scholarly journals Longitudinal recordings of single units in the basal amygdala during fear conditioning and extinction

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Junghwa Lee ◽  
Bobae An ◽  
Sukwoo Choi
Keyword(s):  
Functional Connectivity ◽  
Conditioned Stimulus ◽  
Fear Conditioning ◽  
Single Unit ◽  
Single Units ◽  
Fear Learning ◽  
Comprehensive View ◽  
Basal Amygdala ◽  
Basolateral Nucleus ◽  
Excitatory Responses

AbstractThe balance between activities of fear neurons and extinction neurons in the basolateral nucleus of the basal amygdala (BAL) has been hypothesized to encode fear states after extinction. However, it remains unclear whether these neurons are solely responsible for encoding fear states. In this study, we stably recorded single-unit activities in the BAL during fear conditioning and extinction for 3 days, providing a comprehensive view on how different BAL neurons respond during fear learning. We found BAL neurons that showed excitatory responses to the conditioned stimulus (CS) after fear conditioning (‘conditioning-potentiated neurons’) and another population that showed excitatory responses to the CS after extinction (‘extinction-potentiated neurons’). Interestingly, we also found BAL neurons that developed inhibitory responses to the CS after fear conditioning (‘conditioning-inhibited neurons’) or after extinction (‘extinction-inhibited neurons’). BAL neurons that showed excitatory responses to the CS displayed various functional connectivity with each other, whereas less connectivity was observed among neurons with inhibitory responses to the CS. Intriguingly, we found correlative neuronal activities between conditioning-potentiated neurons and neurons with inhibitory responses to the CS. Our findings suggest that distinct BAL neurons, which are responsive to the CS with excitation or inhibition, encode various facets of fear conditioning and extinction.

scholarly journals Longitudinal Changes of Resting-State Functional Connectivity of Amygdala Following Fear Learning and Extinction

2019 ◽  
Author(s):  
Olga Martynova ◽  
Alina Tetereva ◽  
Vladislav Balaev ◽  
Galina Portnova ◽  
Vadim Ushakov ◽  
...  
Keyword(s):  
Functional Connectivity ◽  
Fear Conditioning ◽  
Resting State ◽  
Fear Extinction ◽  
Fear Learning ◽  
Control Group ◽  
Resting State Functional Connectivity ◽  
Longitudinal Changes ◽  
Functional Connections ◽  
Experimental Group

AbstractAltered functional connectivity of the amygdala has been observed in a resting state immediately after fear learning, even one day after aversive exposure. The persistence of increased resting-state functional connectivity (rsFC) of the amygdala has been a critical finding in patients with stress and anxiety disorders. However, longitudinal changes in amygdala rsFC have rarely been explored in healthy participants. To address this issue, we studied the rsFC of the amygdala in two groups of healthy volunteers. The control group participated in three fMRI scanning sessions of their resting state at the first visit, one day, and one week later. The experimental group participated in three fMRI sessions on the first day: a resting state before fear conditioning, a fear extinction session, and a resting state immediately after fear extinction. Furthermore, this group experienced scanning after one day and week. The fear-conditioning paradigm consisted of visual stimuli with a distinct rate of partial reinforcement by electric shock. During the extinction, we presented the same stimuli in another sequence without aversive pairing. In the control group, rsFC maps were statistically similar between sessions for the left and right amygdala. However, in the experimental group, the increased rsFC mainly of the left amygdala was observed after extinction, one day, and one week. The between-group comparison also demonstrated an increase in the left amygdala rsFC in the experimental group. Our results indicate that functional connections of the left amygdala influenced by fear learning may persist for several hours and days in the human brain.

scholarly journals Fear conditioning and stimulus generalization in association with age in children and adolescents

2021 ◽  
Author(s):  
Julia Reinhard ◽  
Anna Slyschak ◽  
Miriam A. Schiele ◽  
Marta Andreatta ◽  
Katharina Kneer ◽  
...  
Keyword(s):  
Children And Adolescents ◽  
Fear Conditioning ◽  
Repeated Measures ◽  
Conditioned Fear ◽  
Fear Learning ◽  
Stimulus Generalization ◽  
Healthy Children ◽  
Older Individuals ◽  
Age Related ◽  
Current Task

AbstractThe aim of the study was to investigate age-related differences in fear learning and generalization in healthy children and adolescents (n = 133), aged 8–17 years, using an aversive discriminative fear conditioning and generalization paradigm adapted from Lau et al. (2008). In the current task, participants underwent 24 trials of discriminative conditioning of two female faces with neutral facial expressions, with (CS+) or without (CS−) a 95-dB loud female scream, presented simultaneously with a fearful facial expression (US). The discriminative conditioning was followed by 72 generalization trials (12 CS+, 12 GS1, 12 GS2, 12 GS3, 12 GS4, and 12 CS−): four generalization stimuli depicting gradual morphs from CS+ to CS− in 20%-steps were created for the generalization phases. We hypothesized that generalization in children and adolescents is negatively correlated with age. The subjective ratings of valence, arousal, and US expectancy (the probability of an aversive noise following each stimulus), as well as skin conductance responses (SCRs) were measured. Repeated-measures ANOVAs on ratings and SCR amplitudes were calculated with the within-subject factors stimulus type (CS+, CS−, GS1-4) and phase (Pre-Acquisition, Acquisition 1, Acquisition 2, Generalization 1, Generalization 2). To analyze the modulatory role of age, we additionally calculated ANCOVAs considering age as covariate. Results indicated that (1) subjective and physiological responses were generally lower with increasing age irrespective to the stimulus quality, and (2) stimulus discrimination improved with increasing age paralleled by reduced overgeneralization in older individuals. Longitudinal follow-up studies are required to analyze fear generalization with regard to brain maturational aspects and clarify whether overgeneralization of conditioned fear promotes the development of anxiety disorders or vice versa.

Construction of Power Stations Designed and Built as Single Units

1983 ◽  
Vol 197 (1) ◽  
pp. 1-26 ◽  
Author(s):  
H Masding
Keyword(s):  
Power Plant ◽  
Single Unit ◽  
Capital Cost ◽  
Single Units ◽  
Construction Time ◽  
Power Stations ◽  
Engineering Costs ◽  
Running Cost ◽  
The Uk

This paper sets out an assessment of the value and practicality of the construction of fossil fired generating plant designed and built as single units and includes a proposal for the design and layout of a single unit designed to maximize the benefits derived from this concept. The conclusion is that an acceptable design of power plant, based on the construction of single 600 MW units, can be developed for the UK system which could prove to be advantageous in construction time, in capital cost and in running cost. The layout applies equally effectively to large ‘green field’ sites or for replanting existing stations; in addition, the plant can be replicated in detail and thereby reduce design and engineering costs. Finally the layout can also be applied in principle to smaller units for overseas utilities as required by their system developments.

scholarly journals Arterial baroreflex regulation of muscle sympathetic single-unit activity in men: influence of resting blood pressure

2020 ◽  
Vol 318 (4) ◽  
pp. H937-H946 ◽  
Author(s):  
Anthony V. Incognito ◽  
Milena Samora ◽  
Andrew D. Shepherd ◽  
Roberta A. Cartafina ◽  
Gabriel M. N. Guimarães ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Single Unit ◽  
Cardiac Cycle ◽  
Single Units ◽  
Arterial Baroreflex ◽  
Baroreflex Control ◽  
Pharmacological Manipulation ◽  
Operating Range ◽  
Resting Blood Pressure ◽  
Spike Firing

The arterial baroreflex has dominant control over multiunit muscle sympathetic nerve activity (MSNA) burst occurrence, but whether this extends to all single units or is influenced by resting blood pressure status is unclear. In 22 men (32 ± 8 yr), we assessed 68 MSNA single units during sequential bolus injections of nitroprusside and phenylephrine (modified Oxford). Sympathetic baroreflex sensitivity (sBRS) was quantified as the weighted negative linear regression slope between diastolic blood pressure (DBP) and single-unit spike firing probability and multiple spike firing. Strong negative linear relationships ( r ≥ −0.50) between DBP and spike firing probability were observed in 63/68 (93%) single units (−2.27 ± 1.27%·cardiac cycle−1·mmHg−1 [operating range, 18 ± 8 mmHg]). In contrast, only 45/68 (66%) single units had strong DBP-multiple spike firing relationships (−0.13 ± 0.18 spikes·cardiac cycle−1·mmHg−1 [operating range, 14 ± 7 mmHg]). Participants with higher resting DBP (65 ± 3 vs. 77 ± 3 mmHg, P < 0.001) had similar spike firing probability sBRS (low vs. high, −2.08 ± 1.08 vs. −2.46 ± 1.42%·cardiac cycle−1·mmHg−1, P = 0.33), but a smaller sBRS operating range (20 ± 6 vs. 16 ± 9 mmHg, P = 0.01; 86 ± 24 vs. 52 ± 25% of total range, P < 0.001) and a higher proportion of single units without arterial baroreflex control outside this range [6/31 (19%) vs. 21/32 (66%), P < 0.001]. Participants with higher resting DBP also had fewer single units with arterial baroreflex control of multiple spike firing (79 vs. 53%, P = 0.04). The majority of MSNA single units demonstrate strong arterial baroreflex control over spike firing probability during pharmacological manipulation of blood pressure. Changes in single-unit sBRS operating range and control of multiple spike firing may represent altered sympathetic recruitment patterns associated with the early development of hypertension. NEW & NOTEWORTHY Muscle sympathetic single units can be differentially controlled during stress. In contrast, we demonstrate that 93% of single units maintain strong arterial baroreflex control during pharmacological manipulation of blood pressure. Interestingly, the operating range and proportion of single units that lose arterial baroreflex control outside of this range are influenced by resting blood pressure levels. Altered single unit, but not multiunit, arterial baroreflex control may represent changes in sympathetic recruitment patterns in early stage development of hypertension.

Behavioral Neuroscience of Circuits Involved in Fear Processing

2016 ◽  
Author(s):  
Elizabeth P. Bauer ◽  
Denis Paré
Keyword(s):  
Fear Conditioning ◽  
Post Traumatic Stress Disorder ◽  
Traumatic Stress ◽  
Current Knowledge ◽  
Brain Structures ◽  
Fear Learning ◽  
Post Traumatic Stress ◽  
Post Traumatic ◽  
The Brain ◽  
Insight Into

Normal fear regulation includes the ability to learn by experience that some circumstances predict danger. This process, which can be modeled in the laboratory using Pavlovian fear conditioning, appears to be disrupted in individuals with post-traumatic stress disorder (PTSD). Understanding of the mechanisms underlying fear learning has progressed tremendously in the last 25 years, and constitutes a promising paradigm to study the neural bases of PTSD. This chapter first reviews current knowledge of the brain structures involved in fear learning, expression and extinction, including the contributions of the amygdala and prefrontal cortex. It then addresses how these circuits are affected by PTSD and how fear processing is altered in PTSD. Understanding PTSD within a fear-conditioning and extinction framework provides insight into why certain individuals are susceptible to developing PTSD and suggests potential therapies.

scholarly journals Longitudinal changes of resting-state functional connectivity of amygdala following fear learning and extinction

2020 ◽  
Vol 149 ◽  
pp. 15-24 ◽  
Author(s):  
Olga Martynova ◽  
Alina Tetereva ◽  
Vladislav Balaev ◽  
Galina Portnova ◽  
Vadim Ushakov ◽  
...  
Keyword(s):  
Functional Connectivity ◽  
Resting State ◽  
Fear Learning ◽  
Resting State Functional Connectivity ◽  
Longitudinal Changes

scholarly journals Influence of intranasal oxytocin on fear consolidation in healthy humans

2019 ◽  
Vol 32 (6) ◽  
pp. e100131 ◽  
Author(s):  
Elizabeth Hoge ◽  
Eric Bui ◽  
Peter Rosencrans ◽  
Scott Orr ◽  
Rachel Ross ◽  
...  
Keyword(s):  
Fear Conditioning ◽  
Repeated Measures ◽  
Skin Conductance Response ◽  
De Novo ◽  
Fear Learning ◽  
Drug Trials ◽  
Conditioning Procedure ◽  
Double Blind ◽  
Healthy Humans ◽  
Main Effects

BackgroundAlthough recent data in healthy humans suggestthat treatment with intranasal oxytocin (OT) may facilitate extinction recall,to date, little is known about the effects of OT on memory consolidationprocesses.AimTo examine the effect of intranasal administration of OT compared with placebo on memory consolidation blockade of a de novo fear memory in a classical 2-day fear conditioning procedure.ResultsThere were no significant differences between the OT and the placebo groups on the first two extinction trials (mean (SD)=0.01 (0.39) vs 0.15 (0.31), t=−1.092, p=0.28). Similarly, during early extinction, analysis of variance for repeated measures failed to show significant main effects of extinction trials: trials (F(4, 112)=1.58, p=0.18), drug (F(1, 112)=0.13, p=0.72) or drug × trials interaction (F(4, 112)=0.76, p=0.56).ConclusionOur results suggest that OT administered in a double-blind fashion immediately after fear conditioning does not significantly reduce consolidation of fear learning as measured by a differential skin conductance response tested at the beginning of extinction.

scholarly journals Fear Memory

2016 ◽  
Vol 96 (2) ◽  
pp. 695-750 ◽  
Author(s):  
Ivan Izquierdo ◽  
Cristiane R. G. Furini ◽  
Jociane C. Myskiw
Keyword(s):  
Fear Conditioning ◽  
Basolateral Amygdala ◽  
Inhibitory Avoidance ◽  
Long Term Potentiation ◽  
Fear Memory ◽  
Contextual Fear Conditioning ◽  
Fear Learning ◽  
Term Potentiation ◽  
Mechanisms Of Memory

Fear memory is the best-studied form of memory. It was thoroughly investigated in the past 60 years mostly using two classical conditioning procedures (contextual fear conditioning and fear conditioning to a tone) and one instrumental procedure (one-trial inhibitory avoidance). Fear memory is formed in the hippocampus (contextual conditioning and inhibitory avoidance), in the basolateral amygdala (inhibitory avoidance), and in the lateral amygdala (conditioning to a tone). The circuitry involves, in addition, the pre- and infralimbic ventromedial prefrontal cortex, the central amygdala subnuclei, and the dentate gyrus. Fear learning models, notably inhibitory avoidance, have also been very useful for the analysis of the biochemical mechanisms of memory consolidation as a whole. These studies have capitalized on in vitro observations on long-term potentiation and other kinds of plasticity. The effect of a very large number of drugs on fear learning has been intensively studied, often as a prelude to the investigation of effects on anxiety. The extinction of fear learning involves to an extent a reversal of the flow of information in the mentioned structures and is used in the therapy of posttraumatic stress disorder and fear memories in general.

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