Know safety, no fear Sangha, Susan; Diehl, Maria M.; Bergstrom, Hadley C. ...
Neuroscience & biobehavioral reviews/Neuroscience and biobehavioral reviews,
01/2020, Letnik:
108
Journal Article
Recenzirano
Odprti dostop
•learning safety through discrimination.•learning safety through extinction.•learning safety through active avoidance.•in-depth discussion of the behavioral processes.•in-depth discussion of the ...brain substrates within the amygdalo-cortico-hippocampal circuit.
Every day we are bombarded by stimuli that must be assessed for their potential for harm or benefit. Once a stimulus is learned to predict harm, it can elicit fear responses. Such learning can last a lifetime but is not always beneficial for an organism. For an organism to thrive in its environment, it must know when to engage in defensive, avoidance behaviors and when to engage in non-defensive, approach behaviors. Fear should be suppressed in situations that are not dangerous: when a novel, innocuous stimulus resembles a feared stimulus, when a feared stimulus no longer predicts harm, or when there is an option to avoid harm. A cardinal feature of anxiety disorders is the inability to suppress fear adaptively. In PTSD, for instance, learned fear is expressed inappropriately in safe situations and is resistant to extinction. In this review, we discuss mechanisms of suppressing fear responses during stimulus discrimination, fear extinction, and active avoidance, focusing on the well-studied tripartite circuit consisting of the amygdala, medial prefrontal cortex and hippocampus.
The study of active avoidance: A platform for discussion Diehl, Maria M.; Bravo-Rivera, Christian; Quirk, Gregory J.
Neuroscience & biobehavioral reviews/Neuroscience and biobehavioral reviews,
12/2019, Letnik:
107
Journal Article
Recenzirano
Odprti dostop
•The field of active avoidance has used the same task in rodents for over 80 years, without updates.•Platform-mediated avoidance (PMA) models aspects of clinical avoidance that classical tasks do ...not.•Prelimbic cortex promotes PMA by disinhibiting BA-responsive neurons in VS.
Traditional active avoidance tasks have advanced the field of aversive learning and memory for decades and are useful for studying simple avoidance responses in isolation; however, these tasks have limited clinical relevance because they do not model several key features of clinical avoidance. In contrast, platform-mediated avoidance (PMA) more closely resembles clinical avoidance because the response i) is associated with an unambiguous safe location, ii) is not associated with an artificial termination of the warning signal, and iii) is associated with a decision-based appetitive cost. Recent findings on the neuronal circuits of PMA have confirmed that amygdala-striatal circuits are essential for avoidance. In PMA, however, the prelimbic cortex facilitates the avoidance response early during the warning signal, perhaps through disinhibition of the striatum. Future studies on avoidance should account for additional factors such as sex differences and social interactions that will advance our understanding of maladaptive avoidance contributing to neuropsychiatric disorders.
Abstract
Programming for data wrangling and statistical analysis is an essential technical tool of modern epidemiology, yet many epidemiologists receive limited formal training in strategies to ...optimize the quality of our code. In complex projects, coding mistakes are easy to make, even for skilled practitioners. Such mistakes can lead to invalid research claims that reduce the credibility of the field. Code review is a straightforward technique used by the software industry to reduce the likelihood of coding bugs. The systematic implementation of code review in epidemiologic research projects could not only improve science but also decrease stress, accelerate learning, contribute to team building, and codify best practices. In the present article, we argue for the importance of code review and provide some recommendations for successful implementation for 1) the research laboratory, 2) the code author (the initial programmer), and 3) the code reviewer. We outline a feasible strategy for implementation of code review, though other successful implementation processes are possible to accommodate the resources and workflows of different research groups, including other practices to improve code quality. Code review isn’t always glamorous, but it is critically important for science and reproducibility. Humans are fallible; that’s why we need code review.
Social communication relies on the integration of auditory and visual information, which are present in faces and vocalizations. Evidence suggests that the integration of information from multiple ...sources enhances perception compared with the processing of a unimodal stimulus. Our previous studies demonstrated that single neurons in the ventrolateral prefrontal cortex (VLPFC) of the rhesus monkey (Macaca mulatta) respond to and integrate conspecific vocalizations and their accompanying facial gestures. We were therefore interested in how VLPFC neurons respond differentially to matching (congruent) and mismatching (incongruent) faces and vocalizations. We recorded VLPFC neurons during the presentation of movies with congruent or incongruent species-specific facial gestures and vocalizations as well as their unimodal components. Recordings showed that while many VLPFC units are multisensory and respond to faces, vocalizations, or their combination, a subset of neurons showed a significant change in neuronal activity in response to incongruent versus congruent vocalization movies. Among these neurons, we typically observed incongruent suppression during the early stimulus period and incongruent enhancement during the late stimulus period. Incongruent-responsive VLPFC neurons were both bimodal and nonlinear multisensory, fostering their ability to respond to changes in either modality of a face-vocalization stimulus. These results demonstrate that ventral prefrontal neurons respond to changes in either modality of an audiovisual stimulus, which is important in identity processing and for the integration of multisensory communication information.
•Conditional freezing and avoidance are both learned defensive behaviors.•Both behavioral responses require amygdala activity for performance.•Additional neural circuits are recruited with task ...complexity.•Some overlap exists between these circuits suggesting similar underlying processes.
Aversive learning can produce a wide variety of defensive behavioral responses depending on the circumstances, ranging from reactive responses like freezing to proactive avoidance responses. While most of this initial learning is behaviorally supported by an expectancy of an aversive outcome and neurally supported by activity within the basolateral amygdala, activity in other brain regions become necessary for the execution of defensive strategies that emerge in other aversive learning paradigms such as active avoidance. Here, we review the neural circuits that support both reactive and proactive defensive behaviors that are motivated by aversive learning, and identify commonalities between the neural substrates of these distinct (and often exclusive) behavioral strategies.
•Ventral prefrontal neurons exhibit responses to the identity and expression of natural stimuli in a working memory task.•Neurons more commonly encoded identity rather than expression of the nonmatch ...face + vocalization stimulus.•Identity cells were located over a broader region of VLPFC than expression cells which were confined to anterolateral VLPFC.
Evidence has suggested that the ventrolateral prefrontal cortex (VLPFC) processes social stimuli, including faces and vocalizations, which are essential for communication. Features embedded within audiovisual stimuli, including emotional expression and caller identity, provide abundant information about an individual’s intention, emotional state, motivation, and social status, which are important to encode in a social exchange. However, it is unknown to what extent the VLPFC encodes such features. To investigate the role of VLPFC during social communication, we recorded single-unit activity while rhesus macaques (Macaca mulatta) performed a nonmatch-to-sample task using species-specific face-vocalization stimuli that differed in emotional expression or caller identity. 75% of recorded cells were task-related and of these >70% were responsive during the nonmatch period. A larger proportion of nonmatch cells encoded the stimulus rather than the context of the trial type. A subset of responsive neurons were most commonly modulated by the identity of the nonmatch stimulus and less by the emotional expression, or both features within the face-vocalization stimuli presented during the nonmatch period. Neurons encoding identity were found in VLPFC across a broader region than expression related cells which were confined to only the anterolateral portion of the recording chamber in VLPFC. These findings suggest that, within a working memory paradigm, VLPFC processes features of face and vocal stimuli, such as emotional expression and identity, in addition to task and contextual information. Thus, stimulus and contextual information may be integrated by VLPFC during social communication.
The prefrontal cortex (PFC) integrates incoming information to guide our actions. When motivation for food-seeking competes with avoidance of danger, the PFC likely plays a role in selecting the ...optimal choice. In platform-mediated active avoidance, rats avoid a tone-signaled footshock by stepping onto a nearby platform, delaying access to sucrose pellets. This avoidance requires prelimbic (PL) PFC, basolateral amygdala (BLA), and ventral striatum (VS). We previously showed that inhibitory tone responses of PL neurons correlate with avoidability of shock (Diehl et al., 2018). Here, we optogenetically modulated PL terminals in VS and BLA to identify PL outputs regulating avoidance. Photoactivating PL-VS projections reduced avoidance, whereas photoactivating PL-BLA projections increased avoidance. Moreover, photosilencing PL-BLA or BLA-VS projections reduced avoidance, suggesting that VS receives opposing inputs from PL and BLA. Bidirectional modulation of avoidance by PL projections to VS and BLA enables the animal to make appropriate decisions when faced with competing drives.
Much is known about the neural circuits of conditioned fear and its relevance to understanding anxiety disorders, but less is known about other anxiety-related behaviors such as active avoidance. ...Using a tone-signaled, platform-mediated avoidance task, we observed that pharmacological inactivation of the prelimbic prefrontal cortex (PL) delayed avoidance. Surprisingly, optogenetic silencing of PL glutamatergic neurons did not delay avoidance. Consistent with this, inhibitory but not excitatory responses of rostral PL neurons were associated with avoidance training. To test the importance of these inhibitory responses, we optogenetically stimulated PL neurons to counteract the tone-elicited reduction in firing rate. Photoactivation of rostral (but not caudal) PL neurons at 4 Hz impaired avoidance. These findings suggest that inhibitory responses of rostral PL neurons signal the avoidability of a potential threat and underscore the importance of designing behavioral optogenetic studies based on neuronal firing responses.
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