Frontal Norepinephrine Represents a Threat Prediction Error Under Uncertainty

BACKGROUND

To adapt to threats in the environment, animals must predict them and engage in defensive behavior. While the representation of a prediction error signal for reward has been linked to dopamine, a neuromodulatory prediction error for aversive learning has not been identified.

METHODS

We measured and manipulated norepinephrine release during threat learning using optogenetics and a novel fluorescent norepinephrine sensor.

RESULTS

We found that norepinephrine response to conditioned stimuli reflects aversive memory strength. When delays between auditory stimuli and footshock are introduced, norepinephrine acts as a prediction error signal. However, temporal difference prediction errors do not fully explain norepinephrine dynamics. To explain noradrenergic signaling, we used an updated reinforcement learning model with uncertainty about time and found that it explained norepinephrine dynamics across learning and variations in temporal and auditory task structure.

CONCLUSIONS

Norepinephrine thus combines cognitive and affective information into a predictive signal and links time with the anticipation of danger.

I'm just trying to stay: Experiences of temporal uncertainty in modular and supportive housing among young people who use drugs in Vancouver

Over the past decades the city of Vancouver has attempted to address a lack of affordable housing for it most marginalized citizens, including young people who use drugs (YPWUD), by expanding access to temporary modular and supportive housing. These projects are guided by a Housing First philosophy that recognizes housing as a key social determinant of health. In this commentary, we draw attention to how, rather than providing a clear pathway to greater stability, modular and supportive housing have become part of broader "institutional circuits" that reinforce residential transience and what we call "temporal uncertainty." We use this term to describe a painful and frustrating inability to move though time in desired ways despite the promise of greater stability that housing is supposed to engender. Rather than allowing young people to establish more predictable day-to-day rhythms and routines and enact the futures they imagine for themselves, residing in modular and supportive housing environments often generates significant instability and uncertainty. We believe that Housing First interventions have significant potential to reduce harms and improve outcomes for YPWUD. However, chronic temporal uncertainty must be addressed, including through the creation of more permanent, desirable social housing, extending supports to young people beyond tenancies, and working with them to develop timelines and plans for what happens next.

Stimulus temporal uncertainty balances intersensory dominance

Vision is typically dominant over audition or touch in human adults. One classic example is the Colavita visual dominance effect: The presentation of a tone sometimes goes undetected when it is paired with a flash even though it is well detected when presented alone. We investigated whether the Colavita visual dominance effect is modulated by stimulus uncertainty in the temporal and spatial domains. In a simple discrimination task, participants were asked to press a predesignated key when detecting a flash, another key when detecting a tone, and both keys when detecting both a flash and a tone. Temporal uncertainty was increased by introducing temporal jitter between trials (Experiment 1), and spatial uncertainty was increased by shifting the flash to different locations (Experiment 2). The Colavita visual dominance effect was reduced when temporal uncertainty was increased, while it remained similar when spatial uncertainty was increased. We therefore demonstrate a novel consideration, where increasing temporal uncertainty balances the competition between vision and audition, suggesting that people's degree of sensory dominance is malleable. Our result therefore highlights the concept that intersensory competition is susceptible to the temporal predictability of the stimulus, which provides critical insights into the design of effective warning systems in the field of ergonomics.

Uncertainty in when a perturbation will arrive influences the preparation and release of triggered responses

The timing and magnitude of muscle responses to perturbations are critical for acting in uncertain environments. A planned movement can strongly influence average muscle responses to perturbations, but certainty in when a perturbation will arrive changes this effect. The objective of this study was to investigate how uncertainty in perturbation timing influences the preparation and release of involuntary, perturbation-triggered responses. We hypothesized that uncertainty would influence the average magnitude of triggered responses and how they develop in time. We investigated three levels of uncertainty in when a proprioceptive cue to move would arrive by changing the duration and variability of the time between a preparation and movement cue. Participants performed ballistic elbow extension movements in response to the movement cue. Unexpected, large perturbations that flexed the elbow were delivered at various times between the preparation and movement cues to evaluate how cue uncertainty influenced the development of triggered responses. We found that this uncertainty strongly influences how a motor response is prepared, and the efficacy of triggering that response by a postural perturbation. When timing was certain, the motor plan was prepared within 150 ms of the expected disturbance, and consistently released earlier by a perturbation than could be done voluntarily. Less predictable stimuli led to much earlier planning and a lower probability of releasing the plan early. These results clarify how uncertainty in when to move influences the planning and early release of perturbation-triggered responses, demonstrating an effect similar to previous reports on the planning of volitional movements.

Using Rescorla's truly random control condition to measure truly exogenous covert orienting

Studies of exogenous covert orienting use peripheral cues (stimuli) that are spatially uninformative about the locations of subsequent targets. When the time course of the cue's influence on performance is explored (by varying the cue target onset asynchrony; CTOA), a biphasic pattern is usually seen with better performance at the cued location when the CTOA is short (typically attributed to attentional capture) and worse performance at the cued location when the CTOA is long (attributed to inhibition of return). However, while spatially uninformative, these cues (even when a nonaging foreperiod is used) entail a temporal contingency with the subsequent target. Consequently, this so-called capture may reflect an unintended consequence of endogenous allocation of temporal attention. Following Lawrence and Klein (Journal of Experimental Psychology: General, 142(2), 560-572, 2013) we used Rescorla's (Psychological Review, 74, 71-80, 1967) truly random control condition to ensure that the spatially uninformative peripheral stimuli were temporally completely uninformative. Even such completely uninformative peripheral stimuli generated the prototypical biphasic pattern.

The temporal-relevance temporal-uncertainty model of prospective duration judgment

A model aimed at explaining prospective duration judgments in real life settings (as well as in the laboratory) is presented. The model is based on the assumption that situational meaning is continuously being extracted by humans' perceptual and cognitive information processing systems. Time is one of the important dimensions of situational meaning. Based on the situational meaning, a value for Temporal Relevance is set. Temporal Relevance reflects the importance of temporal aspects for enabling adaptive behavior in a specific moment in time. When Temporal Relevance is above a certain threshold a prospective duration judgment process is evoked automatically. In addition, a search for relevant temporal information is taking place and its outcomes determine the level of Temporal Uncertainty which reflects the degree of knowledge one has regarding temporal aspects of the task to be performed. The levels of Temporal Relevance and Temporal Uncertainty determine the amount of attentional resources allocated for timing by the executive system. The merit of the model is in connecting timing processes with the ongoing general information processing stream. The model rests on findings in various domains which indicate that cognitive-relevance and self-relevance are powerful determinants of resource allocation policy. The feasibility of the model is demonstrated by analyzing various temporal phenomena. Suggestions for further empirical validation of the model are presented.