DHPG activation of group 1 mGluRs in BLA enhances fear conditioning

Group 1 metabotropic glutamate receptors are known to play an important role in both synaptic plasticity and memory. We show that activating these receptors prior to fear conditioning by infusing the group 1 mGluR agonist, (R.S.)-3,5-dihydroxyphenylglycine (DHPG), into the basolateral region of the amygdala (BLA) of adult Sprague–Dawley rats enhances freezing normally supported by a weak footshock. This effect of DHPG was blocked when it was co-infused with either the general group 1 mGluR1 antagonist, (R,S)-1-aminoindan-1,5 dicarboxylic acid (AIDA), or with the selective mGluR5 antagonist, 2-methyl-6-(phenylethynyl)-pyridine (MPEP). These results support previous findings by Rodrigues and colleagues that mGluR5s in the lateral region of the amygdala make an import contribution to fear conditioning. More importantly, they support the general ideas embedded in the concept of metaplasticity, as per Abraham, and the synaptic-tagging hypothesis per Frey and Morris—that the processes that specify the content of experience can be experimentally separated from those needed to acquire the memory.The last decade has seen an increased appreciation of the view that the plasticity state of neurons—their ability to be modified by experience—is not fixed. Instead, the effect of experience depends on the physiological or biochemical state of the neurons or synapses that receive and store information contained in the experience, and this state is variable. This perspective is captured by the concept called “metaplasticity” (Abraham and Bear 1996; Abraham and Tate 1997; Abraham 2008), which recognizes that prior events can change the general plasticity or modifiability of neurons and synapses that will potentially store information contained in a subsequent target experience. This idea is also embedded in the synaptic-tagging hypothesis (Frey and Morris 1997, 1998) that will be described in some detail in the Discussion section. This view is important because it recognizes that the processes that specify the content of experience can be experimentally separated from those that are needed to store the memory for the experience.As reviewed by Abraham (2008), the range of prior events that can potentially determine a neuron''s state of plasticity is quite large and can be mediated by their effects on many components of the machinery that supports changes in synaptic strength. They include modification in NMDA-receptor function, AMPA-receptor trafficking, neuronal excitability, and epigenetic modifications.One way that the potential for plasticity can be altered is by activation of group 1 metabotropic glutamate receptors (mGluR1s and mGlur5s) (Abraham 2008). A number of reports based on the in vitro long-term potentiation (LTP) methodology suggest that activating this class of receptors prior to the delivery of a relatively weak inducing stimulus can transform a normally short-lasting form of LTP into a more persistent form (Cohen and Abraham 1996; Cohen et al. 1998; Raymond et al. 2000). For example, an infusion of (R.S.)-3,5-dihydroxyphenylglycine (DHPG), a group 1 mGluR agonist, into the bathing medium 30 min prior to the delivery of a weak inducing stimulus can significantly enhance the persistence of the resulting LTP, while having no effect on the baseline response (Cohen et al. 1998; Raymond et al. 2000). This effect of DHPG, however, is blocked (Raymond et al. 2000) when its administration is accompanied by an infusion of the group 1 mGluR antagonist, (R,S)-1-aminoindan-1,5 dicarboxylic acid (AIDA).Group 1 mGluRs also have been implicated in fear conditioning. For example, Rodrigues et al. (2002) reported that one subtype, mGluR5, is localized in dendrites and spines in neurons in the lateral nucleus of the amygdala, and fear conditioning can be significantly impaired if the mGluR5 antagonist, 2-methyl-6-(phenylethynyl)-pyridine (MPEP), is infused into the lateral nucleus prior to conditioning.These findings, from the studies of synaptic plasticity and fear conditioning, provide the empirical basis for the hypothesis that motivates the experiments reported here—that the plasticity potential of neurons in the amygdala that support fear conditioning can be increased by activating group 1 mGluRs prior to the conditioning experience.To evaluate this idea, we followed a strategy similar to that used to study the role of mGluRs in LTP (Cohen and Abraham 1996; Cohen et al. 1998; Raymond et al. 2000). In these in vitro LTP experiments, a relatively weak inducing stimulus was used to generate a short-lasting LTP. Infusing the group 1 agonist DHPG prior to the delivery of the inducing stimulus transformed this short-lasting LTP into a more persistent form. Their results suggest that the activation of group 1 mGluR1 receptors independently initiates processes that make an important contribution to long-lasting LTP. To apply this strategy to fear conditioning, we used a very low level of shock—one that by itself produced an almost undetectable level of conditioned fear (as measured by freezing, the innate defensive response of rodents). We then determined if the activation of group 1 mGluRs prior to the conditioning experience would transform this outcome and produce a stronger level of freezing. DPHG was infused into the basolateral region of the amygdala (BLA) to activate the mGluRs.     

Apples and oranges? Comparing indirect measures of alcohol-related cognition predicting alcohol use in at-risk adolescents.

Recently, there has been increased interest in the role of implicit cognitive processes in the development of addictive behaviors. In this study, the authors compared 3 indirect measures of alcohol-related cognitions in the prospective prediction of alcohol use in at-risk adolescents. Implicit alcohol-related cognitions were assessed in 88 Dutch at-risk adolescents ranging in age from 14 to 20 years (51 males, 37 females) by means of varieties of word association tasks, Implicit Association Tests, and Extrinsic Affective Simon Tasks adapted for alcohol use. Alcohol use and alcohol-related problems were measured with self-report questionnaires at baseline and after 1 month. Results showed that the indirect measures predicted unique variance in prospective alcohol use after controlling for the direct measure of alcohol-related cognitions and background variables. The results indicate that the word association tasks were the best indirect measure of alcohol-related cognitions. These indirect measures appear to assess cognitive motivational processes that affect behavior in ways not reflected by direct measures of alcohol-related cognitions.     

Bedroom design and decoration: gender differences in preference and activity

This investigation examined gender differences in niche-building preference and activity among 238 8th and 9th grade boys and girls. A questionnaire was developed to measure both the actual and preferred bedroom content, bedroom design activity, and the level of perceived influence by the immediate and extended family, friends, and social institutions. Gender differences were identified for preference, activity, and influence in bedroom design and decoration. Girls and boys differed in the type of items contained in their bedrooms. Girls' rooms contained stuffed animals and pictures of people, including themselves, more frequently than the boys' rooms. In contrast, boys' rooms contained sports-related items, and things for building or that they had built themselves. Although bedroom design activity for both boys and girls was influenced by older teens, friends, media, and popular culture, boys (but not girls) were also influenced by their mothers, fathers, girlfriends, and activities such as sports, Boy or Girl Scouts, and music lessons.     

A behavior genetic investigation of adolescent motherhood and offspring mental health problems

The present study examines the relations between adolescent motherhood and children's behavior, substance use, and internalizing problems in a sample of 1,368 children of 712 female twins from Australia. Adolescent motherhood remained significantly associated with all mental health problems, even when using a quasiexperimental design capable of controlling for genetic and environmental confounds. However, the relation between adolescent motherhood and offspring behavior problems and substance use was partially confounded by family background variables that influence both generations. The results are consistent with a causal relation between adolescent motherhood and offspring mental health problems, and they highlight the usefulness of behavior genetic designs when examining putative environmental risks for the development of psychopathology. The generalizability of these results to the United States, which has a higher adolescent birth rate, is discussed.     

A mediational model of trait negative affectivity, dispositional thought suppression, and intrusive thoughts following laboratory stressors

Two studies examined the relationships among trait negative affectivity, dispositional thought suppression, and intrusions in non-clinical samples. In Study 1 (N=87), participants were presented with a series of emotionally evocative images and intrusions were examined 48 h after presentation via self-report. In Study 2 (N=118), intrusions were examined using a behavioral Key-press and self-report at two time points (5 and 20 min) following exposure to a series of emotionally evocative images. In each study, participants were assessed for trait negative affectivity and the tendency to engage in thought suppression in response to unpleasant cognitions. Results from both studies support a model in which chronic thought suppression fully mediates the relationship between negative affectivity and the frequency of intrusions.     

Retrospective reports of dream characteristics and preferences for organic vs. junk foods

The authors investigated correlations between retrospective dream characteristics, food preferences, and eating attitudes. Graduate students (7 men, 42 women) at Santa Clara University were administered the MEGA food scale and the KJP Dream Inventory. High intake of organic food was positively correlated with reports of multiple dream factors. Conversely, high scores on preferences for fast food, potato chips, and carbohydrates were negatively correlated with several factors. Findings are discussed in terms of the hypothesis that certain foods may influence dreaming.     

Counselors' Attribution of Responsibility,Etiology, and Counseling Strategy

This study surveyed 167 counselors working at university counseling centers on their etiology and responsibility attributions and models of helping. Participants responded to vignettes describing either a male or female client experiencing symptoms of either an identity or adjustment problem. Counselors endorsed all of P. Brickman et al.'s (1982) models of helping for both problem types. Predictions concerning etiology attributions were partially supported. Counselors selected attributions logically consistent with an internal cause for the identity problem. However, counselors did not make external attributions for the adjustment problem. No significant results were observed for the influence of client sex.     

Driving anger: correlates and a test of state-trait theory

A survey and field study evaluated predictions from state-trait theory applied to driving anger. Trait driving anger, the propensity to become angry when driving, correlated positively with anger in frequently occurring driving situations and in day-to-day driving and with aggressive and risky behaviors while driving. Although not correlated with crash rates or moving violations, trait driving anger correlated with crash-related conditions such as loss concentration, loss of vehicular control, and close calls. Results generally supported predictions from state-trait theory and the construct validity of the Driving Anger Scale, as well as mapping correlates of the disposition to become angry while driving.