Immediate and delayed effects of causal uncertainty inductions on uncertainty accessibility

Previous research has focused on enhanced processing as a response to causal uncertainty (CU), but relatively little empirical attention has been given to how CU is activated and the temporal unfolding of this activation. The current research investigates the counterintuitive idea that people inhibit causal uncertainty immediately after its activation. We find that this inhibition weakens over time. Study 1 demonstrates this inhibition effect with self-report uncertainty. Study 2 demonstrates this effect with an implicit accessibility measure. Temporary inhibition of uncertainty may be a general response when uncertainty is activated.     

Ethanol state-dependent memory: involvement of dorsal hippocampal muscarinic and nicotinic receptors

In the present study, the effects of bilateral injections of cholinergic agents into the hippocampal CA1 regions (intra-CA1) on ethanol state-dependent memory were examined in mice. A single-trial step-down passive avoidance task was used for the assessment of memory retention in adult male NMRI mice. Pre-training intraperitoneal injection (i.p.) of ethanol (0.25, 0.5 and 1 g/kg) dose dependently induced impairment of memory retention. Pre-test administration of ethanol (0.5 and 1 g/kg, i.p.) induced state-dependent retrieval of the memory acquired under pre-training ethanol (1 g/kg, i.p.) influence. Pre-test intra-CA1 injection of physostigmine (2.5 and 5 μg/mouse, intra-CA1) or nicotine (0.3 and 0.5 μg/mouse, intra-CA1) improved pre-training ethanol (1 g/kg)-induced retrieval impairment. Moreover, pre-test administration of physostigmine (2.5 and 5 μg/mouse, intra-CA1) or nicotine (0.3 and 0.5 μg/mouse, intra-CA1) with an ineffective dose of ethanol (0.25 g/kg) significantly restored the retrieval and induced ethanol state-dependent memory. Pre-test intra-CA1 injection of the muscarinic receptor antagonist, atropine (4 and 8 μg/mouse, intra-CA1) or the nicotinic receptor antagonist, mecamylamine (2 and 4 μg/mouse, intra-CA1) 5 min before the administration of ethanol (1 g/kg, i.p.) dose dependently inhibited ethanol state-dependent memory. Pre-test intra-CA1 administration of physostigmine (0.5, 2.5 and 5 μg/mouse), atropine (2, 4 and 8 μg/mouse), nicotine (0.1, 0.3 and 0.5 μg/mouse) or mecamylamine (1, 2 and 4 μg/mouse) alone cannot affect memory retention. These findings implicate the involvement of a dorsal hippocampal cholinergic mechanism in ethanol state-dependent memory and also it can be concluded that there may be a cross-state dependency between ethanol and acetylcholine.     

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).     

Mereological nihilism: quantum atomism and the impossibility of material constitution

Mereological nihilism is the philosophical position that there are no items that have parts. If there are no items with parts then the only items that exist are partless fundamental particles, such as the true atoms (also called philosophical atoms) theorized to exist by some ancient philosophers, some contemporary physicists, and some contemporary philosophers. With several novel arguments I show that mereological nihilism is the correct theory of reality. I will also discuss strong similarities that mereological nihilism has with empirical results in quantum physics. And I will discuss how mereological nihilism vindicates a few other theories, such as a very specific theory of philosophical atomism, which I will call quantum abstract atomism. I will show that mereological nihilism also is an interpretation of quantum mechanics that avoids the problems of other interpretations, such as the widely known, metaphysically generated, quantum paradoxes of quantum physics, which ironically are typically accepted as facts about reality. I will also show why it is very surprising that mereological nihilism is not a widely held theory, and not the premier theory in philosophy.     

Intrahippocampal insulin improves memory in a passive-avoidance task in male wistar rats

The main impacts of insulin favor the peripheral organs. Although it functions as a neuropeptide, insulin possesses also some central effects. The aim of this study was to determine the effect of intrahippocampal infusion of insulin on passive avoidance learning in healthy male rats. Thirty male wistar rats were divided into three groups (n=10 each). The experimental group had posttraining insulin infusion into the CA1 region of dorsal hippocampus, after which they were compared with sham (saline) and control (intact) groups. Insulin treated animals had greater latency to enter the dark compartment in compare with saline treated (p=0.023) or control groups (p=0.017). Upon our results, we concluded that intrahippocampal injections of insulin may enhance memory for a simple learning task which supports the concept that insulin possibly plays an endogenous role in memory formation.     

The Prediction of Worry in Non-Clinical Individuals: The Role of Intolerance of Uncertainty,Meta-Worry,and Neuroticism

The present study investigated the relation between intolerance of uncertainty (IU), meta-worry, and neuroticism on the one hand, and worry on the other hand, in a sample of 105 university students. Two different operationalizations of worry were used: trait worry and idiosyncratic worry. Results showed that IU, meta-worry, and neuroticism correlated significantly with trait worry. Further, IU and meta-worry were strongly related but made a unique and independent contribution to trait worry. Finally, IU and meta-worry could be considered as partial mediators of the relation between neuroticism and trait-like worry. Relations of IU, meta-worry, and neuroticism with idiosyncratic worry were weak or even absent, although neuroticism was associated with idiosyncratic worry when the stressful event was more imminent. In conclusion, not IU and meta-worry, but the general vulnerability factor of neuroticism appeared to possess the most declarative value in relation to both trait and idiosyncratic worry.     

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 role of pre-exposure to novel food tastes in activity-based conditioned taste avoidance

Rats were given differential exposure to three distinct and novel foods. One of these foods was exposed for 7 days; another for 2 days, and the last was not exposed. Next, half of the rats received six daily sessions in which a compound of the three flavors was followed by opportunities to run in wheels. The other rats received the food compound but without wheel running. On the next day, all rats were given a choice among the three food flavors presented concurrently in separate dishes. When the compound food had been followed by wheel running, rats ate little of the food given no pre-exposure, more of the food given 2 days of pre-exposure, and considerably more of the food given 7 days of pre-exposure. In comparison, rats who did not receive an opportunity to run ate equal and moderate amounts of the three foods. The results suggest that pre-exposure to a food’s taste produces latent inhibition that interferes with conditioned taste avoidance produced by pairing a taste (CS) with wheel running (US).