scholarly journals Extinction recall of fear memories formed before stress is not affected despite amygdalar hyperactivity

2018 ◽  
Author(s):  
Mohammed Mostafizur Rahman ◽  
Ashutosh Shukla ◽  
Sumantra Chattarji
Keyword(s):  
Normal Stress ◽  
Fear Extinction ◽  
Theta Activity ◽  
Prior Exposure ◽  
Stress Exposure ◽  
Theta Frequency ◽  
Directional Coupling ◽  
Effects Of Stress

AbstractStress is known to exert its detrimental effects not only by enhancing fear, but also by impairing its extinction. However, in earlier studies stress exposure invariably preceded both processes. Thus, compared to unstressed animals, stressed animals had to extinguish fear memories from higher levels of freezing caused by prior exposure to stress. Here we decouple the two processes to examine if stress specifically impairs fear extinction. Strikingly, when fear memories were formed before stress exposure, thereby allowing animals to initiate extinction from comparable levels of fear, recall of fear extinction was unaffected. Despite this we observed a persistent increase in theta activity in the BLA. Theta activity in the mPFC, by contrast, was normal. Stress also disrupted mPFC-BLA theta-frequency synchrony and directional coupling. Thus, in the absence of the fear-enhancing effects of stress, the expression of fear reflects normal regulation of mPFC activity, not stress-induced hyperactivity in the amygdala.

scholarly journals Extinction recall of fear memories formed before stress is not affected despite higher theta activity in the amygdala

eLife ◽  
2018 ◽  
Vol 7 ◽  
Author(s):  
Mohammed Mostafizur Rahman ◽  
Ashutosh Shukla ◽  
Sumantra Chattarji
Keyword(s):  
Normal Stress ◽  
Fear Extinction ◽  
Theta Activity ◽  
Prior Exposure ◽  
Stress Exposure ◽  
Theta Frequency ◽  
Directional Coupling ◽  
Effects Of Stress

Stress is known to exert its detrimental effects not only by enhancing fear, but also by impairing its extinction. However, in earlier studies stress exposure preceded both processes. Thus, compared to unstressed animals, stressed animals had to extinguish fear memories that were strengthened by prior exposure to stress. Here, we dissociate the two processes to examine if stress specifically impairs the acquisition and recall of fear extinction. Strikingly, when fear memories were formed before stress exposure, thereby allowing animals to initiate extinction from comparable levels of fear, recall of fear extinction was unaffected. Despite this, we observed a persistent increase in theta activity in the BLA. Theta activity in the mPFC, by contrast, was normal. Stress also disrupted mPFC-BLA theta-frequency synchrony and directional coupling. Thus, in the absence of the fear-enhancing effects of stress, the expression of fear during and after extinction reflects normal regulation of theta activity in the mPFC, not theta hyperactivity in the amygdala.

scholarly journals Neural mechanisms of infant learning: differences in frontal theta activity during object exploration modulate subsequent object recognition

2015 ◽  
Vol 11 (5) ◽  
pp. 20150041 ◽  
Author(s):  
Katarina Begus ◽  
Victoria Southgate ◽  
Teodora Gliga
Keyword(s):  
Visual Attention ◽  
Theta Activity ◽  
Neural Mechanisms ◽  
Motivation To Learn ◽  
Theta Band ◽  
Learning Mechanisms ◽  
Learning Differences ◽  
Object Exploration ◽  
Theta Frequency ◽  
Infant Learning

Investigating learning mechanisms in infancy relies largely on behavioural measures like visual attention, which often fail to predict whether stimuli would be encoded successfully. This study explored EEG activity in the theta frequency band, previously shown to predict successful learning in adults, to directly study infants' cognitive engagement, beyond visual attention. We tested 11-month-old infants ( N = 23) and demonstrated that differences in frontal theta-band oscillations, recorded during infants' object exploration, predicted differential subsequent recognition of these objects in a preferential-looking test. Given that theta activity is modulated by motivation to learn in adults, these findings set the ground for future investigation into the drivers of infant learning.

scholarly journals Different theta frameworks coexist in the rat hippocampus and are coordinated during memory-guided and novelty tasks

eLife ◽  
2020 ◽  
Vol 9 ◽  
Author(s):  
Víctor J López-Madrona ◽  
Elena Pérez-Montoyo ◽  
Efrén Álvarez-Salvado ◽  
David Moratal ◽  
Oscar Herreras ◽  
...  
Keyword(s):  
Sensory Information ◽  
Gamma Oscillations ◽  
Theta Activity ◽  
Coherent Oscillation ◽  
Phase Coupling ◽  
Internal Memory ◽  
Complex Interactions ◽  
Theta Frequency ◽  
Memory Representations ◽  
Hippocampal Theta

Hippocampal firing is organized in theta sequences controlled by internal memory processes and by external sensory cues, but how these computations are coordinated is not fully understood. Although theta activity is commonly studied as a unique coherent oscillation, it is the result of complex interactions between different rhythm generators. Here, by separating hippocampal theta activity in three different current generators, we found epochs with variable theta frequency and phase coupling, suggesting flexible interactions between theta generators. We found that epochs of highly synchronized theta rhythmicity preferentially occurred during behavioral tasks requiring coordination between internal memory representations and incoming sensory information. In addition, we found that gamma oscillations were associated with specific theta generators and the strength of theta-gamma coupling predicted the synchronization between theta generators. We propose a mechanism for segregating or integrating hippocampal computations based on the flexible coordination of different theta frameworks to accommodate the cognitive needs.

scholarly journals Rapid-Onset Anti-Stress Effects of a Kappa-Opioid Receptor Antagonist, LY2795050, Against Immobility in an Open Space Swim Paradigm in Male and Female Mice

2021 ◽  
Vol 12 ◽  
Author(s):  
Caroline Baynard ◽  
Thomas E. Prisinzano ◽  
Eduardo R. Butelman
Keyword(s):  
Opioid Receptor ◽  
Open Space ◽  
Rapid Onset ◽  
Kappa Opioid Receptor ◽  
Stress Effect ◽  
Stress Exposure ◽  
Kappa Opioid ◽  
Male And Female ◽  
Stress Effects ◽  
Effects Of Stress

The kappa-opioid receptor (KOR) / dynorphin system is implicated with behavioral and neurobiological effects of stress exposure (including heavy exposure to drugs of abuse) in translational animal models. Thus some KOR-antagonists can decrease the aversive, depressant-like and anxiety-like effects caused by stress exposure. The first generation of selective KOR-antagonists have slow onsets (hours) and extremely long durations of action (days-weeks), in vivo. A new generation of KOR antagonists with rapid onset and shorter duration of action can potentially decrease the effects of stress exposure in translational models, and may be of interest for medication development. This study examined the rapid onset anti-stress effects of one of the shorter acting novel KOR-antagonists (LY2795050, (3-chloro-4-(4-(((2S)-2-pyridin-3-ylpyrrolidin-1-yl)methyl) phenoxy)benzamide)) in a single-session open space swim (OSS) stress paradigm (15 min duration), in adult male and female C57BL/6 J mice. LY2795050 (0.32 mg/kg, i.p.) had rapid onset (within 15 min) and short duration (<3 h) of KOR-antagonist effects, based on its blockade of the locomotor depressant effects of the KOR-agonist U50,488 (10 mg/kg). LY2795050 (0.32 mg/kg), when administered only 1 min prior to the OSS stress paradigm, decreased immobility in males, but not females. With a slightly longer pretreatment time (15 min), this dose of LY2795050 decreased immobility in both males and females. A 10-fold smaller dose of LY2795050 (0.032 mg/kg) was inactive in the OSS, showing dose-dependence of this anti-stress effect. Overall, these studies show that a novel KOR-antagonist can produce very rapid onset anti-immobility effects in this model of acute stress exposure.

7 Converging evidence from local field potentials and acute stimulation for subthalamic nucleus theta involvement in internally generated decisions to initiate or withhold actions

2020 ◽  
Vol 91 (8) ◽  
pp. e10.3-e11
Author(s):  
Luis Manssuer ◽  
Valerie Voon ◽  
Chen Cheng Zhang ◽  
Linbin Wang
Keyword(s):  
Subthalamic Nucleus ◽  
Local Field ◽  
Visual Cues ◽  
Local Field Potentials ◽  
Theta Activity ◽  
Field Potentials ◽  
Theta Frequency ◽  
The Right ◽  
Deep Brain

Objectives/AimsTo examine the causal role of the subthalamic nucleus (STN) in externally cued or internally generated decisions to execute or withhold an action by recording and stimulating neural activity in this region using deep brain stimulation (DBS) electrodes implanted for the treatment of Parkinson’s disease (PD).Methods20 PD patients completed an intentional inhibition task in which they were instructed by visual cues to go, stop or choose to go or stop. Each cue was on the screen until the patient pressed a button with their left thumb or for a maximum of 1500 ms and was preceded by a fixation cross for 1000–1500 ms. Local field potentials (LFP) were simultaneously recorded from the left STN and stimulated in the right STN at the clinical frequency of 130Hz or theta frequency 7Hz for 500 ms prior to the onset of the cue on half of the choice trials.ResultsOn non-stimulation choice trials, analysis of the LFP’s showed a significant decrease in theta activity when patients chose to stop compared to go. This difference began prior to the onset of the response. Behaviourally, patients chose to respond less when the STN was stimulated at a frequency of 7 hz for 500 ms prior to the onset of the cue but not at 130 Hz.On non-stimulation choice trials, analysis of the LFP’s also showed that there was a significant decrease in theta activity when patients chose to stop compared to go. This difference began prior to the onset of the response.ConclusionsThe findings suggest that pre-existing theta activity in the STN may bias one’s pre-disposition to choose to initiate an action and that stimulation of this activity may interfere with this process.

scholarly journals Repeated Sevoflurane Exposures in Neonatal Rats Increased the Brain Vulnerability to Future Stress Exposure and Resulted in Fear-extinction Deficit

2021 ◽  
Author(s):  
Ben-zhen Chen ◽  
Li-hua Jiang ◽  
Ming-qiang Zhang ◽  
Ling Tan ◽  
Wen-qin Zhou ◽  
...  
Keyword(s):  
Fear Conditioning ◽  
Fear Extinction ◽  
Male Rats ◽  
Neonatal Rats ◽  
Stress Exposure ◽  
Sprague Dawley ◽  
Juvenile Rats ◽  
Acid Type ◽  
Cation Chloride Cotransporters ◽  
The Brain

Abstract Sevoflurane anesthesia during neonatal period was reported to sensitize the rodent animals to stress later in life. The authors tested the hypothesis that repeated sevoflurane exposures in neonatal rats increased the brain vulnerability to future stress exposure and resulted in fear-extinction deficit, and investigated whether the neonatal brain depolarizing γ-aminobutyric acid type A receptor (GABAAR) is involved in mediating these abnormalities. Neonatal Sprague-Dawley male rats, pretreated with vehicle or the NKCC1 inhibitor, bumetanide, received sequential exposures to 3% sevoflurane for 2 hours on postnatal days (P) 5, 6, 7 and then were exposed to electric foot shock stress in fear conditioning training at P14. Juvenile rats at different developmental brain stage receiving identical sevoflurane exposures on P25, 26, 27 were also studied. The results showed repeated sevoflurane exposures in neonatal rats increased the cation-chloride cotransporters NKCC1/KCC2 ratio in the PFC at P14. Repeated exposures to sevoflurane in neonatal rather than juvenile rats enhanced the stress response and exacerbated neuroapoptosis in the PFC after exposed to electric foot shock in fear conditioning training. Neonatal rather than juvenile sevoflurane-exposed rats exhibited deficits in fear extinction training and recall. Pretreatment of neonatal rats prior to sevoflurane exposures with bumetanide reduced the NKCC1/KCC2 ratio at P14 and ameliorated most of the subsequent adverse effects. Our study indicates that repeated sevoflurane exposures in neonatal rats might increase the brain vulnerability to future stress exposure and resulted in fear-extinction deficit, which might be associated with the neonatal enhanced brain depolarizing GABAAR activity.

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