There is no scientific consensus about whether and how species\' evolutionary age, or the elapsed time since their origination, might affect their probability of going extinct. Different age-dependent extinction (ADE) patterns have been proposed in theoretical and empirical studies, while the existence of a consistent and universal pattern across the tree of life remains debated. If evolutionary age predicts species extinction probability, then the study of ADE should comprise the elapsed time and the ecological process acting on species from their origin to their extinction or to the present for extant species. Additionally, given that closely related species share traits associated with fitness, evolutionary proximity could generate similar ADE patterns. Considering the historical context and extinction selectivity based on evolutionary relatedness, we build on previous theoretical work to formalize the Clade Replacement Theory (CRT) as a framework that considers the ecological and evolutionary aspects of species age and extinction probability to produce testable predictions on ADE patterns. CRT\'s domain is the diversification dynamics of two or more clades competing for environmental space throughout time, and its propositions or derived hypotheses are as follows: (i) incumbency effects by an early arriving clade that limit the colonization and the diversification of a younger clade leading to a negative ADE scenario (younger species more prone to extinction than older ones) and (ii) an ecological shift triggered by an environmental change that imposes a new selective regime over the environmental space and leads to a positive ADE scenario (extinction probability increasing with age). From these propositions, we developed the prediction that the ADE scenario would be defined by whether an ecological shift happens or not. We discuss how the CRT could be tested with empirical data and provide examples where it could be applied. We hope this article will provide a common ground to unify results from different fields and foster new empirical tests of the mechanisms derived here while providing insights into CRT theoretical structuration.

UNASSIGNED: Increasing evidence shows that traditional neuropsychological tests are insensitive for detecting mild unilateral spatial neglect (USN), lack ecological validity, and are unable to clarify USN in all different spatial domains. Here we present a new, fully immersive virtual reality (VR) task battery with integrated eye tracking for mild visual USN and extinction assessment in the acute state of stroke to overthrow these limitations.
UNASSIGNED: We included 11 right-sided stroke patients and 10 healthy controls aged 18-75 years. Three VR tasks named the Extinction, the Storage and the Shoot the target tasks were developed to assess USN. Furthermore, neuropsychological assessment examining various parts of cognitive functioning was conducted to measure general abilities. We compared VR and neuropsychological task performance in stroke patients - those with (USN+, n = 5) and without USN (USN-, n = 6) - to healthy controls (n = 10) and tentatively reported the usability of VR system in the acute state of stroke.
UNASSIGNED: Patients had mostly mild neurological and USN symptoms. Nonetheless, we found several differences between the USN+ and healthy control groups in VR task performance. Compared to controls, USN+ patients showed visual extinction and asymmetry in gaze behavior and detection times in distinct spatial locations. Extinction was most evident in the extrapersonal space and delayed detection times on the extreme left and on the left upper parts. Also, USN+ patients needed more time to complete TMT A compared with USN- patients and TMT B compared with controls. VR system usability and acceptance were rated high; no relevant adverse effects occurred.
UNASSIGNED: New VR technology with eye tracking enables ecologically valid and objective assessment methods with various exact measures for mild USN and thus could potentially improve future clinical assessments.

Facing your fears, or exposure therapy, is an effective psychological intervention for anxiety disorders that is often thought to work through fear extinction learning. Fear extinction learning is a type of associative learning where fear reduces through repeated encounters with a feared situation or stimulus in the absence of aversive outcomes. Laboratory research suggests fear extinction learning is driven by threat prediction errors, defined as when fearful predictions do not eventuate. Threat prediction error and its relationship to exposure therapy outcomes haven\'t been studied enough in actual therapy settings. It remains unclear whether prediction error and extinction learning are central mechanisms of exposure therapy. We are conducting a longitudinal and observational study of how threat prediction error during exposure in social anxiety disorder (SAD) treatment relates to session-by-session symptom change and treatment outcome in addition to exposure surprise and learning outcome. We aim to recruit 65 adults with a primary diagnosis of SAD through an outpatient psychology clinic. Participants will receive 12 sessions of individual manualized cognitive behavioral therapy (CBT), adapted from an efficacious group protocol, that includes graded exposure. Exposure processes, including self-report measures of anxiety, threat prediction, threat outcomes, surprise, and learning outcome, will be measured with smartphone-based event-contingent ecological momentary assessments (EMAs) of all behavioral experiments completed during treatment. Clinical outcomes include self-reported social anxiety symptoms and social threat appraisals, at each session, post and 3-months after treatment. Prediction error will be operationalized as the mismatch between the threat prediction and threat outcome. The joint effect of threat prediction and threat outcome on session-by-session symptom change, treatment outcome, exposure surprise, and learning outcome will be explored using multilevel modeling. The present study will help determine whether threat prediction error during exposures in SAD treatment is related to theoretically implied clinical outcomes. This would contribute to the larger research aim of clarifying exposure therapy mechanisms.

UNASSIGNED: Men and women show different reactions to trauma and that is believed to be the reason behind the higher prevalence of post-traumatic stress disorder (PTSD) in women. Cholinergic signaling has long been known to be involved in the processing of fear-related information and the amygdala is a critical center for fear modulation. The main goal of the current research was to find (a) whether trauma results in different learning/extinction of fear or spatial-related information among male and female rats and (b) if trauma is associated with different acetylcholinesterase (AchE) activity in the amygdala.
UNASSIGNED: We used single prolonged stress (SPS) as a PTSD model in this study. Normal and SPS animals of both sexes were tested in contextual and spatial tasks (learning and extinction). AchE activity in the amygdala was also measured during each process.
UNASSIGNED: Results indicated that fear and spatial learning were impaired in SPS animals. SPS animals also had deficits in fear and spatial memory extinction and the effect was significantly higher in female- SPS than in the male-SPS group. In the enzymatic tests, AchE activity was increased during the fear extinction test and incremental changes were more significant in the female-SPS group.
UNASSIGNED: Collectively, these findings provided evidence that sex differences in response to trauma were at least partly related to less fear extinction potential in female subjects. It also indicated that the extinction deficit was associated with reduced cholinergic activity in the amygdala of female animals.

Fear of enclosed spaces prevents many people from receiving magnetic resonance imaging (MRI) scans. Although exposure therapy can effectively treat such fears, reductions in fear during exposure often do not generalize beyond the context in which they took place. This study tested a strategy designed to increase generalization, which involved revisiting the memory of a prior exposure to enhance retrieval of extinction learning. Forty-five participants with claustrophobia that included fear of MRI scans underwent a series of exposures lying inside a narrow cabinet. One week later, participants were randomly assigned to enhanced mental reinstatement (EMR) or control procedures. Prior to entering a mock MRI scanner, EMR participants recalled the memory of exposure training and listened to an audio recording of themselves describing what they learned, whereas control participants recalled a neutral memory. Compared to the control condition, EMR led to significantly reduced heart rate reactivity in the mock MRI scanner, but not self-reported fear or avoidance. There were no differences between conditions in claustrophobia symptoms or MRI fear at 1-month follow-up. Results suggest some benefits of mental reinstatement for improving generalization of gains following exposure training for claustrophobia, with measures of subjective fear and physiological arousal showing discordant outcomes.

OBJECTIVE: We sought to determine whether acute delta 9-tetrahyrdrocannabidol (THC) administration would facilitate fear extinction in young occasional cannabis users, given that animal models indicate THC facilitates extinction learning, and recent studies indicate THC administration may also enhance threat memory extinction in humans.
METHODS: On each of the 2 days, 24+ hour THC-deprived participants were conditioned to fear visual stimuli in a delay conditioning and extinction paradigm. Both CS+ and CS- were faces of negative emotional valence, with the CS+ paired with mild electric shock. Throughout both conditioning and extinction paradigms, EEG was measured to quantify event-related potentials for these learning processes. Following conditioning, individuals, in a randomized and counter-balanced order, smoked either an active THC cigarette (26.25 mg/2.7% THC) or a placebo marijuana cigarette (0.002% THC) on 1 day and the opposite cigarette on the second day. After smoking, CS+ and CS- were presented without shock, resulting in extinction of conditioned fear.
RESULTS: Relative to placebo, THC facilitated extinction of the conditioned response to the CS+, as reflected by reductions in late positive potential amplitude during extinction learning.
CONCLUSIONS: The results indicate that acute THC administration may facilitate extinction of the conditioned fear response in humans.

Although exposure therapy is an efficacious treatment for anxiety disorders, fear often returns after treatment. From an inhibitory learning perspective, long-term improvement depends not only on learning that feared stimuli are safe, but also that it is safe to experience the emotional response triggered by these stimuli. Accordingly, the current study examined the effects of occasional threat reinforcement during repeated exposure to multiple cues on the return of fear in snake phobia by incorporating reminders of the feared outcome.
Snake fearful community adults (N = 74) were randomized to either repeated exposure to multiple cues or exposure to multiple cues that also explicitly depicted the feared outcome (snake biting someone). A measure of self-reported threat expectancy and a threat-relevant behavioral approach task (BAT) were administered pre-exposure, post-exposure, and at a one-week follow-up.
Compared to the multiple-cue exposure group, the multiple-cue + fear-outcome group showed significantly less subjective expectancy for a snake to bite and increased behavioral approach of snake images at one-week follow-up. The fear-outcome group also reported significantly greater variability in distress during exposure than the multiple-cue exposure group and this difference mediated the intervention effect on behavioral approach at follow-up.
Findings are limited by the use of videos as an analogue to exposure and a computer-delivered BAT.
These findings suggest presentation of the feared outcome may result in more variability in distress during exposure therapy and this may partially explain the maintenance of behavioral gains.

The strength of an association between a cue and its outcome is influenced by both the probability of the outcome given the cue and the probability of the outcome in the absence of the cue. Once an association has been formed, extinction is the procedure for reducing responding indicative of the association by repeated presentation of the cue without the outcome. The present experiments tested whether cumulative frequency and/or cumulative duration of these events affects associative extinction in a streamed trial extinction procedure with human participants. Experiment 1 assessed the effects of parametric manipulations of the frequency and duration of either the cue by itself or cue-outcome co-absence. In Experiment 1, participants proved relatively insensitive to manipulation of the event\'s duration. In contrast, judgements of the association by participants decreased when the frequency of cue-alone events was increased, even when the durations of those events were decreased so that cumulative exposure to the cue was equated. No effect of either the duration or the frequency of cue-outcome co-absence was observed. Experiment 2 demonstrated that the effect of cue-alone (i.e., extinction trial) frequency generalises across a wide range of parameters for initial acquisition achieved by cue-outcome pairings. Experiment 3 tested for an interaction between event duration during initial learning and event duration during extinction. Collectively, these results indicate that the cumulative frequency, and not the cumulative duration, of extinction trials as well as the duration of the cue-outcome co-absences between extinction trials control the effectiveness of an extinction procedure.

Prolonged exposure (PE) therapy is a first-line treatment for posttraumatic stress disorder (PTSD) and involves repeated presentation of trauma-related cues without aversive outcomes. A primary learning mechanism of PE is fear extinction (new learning that a dangerous cue is now safe) and its retention (maintaining this new learning over time). Extant research suggests extinction is impaired in PTSD patients. In this study, we employed an established fear-potentiated startle-based paradigm to examine fear acquisition, extinction learning and retention before and after completion of intensive outpatient treatment. First, PTSD patients undergoing PE (n = 55) were compared to trauma-exposed patients without PTSD (n = 57). We identified excessive fear in PTSD patients during acquisition and extinction before treatment compared to non-PTSD patients. At post-treatment, we examined the return of fear after extinction in PTSD patients showing high or low treatment response to PE (≥50% change in PTSD symptom severity vs. < 50%). High PE responders maintained fear extinction learning whereas low PE responders showed significant return of fear at post-treatment. These results replicate and extend previous findings of impaired extinction in PTSD and provide support for the proposed theoretical link between fear extinction and PE response.

Methods to improve sleep in infants commonly involve some ignoring (extinction) but are often unpopular with mothers worried about infant distress when left to cry. Alternative more responsive methods are needed. This pilot study evaluated stress, maternal depressive symptomology and sleep in mother/infant dyads, between Responsive, Controlled Crying and Control groups. From 199 mother/infant dyads from any cultural background, 41 infants 4-12 months were randomly allocated to Responsive (RG, n = 15), Controlled Crying (CCG, n = 18) or Controls (Treatment as Usual, TAUG, n = 8), with 10 withdrawing after randomisation. Infant sleep (7-day sleep diaries) and stress (oral cortisol on two nights), maternal self-reported stress (Subjective Units of Distress, SUDS), maternal perceived infant distress (MPI-S) and symptoms of maternal depression (Edinburgh Post-natal Depression Scale, EPDS) were measured four times across 8 weeks. Sleep duration was not different between groups but Responsive woke less (p = .008). There were no differences in cortisol between groups across time points. Maternal SUDS was positively correlated with infant cortisol and MPI-S (p < 0.05) and mothers in the Responsive group were significantly less stressed (p = 0.02) and reported less symptoms of depression (p < 0.05). Findings in this small sample show Responsive methods are comparable to the extinction (Controlled Crying) in sleep outcomes but from a relational and maternal mental health perspective, are less stressful, offering families potential choices of sleep interventions.