evolutionarily primitive division associated with the olfactory system (cortical, medial and central nuclei) and an evolutionarily newer division associated with the neocortex (lateral, basal, and accessory basal nuclei). The areas of the older division are sometimes grouped as the cortico-medial region (cortical and medial nuclei) and sometimes as the centro-medial region (the central and medial nuclei). In contrast, the newer structures related to the neocortex are often referred to as the basolateral region. The almond shaped structure that originally defined the amygdala included the basolateral region rather than the whole structure now considered to be the amygdala.
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