Causally Probing the Role of the Hippocampus in Fear Discrimination: A Precision Functional Mapping-Guided, Transcranial Magnetic Stimulation Study in Participants With Posttraumatic Stress Symptoms

Background

Fear overgeneralization is a promising pathogenic mechanism of clinical anxiety. A dominant model posits that hippocampal pattern separation failures drive overgeneralization. Hippocampal network-targeted transcranial magnetic stimulation (HNT-TMS) has been shown to strengthen hippocampal-dependent learning/memory processes. However, no study has examined whether HNT-TMS can alter fear learning/memory.

Methods

Continuous theta burst stimulation was delivered to individualized left posterior parietal stimulation sites derived via seed-based connectivity, precision functional mapping, and electric field modeling methods. A vertex control site was also stimulated in a within-participant, randomized controlled design. Continuous theta burst stimulation was delivered prior to 2 visual discrimination tasks (1 fear based, 1 neutral). Multilevel models were used to model and test data. Participants were undergraduates with posttraumatic stress symptoms (final n = 25).

Results

Main analyses did not indicate that HNT-TMS strengthened discrimination. However, multilevel interaction analyses revealed that HNT-TMS strengthened fear discrimination in participants with lower fear sensitization (indexed by responses to a control stimulus with no similarity to the conditioned fear cue) across multiple indices (anxiety ratings: β = 0.10, 95% CI, 0.04 to 0.17, p = .001; risk ratings: β = 0.07, 95% CI, 0.00 to 0.13, p = .037).

Conclusions

Overgeneralization is an associative process that reflects deficient discrimination of the fear cue from similar cues. In contrast, sensitization reflects nonassociative responding unrelated to fear cue similarity. Our results suggest that HNT-TMS may selectively sharpen fear discrimination when associative response patterns, which putatively implicate the hippocampus, are more strongly engaged.

Does social rigidity predict cognitive rigidity? Profiles of socio-cognitive polarization

Recent research has proposed a relationship between rigid political ideologies and underlying 'cognitive styles'. However, there remain discrepancies in how both social and cognitive rigidity are defined and measured. Problem-solving, or the ability to generate novel ideas by exploring unusual reasoning paths and challenging rigid perspectives around us, is often used to operationalize cognitive flexibility. Thus, we hypothesized a relation between forms of social rigidity, including Socio-cognitive polarization (i.e., a factor capturing conservative political ideology, absolutism/intolerance of ambiguity, and xenophobia), bullshit receptivity (i.e., overestimating pseudo-profound statements), overclaiming (tendency to self-enhance), and cognitive rigidity (i.e., problem-solving). Our results showed differences in performance on problem-solving tasks between four latent profiles of social rigidity identified in our sample. Specifically, those low in socio-cognitive polarization, bullshit, and overclaiming (i.e., less rigid) performed the best on problem-solving. Thus, we conclude that social and cognitive rigidity may share an underlying socio-cognitive construct, wherein those who are more socially rigid are also more likely to be also cognitively rigid when processing non-social information.

Modeling relations between event-related potential factors and broader versus narrower dimensions of externalizing psychopathology

The organization of the Hierarchical Taxonomy of Psychopathology (HiTOP) model provides unique opportunities to evaluate whether neural risk measures operate as indicators of broader latent liabilities (e.g., externalizing proneness) or narrower expressions (e.g., antisociality and alcohol abuse). Following this approach, the current study recruited a sample of 182 participants (54% female) who completed measures of externalizing psychopathology (also internalizing) and associated traits. Participants also completed three tasks (Flanker-No Threat, Flanker-Threat, and Go/No-Go tasks) with event-related potential (ERP) measurement. Three variants of two research domain criteria (RDoC)-based neurophysiological indicators-P3 and error-related negativity (ERN)-were extracted from these tasks and used to model two latent ERP factors. Scores on these two ERP factors independently predicted externalizing factor scores when accounting for their covariance with sex-suggesting distinct neural processes contributing to the broad externalizing factor. No predictive relation with the broad internalizing factor was found for either ERP factor. Analyses at the finer-grained level revealed no unique predictive relations of either ERP factor with any specific externalizing symptom variable when accounting for the broad externalizing factor, indicating that ERN and P3 index general liability for problems in this spectrum. Overall, this study provides new insights about neural processes in externalizing psychopathology at broader and narrower levels of the HiTOP hierarchy. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Precision behavioral phenotyping as a strategy for uncovering the biological correlates of psychopathology

Our capacity to measure diverse aspects of human biology has developed rapidly in the past decades, but the rate at which these techniques have generated insights into the biological correlates of psychopathology has lagged far behind. The slow progress is partly due to the poor sensitivity, specificity and replicability of many findings in the literature, which have in turn been attributed to small effect sizes, small sample sizes and inadequate statistical power. A commonly proposed solution is to focus on large, consortia-sized samples. Yet it is abundantly clear that increasing sample sizes will have a limited impact unless a more fundamental issue is addressed: the precision with which target behavioral phenotypes are measured. Here, we discuss challenges, outline several ways forward and provide worked examples to demonstrate key problems and potential solutions. A precision phenotyping approach can enhance the discovery and replicability of associations between biology and psychopathology.

Counterconditioning reduces contextual renewal in a novel context but not in the acquisition context

As extinction is a context-dependent form of learning, conditioned responses tend to return when the conditioned stimulus (CS) is encountered outside the extinction context, known as contextual renewal. Counterconditioning is a technique that may lead to a more persistent reduction of the conditioned response. However, the effects of aversive-to-appetitive counterconditioning on contextual renewal in rodent studies are mixed. Further, research in humans is sparse, particularly direct statistical comparisons between counterconditioning and standard extinction techniques within the same study. Using a causal associative learning framework (the allergist task) implemented online, we compared the effectiveness of counterconditioning to standard extinction in preventing the renewal of judgements on the allergic properties of different food items (CSs). In a between-subjects design, 328 participants first learned that particular food items (CSs) lead to an allergic reaction in a specific restaurant (context A). Next, one CS was extinguished (no allergic reaction) while another CS was counterconditioned (positive outcome) in restaurant B. Causal judgements of the allergic properties of food items occurred in either the response acquisition context (ABA group, N = 112), the response reduction context where extinction and counterconditioning had occurred (ABB group, N = 107), or a novel context (ABC group, N = 109). Results showed that counterconditioning, compared to extinction, diminished the renewal of causal judgements to the CS in a novel context (ABC group). Still, casual judgements returned for both counter-conditioned and extinguished CSs in the response acquisition context (ABA group). Counterconditioning and extinction were similarly effective at preventing recovery of causal judgements in the response reduction context (ABB group); however, only in context B did participants choose the counter-conditioned CS as less likely to cause an allergic reaction in comparison to the extinguished CS. These findings indicate scenarios in which counterconditioning is more effective than standard extinction at diminishing the return of threat associations, with implications for improving the generalization of safety learning.

The Placement of Obsessive-Compulsive Symptoms Within a Five-Factor Model of Maladaptive Personality

Dimensional models of obsessive-compulsive (OC) symptoms, as seen in obsessive-compulsive disorder (OCD), are instrumental in explaining the heterogeneity observed in this condition and for informing cutting-edge assessments. Prior structural work in this area finds that OC symptoms cross-load under both Negative Affectivity and Psychoticism traits within the Diagnostic and Statistical Manual of Mental Disorders (5th ed.; DSM-5) Alternative Model of Personality Disorder (AMPD). However, tests of OC symptoms in conjunction with assessments of the full AMPD structure and its 25 lower-level facets representing narrower symptom content are lacking. We applied joint exploratory factor analysis to an AMPD measure (Personality Inventory for DSM-5; PID-5) and OC symptom data from two separate samples (total N = 1,506) to locate OC symptoms within AMPD space. OC symptoms cross-loaded on Negative Affectivity, Psychoticism, and on the low end of Disinhibition. We also report exploratory analyses of OC symptom subscales with PID-5 variables. Results are discussed in the context OC symptoms' location in PID-5 space, implications for assessment, and placement of OCD within the Hierarchical Taxonomy of Psychopathology.

Psychological flexibility in South Sudanese female refugees in Uganda as a mechanism for change within a guided self-help intervention

OBJECTIVE

To examine the role of psychological flexibility as a potential mediator in the relationship between involvement in a guided self-help intervention, Self-Help Plus, and psychological distress in a sample of South Sudanese refugee women living in northern Uganda.

METHOD

We conducted secondary analysis of data from a cluster randomized controlled trial conducted in 2018. We used multilevel mediation modeling to explore the relationship of psychological flexibility, as measured by the Acceptance and Action Questionnaire (AAQ-II), as a mediating factor in the relationship between Self-Help Plus involvement and general psychological distress as measured by the Kessler Psychological Distress Scale-6 (K6).

RESULTS

We found strong multilevel mediation of decreased K6 scores in the treatment group by AAQ-II scores (multilevel b = -3.28). A more pronounced mediation effect was discovered immediately post intervention (b = -1.09) compared to 3-month follow-up (b = -0.84). This is in line with the current literature that demonstrates the role of psychological flexibility as a primary mechanism of change in ACT-based interventions.

CONCLUSIONS

Psychological flexibility is a contributing component in the theory of change for this ACT-based intervention. Identifying the core components of interventions allows for more effective adaptation and implementation of relevant services, especially in low-resource contexts. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Test–retest reliability of human threat conditioning and generalization across a 1‐to‐2‐week interval

Given the increasing use of threat conditioning and generalization for clinical-translational research efforts, establishing test-retest reliability of these paradigms is necessary. Specifically, it is an empirical question whether the same participant evinces a similar generalization gradient of conditioned responses across two sessions with the identical contingencies and stimuli. Here, 46 human volunteers participated in an identical auditory threat acquisition and generalization protocol at two sessions separated by 1-to-2 weeks. Skin conductance responses (SCR) and trial-by-trial shock risk ratings served as primary measures. We used linear mixed effects modeling to test differential threat responses and generalization gradients, and Generalizability (G) theory coefficients as our primary formal assessment of test-retest reliability of intraindividual stability and change across time. Results showed largely invariant differential conditioning and generalization gradients across time. G coefficients indicated fair reliability for acquisition and generalization SCR. In contrast, risk rating reliabilities were mixed, and reliability was particularly low for acquisition risk ratings. Our findings generally support reliability of the threat conditioning and generalization paradigm for shorter test-retest intervals and highlight their utility for assessments of behavioral interventions in mental health research, but challenges remain and further work is needed. Threat conditioning and generalization tasks are increasingly used for translational efforts to improve behavioral interventions, and thus test-retest reliability for these tasks needs to be established. Our results support the test-retest reliability of threat conditioning and generalization over a relatively short (1-to-2 week) interval, but this depends on the measure used (physiological vs. self-report). Overall, these tasks could be appropriate for repeated testing over the course of a short-duration intervention study, but more research is needed, particularly in regard to longer-duration studies.

Pattern analysis of neuroimaging data reveals novel insights on threat learning and extinction in humans

Several decades of rodent neurobiology research have identified a network of brain regions that support Pavlovian threat conditioning and extinction, focused predominately on the amygdala, hippocampus, and medial prefrontal cortex (mPFC). Surprisingly, functional magnetic resonance imaging (fMRI) studies have shown inconsistent evidence for these regions while humans undergo threat conditioning and extinction. In this review, we suggest that translational neuroimaging efforts have been hindered by reliance on traditional univariate analysis of fMRI. Whereas univariate analyses average activity across voxels in a given region, multivariate pattern analyses (MVPA) leverage the information present in spatial patterns of activity. MVPA therefore provides a more sensitive analysis tool to translate rodent neurobiology to human neuroimaging. We review human fMRI studies using MVPA that successfully bridge rodent models of amygdala, hippocampus, and mPFC function during Pavlovian learning. We also highlight clinical applications of these information-sensitive multivariate analyses. In sum, we advocate that the field should consider adopting a variety of multivariate approaches to help bridge cutting-edge research on the neuroscience of threat and anxiety.

Fear conditioning and extinction in obsessive-compulsive disorder: A systematic review

Laboratory experiments using fear conditioning and extinction protocols help lay the groundwork for designing, testing, and optimizing innovative treatments for anxiety-related disorders. Yet, there is limited basic research on fear conditioning and extinction in obsessive-compulsive disorder (OCD). This is surprising because exposure-based treatments based on associative learning principles are among the most popular and effective treatment options for OCD. Here, we systematically review and critically assess existing aversive conditioning and extinction studies of OCD. Across 12 studies, there was moderate evidence that OCD is associated with abnormal acquisition of conditioned responses that differ from comparison groups. There was relatively stronger evidence of OCD's association with impaired extinction processes. This included multiple studies finding elevated conditioned responses during extinction learning and poorer threat/safety discrimination during recall, although a minority of studies yielded results inconsistent with this conclusion. Overall, the conditioning model holds value for OCD research, but more work is necessary to clarify emerging patterns of results and increase clinical translational utility to the level seen in other anxiety-related disorders. We detail limitations in the literature and suggest next steps, including modeling OCD with more complex conditioning methodology (e.g., semantic/conceptual generalization, avoidance) and improving individual-differences assessment with dimensional techniques.

Generalization of conditioned disgust and the attendant maladaptive avoidance: Validation of a novel paradigm and effects of trait disgust-proneness

Overgeneralization of conditioned fear to safe stimuli that resemble a previously-learned threat-cue is a well-studied correlate of clinical anxiety, yet whether conditioned disgust generalizes remains unknown, as does the extent to which such generalization is associated with disgust-related traits and maladaptive outcomes. The present study addresses this gap by adapting a validated fear-generalization paradigm to assess conditioned disgust and behavioral avoidance to a disgust-cue (CS+) paired with a disgusting video clip, and safe generalization stimuli parametrically varying in perceptual similarity to CS+. For comparison, levels of fear generalization were also assessed using the original fear-generalization paradigm. In both paradigms, costly and unnecessary avoidance to safe threat-cue approximations analogues maladaptive outcomes of generalization. In the disgust paradigm only, disgust-proneness was associated with elevated perceived risk to safe stimuli and increases in the extent to which such elevations were accompanied by maladaptive avoidance. Comparable levels of generalization, and positive associations between generalization and maladaptive avoidance, were found across disgust and fear paradigms. Results confirm that conditioned disgust is subject to generalization, implicate generalized disgust as a source of maladaptive avoidance particularly among those prone to disgust, and suggest a potential role for these processes in the etiology and maintenance of disgust-related disorders.

Neurobiology and the Hierarchical Taxonomy of Psychopathology: progress toward ontogenetically informed and clinically useful nosology

The Hierarchical Taxonomy of Psychopathology (HiTOP) is an empirical structural model of psychological symptoms formulated to improve the reliability and validity of clinical assessment. Neurobiology can inform assessments of early risk and intervention strategies, and the HiTOP model has greater potential to interface with neurobiological measures than traditional categorical diagnoses given its enhanced reliability. However, one complication is that observed biological correlates of clinical symptoms can reflect various factors, ranging from dispositional risk to consequences of psychopathology. In this paper, we argue that the HiTOP model provides an optimized framework for conducting research on the biological correlates of psychopathology from an ontogenetic perspective that distinguishes among indicators of liability, current symptoms, and consequences of illness. Through this approach, neurobiological research can contribute more effectively to identifying individuals at high dispositional risk, indexing treatment-related gains, and monitoring the consequences of mental illness, consistent with the aims of the HiTOP framework.


Introspective accuracy for substance use across a year of treatment for first episode psychosis

Substance use exacerbates psychosis, mania, depression, and poor functioning in people with first episodes of psychosis (FEP) and is associated with poor treatment outcomes, even when it does not reach the level of a formal disorder. Impaired insight and substance use are common issues that may interfere with treatment outcomes among people experiencing FEP, yet both are treatable. Improvements in these domains are associated with better outcomes. Low insight could increase risk for substance use by impairing the ability to self-appraise and assess consequences. Introspective accuracy (IA) is understudied in this area and is one way of considering self-appraisal. This study is an archival review using data collected from NAVIGATE, a coordinated specialty care program treating people with FEP. IA was operationalized as the difference between clinician and client ratings of substance use. We tested whether IA changed over one year of treatment and whether those changes occurred alongside changes in symptoms and illness self-management. No changes in IA were detected in relation to illness self-management. Changes in IA for substance use occurred midway through treatment—individuals with greater symptom remission had more overconfident IA. Prior research on insight has shown a paradox where greater insight accompanies more symptoms. However, past research has also shown a relationship between IA and functional outcomes, like illness self-management, and that overconfidence in one domain can positively bias clinician ratings in another. Our findings suggest either a positive bias for ratings associated with overconfident IA or an insight paradox type effect.

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Introspective accuracy is a form of insight that can be applied to early psychosis.

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Introspective accuracy for substance use paradoxically interacted with symptoms

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Introspective accuracy for substance use was unrelated to illness self-management.

A continuous metal-insulator transition driven by spin correlations

While Mott insulators induced by Coulomb interactions are a well-recognized class of metal-insulator transitions, insulators purely driven by spin correlations are much less common, as the reduced energy scale often invites competition from other degrees of freedom. Here, we demonstrate a clean example of a spin-correlation-driven metal-insulator transition in the all-in-all-out pyrochlore antiferromagnet Cd₂Os₂O₇, where the lattice symmetry is preserved by the antiferromagnetism. After the antisymmetric linear magnetoresistance from conductive, ferromagnetic domain walls is removed experimentally, the bulk Hall coefficient reveals four Fermi surfaces of both electron and hole types, sequentially departing the Fermi level with decreasing temperature below the Néel temperature, T_N = 227 K. In Cd₂Os₂O₇, the charge gap of a continuous metal-insulator transition opens only at T ~ 10 K << T_N. The insulating mechanism parallels the Slater picture, but without a folded Brillouin zone, and contrasts sharply with Mott insulators and spin density waves, where the electronic gap opens above and at T_N, respectively.

The Mott transition is a celebrated example of a metal-insulator transition driven by electron correlations. Here, using magnetoresistance measurements, the authors demonstrate the presence of a spin-driven metal-insulator transition, where the insulating gap only opens below the Neel temperature.

Co-occurring Deficits in Clinical and Cognitive Insight in Prolonged Schizophrenia-Spectrum Disorders: Relationship to Metacognitive Deficits

People diagnosed with schizophrenia have been broadly observed to experience deficits in clinical and cognitive insight; however, less is understood about how these deficits are related. One possibility is that these deficits co-occur among people when other deficits in cognition are present, such as in executive function, social cognition, and metacognition, which may either promote the development of both forms of poor insight or allow one to negatively influence the other. To explore this possibility, we conducted a cluster analysis using assessments of clinical and cognitive insight among 95 adults with a schizophrenia spectrum disorder. As predicted, this analysis yielded a group with concurrently poor clinical and cognitive insight (n = 36). Additional groups were found with concurrently good clinical and cognitive insight (n = 28) and poor clinical insight and good cognitive insight (n = 31). Groups were then compared on assessments of executive function, social cognition, and metacognition. The group with concurrently lower levels of cognitive and clinical insight had significantly poorer metacognition relative to the other groups. In particular, they tended to form more fragmented and less integrated ideas about themselves and others. No differences were found for executive function or social cognition. The result may suggest that while clinical and cognitive insight is partially orthogonal phenomena, relatively lower levels of metacognition, or difficulties forming integrated ideas about oneself and others, maybe a condition leading to the confluence of lower clinical and cognitive insight. Interventions targeting metacognition may be of particular use for this group.

Optical Raman measurements of low frequency magnons under high pressure

The application of giga-Pascal scale pressures has been widely used as a tool to systematically tune the properties of materials in order to access such general questions as the driving mechanisms underlying phase transitions. While there is a large and growing set of experimental tools successfully applied to high-pressure environments, the compatibility between diamond anvil cells and optical probes offers further potential for examining lattice, magnetic, and electronic states, along with their excitations. Here, we describe the construction of a highly efficient optical Raman spectrometer that enables measurements of magnetic excitations in single crystals down to energies of 9 cm^-1 (1.1 meV or 13 K) at cryogenic temperatures and under pressures of tens of GPa.

Antisymmetric linear magnetoresistance and the planar Hall effect

The phenomena of antisymmetric magnetoresistance and the planar Hall effect are deeply entwined with ferromagnetism. The intrinsic magnetization of the ordered state permits these unusual and rarely observed manifestations of Onsager’s theorem when time reversal symmetry is broken at zero applied field. Here we study two classes of ferromagnetic materials, rare-earth magnets with high intrinsic coercivity and antiferromagnetic pyrochlores with strongly-pinned ferromagnetic domain walls, which both exhibit antisymmetric magnetoresistive behavior. By mapping out the peculiar angular variation of the antisymmetric galvanomagnetic response with respect to the relative alignments of the magnetization, magnetic field, and electrical current, we experimentally distinguish two distinct underlying microscopic mechanisms: namely, spin-dependent scattering of a Zeeman-shifted Fermi surface and anomalous electron velocities. Our work demonstrates that the anomalous electron velocity physics typically associated with the anomalous Hall effect is prevalent beyond the ρ_xy(H_z) channel, and should be understood as a part of the general galvanomagnetic behavior.

Magnetoresitance (MR) is a tool to study electronic transport and spin order in metals. Here, the authors demonstrate two different microscopic origins of antisymmetric linear MR from both Zeeman-split Fermi surface and anomalous electron velocity.

Impaired discriminative fear conditioning during later training trials differentiates generalized anxiety disorder, but not panic disorder, from healthy control participants

BACKGROUND

Fear conditioning is implicated as a central psychopathological mechanism of anxiety disorders. People with anxiety disorders typically demonstrate reduced affective discrimination between conditioned danger and safety cues. Here, affective discrimination refers to the ability to selectively display fear to dangerous but not safe situations. Though both generalized anxiety disorder (GAD) and panic disorder (PD) are linked to impaired affective discrimination, the clinical phenomenology of these disorders suggests that people with GAD versus PD might be less able to overcome such deficits. It is unclear how this potential difference would manifest during lab-based conditioning.

METHODS

We used a classical fear conditioning paradigm over two discrimination training sessions to examine whether those with GAD, but not PD, would display persistent discrimination deficits. Sixty-seven participants (21 GAD, 19 PD, 27 Healthy Controls) completed a task in which conditioned fear was measured psychophysiologically (fear-potentiated startle), behaviorally, and via self-report.

RESULTS

Although similar levels of impaired discrimination were found for both GAD and PD groups during initial training, such impairments tended to persist across a subsequent training session only for patients with GAD when compared with Controls.

CONCLUSION

Our results provide a foundation for additional research of discrimination deficits in specific anxiety disorders, with an ultimate goal of improved customization of psychological treatments.

A Comparison of Food Portion Size Estimation by Older Adults, Young Adults and Nutritionists

OBJECTIVES

To investigate the ability of older adults, younger adults and nutritionists to assess portion size using traditional methods versus a computer-based method. This was to inform the development of a novel dietary assessment method for older adults "The NANA system".

DESIGN

Older and younger adults assessed the portion size of self-served portions of foods from a buffet style set up using traditional and computerised portion size assessment aids. Nutritionists assessed the portion size of foods from digital photographs using computerised portion size aids. These estimates were compared to known weights of foods using univariate analyses of covariance (ANCOVA).

SETTING

The University of Sheffield, United Kingdom.

SUBJECTS

Forty older adults (aged 65 years and over), 41 younger adults (aged between 18 and 40 years) and 25 nutritionists.

RESULTS

There was little difference in the abilities of older and younger adults to assess portion size using both assessment aids with the exception of small pieces morphology. Even though the methods were not directly comparable among the test groups, there was less variability in portion size estimates made by the nutritionists.

CONCLUSION

Older adults and younger adults are similar in their ability to assess food portion size and demonstrate wide variability of estimation compared to the ability of nutritionists to estimate portion size from photographs. The results suggest that the use of photographs of meals consumed for portion size assessment by a nutritionist may improve the accuracy of dietary assessment. Improved portion size assessment aids are required for all age groups.

Comparison of chronic physical and emotional social defeat stress effects on mesocorticolimbic circuit activation and voluntary consumption of morphine

Chronic social defeat stress (CSDS) is a well-established rodent model of depression that induces persistent social avoidance. CSDS triggers molecular adaptations throughout the mesocorticolimbic reward circuit, including changes in the activity of dopamine neurons in the ventral tegmental area (VTA), that may also influence drug reward. One limitation of traditional, physical CSDS (PS) is that injury complicates the study of opiate drugs like morphine. Thus, we sought to characterize a variation of CSDS, termed emotional CSDS (ES), that eliminates this confound. We assessed the effect of PS and ES on mesocorticolimbic circuit activation, VTA gene expression, and morphine intake. We found that PS and ES similarly induced ΔFosB in the hippocampus, but only PS significantly increased ΔFosB expression in the prefrontal cortex and striatum. In contrast, cFos expression was similarly reduced by both PS and ES. Interestingly, we found that PS and ES similarly increased voluntary morphine consumption immediately following stress, despite differences in the magnitude of the depressive phenotype and striatal ΔFosB expression at this time point. Combined, these data suggest that both stress paradigms may be useful for investigation of stress-induced changes in drug behavior.

Neural Substrates of Overgeneralized Conditioned Fear in PTSD

OBJECTIVE

Heightened generalization of fear from an aversively reinforced conditioned stimulus (CS+, a conditioned danger cue) to resembling stimuli is widely accepted as a pathogenic marker of posttraumatic stress disorder (PTSD). Indeed, a distress response to benign stimuli that "resemble" aspects of the trauma is a central feature of the disorder. To date, the link between overgeneralization of conditioned fear and PTSD derives largely from clinical observations, with limited empirical work on the subject. This represents the first effort to examine behavioral and brain indices of generalized conditioned fear in PTSD using systematic methods developed in animals known as generalization gradients: the gradual decline in conditioned responding as the presented stimulus gradually differentiates from CS+.

METHOD

Gradients of conditioned fear generalization were assessed using functional MRI and behavioral measures in U.S. combat veterans who served in Iraq or Afghanistan and had PTSD (N=26), subthreshold PTSD (N=19), or no PTSD (referred to as trauma control subjects) (N=17). Presented stimuli included rings of graded size, with extreme sizes serving as CS+ (paired with shock) and as a nonreinforced conditioned stimulus (CS-, a conditioned safety cue), and with intermediate sizes forming a continuum of similarity between CS+ and CS-. Generalization gradients were assessed as response slopes from CS+, through intermediate ring sizes, to CS-, with less steep slopes indicative of stronger generalization.

RESULTS

Relative to trauma control subjects, PTSD patients showed stronger conditioned generalization, as evidenced by less steep generalization gradients in both behavioral risk ratings and brain responses in the left and right anterior insula, left ventral hippocampus, dorsolateral and dorsomedial prefrontal cortex, and caudate nucleus. Severity of PTSD symptoms across the three study groups was positively correlated with levels of generalization at two such loci: the right anterior insula and left ventral hippocampus.

CONCLUSIONS

The results point to evidence of brain-based markers of overgeneralized fear conditioning related to PTSD. These findings provide further understanding of a central yet understudied symptom of trauma-related psychopathology.

A pilot study of dental students' esthetic perceptions of computer-generated mild dental fluorosis compared to other conditions

OBJECTIVES

Few studies have considered people's opinions about the esthetics of dental fluorosis. Assessments of fluorosis esthetics can be confounded by differences in a number of clinical factors, including tooth shape, color, contour, and gingival status. This pilot study compared esthetic perceptions of mild fluorosis and other conditions using computer-generated images made from a base set of normal appearing teeth.

METHODS

Entering dental students (n = 61) completed questionnaires about four sets of paired photographs. Three sets consisted of fluorotic teeth (very mild to mild) versus other conditions (diastema, isolated enamel opacity, "normal"/control) and the other pair compared two presentations of mild fluorosis (generalized versus limited to incisal one-third). Six questions, both qualitative and quantitative, were asked about each pair of photographs.

RESULTS

Mild fluorosis was assessed less favorably than normal/control, midline diastema was less favorable than mild fluorosis, and mild fluorosis was less favorable than isolated opacity.

CONCLUSIONS

This approach allows fluorosis to be better compared with other oral conditions because the images are standardized. Additional research with this method is warranted, including more variations in conditions, more comparisons, and other study populations.

Defining premature ejaculation for experimental and clinical investigations

Researchers investigating premature ejaculation (PE) have employed widely diverse definitions of it, thereby limiting progress in the field. This study summarizes available research on PE, notes patterns that emerge from these studies, compares patterns across several types of studies, and suggests a common model for defining PE groups to guide future research. We surveyed two bibliographic databases, identifying 45 studies employing a definition or description of a PE group. From these, we extracted a range of information, including descriptions of the participants, recruitment procedures, if PE subtypes were identified, operational criteria for PE classification, relationship and partner information, and additional inclusion/exclusion criteria. Over 50% of studies reported no criteria, or relied on simple self-identification by participants to establish the PE group. Quantifiable behavioral criteria were used in 49% of the studies, with ejaculatory latency reported most frequently. This measure was also used as a criterion more frequently in studies focusing on assessment of sexual response, whereas the number of penile thrusts was used more frequently in studies prior to 1989. Partner information was often included but seldom used as part of the assessment procedure. Progress on research and treatment of PE will continue to be limited by the absence of commonly accepted criteria for PE group membership and by a lack of identification of relevant PE subtypes and etiologies. This paper suggests a flowchart, based on data and a rational analysis of 40 years of research, for characterizing PE in ways that could assist the development of the field.

Effects of inactivation of the anterior interpositus nucleus on the kinematic and dynamic control of multijoint movement

We previously showed that inactivating the anterior interpositus nucleus in cats disrupts prehension; paw paths, normally straight and accurate, become curved, hypometric, and more variable. In the present study, we determined the joint kinematic and dynamic origins of this impairment. Animals were restrained in a hammock and trained to reach and grasp a cube of meat from a narrow food well at varied heights; movements were monitored using the MacReflex analysis system. The anterior interpositus nucleus was inactivated by microinjection of the GABA agonist muscimol (0.25-0.5 microgram in 0.5 microliter saline). For each joint, we computed the torque due to gravity, inertial resistance (termed self torque), interjoint interactions (termed interaction torque), and the combined effects of active muscle contraction and passive soft tissue stretch (termed generalized muscle torque). Inactivation produced significant reductions in the amplitude, velocity, and acceleration of elbow flexion. However, these movements continued to scale normally with target height. Shoulder extension was reduced by inactivation but wrist angular displacement and velocity were not. Inactivation also produced changes in the temporal coordination between elbow, shoulder, and wrist kinematics. Dynamic analysis showed that elbow flexion both before and during inactivation was produced by the combined action of muscle and interaction torque, but that the timing depended on muscle torque. Elbow interaction and muscle torques were scaled to target height both before and during inactivation. Inactivation produced significant reductions in elbow flexor interaction and muscle torques. The duration of elbow flexor muscle torque was prolonged to compensate for the reduction in flexor interaction torque. Shoulder extension was produced by extensor interaction and muscle torques both before and during inactivation. Inactivation produced a reduction in shoulder extension, primarily by reduced interaction torque, but without compensation. Wrist plantarflexion, which occurred during elbow flexion, was driven by plantarflexor interaction and gravitational torques both before and during inactivation. Muscle torque acted in the opposite direction with a phase lead to restrain the plantarflexor interaction torque. During inactivation, there was a reduction in plantarflexor interaction torque and a loss of the phase lead of the muscle torque. Our findings implicate the C1/C3 anterior interpositus zone of the cerebellum in the anticipatory control of intersegmental dynamics during reaching, which zone is required for coordinating the motions of the shoulder and wrist with those of the elbow. In contrast, this cerebellar zone does not play a role in scaling the movement to match a target.

Differential effects of deep cerebellar nuclei inactivation on reaching and adaptive control

This study examined the effects of selective inactivation of the cerebellar nuclei in the cat on the control of multijoint trajectories and trajectory adaptation to avoid obstacles. Animals were restrained in a hammock and trained to perform a prehension task in which they reached to grasp a small cube of meat from a narrow food well. To examine trajectory adaptation, reaching was obstructed by placing a horizontal bar in the limb's path. Inactivation was produced by microinjection of the GABA agonist muscimol (0.25-1.0 microg in 1 microL saline). Fastigial nucleus inactivation produced a severe impairment in balance and in head and trunk control but no effect on reaching and grasping. Dentate inactivation slowed movements significantly and produced a significant increase in tip path curvature but did not impair reaching and grasping. Selective inactivation of the anterior and posterior interpositus nuclei did not impair grasping but severely decreased the accuracy of reaching movements and produced different biases in wrist and paw paths. Anterior interpositus inactivation produced movement slowing (wrist speed) and under-reaching to the food well. Wrist and tip paths showed anterior biases and became more curved. Also animals could no longer make anticipatory adjustments in limb kinematics to avoid obstructions but sensory-evoked corrective responses were preserved. Posterior interpositus inactivation produced a significant increase in wrist speed and overreaching. Wrist and tip paths showed a posterior bias and became more curved, although in a different way than during anterior interpositus inactivation. Posterior interpositus inactivation did not impair trajectory adaptation to reach over the obstacle. During inactivation of either interpositus nucleus, all measures of kinematic temporal and spatial variability increased with somewhat greater effects being produced by anterior interpositus inactivation. We discuss our results in relation to the hypothesis that anterior and posterior interpositus have different roles in trajectory control, related possibly to feed-forward use of cutaneous and proprioceptive inputs, respectively. The loss of adaptive reprogramming during anterior interpositus inactivation further suggests a role in motor learning. Comparison with results from our earlier motor cortical study shows that the distinctive impairments produced by inactivation of these two nuclei are similar to those produced by selective inactivation of different zones in the forelimb area of rostral motor cortex. Our findings are consistent with the hypothesis that there are separate functional output channels from the anterior and posterior interpositus nuclei to rostral motor cortex for distinct aspects of trajectory control and, from anterior interpositus alone, for trajectory adaptation.

A pilot study of esthetic perceptions of dental fluorosis vs. selected other dental conditions

The prevalence of fluorosis has increased over the past fifty years, and with this increase, esthetic concerns pertaining to fluorosis should also be taken into consideration. Canadian, Australian, and British studies have explored perceptions concerning enamel fluorosis, but no studies in this area have been published from the United States. In the previous studies, esthetic concerns resulting from fluorosis generally were not compared with the esthetic perceptions of other conditions such as isolated opacities, tetracycline staining, or various types of malocclusion. In the present investigation, respondents answered written questions about paired photographs, one of fluorotic teeth and the other with one of the other conditions. Results show that not only is fluorosis noticeable, but it may be more of an esthetic concern than the other conditions.

The treatment of premature ejaculation: Psychological and biological strategies

This review provides criteria for defining premature ejaculation (PE) and identifying men with this dysfunction. Included are discussions of possible PE subtypes and causes of PE. Furthermore, two empirically supported cognitive-behavioral approaches for treating PE are described and salient issues surrounding these types of treatment are considered. Biologically based treatments available to PE men are presented, with attention to the relative effectiveness and limitations of the various alternatives. Finally, a model illustrating factors relevant to determining the best therapeutic strategy is described, concluding with a brief discussion of the value of combining biological and psychological modes of treatment.

Genital and psychoaffective response to erotic stimulation in sexually functional and dysfunctional men

To understand the sexual response patterns of men with premature ejaculation and erectile dysfunction, the authors compared genital and affective responses of sexually functional and dysfunctional men with 3 types of sexual stimulation: an erotic video, penile vibrotactile stimulation, and a combination of both. Genital response differed across both groups and stimulus conditions, with an interactive effect indicating that groups showed different response patterns depending on the stimulation. Affective responses also differed across groups and interacted with stimulus conditions. The combination genital and affective response was superior to either alone in distinguishing men with no sexual problems from those with erectile or ejaculatory problems (or both). These factors were particularly useful in discriminating men with premature ejaculation from those with combined premature ejaculation and erectile dysfunction.

A preliminary investigation of affective and cognitive response to erotic stimulation in men before and after sex therapy

Affective and cognitive responses to erotic stimulation were studied in sexually dysfunctional men before and after treatment in a sex therapy program. A comparison group of functional men was studied over the same time interval. A pool of 34 Likert-scaled items assessing various cognitions, affects, and perceptions was administered during baseline and following two erotic audiotapes and a self-generated sexual fantasy. To focus on global response patterns rather than individual item responses, five aggregate indices (sexual arousal, physicality, sensuality, negative affect, positive affect) were derived using a strategy that combined face-validity and reliability analysis. Cluster analysis was employed as an auxiliary technique to confirm the coherence of these groupings. All five indices differentiated dysfunctional men from controls, and further, three indices (physicality, sensuality, sexual arousal) showed significant variation across types of erotic stimulation. Correlations among the five indices, as well as with penile response, revealed two trends that differentiated dysfunctional men from controls during the pretest, but that diminished following sex therapy in the dysfunctional men. Future investigations might further rely on multiple-item indices as described here. Such measures may provide a more integrated view of sexual response in the laboratory and lead to greater understanding of affective and perceptual differences between functional and dysfunctional men.

Kinematic analysis of reaching in the cat

The present study examines the kinematic features of forelimb movements made by cats reaching for food in horizontal target wells located at different heights and distances. Wrist paths consisted of two relatively straight segments joined at a "via-point" in front of the aperture of the food well. In the initial lift phase, the paw was raised to the via-point in front of the target. In the second, or thrust phase, the paw was directed forward into the food well. During the lift, the paw was moved toward the target primarily by elbow flexion, accompanied by a sequence of biphasic shoulder and wrist movements. Thrust was accomplished primarily by shoulder flexion while the wrist and the paw were maintained at near-constant angles. The animals varied the height of the reach primarily by varying elbow flexion with proportional changes in elbow angular velocity and angular acceleration and with corresponding variations in wrist speed. Thus, cats reached for targets at different heights by scaling a common kinematic profile. Over a relatively large range of target heights, animals maintained movement duration constant, according to a simple "pulse-height" control strategy (isochronous scaling). For reaches to a given target height, animals compensated for variability in peak acceleration by variations in movement time. We examined the coordination between the shoulder and the wrist with the elbow. Early during the lift, peak shoulder extensor and peak elbow flexor accelerations were synchronized. Late during the lift phase, wrist extensor acceleration was found to occur during the period of elbow flexor deceleration. We hypothesize that these linkages could, in part, be due to passive mechanical interactions. To determine how the angular trajectories of the different joints were organized in relation to target location, we plotted joint kinematic changes directly on the wrist and MCP joint paths. These plots revealed that for all target heights and movement speeds, wrist extensor deceleration occurred at approximately the same spatial location with respect to the target. This analysis also demonstrated that the second phase of MCP flexion occurred when the paw was below the lower lip of the food well, while the subsequent extension occurred after the tip cleared this obstacle. During thrust, wrist and MCP angles were maintained, reflecting the need to align the paw within the food well. Our findings suggest that cats plan the reaching phase of prehension as a sequence of discrete movement segments, each serving a particular goal in the task, rather than as an single unit.

Accuracy of planar reaching movements. II. Systematic extent errors resulting from inertial anisotropy

This study examines the source of direction-dependent errors in movement extent made by human subjects in a reaching task. As in the preceding study, subjects were to move a cursor on a digitizing tablet to targets displayed on a computer monitor. Movements were made without concurrent visual feedback of cursor position, but movement paths were displayed on the monitor after the completion of each movement. We first examined horizontal hand movements made at waist level with the upper arm in a vertical orientation. Targets were located at five distances and two directions (30 degrees and 150 degrees) from one of two initial positions. Trajectory shapes were stereotyped, and movements to more distant targets had larger accelerations and velocities. Comparison of movements in the two directions showed that in the 30 degrees direction responses were hypermetric, accelerations and velocities were larger, and movement times were shorter. Since movements in the 30 degrees direction required less motion of the upper arm than movements in the 150 degrees direction, we hypothesized that the differences in accuracy and acceleration reflected a failure to take into account the difference in total limb inertia in the two directions. To test this hypothesis we simulated the initial accelerations of a two-segment limb moving in the horizontal plane with the hand at shoulder level when a constant force was applied at the hand in each of 24 directions. We compared these simulated accelerations to ones produced by our subjects with their arms in the same position when they aimed movements to targets in the 24 directions and at equal distances from an initial position. The magnitudes of both simulated and actual accelerations were greatest in the two directions perpendicular to the forearm, where inertial resistance is least, and lowest for movements directed along the axis of the forearm. In all subjects, the directional variation in peak acceleration was similar to that predicted by the model and shifted in the same way when the initial position of the hand was displaced. The pattern of direction-dependent variations in initial acceleration did not depend on the speed of movement. It was also unchanged when subjects aimed their movements toward targets presented within the workspace on the tablet instead of on the computer monitor. These findings indicate that, in programming the magnitude of the initial force that will accelerate the hand, subjects do not fully compensate for direction dependent differences in inertial resistance.(ABSTRACT TRUNCATED AT 400 WORDS)

Differential effects of local inactivation within motor cortex and red nucleus on performance of an elbow task in the cat

This study examined changes in the performance of a single-joint, elbow task produced by reversible inactivation of local regions within the proximal forelimb representation in area 4 gamma of motor cortex (MCx) and the red nucleus (RN) of the cat. Inactivation was carried out by microinjecting lidocaine, gamma-aminobutyric acid, or muscimol into sites where microstimulation evoked contraction of elbow muscles. Reaction time, amplitude, and speed (velocity or dF/dt) of position and force responses elicited during inactivation were compared to control values obtained immediately prior to inactivation. In addition, we assessed qualitatively the effects of inactivation on reaching, placing reactions, and proprioceptive responses to imposed limb displacement. In the single-joint task, injections in MCx did not increase reaction time (simple or choice) and produced modest and inconsistent reductions in response amplitude (mean -8%) and speed (mean -19%). In contrast, injections of the same amounts of inactivating agents in the forelimb representation of RN consistently increased reaction time (34.4%), and increased the reaction time coefficient of variability (32%). There were small reductions in response amplitude (-4%) and speed (-10%) which were less than those produced by MCx inactivation. During reaching, however, these same injections in MCx and RN produced a substantial loss of accuracy. For MCx, this was due, in part, to systematic hypometria: for RN, inaccuracy resulted from increased variability in paw paths. Placing reactions and corrective responses to imposed limb displacements were also depressed by the cortical and rubral injections. Our results suggest that the forelimb representation in RN plays a role in the initiation of the single-joint, elbow tracking response examined here. The RN may mediate cerebellar regulation of response timing, a function that is likely to be important for interjoint coordination. Although neurons in the forelimb representations of MCx may contribute to force generation in single-joint movements, their contribution to multijoint control appears to be more important and is examined in the subsequent report (Martin and Ghez 1993).

The influence of self-concept on outcomes of intensive alcoholism treatment

The hypothesis that self-concept is a valid measure of the outcome of alcoholism treatment was supported, but the hypothesis that self-concept is a predictor of treatment success was not supported.

Survey of studies on alcoholism

The goal of this article is to provide a broad and updated review of the major research studies on alcoholism, and it is intended especially for those who are new to the area or whose work in it is limited. It is primarily an update and extension of the literature review presented by Armor, Polich, and Stambul in their 1978 book Alcoholism and Treatment.