Maintenance of conditioned place avoidance induced by gastric malaise requires NMDA activity within the ventral hippocampus

It has been reported that during chemotherapy treatment, some patients can experience nausea before pharmacological administration, suggesting that contextual stimuli are associated with the nauseating effects. There are attempts to reproduce with animal models the conditions under which this phenomenon is observed to provide a useful paradigm for studying contextual aversion learning and the brain structures involved. This manuscript assessed the hippocampus involvement in acquiring and maintaining long-term conditioned place avoidance (CPA) induced by a gastric malaise-inducing agent, LiCl. Our results demonstrate that a reliable induction of CPA is possible after one acquisition trial. However, CPA establishment requires a 20-min confinement in the compartment associated with LiCl administration. Interestingly, both hippocampal regions seem to be necessary for CPA establishment; nonetheless, inactivation of the ventral hippocampus results in a reversion of avoidance and turns it into preference. Moreover, we demonstrate that activation of dorsal/ventral hippocampal NMDA receptors after CS–US association is required for long-term CPA memory maintenance.

Moderate Alcohol Intake Changes Visual Perception by Enhancing V1 Inhibitory Surround Interactions

Moderate alcohol consumption is considered to enhance the cortical GABA-ergic inhibitory system and it also variously affects visual perception. However, little behavioral evidence indicates changes of visual perception due to V1 modulated by alcohol intoxication. In this study, we investigated this issue by using center-surround tilt illusion (TI) as a probe of V1 inhibitory interactions, by taking into account possible higher-order effects. Participants conducted TI measures under sober, moderate alcohol intoxication, and placebo states. We found alcohol significantly increased repulsive TI effect and weakened orientation discrimination performance, which is consistent with the increase of lateral inhibition between orientation sensitive V1 neurons caused by alcohol intoxication. We also observed no visible changes in the data for global orientation processing but a presence of global attentional modulation. Thus, our results provide psychophysics evidence that alcohol changed V1 processing, which affects visual perception of contextual stimuli.

Same Stimulus, Same Temporal Context, Different Percept? Individual Differences in Hysteresis and Adaptation When Perceiving Multistable Dot Lattices

How we perceptually organize a visual stimulus depends not only on the stimulus itself, but also on the temporal and spatial context in which the stimulus is presented as well as on the individual processing the stimulus and context. Earlier research found both attractive and repulsive context effects in perception (Snyder, Schwiedrzik, Vitela, & Melloni, 2015): tendencies to organize visual input in a similar way as preceding or simultaneous context stimuli (i.e., hysteresis, attraction) co-exist with tendencies that repel or move away the current percept from the organization that is most dominant in these contextual stimuli (i.e., adaptation, repulsion). These processes have been studied mostly on a group level (e.g., Schwiedrzik et al., 2014). The present study will investigate whether consistent individual differences exist in these attractive and repulsive temporal context effects, using multistable dot lattices as stimuli. In addition, the relation of the strength of these effects with the strength of individual biases for absolute orientations will be investigated. In this way, the study will provide insight in how different individuals combine previous input and experience with current input in their perception, and more generally, whether different individuals can perceive identical stimuli differently even within a similar context.

Pavlovian and Instrumental Conditioning

Conditioning is the change in the response to a stimulus either because of the relation of that stimulus to other stimuli (Pavlovian conditioning), or because of the relation between the response and other stimuli (instrumental conditioning). These relations are formulated in terms of differences in conditional probability known as contingencies. Pavlovian contingencies refer to the difference in the conditional probability of one stimulus (the outcome, or O) given the presence vs. the absence of another stimulus (the conditioned stimulus, or CS). A conditioned response (CR) may be strengthened by a positive Pavlovian contingency (excitatory conditioning) or it may be weakened by a negative Pavlovian contingency (inhibitory conditioning). CRs are anticipatory or modified responses to the O, so their topography depends on the nature of the O (appetitive vs. aversive); the proximity between and congruency of O and CS; prior experience with the CS, O, and their contingency; the magnitude of their contingency; and the characteristics of other stimuli in the environment. Instrumental contingencies refer to the relation between one stimulus (the discriminative stimulus, or SD), a response (or operant, R), and the outcome of that response (O). The nature of the O and of its contingency with the R determines whether the O strengthens or weakens the R: Os that introduce an appetitive stimulus (positive reinforcement) or remove an aversive stimulus (negative reinforcement) strengthen the R. Positive reinforcement is typically arranged on a subset of one or more Rs following a set of rules known as a schedule of reinforcement. The probability that an R is reinforced may depend on the number of Rs (ratio schedules) or the amount of time (interval schedules) since the last reinforcer. The topography and strength of instrumental Rs depend on variables that are analogous to those that affect Pavlovian CRs: the amount and nature of prior experience with the O; the proximity, congruency, and contingency of R and O; and characteristics of other stimuli in past and present environments. Contemporary quantitative models of Pavlovian and instrumental conditioning recognize the importance of contextual stimuli that compete for cognitive and behavioral resources, constraining and shaping the expression of target responses. These models have guided the bulk of recent empirical research and conceptual developments, leading to a progressively unified view of learning and motivation processes. Along the way, Pavlovian and instrumental research have demonstrated their utility in addressing a broad range of consequential societal problems.

Hidden by bias: how standard psychophysical procedures conceal crucial aspects of peripheral visual appearance

The perception of a target depends on other stimuli surrounding it in time and space. This contextual modulation is ubiquitous in visual perception, and is usually quantified by measuring performance on sets of highly similar stimuli. Implicit or explicit comparisons among the stimuli may, however, inadvertently bias responses and conceal strong variability of target appearance. Here, we investigated the influence of contextual stimuli on the perception of a repeating pattern (a line triplet), presented in the visual periphery. In the neutral condition, the triplet was presented a single time to capture its minimally biased perception. In the similar and dissimilar conditions, it was presented within stimulus sets composed of lines similar to the triplet, and distinct shapes, respectively. The majority of observers reported perceiving a line pair in the neutral and dissimilar conditions, revealing ‘redundancy masking’, the reduction of the perceived number of repeating items. In the similar condition, by contrast, the number of lines was overestimated. Our results show that the similar context did not reveal redundancy masking which was only observed in the neutral and dissimilar context. We suggest that the influence of contextual stimuli has inadvertently concealed this crucial aspect of peripheral appearance.

Contrast effect of emotional context on interpersonal distance with neutral social stimuli

In social interactions, valence-based judgements are an important component of interpersonal distances regulation. Within the framework of the Range-Frequency model, we tested whether the emotional context, which is known to produce a contrast effect on valence ratings, also contributes to the regulation of interpersonal distances. 51 participants divided in two groups were shown virtual characters with either a neutral facial expression (target-stimuli) or an emotional facial expression (contextual stimuli) in two successive sessions (angry then happy emotional context or vice-versa). The participants rated the valence of the virtual characters and judged the appropriateness of different interpersonal distances. For neutral characters, contrast effect of emotional context was observed, albeit only subtly on interpersonal distance judgments. Overall, the data suggest that although the emotional context influences valence-based judgments of social stimuli, it has a parsimonious effect on interpersonal distance regulation, presumably because the latter relies primarily on emotional facial expression categorical-information.

Smoking-related cue reactivity in a virtual reality setting: association between craving and EEG measures

Background Cue-reactivity is the array of responses that smokers exhibit when exposed to conditioned and contextual stimuli previously associated to substance use. The difficulty to experimentally recreate the complexity of smokers’ spatial experience and context requires more ecological models. Virtual reality (VR) creates a state of immersion close to reality allowing controlled assessments of behavioral responses. To date, no studies investigated brain activation associated to smoking cue-reactivity in VR using electroencephalography (EEG). Aims To investigate whether a VR cue-reactivity paradigm (a) may increase smoking craving, (b) is feasible with EEG recording, and (c) induces craving levels associated to EEG desynchronization. Methods Smokers (N = 20) and non-smokers (N = 20) were exposed to neutral and smoking-related VR scenarios, without and with smoking conditioned stimuli, respectively. EEG was recorded from occipital and parietal leads throughout the sessions to assess alpha band desynchronization. Smoking and food craving and presence visual analogue scales (VAS) were assessed during the session. Results To be smoker, but not non-smoker, significantly influenced smoking craving VAS induced by smoking cue VR but not by neutral VR. No significant food craving changes was observed during the VR sessions. The new finding was that EEG alpha band power in posterior leads was significantly increased by the smoking context scenario only in smokers, and that the degree of smoking (i.e., heavy vs. light) was significantly associated to this neurophysiological measure. Conclusions This study demonstrated, for the first time, the feasibility of EEG recording in a VR setting, suggesting that EEG desynchronization may be a neurophysiological marker of smoking cue-reactivity.

A day in the life of people with severe mental illness living in supported housing

Background People with severe mental illness (SMI) living in supported housing (SH) struggle in everyday life and we currently lack a comprehensive body of knowledge concerning how the residents experience their day. This paper aimed to gain knowledge about how people with SMI describe a day in SH in Sweden, in particular the activities they most frequently engage in and how they experience what they do in or outside their home. Furthermore, it is important to gain knowledge of which activities motivate residents to leave the housing facility and to participate in the community. This new knowledge can help staff to encourage a recovery process among the residents. Methods One hundred thirty-three people living in SH completed a time-use diary and a mixed-methods approach was applied, including calculations of what activity that was most frequently performed and a manifest content analysis addressing experiences of activity. Results The residents had a low activity level and were often alone. Approximately one-half of the reported activities were performed in their own apartments, and generally unaccompanied. A quarter of the activities were performed in the common areas and a further quarter outside the SH. The most frequently performed activities were quiet and tranquil ones, e.g. listening to music and resting. Doing errands and group activities with staff and residents were the main activities that motivated leaving the facility. The participant experience of a day is presented in three categories: “Experiences of chosen and enforced togetherness and overcoming loneliness”, “Environmental change and emotional balance can generate activity”, and “Met and unmet needs for support, friendship and security”. Conclusions The residents were generally satisfied with their quiet and tranquil lifestyle and appeared to demand little of life, which may relate to previous experiences of institutional life and can constitute a challenge for staff. The findings highlight experiences that can help to improve SH. Services need to support individually adjusted contextual stimuli and individualize the support to help residents find a good balance and motivate them to be active in and outside SH, which can support a recovery process.

4R Tau Modulates Cocaine-Associated Memory Through Adult Hippocampal Neurogenesis

Background: Drug memory that generally develops with drug-paired contextual stimuli and drug administration is critical for the development, persistence and relapse of drug addiction. Previous studies have suggested that adult hippocampal neurogenesis (AHN) plays a role in cocaine memory formation; however, the underlying mechanism is not fully understood.Methods: Conditioned place preference (CPP), self-administration and locomotor activity were used to investigate the role of Tau in cocaine-associated memory formation. Virus-mediated gene transfer, western blot, immunohistochemistry, flow cytometry analysis, Tau-interacting proteomics, co-immunoprecipitation, and mutation of 4R Tau were performed. Results: Hippocampal expression of Tau was significantly decreased during the cocaine-associated memory formation. Genetic overexpression of four microtubule-binding repeats Tau (4R Tau) in the hippocampus disrupted cocaine memory by suppressing AHN. Furthermore, 4R Tau directly interacted with phosphoinositide 3-kinase (PI3K)-p85 and impaired its nuclear translocation and PI3K-AKT signaling, processes required for hippocampal neuron proliferation. Conclusions: 4R Tau modulates cocaine memory formation by disrupting AHN, suggesting a novel mechanism underlying cocaine memory formation and provide a new strategy for the treatment of cocaine addiction.