Input-specific long-term potentiation in the rat lateral amygdala of horizontal slices

Long-term potentiation (LTP) at input synapses to the lateral nucleus of the amygdala (LA) is a candidate mechanism for memory storage during fear learning. Cellular mechanisms of LTP have been nearly exclusively investigated in coronal brain slices. In our experiments, we used a horizontal brain slice preparation of rats that preserved most of the connections to cortical areas and the hippocampus. The stimulation electrodes were located either within the external capsule (EC) or the LA. The aim of the present study was to investigate the mechanisms of LTP induced either by weak theta burst stimulation (TBS) or strong high frequency stimulation (HFS) using the two different stimulation sites. Whereas both TBS and HFS of afferences running through the LA induced stable LTP, TBS failed to induce LTP of EC-inputs to the LA. The present findings also show that LTP in the LA exhibits vulnerability at different time windows after induction. The time window was dependent on the kind of stimulated afferences. Later LTP becomes resistant to disruption by low frequency stimulation. We could show that both used inputs depended on NMDA receptors for LTP-induction. LTP induced by stimulation of fibers within the LA was not altered by nifedipine (10 microM). In contrast, EC-induced LTP was dependent on L-type voltage-gated calcium channels (VGCC). Finally, we found a higher magnitude of LTP in females using TBS, whereas HFS did not cause gender-specific differences. Our study supports the conclusion that the form of LA-LTP depend on which afferences are activated and what pattern of stimulation is used to induce LTP.     

Intelligence is differentially related to neural effort in the task-positive and the task-negative brain network

Previous studies on individual differences in intelligence and brain activation during cognitive processing focused on brain regions where activation increases with task demands (task-positive network, TPN). Our study additionally considers brain regions where activation decreases with task demands (task-negative network, TNN) and compares effects of intelligence on neural effort in the TPN and the TNN. In a sample of 52 healthy subjects, functional magnetic resonance imaging was used to determine changes in neural effort associated with the processing of a working memory task. The task comprised three conditions of increasing difficulty: (a) maintenance, (b) manipulation, and (c) updating of a four-letter memory set. Neural effort was defined as signal increase in the TPN and signal decrease in the TNN, respectively. In both functional networks, TPN and TNN, neural effort increased with task difficulty. However, intelligence, as assessed with Raven's Matrices, was differentially associated with neural effort in the TPN and TNN. In the TPN, we observed a positive association, while we observed a negative association in the TNN. In terms of neural efficiency (i.e., task performance in relation to neural effort expended on task processing), more intelligent subjects (as compared to less intelligent subjects) displayed lower neural efficiency in the TPN, while they displayed higher neural efficiency in the TNN. The results illustrate the importance of differentiating between TPN and TNN when interpreting correlations between intelligence and fMRI measures of brain activation. Importantly, this implies the risk of misinterpreting whole brain correlations when ignoring the functional differences between TPN and TNN.     

Learning-induced arg 3.1/arc mRNA expression in the mouse brain

The effector immediate-early gene (IEG) arg 3.1, also called arc, encodes a protein interacting with the neuronal cytoskeleton. The selective localization of arg 3.1/arc mRNA in activated dendritic segments suggests that the arg 3.1/arc protein may be synthesized at activated post-synaptic sites and that arg 3.1/arc could participate in structural and functional modifications underlying cognitive processes like memory formation. To analyze whether learning itself is sufficient to trigger expression of arg 3.1/arc, we developed a one-trial learning paradigm in which mice learned to enter a dark compartment to escape from an aversively illuminated area. Arg 3.1/arc mRNA expression was analyzed by in situ hybridization in three groups of mice as follows: a control group with no access to the dark compartment, a learning group having access to the dark compartment for one trial, and a retrieval group having access to the dark compartment for two trials on consecutive days. All animals from the learning and retrieval groups escaped the illuminated area, and those tested 24 h later (retrieval group) showed a strongly reduced latency to enter the dark compartment, demonstrating the validity of our learning paradigm to induce long-term memory. Our results show that acquisition of a simple task results in a brain area-specific biphasic increase in arg 3.1/arc mRNA expression 15 min and 4.5 h post-training. This increase was detected specifically in the learning group but neither in the control nor in the retrieval groups. The pattern of arg 3.1/arc mRNA expression corresponds temporally to the two mRNA- and protein-synthesis-dependent periods of long-term memory formation. Our study provides the first unequivocal evidence that arg 3.1/arc expression is induced by a learning task and strongly suggests a role of arg 3.1/arc mRNA in the early and late cellular mechanisms underlying the stabilization of the memory trace.     

Association between intermale aggression and genetically-defined tryptophan hydroxylase activity in the mouse brain

The relationship between the genetically defined intensity of intermale aggression and the activity of brain tryptophan hydroxylase (TPH) has been studied in inbred mice. No association between the enzyme activity and the percentage of aggressive mice (reflecting the predisposition to aggressive reaction) was revealed. However, a significant positive interstrain correlation between brain TPH activity and accumulated attacking time (reflecting fight intensity) was identified. No correlation was found between TPH activity and the accumulated attacking time in segregating F2 (BALB × C57BL) mice. In conclusion, TPH is an important, but not the only factor controlling the intensity of intermale aggression in mice. © 1996 Wiley-Liss, Inc.     

The politics of time: Conservatives differentially reference the past and liberals differentially reference the future

Conservatives are thought to favor certainty and value tradition (suggesting a focus on the past), whereas liberals are thought to favor change (suggesting a focus on the future), even when it is associated with some degree of uncertainty. On this basis, two studies contrasted references to the past versus the future in language usage. Study 1 analyzed 600 texts from conservative and liberal websites. After adjusting for normative differences, a cross‐over interaction was obtained: Conservative posts referenced the past to a greater extent than the future and liberal posts referenced the future more than the past. A conceptually parallel cross‐over interaction was obtained in Study 2, which analyzed 145 State of the Union addresses. The temporal orientation of conservatives and liberals, then, appears qualitatively different.     

Evaluating the role of contingency in differentially reinforced tic suppression

The current study evaluated the effects of tokens delivered on differential reinforcement of zero-rate behavior (DRO) schedules or noncontingently on tic suppression in 4 children with tics. Tic frequency was lower in 3 of 4 children when tokens were delivered contingent on the absence of tics than when tokens were delivered noncontingently.     

Colour-identification of differentially valenced words in anxiety

Abstract

Two groups of individuals, one high in trait anxiety and the other low in trait anxiety, performed a Stroop task in which threat, neutral, and pleasant words were presented. The results indicated clear differences between the high- and low-trait groups in their performance on this task. The low-trait group's performance was similar for all three types of sitmuli, whereas the high-trait group's responses were fastest for pleasant stimuli and slowest for threat-related stimuli. A recognition task to examine incidental learning of the “irrelevant” Stroop words showed that whilst the high-trait group had a stronger tendency to respond positively to all trials (critical and distractor) than the low-trait group, there were no differences in sensitivity between the two groups.     

Chronic administration of troxerutin protects mouse brain against d-galactose-induced impairment of cholinergic system

Previous evidence showed that administration of d-galactose (d-gal) increased ROS production and resulted in impairment of cholinergic system. Troxerutin, a natural bioflavonoid, has been reported to have many benefits and medicinal properties. In this study, we evaluated the protective effect of troxerutin against d-gal-induced impairment of cholinergic system, and explored the potential mechanism of its action. Our results displayed that troxerutin administration significantly improved behavioral performance of d-gal-treated mice in step-through test and morris water maze task. One of the potential mechanisms of this action was decreased AGEs, ROS and protein carbonyl levels in the basal forebrain, hippocampus and front cortex of d-gal-treated mice. Furthermore, our results also showed that troxerutin significantly inhibited cholinesterase (AchE) activity, increased the expression of nicotinic acetylcholine receptor alpha 7 (nAchRα7) and enhanced interactions between nAchRα7 and either postsynaptic density protein 95 (PSD95) or N-methyl-d-aspartate receptors subunit 1 (NMDAR1) in the basal forebrain, hippocampus and front cortex of d-gal-treated mice, which could help restore impairment of brain function.     

Use of relaxation skills in differentially skilled athletes

ObjectivesTo examine the use of relaxation skills by differentially skilled athletes in relation to the deliberate practice framework.DesignDifferentially skilled athletes completed a survey about their use of relaxation skills.Method150 athletes representing three skill levels (recreational, college, and professional) completed the deliberate relaxation for sport survey, which assessed relaxation on three deliberate practice dimensions (relevancy, concentration, and enjoyment); time spent in different relaxation skills in a recent typical week; and functions of relaxation.ResultsAthletes perceived relaxation as relevant to performance, requiring concentration, and enjoyable, and the relationships between these dimensions were positive. Professional and college athletes perceived relaxation as more relevant to effective competition than recreational athletes. Professional athletes engaged in more relaxation in a typical week than college and recreational athletes. In a typical week, autogenic, eastern, and muscle relaxation types were used least, deep breathing, meditation, and imagery relaxation types moderately, and stretching most. Athletes reported the primary functions of relaxation were to cope with competitive anxiety and promote recovery but relaxation was also reported to be used to cope with “everyday” anxieties associated with being an athlete. More physical (e.g., muscle relaxation) than mental relaxation types were used in relation to coping with competitive anxiety, whereas more mental (e.g., meditation) than physical relaxation types were used in relation to coping with everyday anxiety.ConclusionsThe study provides support for the sport-specific framework of deliberate practice in relation to use of relaxation skills and informs the current understanding of self-regulation by athletes.     

Transient hippocampal down-regulation of Kv1.1 subunit mRNA during associative learning in rats

Voltage-gated potassium channels (Kv) are critically involved in learning and memory processes. It is not known, however, whether the expression of the Kv1.1 subunit, constituting Kv1 channels, can be specifically regulated in brain areas important for learning and memory processing. Radioactive in situ hybridization was used to evaluate the content of Kv1.1 α-subunit mRNA in the olfactory bulb, ventral, and dorsal hippocampus at different stages of an odor-discrimination associative task in rats. Naive, conditioned, and pseudoconditioned animals were sacrificed at different times either prior to a two-odor significance learning or after odor discrimination was established. Important decreases of Kv1.1 mRNA levels were transiently observed in the ventral hippocampus before successful learning when compared with the pseudoconditioned group. Moreover, temporal group analysis showed significant labeling alterations in the hippocampus of conditioned and pseudoconditioned groups throughout the training. Finally, Kv1.1 mRNA levels in the hippocampus were positively correlated with odor-reward association learning in rats that were beginning to discriminate between odors. These findings indicate that the Kv1.1 subunit is transiently down-regulated in the early stages of learning and suggest that Kv1 channel expression regulation is critical for the modification of neuronal substrates underlying new information acquisition.     

Therapeutic effectiveness of differentially targeted humorous remarks in group psychotherapy

Video records of five different sessions of a single therapy group were scored for the occurrence of laughing, smiling, and talking. Successive five-minute intervals were also scored for therapeutic level through ratings derived from the Hill Interaction Matrix. Humorous remarks were categorized according to humor target: self, other in group, and generalized other. Results indicated that the vast majority of humorous remarks were directed at some specific target, and that over 50% of these remarks were negative in tone. Results also revealed that remarks targeted at others in the group tended to decrease therapeutic effectiveness whereas remarks targeted at individuals or institutions not presently in the group were found to increase therapeutic effectiveness. Selftargeted remarks were found to produce inconsistent effects. These findings are discussed in terms of their significance for a more general analysis of group humor as well as in terms of their more specific implications for therapeutic interventions.     

Children and adults are differentially affected by presentation modality in the DRM paradigm

Using the Deese–Roediger–McDermott (DRM) method for free recall, we examined mode of list presentation and association type in 8–9 year old children and adults. Participants verbally recalled lists of associates that were presented orally (Experiment 1) or visually (Experiment 2). Lists consisted of semantic associates (e.g. hound, puppy, etc.), phonological associates (e.g. log, dot, etc.) and both semantic and phonological associates (e.g. hound, dot, etc.) to a nonpresented lure word (e.g. dog). Interestingly, the ratio of false to true recall was higher in children than adults only when lists were presented orally. These results suggest that children rely more on sublexical information or item‐specific information than adults when reading lists, and, thus, are less likely to activate the critical lure via lexical associations. Furthermore, these results suggest that information processing differences at encoding between children and adults need to be taken into account when interpreting free recall studies. Copyright © 2008 John Wiley & Sons, Ltd.     

Gesture in the developing brain

Speakers convey meaning not only through words, but also through gestures. Although children are exposed to co-speech gestures from birth, we do not know how the developing brain comes to connect meaning conveyed in gesture with speech. We used functional magnetic resonance imaging (fMRI) to address this question and scanned 8- to 11-year-old children and adults listening to stories accompanied by hand movements, either meaningful co-speech gestures or meaningless self-adaptors. When listening to stories accompanied by both types of hand movement, both children and adults recruited inferior frontal, inferior parietal, and posterior temporal brain regions known to be involved in processing language not accompanied by hand movements. There were, however, age-related differences in activity in posterior superior temporal sulcus (STSp), inferior frontal gyrus, pars triangularis (IFGTr), and posterior middle temporal gyrus (MTGp) regions previously implicated in processing gesture. Both children and adults showed sensitivity to the meaning of hand movements in IFGTr and MTGp, but in different ways. Finally, we found that hand movement meaning modulates interactions between STSp and other posterior temporal and inferior parietal regions for adults, but not for children. These results shed light on the developing neural substrate for understanding meaning contributed by co-speech gesture.     

Reinforcement learning in the brain

A wealth of research focuses on the decision-making processes that animals and humans employ when selecting actions in the face of reward and punishment. Initially such work stemmed from psychological investigations of conditioned behavior, and explanations of these in terms of computational models. Increasingly, analysis at the computational level has drawn on ideas from reinforcement learning, which provide a normative framework within which decision-making can be analyzed. More recently, the fruits of these extensive lines of research have made contact with investigations into the neural basis of decision making. Converging evidence now links reinforcement learning to specific neural substrates, assigning them precise computational roles. Specifically, electrophysiological recordings in behaving animals and functional imaging of human decision-making have revealed in the brain the existence of a key reinforcement learning signal, the temporal difference reward prediction error. Here, we first introduce the formal reinforcement learning framework. We then review the multiple lines of evidence linking reinforcement learning to the function of dopaminergic neurons in the mammalian midbrain and to more recent data from human imaging experiments. We further extend the discussion to aspects of learning not associated with phasic dopamine signals, such as learning of goal-directed responding that may not be dopamine-dependent, and learning about the vigor (or rate) with which actions should be performed that has been linked to tonic aspects of dopaminergic signaling. We end with a brief discussion of some of the limitations of the reinforcement learning framework, highlighting questions for future research.