Central stress allostasis among deprived and continuing marijuana users and non-users

Objective: We examined central nervous system stress allostasis (i.e., stress responses) among deprived and continuing heavy marijuana users and non-users. Method: Participants (N=210; 46.7% female; mean age=21.99; 91.4% White, 94.3% Non-Hispanic) were heavy marijuana users (N=134) and non-users (N=76). Heavy users were randomly assigned to a 3-day marijuana deprivation condition (N=68) or to continue using regularly (N=66). Participants completed 2 threat-of-shock stressor tasks that manipulated stressor predictability by varying shock probability or timing. We measured central stress allostasis via startle potentiation (stressor conditions minus matched no-stressor condition). We examined two group contrasts (heavy use: all heavy users vs. non-users; deprivation: deprived vs. continuing heavy users) on startle potentiation overall and moderated by stressor predictability (unpredictable vs. predictable). Results: Deprivation did not affect startle potentiation overall (timing task: p=0.184; probability task: p=0.328) or by stressor predictability (timing task: p=0.340; probability task: p=0.488). Heavy use did not affect startle potentiation overall (timing task: p=0.213; probability task: p=0.843) or by stressor predictability (timing task: p=0.683; probability task: p=0.348). Post-hoc analyses showed a general startle reactivity X deprivation interaction on startle potentiation overall (timing task: p=0.019; probability task: p=0.056) and by stressor predictability in the probability task (p=0.022) but not in the timing task (p=0.374). Conclusions: A history of marijuana use or acute deprivation did not alter central stress allostasis despite prominent theoretical expectations. This study adds to growing research on central stress allostasis in individuals with a history of drug use and begins to parse moderating roles of individual differences and stressor characteristics.

How automated feedback from a digital mathematics textbook affects primary students’ conceptual development: two case studies

One of the most prevalent features of digital mathematics textbooks, compared to traditional ones, is the provision of automated feedback on students’ solutions. Since feedback is regarded as an important factor that influences learning, this is often seen as an affordance of digital mathematics textbooks. While there is a large body of mainly quantitative research on the effectiveness of feedback in general, very little is known about how feedback actually affects students’ individual content specific learning processes and conceptual development. A theoretical framework based on Rabardel’s theory of the instrument and Vergnaud’s theory of conceptual fields is developed to study qualitatively how feedback actually functions in the learning process. This framework was applied in a case study of two elementary school students’ learning processes when working on a probability task from a German 3rd grade digital textbook. The analysis allowed detailed reconstruction of how students made sense of the information provided by the feedback and adjusted their behavior accordingly. This in-depth analysis unveiled that feedback does not necessarily foster conceptual development in the desired way, and a correct solution does not always coincide with conceptual understanding. The results point to some obstacles that students face when working individually on tasks from digital mathematics textbooks with automated feedback, and indicate that feedback needs to be developed in design-based research cycles in order to yield the desired effects.

Endogenous and exogenous control of visuospatial selective attention in freely behaving mice

SUMMARYSelective spatial attention, the ability to dynamically prioritize the most important spatial location, is essential for adaptive behavior. It has been studied primarily in head-fixed animals, and almost exclusively in primates. Here, we report the development of two human-inspired, discrimination-based behavioral paradigms for studying selective visuospatial attention in the freely behaving mouse: the spatial probability task, and the flanker task. In the spatial probability task, we found enhanced response accuracy, perceptual discriminability, and rates of sensory evidence accumulation at the location with higher probability of target occurrence, and opposite effects at the lower probability location. In the absence of systematic differences in sensory input, motor biases, and trial structure, these results demonstrated endogenous expectation-driven shifts of spatial attention. In the flanker task, we found that a second, ‘flanker’ stimulus presented with the target, but with incongruent information, caused switch-like decrements in response accuracy and perceptual discriminability as a function of flanker contrast, as well as a reduced rate of evidence accumulation. These results demonstrated exogenous capture of spatial attention. The innovation of behavioral tasks for selective visuospatial attention in unrestrained mice opens up a rich avenue for future research dissecting the neural circuit mechanisms underlying this critical executive function.

Preprint: Using the Threat Probability Task to assess anxiety and fear during uncertain and certain threat

Fear of certain threat and anxiety about uncertain threat are distinct emotions with unique behavioral, cognitive-attentional, and neuroanatomical components. Both fear and anxiety can be studied in the laboratory by measuring the potentiation of the startle reflex. The startle reflex is a defensive reflex that is potentiated when an organism is threatened and the need for defense is high. The startle reflex is assessed via electromyography (EMG) in the orbicularis oculi muscle elicited by brief, intense, bursts of acoustic white noise (i.e., “startle probes”). Startle potentiation is calculated as the increase in startle response magnitude during presentation of sets of visual threat cues that signal delivery of mild electric shock relative to sets of matched cues that signal the absence of shock (no-threat cues). In the Threat Probability Task, fear is measured via startle potentiation to high probability (100% cue-contingent shock; certain) threat cues whereas anxiety is measured via startle potentiation to low probability (20% cue-contingent shock; uncertain) threat cues. Measurement of startle potentiation during the Threat Probability Task provides an objective and easily implemented alternative to assessment of negative affect via self-report or other methods (e.g., neuroimaging) that may be inappropriate or impractical for some researchers. Startle potentiation has been studied rigorously in both animals (e.g., rodents, non-human primate) and humans which facilitates animal-to-human translational research. Startle potentiation during certain and uncertain threat provides an objective measure of negative affective and distinct emotional states (fear, anxiety) to use in research on psychopathology, substance use/abuse and broadly in affective science. As such, it has been used extensively by clinical scientists interested in psychopathology etiology and by affective scientists interested in individual differences in emotion.

Put the Right Spin on Student Work

A Compound Probability Task And Rich Classroom Discussion Promote High-Level Understanding.