The effects of acute stress on Pavlovian-instrumental transfer in rats

Pavlovian stimuli invigorate ongoing instrumental action, a phenomenon termed the Pavlovian–instrumental transfer (PIT) effect. Acute stressors can markedly enhance the release of corticotropin-releasing factor (CRF), and CRF injection into the nucleus accumbens increases the PIT effect. However, it is unknown whether acute stressors by themselves would amplify the PIT effect. Here, we examined the effects of acute stressors on PIT. Rats first received Pavlovian and instrumental training, and then the impact of the Pavlovian stimuli on instrumental responding was analyzed in the subsequent PIT test. Acute stressors were applied prior to the PIT test. Because the effects of acute stressors critically depend on stressor type and time of day, we used two acute stressors that involved one or several distinct stressors (denoted here as “single” vs. “multiple” stressors) applied either in the light or the dark period of the light:dark cycle. The results revealed that single and multiple stressors applied in the light period did not alter the PIT effect—that is, the ability of an appetitive Pavlovian stimulus to enhance leverpressing—or the basal leverpress rate. When applied in the dark period, single and multiple stressors also did not alter the PIT effect, but they did markedly reduce the basal leverpress rate. Diazepam pretreatment did not counteract the declines in basal instrumental responding in the PIT test that were induced by either a single or multiple stressors. Our findings suggest that acute stressors were unable to amplify the incentive salience of reward-predictive Pavlovian stimuli to activate instrumental responding, but, depending on the time of day of stressor exposure, they did reduce basal instrumental responding.     

How Emotional Stability and Openness to Experience Support Invention: A Study with German Independent Inventors

How does invention depend on personality? Do inventors differ from noninventors? This study investigated the personal factors influencing a sample of independent inventors in Germany (N = 69). Standardized psychological questionnaires were employed to assess the Big Five personality dimensions, willingness to take risks, self-concept, and self-efficacy. For a comparison with noninventors, scores from reference samples were taken. Hypotheses were formulated based on research into creativity and entrepreneurship and the normative DABEI Stage Model of invention. As expected, the independent inventors showed higher levels of extraversion and openness to experience. In addition, independent inventors stood out in terms of emotional stability (low neuroticism scores). Surprisingly, in this sample success as an inventor correlated negatively with openness to experience. The interpretation is along the lines that inventors may work in a focused manner and technical implementation of an innovative idea may be optimized with great persistence. Discussion centers around the generalizability of the results.     

Structure-from-motion: dissociating perception, neural persistence, and sensory memory of illusory depth and illusory rotation

In the structure-from-motion paradigm, physical motion on a screen produces the vivid illusion of an object rotating in depth. Here, we show how to dissociate illusory depth and illusory rotation in a structure-from-motion stimulus using a rotationally asymmetric shape and reversals of physical motion. Reversals of physical motion create a conflict between the original illusory states and the new physical motion: Either illusory depth remains constant and illusory rotation reverses, or illusory rotation stays the same and illusory depth reverses. When physical motion reverses after the interruption in presentation, we find that illusory rotation tends to remain constant for long blank durations (T _blank ≥ 0.5 s), but illusory depth is stabilized if interruptions are short (T _blank ≤ 0.1 s). The stability of illusory depth over brief interruptions is consistent with the effect of neural persistence. When this is curtailed using a mask, stability of ambiguous vision (for either illusory depth or illusory rotation) is disrupted. We also examined the selectivity of the neural persistence of illusory depth. We found that it relies on a static representation of an interpolated illusory object, since changes to low-level display properties had little detrimental effect. We discuss our findings with respect to other types of history dependence in multistable displays (sensory stabilization memory, neural fatigue, etc.). Our results suggest that when brief interruptions are used during the presentation of multistable displays, switches in perception are likely to rely on the same neural mechanisms as spontaneous switches, rather than switches due to the initial percept choice at the stimulus onset.     

Visual snake aversion in Octodon degus and C57BL/6 mice

Animal Cognition - Phobia against spiders or snakes is common in humans, and similar phobia-like behaviors have been observed in non-human animals. Visual images of snakes elicit phobia in humans,...     

Neural responses to meaningless pseudosigns: evidence for sign-based phonetic processing in superior temporal cortex

To identify neural regions that automatically respond to linguistically structured, but meaningless manual gestures, 14 deaf native users of American Sign Language (ASL) and 14 hearing non-signers passively viewed pseudosigns (possible but non-existent ASL signs) and non-iconic ASL signs, in addition to a fixation baseline. For the contrast between pseudosigns and baseline, greater activation was observed in left posterior superior temporal sulcus (STS), but not in left inferior frontal gyrus (BA 44/45), for deaf signers compared to hearing non-signers, based on VOI analyses. We hypothesize that left STS is more engaged for signers because this region becomes tuned to human body movements that conform the phonological constraints of sign language. For deaf signers, the contrast between pseudosigns and known ASL signs revealed increased activation for pseudosigns in left posterior superior temporal gyrus (STG) and in left inferior frontal cortex, but no regions were found to be more engaged for known signs than for pseudosigns. This contrast revealed no significant differences in activation for hearing non-signers. We hypothesize that left STG is involved in recognizing linguistic phonetic units within a dynamic visual or auditory signal, such that less familiar structural combinations produce increased neural activation in this region for both pseudosigns and pseudowords.     

New variations of intrahemispheric and interhemispheric processing indexed by the dimond paradigm

We report 2 experiments designed to demonstrate that unilateral tachistoscopic stimulation would yield a response time (RT) advantage over bilateral stimulation in a simple experiment, whereas the opposite pattern would occur in a complex version of the same task, as predicted by the intrahemispheric resource limitation model of Banich and colleagues. Experiment 1 was a go/no-go task in which participants had to press a key when two shapes (circles or squares) were identical on the computer screen. A unilateral field advantage was obtained that was accentuated in several task conditions that yielded overall longer RTs, mostly in the bilateral condition. Experiment 2 was similar but required a more complex judgment: The go trials were to 2 stimuli identical on 1 dimension (shape or color) but not both or neither. The RTs were significantly and substantially longer than in Experiment 1 and exhibited a nonsignificant bilateral field advantage, which differed significantly from the unilateral field advantage obtained in Experiment 1. These results support the intrahemispheric resource limitation model of Banich and colleagues. However, several within-experiment effects are in direct opposition to this model and are best explained as limitations of commissural relay of perceptual information.     

A cautionary note on modeling growth trends in longitudinal data

Random coefficient and latent growth curve modeling are currently the dominant approaches to the analysis of longitudinal data in psychology. The application of these models to longitudinal data assumes that the data-generating mechanism behind the psychological process under investigation contains only a deterministic trend. However, if a process, at least partially, contains a stochastic trend, then random coefficient regression results are likely to be spurious. This problem is demonstrated via a data example, previous research on simple regression models, and Monte Carlo simulations. A data analytic strategy is proposed to help researchers avoid making inaccurate inferences when observed trends may be due to stochastic processes.