Rigidity in social and emotional memory in the R6/2 mouse model of Huntington's disease

Four experiments were conducted to examine social and emotional memory in the R6/2 transgenic mouse model of Huntington’s disease. First, R6/2 mice were tested in a social transmission of food preference task where they had to acquire a preference for a flavoured food (acquisition) and subsequently to learn a preference for a different flavour (shifted reinforcement). R6/2 mice performed well in the acquisition trial. However, they were impaired in the shifted reinforcement trial and perseverated on the first preference learned. Second, mice were trained in an inhibitory avoidance paradigm, with either one or two footshocks delivered during the training. WT mice given one footshock showed retention levels lower than those of mice trained with two footshocks. By contrast, there was no difference in retention levels of R6/2 mice given either one or two footshocks. Third, mice were tested in an active avoidance task that paired a mild footshock with a warning light. R6/2 mice had a strong age-dependent deficit in this task. Finally, mice were tested in a conditioned taste aversion task that paired a saccharine solution with a nausea-inducing agent (LiCl). R6/2 mice displayed normal aversion, however this was not extinguished following repeated exposure to saccharine solution alone. Our data show that while R6/2 mice have functional hippocampus-based memory, they have deficits in striatum-based memory skills. Further, social and emotional memories appear to be encoded in a rigid way that is not influenced by subsequent learning or by arousal levels.     

Upregulation of hippocampal TrkB and synaptotagmin is involved in treadmill exercise-enhanced aversive memory in mice

Cognitive functions usually involve various synaptic proteins and neurotrophic factors in the hippocampus. However, whether treadmill exercise can improve learning and memory by upregulating some of these molecules remain unraveled. To address this question, male BALB/c mice were divided into control and exercise groups, the latter group went through 4 weeks of treadmill exercise training. At the end of exercise training period, they were either tested for passive avoidance (PA) performance or sacrificed for quantifying the hippocampal levels of brain-derived neurotrophic factor (BDNF), tropomyosin-related kinase B (TrkB, the BDNF receptor), synaptotagmin (a Ca²⁺-dependent synaptic vesicle protein), and SNAP-25 (a presynaptic vesicular fusion protein). Our results showed that treadmill exercise training (1) increased the retention latency without affecting the fear acquisition in the PA test, (2) transiently increased the hippocampal BDNF level at 1, 2, and 4 h after the completion of exercise training, and (3) persistently increased the hippocampal protein levels of full-length TrkB, phosphorylated TrkB and synaptotagmin, but not truncated TrkB or SNAP-25. Moreover, the protein expression level of full-length TrkB or synaptotagmin was positively correlated with PA performance in mice. Finally, inhibition of TrkB signaling by K252a abolished the exercise-facilitated PA performance and upregulation of TrkB and synaptotagmin. Taken together, these data suggest that the upregulation of TrkB and synaptotagmin in the hippocampus contributes to the exercise-facilitated aversive memory.     

Avoidance of timeout from response-independent food: effects of delivery rate and quality

In three experiments, a rat's lever presses could postpone timeouts from food pellets delivered on response-independent schedules. In Experiment 1, the pellets were delivered at variable-time (VT) rates ranging from VT 0.5 to VT 8 min. Experiment 2 replicated the VT 1 min and VT 8 min conditions of Experiment 1 with new subjects. Finally, subjects in Experiment 3 could postpone timeouts from delivery of pellets that differed in quality rather than quantity (unsweetened versus sweetened pellets). In general, response rates and success in avoiding increased as a function of the rate and quality of the pellets. Also, performance efficiency increased as the experiments progressed, that is, the avoidance response occurred later and later in the response-timeout interval. The results support the conclusion that timeout from reinforcement has functional properties similar to those of more commonly studied aversive stimuli (e.g., shock).     

Electrical stimulation of the pedunculopontine tegmental nucleus in freely moving awake rats: time- and site-specific effects on two-way active avoidance conditioning

The pedunculopontine tegmental nucleus (PPTg) is involved in the regulation of thalamocortical transmission and of several functions related to ventral and dorsal striatal circuits. Stimulation of the PPTg in anesthetized animals increases cortical arousal, cortical acetylcholine release, bursting activity of mesopontine dopaminergic cells, and striatal dopamine release. It was hypothetized that PPTg stimulation could improve learning by enhancing cortical arousal and optimizing the activity of striatal circuits. We tested whether electrical stimulation (ES) of the PPTg, applied to freely-moving awake rats previously implanted with a chronic electrode, would improve the acquisition and/or the retention of two-way active avoidance conditioning, and whether this effect would depend on the specific PPTg region stimulated (anterior vs posterior) and on the time of ES: just before (pre-training) or after (post-training) each of three training sessions. The treatment consisted of 20 min of ES (0.2 ms pulses at 100 Hz; current intensity: 40-80 microA). The results showed that (1) this stimulation did not induce either any signs of distress nor abnormal behaviors, apart from some motor stereotyped behaviors that disappeared when current intensity was lowered; (2) pre-training ES applied to the anterior PPTg improved the acquisition of two-way active avoidance, (3) no learning improvement was found after either post-training ES of the anterior PPTg, or pre- and post-training ES of the posterior PPTg. The results give support to a role of PPTg in learning-related processes, and point to the existence of functional PPTg regions.     

The impact of experiential avoidance on the reduction of depression in treatment for borderline personality disorder

Background

Reducing symptoms of depression is an important target in the treatment of borderline personality disorder (BPD). Although current treatments for BPD are effective in reducing depression, the average post-treatment level of depression remains high.

Aim

To test whether experiential avoidance (EA) impedes the reduction of depression during treatment for BPD.

Method

EA and depression were assessed in 81 clients at baseline and 4-month intervals during 1 year of therapy. Simple correlations, hierarchical linear modeling, and latent difference score models were used to investigate the association between self-reports of EA and both self-reports and observer-based ratings of depression.

Results

EA was positively associated with greater severity of depression at all points of assessment, and changes in EA were positively associated with changes in depression. Moreover, EA significantly predicted less subsequent reduction in depression whereas no such effect was found for depression on subsequent EA.

Conclusion

The findings are consistent with the hypothesis that EA impedes the reduction of depression in the treatment of BPD and should thus be considered an important treatment target.     

Is the attribution of cultural differences to minorities an expression of racial prejudice?

The social psychological literature considers two main perspectives on the study of perceived cultural differences between majorities and minorities: one proposes that perception of cultural differences is an antecedent of prejudice and another states that the attribution of cultural differences to minorities is already a hidden expression of racial prejudice. This paper offers further support to this latter perspective. One hundred and ninety-four participants answered a questionnaire measuring (1) general racist belief; (2) cultural differences attributed to Black people (hetero-ethnicization); (3) the asymmetric attribution of secondary and primary emotions to the in-group and to Black people (infra-humanization); (4) the asymmetric attribution of natural and cultural traits to in-group members and to Black people (ontologization); and (5) negative evaluation of this social category. The general racist belief scale was not anchored in a specific group and measured the belief in the inferiority of certain social groups or peoples based on biological or cultural factors. Relationships between the scales were analysed through a set of Structural Equation Models. According to the predictions, results showed that the attribution of cultural differences is a dimension of prejudice. Results also showed that attribution of cultural differences, negative evaluation of Black people, ontologization, and infra-humanization were different dimensions of a common latent factor that can be identified as racial prejudice; and that prejudice was predicted by general racist belief. Results are discussed in the light of the study of the impact of perceived cultural differences on intergroup relations and in the light of the "new racism" approaches.     

Unconstraining theories of embodied cognition

The approach/avoidance effect refers to the finding that valenced stimuli trigger approach and avoidance actions. Markman and Brendl [Markman, A. B., & Brendl, M. (2005). Constraining theories of embodied cognition. Psychological Science, 16, 6-16] argued that this effect is not a truly embodied phenomenon, but depends on participants’ symbolic representation of the self.In their study, participants moved valenced words toward or away from their own name on the computer screen. This would induce participants to form a ‘disembodied’ self-representation at the location of their name, outside of the body. Approach/avoidance effects occurred with respect to the participant’s name, rather than with respect to the body.In three experiments, we demonstrate that similar effects are found when the name is replaced by a positive word, a negative word or even when no word is presented at all. This suggests that the ‘disembodied self’ explanation of Markman and Brendl is incorrect, and that their findings do not necessarily constrain embodied theories of cognition.     

Uncertainty Avoidance Influences Choices for Potential Gains but not Losses

Uncertainty of outcomes is a primary dimension underlying human judgment and decision making, and is a defining feature of risk. Even though uncertainty almost always exists in decision making contexts, individuals and cultures vary in their preference for avoiding uncertainty. This study examines how uncertainty avoidance influences judgments involving uncertain and risky alternatives. Participants were presented with problems that involve potential gains or losses and contain options reflecting uncertain or certain outcomes. Greater uncertainty avoidance predicted choices for uncertain outcomes that involved gains, which tend to promote risk aversion, but not for uncertain outcomes that led to losses, which tend to promote risk seeking. These results demonstrate that culturally-relevant dispositions such as uncertain avoidance can have complex effects on judgment.     

Bobwhite quail (Colinus virginianus) hatchlings track the direction of human gaze

Gaze following allows individuals to detect the locus of attention of both conspecifics and other species. However, little is known about how this ability develops. We explored the emergence of bobwhite quail hatchlings’ ability to track human gaze by assessing their avoidance behavior in an open arena under five testing conditions: (1) a Direct Gaze condition, in which an experimenter looking down was positioned above one of two approach areas; (2) a Gaze Follow condition in which an experimenter, positioned equidistant between two approach areas, directed his/her gaze towards one of the areas; (3) a Masked Gaze Follow condition, in which the experimenter wore a mask during the Gaze Follow test; (4) a Deprived Face Experience condition, in which hatchlings were deprived of experience with human faces prior to the Gaze Follow test; and (5) a Control condition in which no experimenter was present during testing. Results revealed that hatchlings from the Direct Gaze condition preferred the non-gazed approach area at all ages tested. Hatchlings from the Gaze Follow condition preferred the non-gazed approach area at 48 and 72 h, but not at 24 h of age. In contrast, hatchlings from the Masked Gaze Follow, Deprived Face and Control conditions did not prefer either approach area at any age tested. These results indicate that experience with human faces plays a key role in the rapid emergence of gaze following behavior in bobwhite quail hatchlings.     

Spatial cognition in the gerbil: computing optimal escape routes from visual threats

Previous studies in our laboratory have shown that when presented with a sudden stimulus simulating an oncoming predator, Mongolian gerbils can compute the optimal trajectory to a safe refuge, taking into account the position of the threat, the location of a clearly visible refuge, and several other contextual variables as well. In the present studies, the main goal was to explore the abilities of gerbils to use mental representations of spaces that were visually occluded by opaque barriers to compute efficient escape trajectories. In all studies, gerbils were placed into a round open field containing a single refuge. On each trial, an overhead visual stimulus was caused to ‘fly’ overhead, eliciting robust escape movements from the gerbils. By manipulating the shape and position of a series of opaque barriers that were interposed between the gerbils and the refuge, we were able to show that gerbils can compute the shortest route to an invisible target, even when the available routes to the target are made complex by using elaborate barrier shapes. These findings suggest that gerbils can maintain representations of their locations with respect to salient environmental landmarks and refuges, even when such locations are not continuously visible.