Basolateral amygdala

Last updated
Basolateral amygdala
Gray 718-amygdala.png
Coronal section of brain through intermediate mass of third ventricle. Amygdala is shown in purple.
Details
Part of Amygdala
Identifiers
Acronym(s)BL
NeuroNames 244
NeuroLex ID BIRNLEX:2679
FMA 84609
Anatomical terms of neuroanatomy

The basolateral amygdala, or basolateral complex, consists of the lateral, basal and accessory-basal nuclei of the amygdala. The lateral nuclei receives the majority of sensory information, which arrives directly from the temporal lobe structures, including the hippocampus and primary auditory cortex. The basolateral amygdala also receives dense neuromodulatory inputs from ventral tegmental area (VTA), [1] [2] locus coeruleus (LC), [3] and basal forebrain, [4] 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. [5]

Contents

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. [6] [7] 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, 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. [8] 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. [9]

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 [10] that conduct inhibitory M current. [11] The neuron then becomes more excitable and the consolidation of memory is enhanced. [10]

Pain memory

Distinct ensembles of neurons within the basolateral amygdala play a role in encoding associative memories and the response to painful stimuli. [12] 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. [13] 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.

Related Research Articles

<span class="mw-page-title-main">Striatum</span> Nucleus in the basal ganglia of the brain

The striatum or corpus striatum is a nucleus in the subcortical basal ganglia of the forebrain. The striatum is a critical component of the motor and reward systems; receives glutamatergic and dopaminergic inputs from different sources; and serves as the primary input to the rest of the basal ganglia.

<span class="mw-page-title-main">Amygdala</span> Each of two small structures deep within the temporal lobe of complex vertebrates

The amygdala is a paired nuclear complex present in the cerebral hemispheres of vertebrates. It is considered part of the limbic system. In primates, it is located medially within the temporal lobes. It consists of many nuclei, each made up of further subnuclei. The subdivision most commonly made is into the basolateral, central, cortical, and medial nuclei together with the intercalated cell clusters. The amygdala has a primary role in the processing of memory, decision-making, and emotional responses. The amygdala was first identified and named by Karl Friedrich Burdach in 1822.

The mesolimbic pathway, sometimes referred to as the reward pathway, is a dopaminergic pathway in the brain. The pathway connects the ventral tegmental area in the midbrain to the ventral striatum of the basal ganglia in the forebrain. The ventral striatum includes the nucleus accumbens and the olfactory tubercle.

<span class="mw-page-title-main">Fear conditioning</span> Behavioral paradigm in which organisms learn to predict aversive events

Pavlovian fear conditioning is a behavioral paradigm in which organisms learn to predict aversive events. It is a form of learning in which an aversive stimulus is associated with a particular neutral context or neutral stimulus, resulting in the expression of fear responses to the originally neutral stimulus or context. This can be done by pairing the neutral stimulus with an aversive stimulus. Eventually, the neutral stimulus alone can elicit the state of fear. In the vocabulary of classical conditioning, the neutral stimulus or context is the "conditional stimulus" (CS), the aversive stimulus is the "unconditional stimulus" (US), and the fear is the "conditional response" (CR).

<span class="mw-page-title-main">Nucleus accumbens</span> Region of the basal forebrain

The nucleus accumbens is a region in the basal forebrain rostral to the preoptic area of the hypothalamus. The nucleus accumbens and the olfactory tubercle collectively form the ventral striatum. The ventral striatum and dorsal striatum collectively form the striatum, which is the main component of the basal ganglia. The dopaminergic neurons of the mesolimbic pathway project onto the GABAergic medium spiny neurons of the nucleus accumbens and olfactory tubercle. Each cerebral hemisphere has its own nucleus accumbens, which can be divided into two structures: the nucleus accumbens core and the nucleus accumbens shell. These substructures have different morphology and functions.

<span class="mw-page-title-main">Dopaminergic pathways</span> Projection neurons in the brain that synthesize and release dopamine

Dopaminergic pathways in the human brain are involved in both physiological and behavioral processes including movement, cognition, executive functions, reward, motivation, and neuroendocrine control. Each pathway is a set of projection neurons, consisting of individual dopaminergic neurons.

<span class="mw-page-title-main">Ventral tegmental area</span> Group of neurons on the floor of the midbrain

The ventral tegmental area (VTA), also known as the ventral tegmental area of Tsai, or simply ventral tegmentum, is a group of neurons located close to the midline on the floor of the midbrain. The VTA is the origin of the dopaminergic cell bodies of the mesocorticolimbic dopamine system and other dopamine pathways; it is widely implicated in the drug and natural reward circuitry of the brain. The VTA plays an important role in a number of processes, including reward cognition and orgasm, among others, as well as several psychiatric disorders. Neurons in the VTA project to numerous areas of the brain, ranging from the prefrontal cortex to the caudal brainstem and several regions in between.

Motivational salience is a cognitive process and a form of attention that motivates or propels an individual's behavior towards or away from a particular object, perceived event or outcome. Motivational salience regulates the intensity of behaviors that facilitate the attainment of a particular goal, the amount of time and energy that an individual is willing to expend to attain a particular goal, and the amount of risk that an individual is willing to accept while working to attain a particular goal.

An avoidance response is a natural adaptive behavior performed in response to danger. Excessive avoidance has been suggested to contribute to anxiety disorders, leading psychologists and neuroscientists to study how avoidance behaviors are learned using rat or mouse models. Avoidance learning is a type of operant conditioning.

The amygdalofugal pathway is one of the three major efferent pathways of the amygdala, meaning that it is one of the three principal pathways by which fibers leave the amygdala. It leads from the basolateral nucleus and central nucleus of the amygdala. The amygdala is a limbic structure in the medial temporal lobe of the brain. The other main efferent pathways from the amygdala are the stria terminalis and anterior commissure.

<span class="mw-page-title-main">Medium spiny neuron</span> Type of GABAergic neuron in the striatum

Medium spiny neurons (MSNs), also known as spiny projection neurons (SPNs), are a special type of GABAergic inhibitory cell representing 95% of neurons within the human striatum, a basal ganglia structure. Medium spiny neurons have two primary phenotypes : D1-type MSNs of the direct pathway and D2-type MSNs of the indirect pathway. Most striatal MSNs contain only D1-type or D2-type dopamine receptors, but a subpopulation of MSNs exhibit both phenotypes.

<span class="mw-page-title-main">Reward system</span> Group of neural structures responsible for motivation and desire

The reward system is a group of neural structures responsible for incentive salience, associative learning, and positively-valenced emotions, particularly ones involving pleasure as a core component. Reward is the attractive and motivational property of a stimulus that induces appetitive behavior, also known as approach behavior, and consummatory behavior. A rewarding stimulus has been described as "any stimulus, object, event, activity, or situation that has the potential to make us approach and consume it is by definition a reward". In operant conditioning, rewarding stimuli function as positive reinforcers; however, the converse statement also holds true: positive reinforcers are rewarding.

<span class="mw-page-title-main">Synaptic gating</span>

Synaptic gating is the ability of neural circuits to gate inputs by either suppressing or facilitating specific synaptic activity. Selective inhibition of certain synapses has been studied thoroughly, and recent studies have supported the existence of permissively gated synaptic transmission. In general, synaptic gating involves a mechanism of central control over neuronal output. It includes a sort of gatekeeper neuron, which has the ability to influence transmission of information to selected targets independently of the parts of the synapse upon which it exerts its action.

The Intercalatedcells of the amygdala are GABAergic neurons situated between the basolateral and central nuclei of the amygdala that play a significant role in inhibitory control over the amygdala. They regulate amygdala-dependent emotional processing like fear memory and social behavior. Their function has been best studied with selective ITC ablation which impairs fear extinction, fear generalization, and social behavior. Studies have begun to recognize that ITC clusters may be implicated in reward, addiction, and withdrawal circuits given their heavy expression of dopamine and opioid receptors.

Many experiments have been done to find out how the brain interprets stimuli and how animals develop fear responses. The emotion, fear, has been hard-wired into almost every individual, due to its vital role in the survival of the individual. Researchers have found that fear is established unconsciously and that the amygdala is involved with fear conditioning.

Addiction is a state characterized by compulsive engagement in rewarding stimuli, despite adverse consequences. The process of developing an addiction occurs through instrumental learning, which is otherwise known as operant conditioning.

<span class="mw-page-title-main">Central nucleus of the amygdala</span> Nucleus within the amygdala

The central nucleus of the amygdala is a nucleus within the amygdala. It "serves as the major output nucleus of the amygdala and participates in receiving and processing pain information."

Pavlovian-instrumental transfer (PIT) is a psychological phenomenon that occurs when a conditioned stimulus that has been associated with rewarding or aversive stimuli via classical conditioning alters motivational salience and operant behavior. Two distinct forms of Pavlovian-instrumental transfer have been identified in humans and other animals – specific PIT and general PIT – with unique neural substrates mediating each type. In relation to rewarding stimuli, specific PIT occurs when a CS is associated with a specific rewarding stimulus through classical conditioning and subsequent exposure to the CS enhances an operant response that is directed toward the same reward with which it was paired. General PIT occurs when a CS is paired with one reward and it enhances an operant response that is directed toward a different rewarding stimulus.

<span class="mw-page-title-main">Kate Wassum</span> American neuroscientist

Kate Wassum is an American neuroscientist and professor of behavioral neuroscience at the University of California, Los Angeles. Wassum probes the neural circuits underlying appetitive associative learning the circuit dynamics that give rise to diverse motivated behaviors.

Fan Wang is a neuroscientist and professor in the MIT Department of Brain and Cognitive Sciences. She is an investigator at the McGovern Institute for Brain Research. Wang is known for her work identifying neural circuits underlying touch, pain, and anesthesia; and the development of a technique for capturing activated neuronal ensembles (CANE) to label and manipulate neurons activated by stimuli or behavioral paradigms.

References

  1. Mingote S, Chuhma N, Kusnoor SV, Field B, Deutch AY, Rayport S (December 2015). "Functional Connectome Analysis of Dopamine Neuron Glutamatergic Connections in Forebrain Regions". The Journal of Neuroscience. 35 (49): 16259–16271. doi:10.1523/JNEUROSCI.1674-15.2015. PMC   4682788 . PMID   26658874.
  2. Tang W, Kochubey O, Kintscher M, Schneggenburger R (May 2020). "A VTA to Basal Amygdala Dopamine Projection Contributes to Signal Salient Somatosensory Events during Fear Learning". The Journal of Neuroscience. 40 (20): 3969–3980. doi:10.1523/JNEUROSCI.1796-19.2020. PMC   7219297 . PMID   32277045.
  3. Giustino TF, Maren S (2018). "Noradrenergic Modulation of Fear Conditioning and Extinction". Frontiers in Behavioral Neuroscience. 12: 43. doi: 10.3389/fnbeh.2018.00043 . PMC   5859179 . PMID   29593511.
  4. Crouse RB, Kim K, Batchelor HM, Girardi EM, Kamaletdinova R, Chan J, et al. (September 2020). Hill MN, Colgin LL, Lovinger DM, McNally GP (eds.). "Acetylcholine is released in the basolateral amygdala in response to predictors of reward and enhances the learning of cue-reward contingency". eLife. 9: e57335. doi: 10.7554/eLife.57335 . PMC   7529459 . PMID   32945260.
  5. Baars BJ, Gage NM (2010). Cognition, Brain, and Consciousness: introduction to cognitive neuroscience (second ed.). Burlington MA: Academic Press.
  6. Cartoni E, Puglisi-Allegra S, Baldassarre G (November 2013). "The three principles of action: a Pavlovian-instrumental transfer hypothesis". Frontiers in Behavioral Neuroscience. 7: 153. doi: 10.3389/fnbeh.2013.00153 . PMC   3832805 . PMID   24312025.
  7. Salamone JD, Pardo M, Yohn SE, López-Cruz L, SanMiguel N, Correa M (2016). "Mesolimbic Dopamine and the Regulation of Motivated Behavior". Current Topics in Behavioral Neurosciences. 27: 231–257. doi:10.1007/7854_2015_383. ISBN   978-3-319-26933-7. PMID   26323245. Considerable evidence indicates that accumbens DA is important for Pavlovian approach and Pavlovian-to-instrumental transfer [(PIT)] ... PIT is a behavioral process that reflects the impact of Pavlovian-conditioned stimuli (CS) on instrumental responding. For example, presentation of a Pavlovian CS paired with food can increase output of food-reinforced instrumental behaviors, such as lever pressing. Outcome-specific PIT occurs when the Pavlovian unconditioned stimulus (US) and the instrumental reinforcer are the same stimulus, whereas general PIT is said to occur when the Pavlovian US and the reinforcer are different. ... More recent evidence indicates that accumbens core and shell appear to mediate different aspects of PIT; shell lesions and inactivation reduced outcome-specific PIT, while core lesions and inactivation suppressed general PIT (Corbit and Balleine 2011). These core versus shell differences are likely due to the different anatomical inputs and pallidal outputs associated with these accumbens subregions (Root et al. 2015). These results led Corbit and Balleine (2011) to suggest that accumbens core mediates the general excitatory effects of reward-related cues. PIT provides a fundamental behavioral process by which conditioned stimuli can exert activating effects upon instrumental responding
  8. Breedlove S, Watson N (2013). Biological Psychology: an introduction to behavioral cognitive, and clinical neuroscience (Seventh ed.). Sunderland: MA: Sinauer Associates, Inc.
  9. Smith C, Kirby L (2001). "Toward delivering on the promise of appraisal theory.". In Scherer KR, Schorr A, Johnstone T (eds.). Appraisal processes in emotion: Theory, methods, research. Oxford, UK: Oxford University Press.
  10. 1 2 Young MB, Thomas SA (January 2014). "M1-muscarinic receptors promote fear memory consolidation via phospholipase C and the M-current". The Journal of Neuroscience. 34 (5): 1570–1578. doi:10.1523/JNEUROSCI.1040-13.2014. PMC   3905134 . PMID   24478341.
  11. Schroeder BC, Hechenberger M, Weinreich F, Kubisch C, Jentsch TJ (August 2000). "KCNQ5, a novel potassium channel broadly expressed in brain, mediates M-type currents". The Journal of Biological Chemistry. 275 (31): 24089–24095. doi: 10.1074/jbc.M003245200 . PMID   10816588.
  12. Grewe BF, Gründemann J, Kitch LJ, Lecoq JA, Parker JG, Marshall JD, et al. (March 2017). "Neural ensemble dynamics underlying a long-term associative memory". Nature. 543 (7647): 670–675. Bibcode:2017Natur.543..670G. doi:10.1038/nature21682. PMC   5378308 . PMID   28329757.
  13. Corder G, Ahanonu B, Grewe BF, Wang D, Schnitzer MJ, Scherrer G (January 2019). "An amygdalar neural ensemble that encodes the unpleasantness of pain". Science. 363 (6424): 276–281. doi:10.1126/science.aap8586. PMC   6450685 . PMID   30655440.