Impaired recognition of fear facial expressions in 5-HTTLPR S-polymorphism carriers following tryptophan depletion

Neurotransmitter modulation of human facial emotion recognition

Human facial emotion recognition (FER) is an evolutionarily preserved process that influences affiliative behaviours, approach/avoidance and fight-or-flight responses in the face of detecting threat cues, thus enhancing adaptation and survival in social groups. Here, we provide a narrative literature review on how human FER is modulated by neurotransmitters and pharmacological agents, classifying the documented effects by central neurotransmitter systems. Synthesising the findings from studies involving functional neuroimaging and FER tasks, we highlight several emerging themes; for example, noradrenaline promotes an overall positive bias in FER, while serotonin, dopamine and gamma-aminobutyric acid modulate emotions relating to self-preservation. Finally, other neurotransmitters including the cholinergic and glutamatergic systems are responsible for rather non-specific pro-cognitive effects in FER. With the ongoing accumulation of evidence further characterising the individual contributions of each neurotransmitter system, we argue that a sensible next step would be the integration of experimental neuropharmacology with computational models to infer further insights into the temporal dynamics of different neurotransmitter systems modulating FER.

Alteration of the α5 GABA receptor and 5HTT lead to cognitive deficits associated with major depressive-like behaviors in a 14-day combined stress rat model

INTRODUCTION

Current models used to study the pathophysiology of major depressive disorder (MDD) are laborious and time consuming. This study examined the effect of a 14-day combined stress model (CS; corticosterone injection and restraint stress) in male Sprague-Dawley rats and also compare the effect of CS versus 28-day corticosterone treatment on depressive-like behaviour and cognitive deficits.

MATERIEL AND METHODS

Depressive-like behaviours and cognitive deficits were assessed in the forced swim test (FST), sucrose preference (SPT), Morris water maze (MWM) and novel object recognition (NORT) tests. Real-time PCR and ELISA were respectively used to detect expression of the serotonin transporter (5-HTT), serotonin 1 A receptor (5-HT1A), α5 GABAA receptor, and the concentrations of corticosterone (plasma), GABA and acetylcholinesterase (AChE) in the hippocampus and Prefrontal cortex (PFC).Results CS group showed increased immobility time in the FST, time to reach the MWM platform, higher corticosterone level, and increased expressions of hippocampal and PFC 5-HT1A and α5 GABAA receptors, and AChE compared to their control groups. In contrast, reductions in SPT ratio, discrimination index in NORT, time in target quadrant, and hippocampal 5-HTT expression was noted relative to their control group. Compared to the 28-day corticosterone only group, PFC 5-HT1A, Hippocampal 5-HTT were reduced, while PFC 5-HTT, Hippocampal α5 GABAA receptors, and AChE concentrations were higher in the CS group.

CONCLUSION

Our CS model induced depressive-like behaviour with early cognitive deficits in rats affecting both hippocampus and PFC. The CS model may be useful in investigating new and comprehensive treatment strategies for MDD.

Threat-Avoidance Tendencies Moderate the Link Between Serotonin Transporter Genetic Variation and Reactive Aggression

The short (S) allele of the serotonin transporter-linked promoter region (5-HTTLPR) polymorphism has been linked to reactive aggression in men, but this association is less consistent in females. Reactive aggression has been particularly described as a result of fear-driven defense to threat, but how this interaction between defensive behavior and aggression is expressed in S-allele carriers remains unknown. In order to explore this interplay between 5-HTTLPR genotype, defensive behavior and reactive aggression, we combined genotyping with objective measures of action tendencies toward angry faces in an approach-avoidance task (AAT) and reactive aggression in the Taylor aggression paradigm (TAP) in healthy females, N = 95. This study shows that female S-allele carriers in general display increased implicit reactive aggression (administering aversive white noise) toward opponents. Furthermore, we found that threat-avoidance tendencies moderate the association between 5-HTTLPR genotype and aggression displayed on the TAP. Together, these findings indicate a positive correlation between avoidance of angry faces in the AAT and reactive aggression in the TAP exclusively present in S-allele carriers.

Psychological mechanisms and functions of 5-HT and SSRIs in potential therapeutic change: Lessons from the serotonergic modulation of action selection, learning, affect, and social cognition

Uncertainty regarding which psychological mechanisms are fundamental in mediating SSRI treatment outcomes and wide-ranging variability in their efficacy has raised more questions than it has solved. Since subjective mood states are an abstract scientific construct, only available through self-report in humans, and likely involving input from multiple top-down and bottom-up signals, it has been difficult to model at what level SSRIs interact with this process. Converging translational evidence indicates a role for serotonin in modulating context-dependent parameters of action selection, affect, and social cognition; and concurrently supporting learning mechanisms, which promote adaptability and behavioural flexibility. We examine the theoretical basis, ecological validity, and interaction of these constructs and how they may or may not exert a clinical benefit. Specifically, we bridge crucial gaps between disparate lines of research, particularly findings from animal models and human clinical trials, which often seem to present irreconcilable differences. In determining how SSRIs exert their effects, our approach examines the endogenous functions of 5-HT neurons, how 5-HT manipulations affect behaviour in different contexts, and how their therapeutic effects may be exerted in humans - which may illuminate issues of translational models, hierarchical mechanisms, idiographic variables, and social cognition.

No evidence for the involvement of serotonin or the 5-HTTLPR genotype in intertemporal choice in a larger community sample

BACKGROUND

Serotonin has been implicated in impulsive behaviours such as temporal discounting. While animal studies and theoretical approaches suggest that reduced tonic serotonin levels increase temporal discounting rates and vice versa, evidence from human studies is scarce and inconclusive. Furthermore, an important modulator of serotonin signalling, a genetic variation in the promoter region of the serotonin transporter gene (5-HTTLPR), has not been investigated for temporal discounting so far.

OBJECTIVE

First, the purpose of this study was to test for a significant association between 5-HTTLPR and temporal discounting. Second, we wished to investigate the effect of high/low tonic serotonin levels on intertemporal choice and blood oxygen-level-dependent response, controlling for 5-HTTLPR.

METHODS

We tested the association of 5-HTTLPR with temporal discounting rates using an intertemporal choice task in 611 individuals. We then manipulated tonic serotonin levels with acute tryptophan interventions (depletion, loading, balanced) in a subsample of 45 short (S)-allele and 45 long (L)/L-allele carriers in a randomised double-blind crossover design using functional magnetic resonance imaging and an intertemporal choice task.

RESULTS

Overall, we did not find any effect of serotonin and 5-HTTLPR on temporal discounting rates or the brain networks associated with valuation and cognitive control.

CONCLUSION

Our findings indicate that serotonin may not be directly involved in choices including delays on longer timescales such as days, weeks or months. We speculate that serotonin plays a stronger role in dynamic intertemporal choice tasks where the delays are on a timescale of seconds and hence are therefore directly experienced during the experiment.

Differences in how macaques monitor others: Does serotonin play a central role?

Primates must balance the need to monitor other conspecifics to gain social information while not losing other resource opportunities. We consolidate evidence across the fields of primatology, psychology, and neuroscience to examine individual, population, and species differences in how primates, particularly macaques, monitor conspecifics. We particularly consider the role of serotonin in mediating social competency via social attention, aggression, and dominance behaviors. Finally, we consider how the evolution of variation in social tolerance, aggression, and social monitoring might be explained by differences in serotonergic function in macaques. This article is categorized under: Economics > Interactive Decision-Making Psychology > Comparative Psychology Neuroscience > Behavior Cognitive Biology > Evolutionary Roots of Cognition.

The genetic underpinnings of callous-unemotional traits: A systematic research review

BACKGROUND

Callous-unemotional (CU) traits represent the affective features of psychopathy used to delineate youth at high risk for externalizing pathology. The genetic etiology CU traits is not currently well-understood.

METHODS

The current review surveyed the literature for studies on the genetic underpinnings of CU traits and integrated information from 39 genetic studies.

RESULTS

The results from 24 studies with quantitative data suggest that the heritability for CU traits is likely between 36-67%. A majority of the 16 molecular genetic studies focused on candidate genes in the serotonin and oxytocin systems with results that have not been well replicated. Although two genome-wide association studies have been conducted, no genome-wide significant loci have been discovered.

DISCUSSION

There is some evidence to suggest that the serotonin and oxytocin systems may play a role in CU traits; however, there is currently not enough evidence to implicate specific genetic mechanisms. The authors encourage researchers to continue to apply the most up-to-date and relevant methodology, specifically collaborations and consortiums using genome-wide and polygenic methods.

Risk-seeking for losses is associated with 5-HTTLPR, but not with transient changes in 5-HT levels

RATIONALE

Serotonin (5-HT) plays a key role in different aspects of value-based decision-making. A recent framework proposed that tonic 5-HT (together with dopamine, DA) codes future average reward expectations, providing a baseline against which possible choice outcomes are compared to guide decision-making.

OBJECTIVES

To test whether high 5-HT levels decrease loss aversion, risk-seeking for gains, and risk-seeking for losses.

METHODS

In a first session, 611 participants were genotyped for 5-HTTLPR and performed a mixed gambles (MGA) task and two probability discounting tasks for gains and losses, respectively (PDG/PDL). Afterwards, a subsample of 105 participants (44 with S/S, 6 with S/L, 55 with L/L genotype) completed the pharmacological study using a crossover design with tryptophan depletion (ATD), loading (ATL), and balanced (BAL) conditions. The same decision constructs were assessed.

RESULTS

We found increased risk-seeking for losses in S/S compared to L/L individuals at the first visit (p = 0.002). Neither tryptophan depletion nor loading affected decision-making, nor did we observe an interaction between intervention and 5-HTTLPR genotype.

CONCLUSION

Our data do not support the idea that transient changes of tonic 5-HT affect value-based decision-making. We provide evidence for an association of 5-HTTLPR with risk-seeking for losses, independent of acute 5-HT levels. This indicates that the association of 5-HTTLPR and risk-seeking for losses is mediated via other mechanisms, possibly by differences in the structural development of neural circuits of the 5-HT system during early life phases.

The Neurodevelopmental Basis of Early Childhood Disruptive Behavior: Irritable and Callous Phenotypes as Exemplars

The arrival of the Journal's 175th anniversary occurs at a time of recent advances in research, providing an ideal opportunity to present a neurodevelopmental roadmap for understanding, preventing, and treating psychiatric disorders. Such a roadmap is particularly relevant for early-childhood-onset neurodevelopmental conditions, which emerge when experience-dependent neuroplasticity is at its peak. Employing a novel developmental specification approach, this review places recent neurodevelopmental research on early childhood disruptive behavior within the historical context of the Journal. The authors highlight irritability and callous behavior as two core exemplars of early disruptive behavior. Both phenotypes can be reliably differentiated from normative variation as early as the first years of life. Both link to discrete pathophysiology: irritability with disruptions in prefrontal regulation of emotion, and callous behavior with abnormal fear processing. Each phenotype also possesses clinical and predictive utility. Based on a nomologic net of evidence, the authors conclude that early disruptive behavior is neurodevelopmental in nature and should be reclassified as an early-childhood-onset neurodevelopmental condition in DSM-5. Rapid translation from neurodevelopmental discovery to clinical application has transformative potential for psychiatric approaches of the millennium. [AJP at 175: Remembering Our Past As We Envision Our Future November 1938: Electroencephalographic Analyses of Behavior Problem Children Herbert Jasper and colleagues found that brain abnormalities revealed by EEG are a potential causal factor in childhood behavioral disorders. (Am J Psychiatry 1938; 95:641-658 )].

[A role of interactions between N-methyl-D-aspartate and dopamine receptors in facial emotion recognition impairment in schizophrenia]

AIM

To search for genetic mechanisms of facial emotion recognition (FER) impairment, one of the features of schizophrenia that affects social adaptation of patients. Based on the view implicating the interplay between dopaminergic and glutamatergic systems into the pathogenesis of schizophrenia, authors explored the interaction effects of the C366G polymorphism in the GRIN2B gene encoding NMDA receptor subunit NR2B with ANKK1/DRD2 Taq1A and 48-VNTR DRD4 polymorphisms on FER.

MATERIAL AND METHODS

GRIN2B -DRD2 interaction effects were studied in a sample of 237 patients and 235 healthy controls, GRIN2B - DRD4 in 268 patients and 208 controls.

RESULTS AND CONCLUSION

Both effects were significant in combined samples of patients and controls (GRIN2B X DRD2, F=4.12, p=0.043; GRIN2B X DRD4, F=6.43, p=0.012). Further analysis confirmed the interaction effect of GRIN2B and DRD2 polymorphisms on FER in patients with schizophrenia. In patients with a less efficient allele of the DRD2 in the absence of the minor allele of the GRIN2B C366G polymorphism, the results were close to normal values while patients with minor alleles of both polymorphisms showed the worst results. This finding is in line with the conceptions on a possible role of NMDA-receptor hypofunction and D2-mediated regulation of NMDA-receptor activity in FER impairments in schizophrenia.

The pharmacological treatment of aggression in children and adolescents with conduct disorder. Do callous-unemotional traits modulate the efficacy of medication?

BACKGROUND

Children and adolescents with conduct disorder (CD) show repetitive and persistent patterns of aggressive behaviour and the more severe forms are often associated with callous-unemotional (CU) traits.

OBJECTIVES

To systematically review and, where data are adequate, conduct meta-analyses on the efficacy of medication on aggression in children and adolescent with CD considering the impact of CU traits.

RESULTS

Few studies have investigated patients with CD as primary diagnosis, and few of these have discriminated between different types of aggression or reported measures of CU traits. Methylphenidate and risperidone showed the largest effects on aggression in randomized controlled trials; other antipsychotics showed clinical efficacy on CD but this evidence is mainly revealed by open label trials. There is some low quality evidence to support a small effect of mood stabilizers and other agents. There were only two papers describing the effects of CU traits thus providing inconclusive results.

CONCLUSION

Considering heterogeneity of the disorder, more proof-of-concept clinical studies are needed to define effects of medication and role of CU traits.

Empathic accuracy and oxytocin after tryptophan depletion in adults at risk for depression

RATIONALE

Major depressive disorder (MDD) has been associated with disturbances in social functioning and in the brain serotonin system. Reduced levels of serotonin may negatively influence social functioning, for example by impairing the recognition of facial emotion expressions.

OBJECTIVES

The present study investigated the effect of acute tryptophan depletion (ATD), which reduces brain serotonin, on a related component of social functioning, empathic accuracy (EA), and oxytocin levels.

METHODS

Individuals with (FH+) and without (FH−) a family history of MDD participated in a randomized, double-blind, crossover study. On two separate test days, participants ingested tryptophan-deficient and nutritionally balanced amino acid mixtures. Six hours later, they performed an EA task, which involved watching videos of people recounting autobiographical emotional events. While watching, participants continuously rated how these people felt during the recounting. Mood state was repeatedly assessed using the Positive Affect and Negative Affect Schedule and a series of visual analogue scales. Blood samples obtained at baseline and 5 h after mixture ingestion were assessed for tryptophan and oxytocin levels.

RESULTS

ATD decreased circulating levels of tryptophan and oxytocin. Nevertheless, there were no significant effects of ATD on EA or mood in either FH group.

CONCLUSIONS

While previous studies have shown that acute reductions in brain serotonin alter the recognition of facial emotion expressions in never-depressed individuals, the present study suggests that empathic abilities may remain unaffected.

5-HTTLPR modulates the recognition accuracy and exploration of emotional facial expressions

Individual genetic differences in the serotonin transporter-linked polymorphic region (5-HTTLPR) have been associated with variations in the sensitivity to social and emotional cues as well as altered amygdala reactivity to facial expressions of emotion. Amygdala activation has further been shown to trigger gaze changes toward diagnostically relevant facial features. The current study examined whether altered socio-emotional reactivity in variants of the 5-HTTLPR promoter polymorphism reflects individual differences in attending to diagnostic features of facial expressions. For this purpose, visual exploration of emotional facial expressions was compared between a low (n = 39) and a high (n = 40) 5-HTT expressing group of healthy human volunteers in an eye tracking paradigm. Emotional faces were presented while manipulating the initial fixation such that saccadic changes toward the eyes and toward the mouth could be identified. We found that the low vs. the high 5-HTT group demonstrated greater accuracy with regard to emotion classifications, particularly when faces were presented for a longer duration. No group differences in gaze orientation toward diagnostic facial features could be observed. However, participants in the low 5-HTT group exhibited more and faster fixation changes for certain emotions when faces were presented for a longer duration and overall face fixation times were reduced for this genotype group. These results suggest that the 5-HTT gene influences social perception by modulating the general vigilance to social cues rather than selectively affecting the pre-attentive detection of diagnostic facial features.

The neurobiology of psychopathic traits in youths

Conduct disorder is a childhood behaviour disorder that is characterized by persistent aggressive or antisocial behaviour that disrupts the child's environment and impairs his or her functioning. A proportion of children with conduct disorder have psychopathic traits. Psychopathic traits consist of a callous-unemotional component and an impulsive-antisocial component, which are associated with two core impairments. The first is a reduced empathic response to the distress of other individuals, which primarily reflects reduced amygdala responsiveness to distress cues; the second is deficits in decision making and in reinforcement learning, which reflects dysfunction in the ventromedial prefrontal cortex and striatum. Genetic and prenatal factors contribute to the abnormal development of these neural systems, and social-environmental variables that affect motivation influence the probability that antisocial behaviour will be subsequently displayed.

Acute responsivity of the serotonergic system to S-citalopram and positive emotionality-the moderating role of the 5-HTTLPR

According to the idea that the central serotonergic system has a modulatory function on behavior and personality in general, we aimed to highlight its association to habitual positive emotionality. In a placebo-controlled double-blind and randomized cross-over neuroendocrine challenge design (n = 72 healthy males) we investigated the association of the central serotonergic responsivity, 5-HTTLPR-genotype as well as their combined effects on positive emotionality. Regression analyses revealed an involvement of the serotonergic system in positive emotionality. There was, however, no direct association between positive emotionality and cortisol responses to S-citalopram; rather 5-HTTLPR-genotype showed an association (p < 0.05). That is, positive emotionality scores increased with the number of s-alleles carried by the individuals. Most notable was the moderating role of 5-HTTLPR-genotype (p < 0.05) on the association between acute serotonergic responsivity and positive emotionality. Indeed, this association was only found in ss-homozygotes, in which the acute responsivity of the serotonergic system additionally seems to contribute to the level of positive emotionality (r = 0.70, p < 0.05). The findings correspond to previous research demonstrating that the 5-HTTLPR is not only involved in the negative-emotional aspects of behavior and temperament, but is associated, moreover, with positive affectivity-supporting the assumption of its valence-neutrality. In addition, our data are in line with the idea of possible influences of the 5-HTTLPR-genotype on early neuronal development. They also indicate the need for further studies in order to clearly elucidate the role of the serotonergic system and its subcomponents in the regulation of positive emotionality.

The effect of raising and lowering tryptophan levels on human mood and social behaviour

Acute tryptophan depletion (ATD) studies indicate that low serotonin can lower mood and also increase aggression, although results vary somewhat between studies with similar participants. Lowering of mood after ATD is related to the susceptibility of the study participants to clinical depression, and some participants show no effect on mood. This indicates that low serotonin can contribute to lowered mood, but cannot-by itself-cause lowered mood, unless other unknown systems interact with serotonin to lower mood. Studies using tryptophan supplementation demonstrate that increased serotonin can decrease quarrelsomeness and increase agreeableness in everyday life. Social interactions that are more agreeable and less quarrelsome are associated with better mood. Thus, serotonin may have direct effects on mood, but may also be able to influence mood through changes in social behaviour. The increased agreeableness and decreased quarrelsomeness resulting from increases in serotonin will help foster congenial relations with others and should help to increase social support. As social support and social isolation have an important relationship with both physical and mental health, more research is needed on the implications of the ability of serotonin to modulate social behaviour for the regulation of mood, and for future physical and mental health.

The neurobiology of oppositional defiant disorder and conduct disorder: altered functioning in three mental domains

This review discusses neurobiological studies of oppositional defiant disorder and conduct disorder within the conceptual framework of three interrelated mental domains: punishment processing, reward processing, and cognitive control. First, impaired fear conditioning, reduced cortisol reactivity to stress, amygdala hyporeactivity to negative stimuli, and altered serotonin and noradrenaline neurotransmission suggest low punishment sensitivity, which may compromise the ability of children and adolescents to make associations between inappropriate behaviors and forthcoming punishments. Second, sympathetic nervous system hyporeactivity to incentives, low basal heart rate associated with sensation seeking, orbitofrontal cortex hyporeactiviy to reward, and altered dopamine functioning suggest a hyposensitivity to reward. The associated unpleasant emotional state may make children and adolescents prone to sensation-seeking behavior such as rule breaking, delinquency, and substance abuse. Third, impairments in executive functions, especially when motivational factors are involved, as well as structural deficits and impaired functioning of the paralimbic system encompassing the orbitofrontal and cingulate cortex, suggest impaired cognitive control over emotional behavior. In the discussion we argue that more insight into the neurobiology of oppositional defiance disorder and conduct disorder may be obtained by studying these disorders separately and by paying attention to the heterogeneity of symptoms within each disorder.

Interactive effects of estrogen and serotonin on brain activation during working memory and affective processing in menopausal women

While cognitive changes and mood instability are frequent symptoms reported by menopausal women, the degree to which the decline in estrogen production is responsible is not yet clear. Several lines of evidence suggest that estrogen may produce its effects on cognition and mood through modulation of serotonergic function. To test this hypothesis, we used the tryptophan depletion (TD) paradigm to lower central serotonin levels and pharmacologically manipulated estrogen levels in healthy menopausal women. We examined the individual and combined effects of estradiol and serotonin on working memory, emotion processing and task-related brain activation. Eight healthy predominantly early postmenopausal women underwent TD or sham depletion followed by functional magnetic resonance imaging (fMRI) both before and after short-term transdermal estradiol 75-150 μg/d administration. There was an estradiol treatment by TD interaction for brain activation during performance on both the N-back Task (working memory) and Emotion Identification Task (affective processing). During the 2-back condition, TD attenuated activation prior to, but not after, estradiol treatment in the right and left dorsal lateral prefrontal and middle frontal/cingulate gyrus. During emotion identification, TD heightened activation in the orbital frontal cortex and bilateral amygdala, and this effect was attenuated by estradiol treatment. These results provide preliminary evidence that serotonergic effects directly mediate the impact of estrogen on brain activation during working memory and affective processing.

Affective cognition and its disruption in mood disorders

In this review, we consider affective cognition, responses to emotional stimuli occurring in the context of cognitive evaluation. In particular, we discuss emotion categorization, biasing of memory and attention, as well as social/moral emotion. We discuss limited neuropsychological evidence suggesting that affective cognition depends critically on the amygdala, ventromedial frontal cortex, and the connections between them. We then consider neuroimaging studies of affective cognition in healthy volunteers, which have led to the development of more sophisticated neural models of these processes. Disturbances of affective cognition are a core and specific feature of mood disorders, and we discuss the evidence supporting this claim, both from behavioral and neuroimaging perspectives. Serotonin is considered to be a key neurotransmitter involved in depression, and there is a considerable body of research exploring whether serotonin may mediate disturbances of affective cognition. The final section presents an overview of this literature and considers implications for understanding the pathophysiology of mood disorder as well as developing and evaluating new treatment strategies.

Maternal depressive history, teen 5HTTLPR genotype, and the processing of emotional faces: Exploring mechanisms of risk

Variations in the serotonin transporter gene (5HTTLPR) and biased processing of face-emotion displays both have been implicated in the transmission of depression risk, but little is known about developmental influences on these relationships. Within a community sample of adolescents, we examine whether 5HTTLPR genotype moderates the link between maternal depressive history and errors in face-emotion labeling. When controlling for current levels of depression and anxiety among youth, a two-way interaction between maternal depressive history and 5HTTLPR genotype was detected. Specifically, adolescents whose mothers reported a depressive history and who had a low expressing genotype made more errors in classifying emotional faces when compared with adolescents with an intermediate or high expressing genotype, with or without maternal depression history. These findings highlight the complex manner in which maternal depression and genetic risk may interact to predict individual differences in social information processing.

Recognizing emotions in faces: effects of acute tryptophan depletion and bright light

In healthy never-depressed individuals, acute tryptophan depletion (ATD) may selectively decrease the accurate recognition of fearful facial expressions. Here we investigated the perception of facial emotions after ATD in more detail. We also investigated whether bright light, which can reverse ATD's mood-lowering effect, can also reverse its effect on the perception of facial emotions. On two separate test days, spent in a room that was either bright (n = 14) or dim (n = 16), healthy never-depressed women completed a facial emotion perception task six hours after ingesting tryptophan-deficient and balanced amino acid mixtures. Treatments were administered double blind and in randomized order using a crossover design. In dim light ATD decreased recognition accuracy of anger, disgust, and surprise. The labeling of fear and sadness was not affected. In bright light no effects of ATD were seen. Bright light was identified as a potential confounding factor in task performance. The effects of ATD on facial emotion perception may be less emotion-specific than thought previously, and occurred in a direction opposite to what might be expected based on theories of mood-congruent bias.

Electrocortical effects of acute tryptophan depletion on emotive facial processing in depression-prone individuals

This study assessed the effects of acute tryptophan depletion (ATD), which transiently lowers CNS 5-HT, on electrocortical responses to facial expression processing in individuals with a family history of depression (FH+). Electroencephalograph (EEG)-derived event-related potentials (ERPs) were acquired from 18 FH+ individuals during a facial expression recognition task (neutral and sad, joy and surprise at 50% and 100% intensities). Both early positive (P1 and P2) and the face-specific N170 ERP components were differentially altered by emotional intensity and valence. Increased depression, confusion and total mood disturbance scores, and decreased calmness, were observed with ATD (versus placebo). ATD was also associated with enhanced P1 and P2 amplitudes for sad versus joyful expressions. The N170 was not modulated by treatment, but was affected by emotive valence. Therefore, ATD enhanced ERP-indexed early processing of sad facial expressions, and altered the processing of positive ones, in FH+ individuals.

Effects of acute tryptophan depletion on neural processing of facial expressions of emotion in humans

INTRODUCTION

Acute tryptophan depletion (ATD) temporarily lowers brain serotonin (5-HT) synthesis, and behavioral studies have shown that this alters the processing of facial expressions of emotion.

MATERIALS AND METHODS

The neural basis for these alterations is not known. Therefore, we employed ATD and event-related functional magnetic resonance imaging (fMRI) to examine neural responses during incidental processing of fearful, happy, sad, and disgusted facial expressions. Fourteen healthy male controls (age, 28 +/- 10) were scanned under both placebo (SHAM) and depletion (ATD) conditions.

RESULTS AND DISCUSSION

We predicted that ATD would be associated with changes in neural activity within facial emotion-processing networks. We found that serotonergic modulation did not affect performance on the fMRI tasks, but was associated with widespread effects on neural response to components of face processing networks for fearful, disgusted, and happy but not sad expressions across differing intensities.

CONCLUSION

Hence, the 5-HT system affects brain function (in 'limbic' and 'face processing' regions) during incidental processing of emotional facial expressions; but this varies with emotion type and intensities.

Development and validation of the high-quality 'rapid method for swab' to genotype the HTTLPR serotonin transporter (SLC6A4) promoter polymorphism

BACKGROUND

The importance of genetic variation to the etiology of neuropsychiatric disorders is well established and is currently being examined for diagnosis and treatment. The most popular method of obtaining material for genotype analysis, high-yielding DNA extraction from blood, has several limitations, including invasiveness, need for skilled individuals to collect material, and requirement for cold storage. Saliva sampling is noninvasive and trained personnel are less necessary, but it still requires a relatively high level of subject compliance. Buccal mucosa cells sampling is almost completely noninvasive, reducing compliance issues significantly. Samples collected have been shown to produce usable DNA after shipment through conventional mail. The DNA produced by rapid elution of these swabs in chaotropic buffers is, however, of limited quality and low purity.

OBJECTIVE

Our aim was to develop a rapid, economical, and environmentally safe method for extraction of high-quality genomic DNA, which can be used to determine clinically important genotypes from trace quantity samples and which has sufficient yield for multiple assays.

METHODS

We developed a method of extracting high-quality genomic DNA from buccal swab, which we termed the 'rapid method for swab' (RMS). We compared RMS with two established procedures, specifically the original rapid method and the commercially available Buccal Amp method. We assessed the generated genomic DNAs by their (i) quality, (ii) quantity, (iii) restriction enzyme digestibility, and (iv) PCR-based genotyping in addition to time, cost, and environmental impact of the procedures.

MAIN RESULTS

DNA generated by RMS was of higher purity than that by Buccal Amp. RMS is nonenzymatic and does not use strong chaotropic salts or extreme pH. We also showed the suitability of RMS-DNA for LA/LG genotyping as generated by PCR using 7-deaza-dGTP.

CONCLUSION

The RMS procedure is novel, efficient, safe, and yields sufficient material for multiple genotyping analyses. The RMS produces DNA of high quality from a single human buccal swab. RMS is a noninvasive technique and particularly suitable for children and older individuals and in field collection settings.

Differential effects of 5-HTTLPR genotypes on mood, memory, and attention bias following acute tryptophan depletion and stress exposure

RATIONALE

Polymorphisms of the serotonin transporter gene (5-HTTLPR) may be associated with increased vulnerability to acute tryptophan depletion (ATD) and depression vulnerability especially following stressful life events.

OBJECTIVE

The aim of the present study was to investigate the effects of ATD in subjects with different 5-HTTLPR profiles before and after stress exposure on affective and cognitive-attentional changes.

MATERIALS AND METHODS

Eighteen subjects with homozygotic short alleles (S'/S') and 17 subjects with homozygotic long alleles (L'/L') of the 5-HTTLPR participated in a double-blind, placebo-controlled, crossover design to measure the effects of ATD on mood, memory, and attention before and after acute stress exposure.

RESULTS

ATD lowered mood in all subjects independent of genotype. In S'/S' genotypes, mild acute stress increased depressive mood and in L'/L' genotypes increased feelings of vigor. Furthermore, S'/S' genotypes differed from L'/L' genotypes on measures of attention independent of treatment and memory following ATD.

CONCLUSIONS

Polymorphisms of the 5-HTTLPR differentially affect responses to mild stress and ATD, suggesting greater vulnerability of S'/S' carriers to serotonergic manipulations and supporting increased depression vulnerability.

Antagonism of serotonergic 5-HT2A/2C receptors: mutual improvement of sleep, cognition and mood?

Serotonin [5-hydroxytryptamine (5-HT)] and 5-HT receptors are involved in sleep and in waking functions such as cognition and mood. Animal and human studies support a particular role for the 5-HT(2A) receptor in sleep, which has led to renewed interest in this receptor subtype as a target for the development of novel pharmacological agents to treat insomnia. Focusing primarily on findings in healthy human volunteers, a review of the available data suggests that antagonistic interaction with 5-HT(2A) receptors (and possibly also 5-HT(2C) receptors) prolongs the duration of slow wave sleep and enhances low-frequency (< 7 Hz) activity in the sleep electroencephalogram (EEG), a widely accepted marker of sleep intensity. Despite certain differences, the changes in sleep and the sleep EEG appear to be remarkably similar to those of physiologically more intense sleep after sleep deprivation. It is currently unclear whether these changes in sleep are associated with improved vigilance, cognition and mood during wakefulness. While drug-induced interaction with sleep must be interpreted cautiously, too few studies are available to provide a clear answer to this question. Moreover, functional relationships between sleep and waking functions may differ between healthy controls and patients with sleep disorders. A multimodal approach investigating subjective and objective aspects of sleep and wakefulness provides a promising research avenue for shedding light on the complex relationships among 5-HT(2A/2C) receptor-mediated effects on sleep, the sleep EEG, cognition and mood in health and various diseases associated with disturbed sleep and waking functions.

CNTRICS final task selection: social cognitive and affective neuroscience-based measures

This article describes the results and recommendations of the third Cognitive Neuroscience Treatment Research to Improve Cognition in Schizophrenia meeting related to measuring treatment effects on social and affective processing. At the first meeting, it was recommended that measurement development focuses on the construct of emotion identification and responding. Five Tasks were nominated as candidate measures for this construct via the premeeting web-based survey. Two of the 5 tasks were recommended for immediate translation, the Penn Emotion Recognition Task and the Facial Affect Recognition and the Effects of Situational Context, which provides a measure of emotion identification and responding as well as a related, higher level construct, context-based modulation of emotional responding. This article summarizes the criteria-based, consensus building analysis of each nominated task that led to these 2 paradigms being recommended as priority tasks for development as measures of treatment effects on negative symptoms in schizophrenia.

Acute tryptophan depletion dose dependently impairs object memory in serotonin transporter knockout rats

RATIONALE

Acute tryptophan depletion (ATD) transiently lowers central serotonin levels and can induce depressive mood states and cognitive defects. Previous studies have shown that ATD impairs object recognition in rats.

OBJECTIVES

As individual differences exist in central serotonin neurotransmission, the impact of ATD may vary accordingly. In this experiment, we investigated the hypothesis that male serotonin transporter knockout (SERT(-/-)), rats marked by a lower SERT function, are more vulnerable to the effects of ATD in an object recognition task than male wildtype (SERT(+/+)) and heterozygous (SERT(+/-)) rats.

MATERIALS AND METHODS

Twelve male SERT(+/+), SERT(+/-), and SERT(-/-) rats were treated with standard dose and low-dose ATD using a gelatine-based protein-carbohydrate mixture lacking tryptophan. In the control treatment, L: -tryptophan was added to the mixture. Four hours after treatment, the rats were subjected to the object recognition task. In addition, the effects of ATD on plasma amino acid concentrations were measured, and concentrations of 5-HT and 5-HIAA were measured in the frontal cortex and hippocampus of these rats.

RESULTS

Plasma TRP levels and central 5-HT and 5-HIAA levels were decreased in all genotypes after ATD, but effects were stronger in SERT(-/-) rats. The standard dose of ATD impaired object recognition in all genotypes. SERT(-/-) and SERT(+/-) rats were more vulnerable to low dose of ATD in the object recognition task compared to SERT(+/+) rats.

CONCLUSIONS

These results indicate a greater sensitivity to ATD in SERT(-/-) and SERT(+/-) rats, which may be related to stronger central depletion effects in these rats.

Serotonergic modulation of face-emotion recognition

Facial expressions of basic emotions have been widely used to investigate the neural substrates of emotion processing, but little is known about the exact meaning of subjective changes provoked by perceiving facial expressions. Our assumption was that fearful faces would be related to the processing of potential threats, whereas angry faces would be related to the processing of proximal threats. Experimental studies have suggested that serotonin modulates the brain processes underlying defensive responses to environmental threats, facilitating risk assessment behavior elicited by potential threats and inhibiting fight or flight responses to proximal threats. In order to test these predictions about the relationship between fearful and angry faces and defensive behaviors, we carried out a review of the literature about the effects of pharmacological probes that affect 5-HT-mediated neurotransmission on the perception of emotional faces. The hypothesis that angry faces would be processed as a proximal threat and that, as a consequence, their recognition would be impaired by an increase in 5-HT function was not supported by the results reviewed. In contrast, most of the studies that evaluated the behavioral effects of serotonin challenges showed that increased 5-HT neurotransmission facilitates the recognition of fearful faces, whereas its decrease impairs the same performance. These results agree with the hypothesis that fearful faces are processed as potential threats and that 5-HT enhances this brain processing.

The role of 5-HTTLPR in choosing the lesser of two evils, the better of two goods: examining the impact of 5-HTTLPR genotype and tryptophan depletion in object choice

RATIONALE

The serotonin (5-HT) system is considered important for decision-making. However, its role in reward- and punishment-based processing has not yet been clearly determined.

OBJECTIVES

The present study examines the effect of 5-HTTLPR genotype and tryptophan depletion on reward- and punishment-related processing, using a task that considers decision-making in situations of subtlety of choice. Thus, it considers that response choice often occurs in situations where both options are desirable (e.g., choosing between mousse au chocolat or crème caramel cheesecake from a menu) or undesirable. It also considers that response choice is easier when the reinforcements associated with the options are far apart, rather than close, in value.

MATERIALS AND METHODS

Healthy volunteers underwent acute tryptophan depletion (ATD) or control procedures and genotyping of the 5-HTTLPR for long and short allele variants. We then examined the effects and interactions of ATD and the serotonin promoter polymorphism genotype on two aspects of decision-making: (a) decision form, choosing between two objects to gain the greater reward or lesser punishment and (b) between-object reinforcement distance, the difference in reinforcements associated with two options.

RESULTS

ATD and LL homozygosity had comparable interactions with decision form and between-object reinforcement distance. Specifically, both modulated the effect of between-object reinforcement distance when deciding between objects both associated with punishment. Moreover, ATD and genotype interacted with ATD disproportionately affecting the performance of the LL homozygous group.

CONCLUSIONS

These results suggest that serotonin is particularly associated with punishment, rather than reward-related processing, and that individual sensitivity to punishment-related information and tryptophan depletion varies with genotype.