The basolateral amygdala, or basolateral complex, or basolateral nuclear complex consists of the lateral, basal and accessory-basal nuclei of the

amygdala The amygdala (; : amygdalae or amygdalas; also '; Latin from Greek language, Greek, , ', 'almond', 'tonsil') is a paired nucleus (neuroanatomy), nuclear complex present in the Cerebral hemisphere, cerebral hemispheres of vertebrates. It is c ...

. The lateral nuclei receives the majority of sensory information, which arrives directly from the

temporal lobe The temporal lobe is one of the four major lobes of the cerebral cortex in the brain of mammals. The temporal lobe is located beneath the lateral fissure on both cerebral hemispheres of the mammalian brain. The temporal lobe is involved in pr ...

structures, including the

hippocampus The hippocampus (: hippocampi; via Latin from Ancient Greek, Greek , 'seahorse'), also hippocampus proper, is a major component of the brain of humans and many other vertebrates. In the human brain the hippocampus, the dentate gyrus, and the ...

and primary auditory cortex. The basolateral amygdala also receives dense neuromodulatory inputs from ventral tegmental area (VTA), locus coeruleus (LC), and basal forebrain, whose integrity are important for associative learning. The information is then processed by the basolateral complex and is sent as output to the central nucleus of the amygdala. This is how most emotional arousal is formed in mammals.

Function

The amygdala has several different nuclei and internal pathways; the basolateral complex (or basolateral amygdala), the central nucleus, and the cortical nucleus are the most well-known. Each of these has a unique function and purpose within the amygdala.

Fear response

The basolateral amygdala and nucleus accumbens shell together mediate specific Pavlovian-instrumental transfer, a phenomenon in which a classically conditioned stimulus modifies operant behavior. One of the main functions of the basolateral complex is to stimulate the fear response. The fear system is intended to avoid pain or injury. For this reason the responses must be quick, and reflex-like. To achieve this, the “low-road” or a bottom-up process is used to generate a response to stimuli that are potentially hazardous. The stimulus reaches the

thalamus The thalamus (: thalami; from Greek language, Greek Wikt:θάλαμος, θάλαμος, "chamber") is a large mass of gray matter on the lateral wall of the third ventricle forming the wikt:dorsal, dorsal part of the diencephalon (a division of ...

, and information is passed to the lateral nucleus, then the basolateral system, and immediately to the central nucleus where a response is then formed. There is no conscious cognition involved in these responses. Other non-threatening stimuli are processed via the “high road” or a top-down form of processing. In this case, the stimulus input reaches the sensory cortex first, leading to more conscious involvement in the response. In immediately threatening situations, the fight-or-flight response is reflexive, and conscious thought processing doesn’t occur until later. An important process that occurs in basolateral amygdala is consolidation of cued fear memory. One proposed molecular mechanism for this process is collaboration of M₁-Muscarinic receptors, D₅ receptors and beta-2 adrenergic receptors to redundantly activate phospholipase C, which inhibits the activity of KCNQ channels that conduct inhibitory M current. The neuron then becomes more excitable and the consolidation of memory is enhanced.

Pain memory

Distinct ensembles of neurons within the basolateral amygdala play a role in encoding associative memories and the response to painful stimuli. The ensemble activated in response to noxious stimuli are of particular interest for targeting treatments of chronic pain and cold allodynia. When neurons within this ensemble are silenced in a rodent model the affective component of pain is essentially erased, while a robust reflex response is maintained. This is thought to implicate the basolateral amygdala in assigning a “pain tag” to valence information which may intrinsically encode that there is a priority to engage in pain-protective behaviors.

References

{{authority control Amygdala