The Role of Serotonin in Fear Learning and Memory: A Systematic Review of Human Studies

'Nip it in the bud': Low-frequency rTMS of the prefrontal cortex disrupts threat memory consolidation in humans

It is still unclear how the human brain consolidates aversive (e.g., traumatic) memories and whether this process can be disrupted. We hypothesized that the dorsolateral prefrontal cortex (dlPFC) is crucially involved in threat memory consolidation. To test this, we used low-frequency repetitive transcranial magnetic stimulation (LF-rTMS) within the memory stabilization time window to disrupt the expression of threat memory. We combined a differential threat-conditioning paradigm with LF-rTMS targeting the dlPFC in the critical condition, and occipital cortex stimulation, delayed dlPFC stimulation, and sham stimulation as control conditions. In the critical condition, defensive reactions to threat were reduced immediately after brain stimulation, and 1 h and 24 h later. In stark contrast, no decrease was observed in the control conditions, thus showing both the anatomical and temporal specificity of our intervention. We provide causal evidence that selectively targeting the dlPFC within the early consolidation period prevents the persistence and return of conditioned responses. Furthermore, memory disruption lasted longer than the inhibitory window created by our TMS protocol, which suggests that we influenced dlPFC neural activity and hampered the underlying, time-dependent consolidation process. These results provide important insights for future clinical applications aimed at interfering with the consolidation of aversive, threat-related memories.

Unveiling productivity: The interplay of cognitive arousal and expressive typing in remote work

Cognitive Arousal, frequently elicited by environmental stressors that exceed personal coping resources, manifests in measurable physiological markers, notably in galvanic skin responses. This effect is prominent in cognitive tasks such as composition, where fluctuations in these biomarkers correlate with individual expressiveness. It is crucial to understand the nexus between cognitive arousal and expressiveness. However, there has not been a concrete study that investigates this inter-relation concurrently. Addressing this, we introduce an innovative methodology for simultaneous monitoring of these elements. Our strategy employs Bayesian analysis in a multi-state filtering format to dissect psychomotor performance (captured through typing speed), galvanic skin response or skin conductance (SC), and heart rate variability (HRV). This integrative analysis facilitates the quantification of expressive behavior and arousal states. At the core, we deploy a state-space model connecting one latent psychological arousal condition to neural activities impacting sweating (inferred through SC responses) and another latent state to expressive behavior during typing. These states are concurrently evaluated with model parameters using an expectation-maximization algorithms approach. Assessments using both computer-simulated data and experimental data substantiate the validity of our approach. Outcomes display distinguishable latent state patterns in expressive typing and arousal across different computer software used in office management, offering profound implications for Human-Computer Interaction (HCI) and productivity analysis. This research marks a significant advancement in decoding human productivity dynamics, with extensive repercussions for optimizing performance in telecommuting scenarios.

A Decade of Dedication: Pioneering Perspectives on Neurological Diseases and Mental Illnesses

Welcome to Biomedicines' 10th Anniversary Special Issue, a journey through the human mind's labyrinth and complex neurological pathways [...].

Methylphenidate, but not citalopram, decreases impulsive choice in rats performing a temporal discounting task

Introduction

Drugs targeting monoamine systems remain the most common treatment for disorders with impulse control impairments. There is a body of literature suggesting that drugs affecting serotonin reuptake and dopamine reuptake can modulate distinct aspects of impulsivity - though such tests are often performed using distinct behavioral tasks prohibiting easy comparisons.

Methods

Here, we directly compare pharmacologic agents that affect dopamine (methylphenidate) vs serotonin (citalopram) manipulations on choice impulsivity in a temporal discounting task where rats could choose between a small, immediate reward or a large reward delayed at either 2 or 10s. In control conditions, rats preferred the large reward at a small (2s) delay and discounted the large reward at a long (10s) delay.

Results

Methylphenidate, a dopamine transport inhibitor that blocks reuptake of dopamine, dose-dependently increased large reward preference in the long delay (10s) block. Citalopram, a selective serotonin reuptake inhibitor, had no effect on temporal discounting behavior. Impulsive behavior on the temporal discounting task was at least partially mediated by the nucleus accumbens shell. Bilateral lesions to the nucleus accumbens shell reduced choice impulsivity during the long delay (10s) block. Following lesions, methylphenidate did not impact impulsivity.

Discussion

Our results suggest that striatal dopaminergic systems modulate choice impulsivity via actions within the nucleus accumbens shell, whereas serotonin systems may regulate different aspects of behavioral inhibition/impulsivity.

Innovation at the Intersection: Emerging Translational Research in Neurology and Psychiatry

Translational research in neurological and psychiatric diseases is a rapidly advancing field that promises to redefine our approach to these complex conditions [...].

Intranasal Administration of Mesenchymal Stem Cell-Derived Exosome Alleviates Hypoxic-Ischemic Brain Injury

Hypoxic-ischemic brain injury arises from inadequate oxygen delivery to the brain, commonly occurring following cardiac arrest, which lacks effective treatments. Recent studies have demonstrated the therapeutic potential of exosomes released from mesenchymal stem cells. Given the challenge of systemic dilution associated with intravenous administration, intranasal delivery has emerged as a promising approach. In this study, we investigate the effects of intranasally administered exosomes in an animal model. Exosomes were isolated from the cell supernatants using the ultracentrifugation method. Brain injury was induced in Sprague-Dawley rats through a transient four-vessel occlusion model. Intranasal administration was conducted with 3 × 108 exosome particles in 20 µL of PBS or PBS alone, administered daily for 7 days post-injury. Long-term cognitive behavioral assessments, biodistribution of exosomes, and histological evaluations of apoptosis and neuroinflammation were conducted. Exosomes were primarily detected in the olfactory bulb one hour after intranasal administration, subsequently distributing to the striatum and midbrain. Rats treated with exosomes exhibited substantial improvement in cognitive function up to 28 days after the insult, and demonstrated significantly fewer apoptotic cells along with higher neuronal cell survival in the hippocampus. Exosomes were found to be taken up by microglia, leading to a decrease in the expression of cytotoxic inflammatory markers.

Innovations in Pharmacology: Enhancing Bioavailability and Efficacy through Novel Compositions

This Patent Highlight explores ground-breaking advancements in pharmaceutical compositions, revealing the integration of serotonergic tryptamine compounds and microbial-produced biosurfactants. These innovations aim to enhance the bioavailability and efficacy of health-promoting substances significantly. The article examines the existing challenges in pharmacological treatments and the inventive solutions proposed by recent developments. It discusses compositions that reduce inflammation and improve mental and physical health, the use of serotonergic tryptamine compounds in mood and neurological disorders, and novel methods for boosting bioavailability with biosurfactants. The article provides an overview of these strategies and their potential to influence future pharmacological approaches.

Neural Correlates and Molecular Mechanisms of Memory and Learning

Memory and learning are essential cognitive processes that enable us to obtain, retain, and recall information [...].

Differences in proximal and intimacy-related defense mechanisms among patients with cancer in different psychological stages of dying

Purpose

This study measured three of the psychological stages of dying in patients with cancer and explored the differences in proximal and intimacy-related defense mechanisms at each stage.

Patients and methods

A total of 220 cancer patients were recruited for this study; 168 patients met the inclusion criteria and were included in the data analysis. The participants were divided into three groups using the "Death Attitudes Questionnaire Revised" (1994) and then completed the Death-Thought Accessibility Test, Self-Control Questionnaire, Rumination Reflection Questionnaire, Attachment Type Test, Intimacy Test, External Control Test, and Positive and Negative Affect Scale.

Results

In the death avoidance stage, which represents a defense stage without cognitive processes, patients are in an irrational state with the highest level of self-control and the lowest level of external control; they tend to prefer close relationships with many people while experiencing high levels of fear and depression. In the bargaining stage, which represents a biased cognitive defense stage, the level of rationality increases, the level of fear and depression decreases, and patients tend to prefer relationships with many people that do not involve intimacy. In the neutral death acceptance stage, which represents a defense stage without cognitive bias, self-control is lowest, external control is highest, patients tend to prefer intimate relationships with a few people, and experience the lowest levels of fear and depression.

Conclusion

Three psychological stages of death exist in cancer patients, with differences in proximal and intimacy-related defense mechanisms in each stage. The findings have theoretical and practical implications for psychological interventions for cancer patients.

Neuropharmacological Advances: Harnessing 5-HT2A Receptor Modulators and Psychoplastogens

This Patent Highlight explores the emerging role of 5-HT2A receptor modulators and psychoplastogens in neuropsychiatric treatment. It delves into these novel compounds' molecular mechanisms, therapeutic potential, and challenges, highlighting their therapeutic potential in mental health care.

Error-related cardiac deceleration: Functional interplay between error-related brain activity and autonomic nervous system in performance monitoring

Coordinated interactions between the central and autonomic nervous systems are crucial for survival due to the inherent propensity for human behavior to make errors. In our ever-changing environment, when individuals make mistakes, these errors can have life-threatening consequences. In response to errors, specific reactions occur in both brain activity and heart rate to detect and correct errors. Specifically, there are two brain-related indicators of error detection and awareness known as error-related negativity and error positivity. Conversely, error-related cardiac deceleration denotes a momentary slowing of heart rate following an error, signaling an autonomic response. However, what is the connection between the brain and the heart during error processing? In this review, we discuss the functional and neuroanatomical connections between the brain and heart markers of error processing, exploring the experimental conditions in which they covary. Given the current limitations of available data, future research will continue to investigate the neurobiological factors governing the brain-heart interaction, aiming to utilize them as combined markers for assessing cognitive control in healthy and pathological conditions.

Targeting Human Glucocorticoid Receptors in Fear Learning: A Multiscale Integrated Approach to Study Functional Connectivity

Fear extinction is a phenomenon that involves a gradual reduction in conditioned fear responses through repeated exposure to fear-inducing cues. Functional brain connectivity assessments, such as functional magnetic resonance imaging (fMRI), provide valuable insights into how brain regions communicate during these processes. Stress, a ubiquitous aspect of life, influences fear learning and extinction by changing the activity of the amygdala, prefrontal cortex, and hippocampus, leading to enhanced fear responses and/or impaired extinction. Glucocorticoid receptors (GRs) are key to the stress response and show a dual function in fear regulation: while they enhance the consolidation of fear memories, they also facilitate extinction. Accordingly, GR dysregulation is associated with anxiety and mood disorders. Recent advancements in cognitive neuroscience underscore the need for a comprehensive understanding that integrates perspectives from the molecular, cellular, and systems levels. In particular, neuropharmacology provides valuable insights into neurotransmitter and receptor systems, aiding the investigation of mechanisms underlying fear regulation and potential therapeutic targets. A notable player in this context is cortisol, a key stress hormone, which significantly influences both fear memory reconsolidation and extinction processes. Gaining a thorough understanding of these intricate interactions has implications in terms of addressing psychiatric disorders related to stress. This review sheds light on the complex interactions between cognitive processes, emotions, and their neural bases. In this endeavor, our aim is to reshape the comprehension of fear, stress, and their implications for emotional well-being, ultimately aiding in the development of therapeutic interventions.

Emerging Translational Research in Neurological and Psychiatric Diseases: From In Vitro to In Vivo Models

Revealing the underlying pathomechanisms of neurological and psychiatric disorders, searching for new biomarkers, and developing novel therapeutics all require translational research [...].