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The entorhinal cortex (EC) is an area of the brain's allocortex, located in the medial temporal lobe, whose functions include being a widespread network hub for memory, navigation, and the perception of time. The EC is the main interface between the hippocampus and neocortex. The EC-hippocampus system plays an important role in declarative (autobiographical/episodic/semantic) memories and in particular spatial memories including memory formation, memory consolidation, and memory optimization in sleep. The EC is also responsible for the pre-processing (familiarity) of the input signals in the reflex nictitating membrane response of classical trace conditioning; the association of impulses from the eye and the ear occurs in the entorhinal cortex.
The amygdala is one of two almond-shaped clusters of nuclei located deep and medially within the temporal lobes of the brain's cerebrum in complex vertebrates, including humans. Shown to perform a primary role in the processing of memory, decision making, and emotional responses, the amygdalae are considered part of the limbic system. The term "amygdala" was first introduced by Karl Friedrich Burdach in 1822.
The olfactory bulb is a neural structure of the vertebrate forebrain involved in olfaction, the sense of smell. It sends olfactory information to be further processed in the amygdala, the orbitofrontal cortex (OFC) and the hippocampus where it plays a role in emotion, memory and learning. The bulb is divided into two distinct structures: the main olfactory bulb and the accessory olfactory bulb. The main olfactory bulb connects to the amygdala via the piriform cortex of the primary olfactory cortex and directly projects from the main olfactory bulb to specific amygdala areas. The accessory olfactory bulb resides on the dorsal-posterior region of the main olfactory bulb and forms a parallel pathway. Destruction of the olfactory bulb results in ipsilateral anosmia, while irritative lesions of the uncus can result in olfactory and gustatory hallucinations.
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).
Brodmann area 10 is the anterior-most portion of the prefrontal cortex in the human brain. BA10 was originally defined broadly in terms of its cytoarchitectonic traits as they were observed in the brains of cadavers, but because modern functional imaging cannot precisely identify these boundaries, the terms anterior prefrontal cortex, rostral prefrontal cortex and frontopolar prefrontal cortex are used to refer to the area in the most anterior part of the frontal cortex that approximately covers BA10—simply to emphasize the fact that BA10 does not include all parts of the prefrontal cortex.
Pyramidal cells, or pyramidal neurons, are a type of multipolar neuron found in areas of the brain including the cerebral cortex, the hippocampus, and the amygdala. Pyramidal cells are the primary excitation units of the mammalian prefrontal cortex and the corticospinal tract. Pyramidal neurons are also one of two cell types where the characteristic sign, Negri bodies, are found in post-mortem rabies infection. Pyramidal neurons were first discovered and studied by Santiago Ramón y Cajal. Since then, studies on pyramidal neurons have focused on topics ranging from neuroplasticity to cognition.
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.
Extinction is a behavioral phenomenon observed in both operantly conditioned and classically conditioned behavior, which manifests itself by fading of non-reinforced conditioned response over time. When operant behavior that has been previously reinforced no longer produces reinforcing consequences the behavior gradually stops occurring. In classical conditioning, when a conditioned stimulus is presented alone, so that it no longer predicts the coming of the unconditioned stimulus, conditioned responding gradually stops. For example, after Pavlov's dog was conditioned to salivate at the sound of a metronome, it eventually stopped salivating to the metronome after the metronome had been sounded repeatedly but no food came. Many anxiety disorders such as post traumatic stress disorder are believed to reflect, at least in part, a failure to extinguish conditioned fear.
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 orbitofrontal cortex (OFC) is a prefrontal cortex region in the frontal lobes of the brain which is involved in the cognitive process of decision-making. In non-human primates it consists of the association cortex areas Brodmann area 11, 12 and 13; in humans it consists of Brodmann area 10, 11 and 47.
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 ventromedial prefrontal cortex (vmPFC) is a part of the prefrontal cortex in the mammalian brain. The ventral medial prefrontal is located in the frontal lobe at the bottom of the cerebral hemispheres and is implicated in the processing of risk and fear, as it is critical in the regulation of amygdala activity in humans. It also plays a role in the inhibition of emotional responses, and in the process of decision-making and self-control. It is also involved in the cognitive evaluation of morality.
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), 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.
The infralimbic cortex (IL) is a cortical region in the ventromedial prefrontal cortex which is important in tonic inhibition of subcortical structures and emotional responses, such as fear.
Optogenetics is a biological technique to control the activity of neurons or other cell types with light. This is achieved by expression of light-sensitive ion channels, pumps or enzymes specifically in the target cells. On the level of individual cells, light-activated enzymes and transcription factors allow precise control of biochemical signaling pathways. In systems neuroscience, the ability to control the activity of a genetically defined set of neurons has been used to understand their contribution to decision making, learning, fear memory, mating, addiction, feeding, and locomotion. In a first medical application of optogenetic technology, vision was partially restored in a blind patient.
Retrograde tracing is a research method used in neuroscience to trace neural connections from their point of termination to their source. Retrograde tracing techniques allow for detailed assessment of neuronal connections between a target population of neurons and their inputs throughout the nervous system. These techniques allow the "mapping" of connections between neurons in a particular structure and the target neurons in the brain. The opposite technique is anterograde tracing, which is used to trace neural connections from their source to their point of termination. Both the anterograde and retrograde tracing techniques are based on the visualization of axonal transport.
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.
Parental experience, as well as changing hormone levels during pregnancy and postpartum, cause changes in the parental brain. Displaying maternal sensitivity towards infant cues, processing those cues and being motivated to engage socially with her infant and attend to the infant's needs in any context could be described as mothering behavior and is regulated by many systems in the maternal brain. Research has shown that hormones such as oxytocin, prolactin, estradiol and progesterone are essential for the onset and the maintenance of maternal behavior in rats, and other mammals as well. Mothering behavior has also been classified within the basic drives.
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."
Daniela Schiller is a neuroscientist who leads the Affective Neuroscience Lab at the Mount Sinai School of Medicine. She is best known for her work on memory reconsolidation, and on modification of emotional learning and memory.
References
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- ↑ Kuerbitz J, Arnett M, Ehrman S, Williams MT, Vorhees CV, Fisher SE, et al. (January 2018). "Loss of Intercalated Cells (ITCs) in the Mouse Amygdala of Tshz1 Mutants Correlates with Fear, Depression, and Social Interaction Phenotypes". The Journal of Neuroscience. 38 (5): 1160–1177. doi:10.1523/JNEUROSCI.1412-17.2017. PMC 5792476 . PMID 29255003.
- ↑ Gregoriou, Gabrielle C.; Patel, Sahil D.; Pyne, Sebastian; Winters, Bryony L.; Bagley, Elena E. (2021-12-23). "Opioid withdrawal abruptly disrupts amygdala circuit function by reducing peptide actions". doi:10.1101/2021.12.22.471860 . Retrieved 2023-03-11.
- 1 2 Busti D, Geracitano R, Whittle N, Dalezios Y, Mańko M, Kaufmann W, et al. (March 2011). "Different fear states engage distinct networks within the intercalated cell clusters of the amygdala". The Journal of Neuroscience. 31 (13): 5131–5144. doi:10.1523/JNEUROSCI.6100-10.2011. PMC 6622967 . PMID 21451049.
- 1 2 3 4 5 Hagihara KM, Bukalo O, Zeller M, Aksoy-Aksel A, Karalis N, Limoges A, et al. (June 2021). "Intercalated amygdala clusters orchestrate a switch in fear state". Nature. 594 (7863): 403–407. Bibcode:2021Natur.594..403H. doi:10.1038/s41586-021-03593-1. PMC 8402941 . PMID 34040259.
- ↑ Asede D, Doddapaneni D, Chavez A, Okoh J, Ali S, Von-Walter C, Bolton MM (May 2021). "Apical intercalated cell cluster: A distinct sensory regulator in the amygdala". Cell Reports. 35 (7): 109151. doi: 10.1016/j.celrep.2021.109151 . PMID 34010641. S2CID 234792714.
- ↑ Aksoy-Aksel, Ayla; Gall, Andrea; Seewald, Anna; Ferraguti, Francesco; Ehrlich, Ingrid (2021-05-24). Shansky, Rebecca; Huguenard, John R; Likhtik, Ekaterina (eds.). "Midbrain dopaminergic inputs gate amygdala intercalated cell clusters by distinct and cooperative mechanisms in male mice". eLife. 10: e63708. doi: 10.7554/eLife.63708 . ISSN 2050-084X. PMC 8143799 . PMID 34028352.
- 1 2 Asede, Douglas; Doddapaneni, Divyesh; Bolton, M. McLean (2022-12-07). "Amygdala Intercalated Cells: Gate Keepers and Conveyors of Internal State to the Circuits of Emotion". Journal of Neuroscience. 42 (49): 9098–9109. doi:10.1523/JNEUROSCI.1176-22.2022. ISSN 0270-6474. PMC 9761677 . PMID 36639901.
- ↑ Adhikari A, Lerner TN, Finkelstein J, Pak S, Jennings JH, Davidson TJ, et al. (November 2015). "Basomedial amygdala mediates top-down control of anxiety and fear". Nature. 527 (7577): 179–185. Bibcode:2015Natur.527..179A. doi:10.1038/nature15698. PMC 4780260 . PMID 26536109.