Amygdala

– anterior and medial to the hippocampus, occupies much of the uncus

Major inputs

1. olfactory from the olfactory bulb and laterally from the primary olfactory cortex (pyriform cortex)
2. multisensory cortical association areas of frontal, parietal, occipital and temporal lobes via the cingulum (draped over the corpus callosum)
3. hypothalamus via the stria terminalis (draped over the thalami) and ventral amygdalopetal (direct from temporal lobe to hypothalamus)
4. Also receives cholinergic fibers from the base of the frontal lobes (a.k.a. basal forebrain where the septal nuclei and basal nucleus of Meynert are located), dopaminergic fibers from the ventral tegmental area of the midbrain, serotonergic fibers from the raphe nuclei (located just inferior to the ventral tegmental area), and noradrenergic fibers from the locus ceruleus (just inferior to the raphe nuclei)

Major outputs

1. over both the stria terminalis and ventral amygdalofugal path (direct connection from amygdala to basal forebrain) Remember: amygdalopetal in, amygdalofugal out
   1. direct fibers to the prefrontal cortex, basal forebrain and anterior cingulated gyrus
   2. nucleus accumbens (at the inferior edge of the anterior putamen)
   3. hypothalamus
   4. reticular formation

Function

1. arousal and increased attentiveness via the basal forebrain and reticular formation projections
2. stimulation mediates fear, anger, and rage
3. ablation causes decreased aggressive and assaultive behavior
4. sympathetic and parasympathetic responses
5. amygdala plays a role in establishing appropriate links between stimuli and their emotional value, detects gaze direction and facial orientation of others that reveals emotional signals
6. increases ACTH secretion and regulates secretion of LH and FSH (hypersexuality occurs in bilateral destruction of the amygdala); has high concentrations of enkephalins, somatostatin, and dopamine
7. basolateral amygdala inhibits the hypothalamic feeding center while the corticomedial amygdala stimulates the feeding center Remember: Lateral - Lose weight, Medial - Munch a lot
8. Note: Kluver-Bucy syndrome: bilateral ablation of amygdala (although the hippocampus is also involved) leading to hyperphagia, obliteration of rage and fear, increased exploratory behavior (psychic blindness), hypersexuality, memory deficits, compulsive tendencies. Remember: big, fat, orally fixated, horny stupid guy who is passive and compulsive