amygdala
Acronym:
AMG
The term amygdala (AMG) refers to a histologically defined structure at the rostral extreme of the ventral limb of the limbic lobe (LLBv), which has a cortical component on the medial aspect of the anterior parahippocampal gyrus (PHGa) of the human and macaque ( Amaral-1992 ). In the rat ( Swanson-2004 ) and mouse ( Hof-2000 ), it is located ventromedially in the cerebral hemisphere about midway between the frontal pole (frp) and occipital pole (ocp). It has two parts: periamygdalar cortex (PAC) and amygdalar nuclei (AMN).
The PAC is more cortex-like in that the neurons are organized in layers. Receiving direct input from the olfactory bulb (OLB), the PAC is the most central component of the olfactory system (OLS) ( Buck-2013 ). As the executive component of the instinctive behavioral control system, it transmits olfactory signals via stria terminalis (st) to motor component, the hypothalamus (HYP). It also transmits signals to HYP by an indirect pathway through the nuclei of stria terminalis (NST) and ( Olmos-1990 ). In the AMN neurons and myelinated axons are more homogeneously distributed. They receive input from the olfactory system through PAC and directly from all of the other sensory systems ( Wright-1997 ).
Two major functions of the amygdala are to mediate fast stereotypic instinctive responses to natural stimuli and to mediate the performance of learned responses to stimuli signalling opportunity to seek reward or to avoid harm ( Bowden-2021 ).
Some evidence indicates that the AMG can mediate instinctive responses to quite complex visual and auditory stimuli subconsciously, i.e., without conscious awareness of the stimulus. . Studies of blindsight in humans and macaques indicate an ability to categorize visual stimuli with considerable precision and to formulate appropriate responses to positive and negative, natural, emotional and symbolic stimuli without conscious awareness of having sensed them ( Weiskrantz, 2004). Updated 15 Jan 2025.
Also known as: amygdaloid body, amygdaloid complex, amygdaloid nuclear complex, amygdaloid nucleus, archistriatum, Corpus amygdalae, Corpus amygdaloideum, nucleus amygdalaeNeuroNames ID : 237
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