Acute SSRI administration affects the processing of social cues in healthy volunteers

Fluoxetine (prozac) and serotonin act on excitatory synaptic transmission to suppress single layer 2/3 pyramidal neuron-triggered cell assemblies in the human prefrontal cortex

Selective serotonin reuptake inhibitors are the most widely prescribed drugs targeting the CNS with acute and chronic effects in cognitive, emotional and behavioral processes. This suggests that microcircuits of the human cerebral cortex are powerfully modulated by selective serotonin reuptake inhibitors, however, direct measurements of serotonergic regulation on human synaptic interactions are missing. Using multiple whole-cell patch-clamp recordings from neurons in acute cortical slices derived from nonpathological human samples of the prefrontal cortex, we show that neuronal assemblies triggered by single action potentials of individual neurons in the human cortex are suppressed by therapeutic doses of fluoxetine (Prozac). This effect is boosted and can be mimicked by physiological concentrations of serotonin through 5HT-2A and 5HT-1A receptors. Monosynaptic excitatory connections from pyramidal cells to interneurons were suppressed by application of serotonin leaving the monosynaptic output of GABAergic cells unaffected. Changes in failure rate, in paired-pulse ratio, and in the coefficient of variation of the amplitude of EPSPs suggest a presynaptic action of serotonin. In conclusion, activation of neuronal assemblies, which were suggested as building blocks of high order cognitive processes, are effectively downregulated by the acute action of selective serotonin reuptake inhibitors or serotonin at the site of pyramidal output in human microcircuits.

The NMDA antagonist ketamine and the 5-HT agonist psilocybin produce dissociable effects on structural encoding of emotional face expressions

RATIONALE

Both glutamate and serotonin (5-HT) play a key role in the pathophysiology of emotional biases. Recent studies indicate that the glutamate N-methyl-D-aspartate (NMDA) receptor antagonist ketamine and the 5-HT receptor agonist psilocybin are implicated in emotion processing. However, as yet, no study has systematically compared their contribution to emotional biases.

OBJECTIVES

This study used event-related potentials (ERPs) and signal detection theory to compare the effects of the NMDA (via S-ketamine) and 5-HT (via psilocybin) receptor system on non-conscious or conscious emotional face processing biases.

METHODS

S-ketamine or psilocybin was administrated to two groups of healthy subjects in a double-blind within-subject placebo-controlled design. We behaviorally assessed objective thresholds for non-conscious discrimination in all drug conditions. Electrophysiological responses to fearful, happy, and neutral faces were subsequently recorded with the face-specific P100 and N170 ERP.

RESULTS

Both S-ketamine and psilocybin impaired the encoding of fearful faces as expressed by a reduced N170 over parieto-occipital brain regions. In contrast, while S-ketamine also impaired the encoding of happy facial expressions, psilocybin had no effect on the N170 in response to happy faces.

CONCLUSION

This study demonstrates that the NMDA and 5-HT receptor systems differentially contribute to the structural encoding of emotional face expressions as expressed by the N170. These findings suggest that the assessment of early visual evoked responses might allow detecting pharmacologically induced changes in emotional processing biases and thus provides a framework to study the pathophysiology of dysfunctional emotional biases.

The neurobiology of depression and antidepressant action

We present a comprehensive overview of the neurobiology of unipolar major depression and antidepressant drug action, integrating data from affective neuroscience, neuro- and psychopharmacology, neuroendocrinology, neuroanatomy, and molecular biology. We suggest that the problem of depression comprises three sub-problems: first episodes in people with low vulnerability ('simple' depressions), which are strongly stress-dependent; an increase in vulnerability and autonomy from stress that develops over episodes of depression (kindling); and factors that confer vulnerability to a first episode (a depressive diathesis). We describe key processes in the onset of a 'simple' depression and show that kindling and depressive diatheses reproduce many of the neurobiological features of depression. We also review the neurobiological mechanisms of antidepressant drug action, and show that resistance to antidepressant treatment is associated with genetic and other factors that are largely similar to those implicated in vulnerability to depression. We discuss the implications of these conclusions for the understanding and treatment of depression, and make some strategic recommendations for future research.

Psilocybin biases facial recognition, goal-directed behavior, and mood state toward positive relative to negative emotions through different serotonergic subreceptors

BACKGROUND

Serotonin (5-HT) 1A and 2A receptors have been associated with dysfunctional emotional processing biases in mood disorders. These receptors further predominantly mediate the subjective and behavioral effects of psilocybin and might be important for its recently suggested antidepressive effects. However, the effect of psilocybin on emotional processing biases and the specific contribution of 5-HT2A receptors across different emotional domains is unknown.

METHODS

In a randomized, double-blind study, 17 healthy human subjects received on 4 separate days placebo, psilocybin (215 μg/kg), the preferential 5-HT2A antagonist ketanserin (50 mg), or psilocybin plus ketanserin. Mood states were assessed by self-report ratings, and behavioral and event-related potential measurements were used to quantify facial emotional recognition and goal-directed behavior toward emotional cues.

RESULTS

Psilocybin enhanced positive mood and attenuated recognition of negative facial expression. Furthermore, psilocybin increased goal-directed behavior toward positive compared with negative cues, facilitated positive but inhibited negative sequential emotional effects, and valence-dependently attenuated the P300 component. Ketanserin alone had no effects but blocked the psilocybin-induced mood enhancement and decreased recognition of negative facial expression.

CONCLUSIONS

This study shows that psilocybin shifts the emotional bias across various psychological domains and that activation of 5-HT2A receptors is central in mood regulation and emotional face recognition in healthy subjects. These findings may not only have implications for the pathophysiology of dysfunctional emotional biases but may also provide a framework to delineate the mechanisms underlying psylocybin's putative antidepressant effects.

Using an experimental medicine model to understand the antidepressant potential of the N-Methyl-D-aspartic acid (NMDA) receptor antagonist memantine

There is growing interest in the role of the glutamatergic system both in depression and as a novel target for treatments. Preclinical studies suggested that the non-competitive N-Methyl-D-aspartic acid (NMDA) receptor antagonist memantine might have antidepressant properties, but a randomised controlled trial failed to support this. A healthy volunteer model of emotional processing was used to assess the neuropsychological profile of action of memantine. Healthy volunteers (n=32) were randomised to receive a single dose of memantine (10 mg) or placebo, and subsequently completed a battery of tasks measuring emotional processing, including facial expression recognition, emotional memory, dot-probe and emotion-potentiated startle tasks, as well as working and verbal memory. Memantine treated volunteers showed an increased emotion-potentiated startle, and a reduced bias for negative items in emotional recognition memory. There were no effects of the drug on any other aspect of emotional or non-emotional information processing. These results suggest that a single dose of memantine produces an early anxiogenic response in the emotion-potentiated startle similar to that seen following a single dose of the selective serotonin reuptake inhibitor, citalopram. However, the overall profile of effects is more limited than that which might be expected in response to a conventional antidepressant.

Effects of delta-9-tetrahydrocannabinol on evaluation of emotional images

There is growing evidence that drugs of abuse alter processing of emotional information in ways that could be attractive to users. Our recent report that Δ⁹-tetrahydrocannabinol (THC) diminishes amygdalar activation in response to threat-related faces suggests that THC may modify evaluation of emotionally-salient, particularly negative or threatening, stimuli. In this study, we examined the effects of acute THC on evaluation of emotional images. Healthy volunteers received two doses of THC (7.5 and 15 mg; p.o.) and placebo across separate sessions before performing tasks assessing facial emotion recognition and emotional responses to pictures of emotional scenes. THC significantly impaired recognition of facial fear and anger, but it only marginally impaired recognition of sadness and happiness. The drug did not consistently affect ratings of emotional scenes. THC's effects on emotional evaluation were not clearly related to its mood-altering effects. These results support our previous work, and show that THC reduces perception of facial threat. Nevertheless, THC does not appear to positively bias evaluation of emotional stimuli in general.

Associations between hypothalamic-pituitary-adrenal axis function and facial emotion processing in depressed and control participants

AIM

The current study examined the relation between facial emotion processing accuracy and an aspect of hypothalamic-pituitary-adrenal axis function in 64 inpatients with major depression and 49 healthy controls over a 2-week period.

METHODS

The Dexamethasone Suppression Test and a Facial Expression Recognition Task were completed at baseline and 10-14 days after baseline. Treatment response was determined 6 weeks after baseline by change in the Montgomery-Asberg Depression Rating Scale.

RESULTS

Increased cortisol response to dexamethasone was significantly correlated with reduced ability to recognize facial expressions of anger, sadness and disgust within the total sample, but these correlations did not remain significant at 10-14 days. Surprisingly, cortisol response to dexamethasone was comparable in acutely depressed inpatients and healthy controls, and did not change over time in relation to treatment response.

CONCLUSION

The study findings provide preliminary evidence that hypothalamic-pituitary-adrenal axis functioning and processing threat-related facial expressions are related, perhaps through involvement of the amygdala.

Hyporeactivity of ventral striatum towards incentive stimuli in unmedicated depressed patients normalizes after treatment with escitalopram

Major Depressive Disorder (MDD) involves deficits in the reward system. While neuroimaging studies have focused on affective stimulus processing, few investigations have directly addressed deficits in the anticipation of incentives. We examined neural responses during gain and loss anticipation in patients with MDD before and after treatment with a selective serotonin reuptake inhibitor (SSRI). Fifteen adults with MDD and 15 healthy participants, matched for age, verbal IQ and smoking habits, were investigated in a functional magnetic resonance imaging (fMRI) study using a monetary incentive delay task. Patients were scanned drug-free and after 6 weeks of open-label treatment with escitalopram; controls were scanned twice at corresponding time points. We compared the blood oxygenation level dependent (BOLD) response during the anticipation of gain and loss with a neutral condition. A repeated measures ANOVA was calculated to identify effects of group (MDD vs. controls), time (first vs. second scan) and group-by-time interaction. Severity of depression was measured with the Hamilton Rating Scale of Depression and the Beck Depression Inventory. MDD patients showed significantly less ventral striatal activation during anticipation of gain and loss compared with controls before, but not after, treatment. There was a significant group-by-time interaction during anticipation of loss in the left ventral striatum due to a signal increase in patients after treatment. Ventral striatal hyporesponsiveness was associated with the severity of depression and in particular anhedonic symptoms. These findings suggest that MDD patients show ventral striatal hyporesponsiveness during incentive cue processing, which normalizes after successful treatment.

Effects of low dose tryptophan depletion on emotional processing in dieters

Biased processing of ED-relevant stimuli (eg Fairburn, Shafran, & Cooper, 1999) and 5-HT function (Kaye, Fudge, & Paulus, 2009) are implicated in vulnerability to and the maintenance of eating disorders (EDs), but it is not known if these findings are connected: Could manipulating 5-HT function affect the processing of ED-relevant stimuli? To address this question we assessed emotional processing in female dieters (T+n=12, T-n=14) following acute low dose tryptophan depletion. ATD increased interference in the masked condition of the emotional Stroop to all negative emotional stimuli, in the absence of any other differences in emotional processing. These results suggest that ATD affects the processing of some negative (including ED-relevant) stimuli, and that reduced 5-HT function may be involved in some aspects of psychological vulnerability to EDs.

Piccolo genotype modulates neural correlates of emotion processing but not executive functioning

Major depressive disorder (MDD) is characterized by affective symptoms and cognitive impairments, which have been associated with changes in limbic and prefrontal activity as well as with monoaminergic neurotransmission. A genome-wide association study implicated the polymorphism rs2522833 in the piccolo (PCLO) gene--involved in monoaminergic neurotransmission--as a risk factor for MDD. However, the role of the PCLO risk allele in emotion processing and executive function or its effect on their neural substrate has never been studied. We used functional magnetic resonance imaging (fMRI) to investigate PCLO risk allele carriers vs noncarriers during an emotional face processing task and a visuospatial planning task in 159 current MDD patients and healthy controls. In PCLO risk allele carriers, we found increased activity in the left amygdala during processing of angry and sad faces compared with noncarriers, independent of psychopathological status. During processing of fearful faces, the PCLO risk allele was associated with increased amygdala activation in MDD patients only. During the visuospatial planning task, we found no genotype effect on performance or on BOLD signal in our predefined areas as a function of increasing task load. The PCLO risk allele was found to be specifically associated with altered emotion processing, but not with executive dysfunction. Moreover, the PCLO risk allele appears to modulate amygdala function during fearful facial processing in MDD and may constitute a possible link between genotype and susceptibility for depression via altered processing of fearful stimuli. The current results may therefore aid in better understanding underlying neurobiological mechanisms in MDD.

Sensitivity to posed and genuine facial expressions of emotion in severe depression

The aim of the current study was to investigate whether the ability to distinguish genuine from non-genuine (neutral or posed) facial expressions of emotion (happiness, sadness, fear and disgust) is impaired in depression, and whether improvement in this ability occurs with treatment response. Sixty-eight depressed inpatients and 50 matched healthy controls performed the Emotion Categorisation Task three times over 6 weeks. All participants showed some sensitivity to the meaningful differences between genuine and non-genuine expressions of emotion, with an increasing percentage of faces labelled as genuinely feeling the emotion from neutral to posed to genuine presentations. Depressed patients showed significantly less sensitivity in differentiating non-genuine from genuine expressions of sadness, compared with healthy controls. Performance on the Emotion Categorisation Task did not change over time in treatment responders compared with treatment non-responders. These findings have implications for understanding why depressed individuals may have difficulties in social interactions.

Effects of amphetamine on reactivity to emotional stimuli

RATIONALE

Most studies of the reinforcing effects of stimulants have focused on the drugs' capacity to induce positive mood (i.e., euphoria). However, recent findings suggest drugs may also alter emotional reactivity to external stimuli, and that this may occur independently of direct effects on mood.

OBJECTIVES

We aimed to examine effects of D: -amphetamine, a prototypic stimulant, on self-reported and psychophysiological reactivity to emotional stimuli as well as overall subjective mood. We predicted that amphetamine would enhance reactivity to pleasant stimuli, particularly, stimuli with social content and that these effects would be independent of the drug's direct effects on mood.

METHODS

Over three sessions, 36 healthy normal adults received placebo, D: -amphetamine 10 and 20 mg under counterbalanced double-blind conditions. At each session, emotional reactivity to standardized positive, neutral, and negative pictures with and without social content was measured in self-reports and facial muscles sensitive to emotional state. Drug effects on cardiovascular variables and subjective mood were also measured.

RESULTS

Amphetamine produced euphoria, feelings of drug effect, and increased blood pressure. Most notably, amphetamine enhanced self-reported positive reactions to all pictures and psychophysiological reactions to positive pictures. These effects were not significantly related to drug-induced mood changes. Contrary to our hypothesis, effects of amphetamine on emotional reactivity were not moderated by social content.

CONCLUSIONS

This study demonstrates a previously unexamined and potentially reinforcing effect of stimulant drugs in humans, distinct from more typically measured euphorigenic effects, and suggests new areas of research in stimulant abuse risk and adaptations occurring during drug dependence.

Serotonin at the level of the amygdala and orbitofrontal cortex modulates distinct aspects of positive emotion in primates

Impaired top-down regulation of the amygdala, and its modulation by serotonin (5-HT), is strongly implicated in the dysregulation of negative emotion that characterizes a number of affective disorders. However, the contribution of these mechanisms to the regulation of positive emotion is not well understood. This study investigated the role of 5-HT within the amygdala and the orbitofrontal cortex (OFC), on the expression of appetitive Pavlovian conditioned emotional responses and their reversal in a primate, the common marmoset. Its effects were compared to those of the amygdala itself. Having developed conditioned autonomic and behavioural responses to an appetitive cue prior to surgery, marmosets with excitotoxic amygdala lesions failed to display such conditioned autonomic arousal at retention, but still displayed intact cue-directed conditioned behaviours. In contrast, 5,7-DHT infusions into the amygdala, reducing extracellular 5-HT levels, selectively enhanced the expression of appetitive conditioned behaviour at retention. Similar infusions into the OFC, producing marked reductions in post-mortem 5-HT tissue levels, had no overall effect on autonomic or behavioural responses, either at retention or during reversal learning, but caused an uncoupling of these responses, thereby fractionating emotional output. These data demonstrate the critical role of the amygdala in the expression of appetitive autonomic conditioning, and the region-selective contribution of 5-HT in the amygdala and OFC, respectively, to the expression of conditioned behaviour and the overall coordination of the emotional response. They provide insight into the neurochemical mechanisms underlying the regulation of positive emotional responses, advancing our understanding of the neural basis of pathologically dysregulated emotion.

Erythropoietin: a candidate treatment for mood symptoms and memory dysfunction in depression

OBJECTIVE

Current pharmacological treatments for depression have a significant treatment-onset-response delay, an insufficient efficacy for many patients and fail to reverse cognitive dysfunction. Erythropoietin (EPO) has neuroprotective and neurotrophic actions and improves cognitive function in animal models of acute and chronic neurodegenerative conditions and in patients with cognitive decline.

METHODS

We systematically reviewed the published findings from animal and human studies exploring the potential of EPO to treat depression-related cognitive dysfunction and depression.

RESULTS

We identified five animal studies (two in male rats, two in male mice and one in male rats and mice) and seven human proof-of-concept studies (five in healthy volunteers and two in depressed patients) that investigated the above. All of the reviewed animal studies but one and all human studies demonstrated beneficial effects of EPO on hippocampus-dependent memory and antidepressant-like effects. These effects appear to be mediated through direct neurobiological actions of EPO rather than upregulation of red cell mass.

CONCLUSIONS

The reviewed studies demonstrate beneficial effects of EPO on hippocampus-dependent memory function and on depression-relevant behavior, thus highlighting EPO as a candidate agent for future management of cognitive dysfunction and mood symptoms in depression. Larger-scale clinical trials of EPO as a treatment for mood and neurocognitive symptoms in patients with mood disorder are therefore warranted.

Paroxetine reduces crying in young women watching emotional movies

RATIONALE

Crying is a unique human emotional reaction that has not received much attention from researchers. Little is known about its underlying neurobiological mechanisms, although there is some indirect evidence suggesting the involvement of central serotonin.

OBJECTIVES

We examined the acute effects of the administration of 20 mg paroxetine on the crying of young, healthy females in response to emotional movies.

METHODS

We applied a double-blind, crossover randomised design with 25 healthy young females as study participants. On separate days, they received either paroxetine or placebo and were exposed to one of two emotional movies: 'Once Were Warriors' and 'Brian's Song'. Crying was assessed by self-report. In addition, the reactions to emotional International Affective Picture System (IAPS) pictures and mood were measured.

RESULTS

Paroxetine had a significant inhibitory effect on crying. During both films, the paroxetine group cried significantly less than the placebo group. In contrast, no effects on mood and only minor effects on the reaction to the IAPS pictures were observed.

CONCLUSIONS

A single dose of paroxetine inhibits emotional crying significantly. It is not sure what the underlying mechanism is. However, since there was no effect on mood and only minor effects on the response to emotional pictures, we postulate that paroxetine mainly acts on the physiological processes involved in the crying response.

Cognitive mechanisms of treatment in depression

Cognitive abnormalities are a core feature of depression, and biases toward negatively toned emotional information are common, but are they a cause or a consequence of depressive symptoms? Here, we propose a 'cognitive neuropsychological' model of depression, suggesting that negative information processing biases have a central causal role in the development of symptoms of depression, and that treatments exert their beneficial effects by abolishing these biases. We review the evidence pertaining to this model: briefly with respect to currently depressed patients, and in more detail with respect to individuals at risk for depression and the effects of antidepressant treatments. As well as being present in currently depressed individuals, negative biases are detectable in those vulnerable for depression due to neuroticism, genetic risk, or previous depressive illness. Recent evidence provides strong support for the notion that both antidepressant drugs and psychological therapies modify negative biases, providing a common mechanism for understanding treatments for depression. Intriguingly, it may even be possible to predict which patients will benefit most from which treatments on the basis of neural responses to negative stimuli. However, further research is required to ascertain whether negative processing biases will be useful in predicting, detecting, and treating depression, and hence in preventing a chronic, relapsing course of illness.

Using an experimental medicine model to explore combination effects of pharmacological and cognitive interventions for depression and anxiety

Selective serotonergic reuptake inhibitors (SSRIs) and cognitive therapies are effective in the treatment of anxiety and depression. Previous research suggests that both forms of treatments may work by altering cognitive biases in the processing of affective information. The current study assessed the effects of combining an SSRI with a cognitive intervention on measures of affective processing bias and resilience to external challenge. A total of 62 healthy participants were randomly assigned to receive either 7 days of citalopram (20 mg) or placebo capsules while also completing either an active or a control version of a computerized cognitive bias training task. After treatment, standard measures of affective processing bias were collected. Participants' resilience to external stress was also tested by measuring the increase in negative symptoms induced by a negative mood induction. Participants who received both citalopram and the active cognitive bias training task showed a smaller alteration in emotional memory and categorization bias than did those who received either active intervention singly. The degree to which memory for negative information was altered by citalopram predicted participants' resistance to the negative mood induction. These results suggest that co-administration of an SSRI and a cognitive training intervention can reduce the effectiveness of either treatment alone in terms of anxiety- and depression-relevant emotional processing. More generally, the findings suggest that pinpointing the cognitive actions of treatments may inform future development of combination strategies in mental health.

Mood and personality effects in healthy participants after chronic administration of sertraline

BACKGROUND

Selective serotonin reuptake inhibitors (SSRIs) are utilised in the treatment of a wide range of disorders but the neuropsychological basis of their therapeutic efficacy remains unclear. In this study we examine the impact of 3 weeks administration of sertraline, an SSRI, on mood and personality in a group of healthy volunteers to understand the effect of these agents in the absence of clinical disorder.

METHODS

Thirty-eight healthy women and men, with no personal or familial history of Axis I disorder were randomised to receive either a placebo or sertraline (50mg/day p.o.) for an average of 23 days, in a double-blind design. Self-report indices of mood and personality, and genotype (5-HTTLPR) and sertraline bioavailability were assessed.

RESULTS

Chronic administration of an SSRI was found to alter mood and personality. The SSRI group experienced a significant decrease in negative affect (NA), guilt and attentiveness, and significant increases in positive affect (PA), joviality, self-assurance and serenity. Genotype and bioavailability of sertraline did not moderate these findings, however gender did. Only females demonstrated increased PA and joviality, and decreased NA; whereas, only males demonstrated decreased attentiveness.

LIMITATIONS

Greater power and a more specific manipulation of serotonergic functioning would help clarify the neurochemical basis of these findings.

CONCLUSIONS

Results from the current study demonstrate that longer term administration of SSRIs alters aspects of mood and personality in the absence of disorder. This suggests that these agents have effects on basic psychological processes that may in turn form the basis of their therapeutic efficacy.

The effects of sertraline on psychopathic traits

We examined whether antidepressants alter expression of psychopathic personality traits in patients with major depressive disorder (MDD). Data were collected from a double-blind, placebo-controlled 8-week trial evaluating the efficacy of sertraline (50-200 mg/day) combined with either tri-iodothyronine (T3) or matching placebo in adult outpatients with major depressive disorder. Administration of sertraline was open-label; T3/placebo was double-blind. At the baseline and week 8 visits, patients completed the short form of the Psychopathic Personality Inventory (PPI), a well-validated self-report measure assessing two major factors of psychopathy: Fearless Dominance (PPI-1) and Self-Centered Impulsivity (PPI-2). Change in PPI scores were assessed using paired t-tests for all participants who completed a baseline and postrandomization PPI. Ninety patients (84 completers and six who terminated the trial early) were eligible for the analysis. Both PPI factors changed significantly from baseline to endpoint, but in opposing directions. The mean score on PPI-1 increased significantly during treatment; this change was weakly correlated with change in depression scores. In contrast, the mean score on PPI-2 decreased significantly, but these changes were not correlated with changes in depression scores. Independent of their effects on depression, antidepressants increase adaptive traits traditionally observed in psychopathic individuals, such as social charm and interpersonal and physical boldness. Antidepressants reduce other, more maladaptive, traits associated with psychopathy, including dysregulated impulsivity and externalization.

Social cognition in bulimia nervosa: a systematic review

OBJECTIVE

Clinical accounts and previous evidence suggest that socio-emotional impairments may be present in people with bulimia nervosa (BN). The aim of this paper was to systematically review studies of social cognition, and to evaluate whether social cognitive deficits exist in BN.

METHOD

Keywords were identified using an existing model of social cognition (Green et al., 2007) [16], and used to search for relevant papers in three online databases. Records were then screened according to a priori inclusion/exclusion criteria.

RESULTS

Five papers reporting seven social cognition tasks were identified as pertinent to the review. All involved either theory of mind ability or emotional processing skills. Participants with BN had impaired performance on the Levels of Emotional Awareness Scale and showed greater attentional bias than controls on an emotional Stroop task. There were no overall group differences for any other tasks, although there were small differences for some specific test items.

CONCLUSIONS

Basic social cognition does not appear to be impaired in people with BN. Future research should make use of more complex, ecologically valid measures, and consider the relationship between task performance and everyday social functioning.

Efficacy markers in depression

Current antidepressant agents are similar in efficacy to the original drugs discovered in the 1950s. The development of new treatments for depression is, however, limited by the absence of validated human biomarker models to predict efficacy, clinical profile and dosing. Such models need to meet key criteria for biomarkers including sensitivity, specificity and relevance to depression. Here we review studies exploring whether early changes in emotional processing with antidepressant drug administration meet these criteria. A large body of evidence suggests that changes in emotional memory are particularly relevant to depression and to antidepressant drug action whereas changes in attentional processing are sensitive to anxiolytic drugs. These tasks are not consistently affected by agents which have failed in clinical trials in depression, but do show changes in the predicted direction with agents associated either with amelioration or induction of symptoms. Hence, early assessment of novel drugs on emotional processing may predict likely clinical effects and dosing prior to randomized controlled trials. Greater validation is required to assess whether these effects are an obligatory component of effective treatment of depression and whether use of these models can improve the accuracy of go/no-go decisions in drug development.

Chronic modulation of serotonergic neurotransmission with sertraline attenuates the loudness dependence of the auditory evoked potential in healthy participants

RATIONALE

The loudness dependence of the auditory evoked potential (LDAEP) has been reported to be an effective non-invasive measure of central serotonergic neurotransmission. However, acute manipulations of the serotonergic system in humans and animals have yielded inconsistent findings.

OBJECTIVES

In this study, we examined the chronic effect of serotonergic manipulation using the selective serotonin reuptake inhibitor, sertraline, on the LDAEP. In addition, we examined the influence of 5-HTTLPR genotype and individual differences in plasma drug concentrations on the LDAEP.

METHODS

The study utilised a double-blind, placebo-controlled, between-group design in which 40 (24 female) healthy adults (M age = 22.0 years, SE = 0.7) were tested following placebo or sertraline for an average of 24 days. The LDAEP was assessed 6 h post-final dose, and changes in the slope of amplitude of the N1/P2 across intensities (60, 70, 80, 90, 100 dB) were examined at Cz.

RESULTS

The sertraline group had a significantly smaller LDAEP than the placebo group [F(1,38) = 5.97, p = 0.02]. Drug plasma levels did not correlate with the LDAEP in the sertraline group, and there was no influence of 5-HTTLPR genotype.

CONCLUSIONS

We show for the first time that chronically modulating serotonin neurotransmission alters the LDAEP in healthy adults, consistent with extant literature indicating a moderating role of serotonin on this neurophysiological biomarker. The findings from this study together with previous studies suggest that the LDAEP may be a more sensitive marker of long-term or chronic rather than acute changes in the serotonin system.

A cognitive neuropsychological model of antidepressant drug action

The psychological mechanisms by which antidepressant drugs act to improve mood remain underspecified. In this paper we consider the evidence to suggest that early changes in emotional processing underlie subsequent mood improvement following antidepressant treatment. Negative biases in information processing are consistently found in depression, and we argue that primary mode of action of antidepressant drugs may be to remediate these biases providing a more positive social environment in which the patient can relearn emotional associations fostering later improvement in mood. Evidence from behavioural and functional magnetic resonance imaging studies supports this hypothesis. Experimental medicine models developed under this premise have the potential to screen for new treatments, to predict individual treatment response and to consider the effects of pharmacological vs psychological treatments.

Differential modulation of emotion processing brain regions by noradrenergic and serotonergic antidepressants

RATIONALE

Most widely used antidepressant drugs affect the serotonergic and noradrenergic pathways. However, there are currently no neurobiological criteria for selecting between these targets and predicting the treatment response in individual depressed patients.

OBJECTIVES

The current study is aimed at differentiating brain regions known to be pathophysiologically and functionally involved in depression-related emotion processing with respect to their susceptibility to serotonergic and noradrenergic modulation.

METHODS

In a single-blind pseudo-randomized crossover study, 16 healthy subjects (out of 21 enrolled) were included in analysis after ingesting a single dose of citalopram (a selective serotonin-reuptake inhibitor, 40 mg), reboxetine (a selective noradrenaline-reuptake inhibitor, 8 mg), or placebo at three time points prior to functional magnetic resonance imaging (fMRI). During fMRI, subjects anticipated and subsequently viewed emotional pictures. Effects of serotonergic and noradrenergic modulation versus placebo on brain activity during the perception of negative pictures were analyzed with a repeated measures ANOVA in the whole brain and in specific regions of interest relevant to depression.

RESULTS

Noradrenergic modulation by reboxetine increased brain activity in the thalamus, right dorsolateral prefrontal cortex and occipital regions during the perception of negative emotional stimuli. Citalopram primarily affected the ventrolateral prefrontal cortical regions.

CONCLUSION

The brain regions involved in the processing of negative emotional stimuli were differentially modulated by selective noradrenergic and serotonergic drugs: thalamic activity was increased by reboxetine, whereas citalopram primarily affected ventrolateral prefrontal regions. Thus, dysfunction in these regions, which could be identified in depressed patients, may predict treatment responses to either noradrenergic or serotonergic antidepressants.

Serotonergic contribution to boys' behavioral regulation

Objectives

Animal and human adult studies reveal a contribution of serotonin to behavior regulation. Whether these findings apply to children is unclear. The present study investigated serotonergic functioning in boys with a history of behavior regulation difficulties through a double-blind, acute tryptophan supplementation procedure.

Method

Participants were 23 boys (age 10 years) with a history of elevated physical aggression, recruited from a community sample. Eleven were given a chocolate milkshake supplemented with 500mg tryptophan, and 12 received a chocolate milkshake without tryptophan. Boys engaged in a competitive reaction time game against a fictitious opponent, which assessed response to provocation, impulsivity, perspective taking, and sharing. Impulsivity was further assessed through a Go/No-Go paradigm. A computerized emotion recognition task and a staged instrumental help incident were also administered.

Results

Boys, regardless of group, responded similarly to high provocation by the fictitious opponent. However, boys in the tryptophan group adjusted their level of responding optimally as a function of the level of provocation, whereas boys in the control group significantly decreased their level of responding towards the end of the competition. Boys in the tryptophan group tended to show greater perspective taking, tended to better distinguish facial expressions of fear and happiness, and tended to provide greater instrumental help to the experimenter.

Conclusions

The present study provides initial evidence for the feasibility of acute tryptophan supplementation in children and some effect of tryptophan supplementation on children's behaviors. Further studies are warranted to explore the potential impact of increased serotonergic functioning on boys' dominant and affiliative behaviors.

Emotional processing as a predictor of symptom change: an acute tryptophan depletion study in depressed patients

Acute tryptophan depletion (ATD) in currently depressed patients has no immediate effect on symptoms, but leads to transient symptom improvement or worsening the next day. In view of recent findings concerning the cognitive effects of serotonin manipulations, we used ATD in fourteen depressed patients to investigate whether cognitive effects following ATD predict symptom changes. We found that symptom improvement 24h after ATD was associated with an improved recall of positive words and with less attentional bias and recall of negative words, 5h after ATD. These results indicate that serotonergic alterations affect emotional processing which may subsequently lead to symptom changes.

What is the relationship between the recognition of emotions and core beliefs: Associations between the recognition of emotions in facial expressions and the maladaptive schemas in depressed patients

BACKGROUND

Depressed patients are both characterized by social reality distorting maladaptive schemas and facial expression recognition impairments. The aim of the present study was to identify specific associations among symptom severity of depression, early maladaptive schemas and recognition patterns of facially expressed emotions.

METHODS

The subjects were inpatients, diagnosed with depression. We used 2 virtual humans for presenting the basic emotions to assess emotion recognition. The Symptom Check List 90 (SCL-90) was used as a self-report measure of psychiatric symptoms and the Beck Depression Inventory (BDI) was applied to assess symptoms of depression. The Young Schema Questionnaire Long Form (YSQ-L) was used to assess the presence of early maladaptive schemas.

RESULTS

The recognition rate for happiness showed significant associations with both the BDI and the depression subscale of the SCL-90. After performing the second order factor analysis of the YSQ-L, we found statistically significant associations between the recognition indices of specific emotions and the main factors of the YSQ-L.

CONCLUSIONS

In this study we found correlations between maladaptive schemas and emotion recognition impairments. While both domains likely contribute to the symptoms of depression, we believe that the results will help us to better understand the social cognitive deficits of depressed patients at the schema level and at the emotion recognition level.

Attentional bias in untreated panic disorder

The role of attentional biases in panic disorder has been well characterised. However, recent studies suggest an important effect of antidepressant and anxiolytic drugs on cognitive bias and most studies have included medicated patients in their sample. This study therefore examined cognitive bias in an untreated sample of participants with panic disorder (PD). A sample of 23 untreated participants with panic disorder with or without agoraphobia (PPD) and 22 healthy controls (HC) were tested with a Facial Expression Recognition task featuring different emotional intensities, a Faces Dot Probe task, a Self Beliefs task and an Emotional Stroop task. PPD showed exaggerated attentional biases to negative face and word stimuli in two different paradigms and endorsed more panic-related and negative self-attributions. They also showed enhanced perception of facial expressions of sadness. These tasks are sensitive to cognitive bias in a community-based sample of untreated PD participants. Attentional biases in panic disorder cannot be explained by the use of medication in this group and may therefore play a critical role in the underlying pathogenesis of the disorder.

Neuropsychological changes and treatment response in severe depression

BACKGROUND

Impaired neuropsychological function and differences in facial emotion processing are features of major depression. Some aspects of these functions may change during treatment and may be useful in assessing treatment response, even at an early stage of treatment.

AIMS

To examine early and later changes in neuropsychological functioning and facial emotion processing as potential markers of treatment response in major depression.

METHOD

In total, 68 newly admitted in-patients with a primary diagnosis of major depression and 50 healthy controls completed an assessment, including mood ratings, neuropsychological measures and facial emotion processing measures at three time points (baseline, 10-14 days and 6 weeks).

RESULTS

Pervasive neuropsychological impairment was evident at baseline in patients with depression compared with healthy controls. During 6 weeks of treatment, only simple reaction time, verbal working memory and the recognition of angry facial expressions showed differential change in those whose depression responded to treatment compared with treatment non-responders in the depression group. None of the measures showed a significant difference between treatment responders and non-responders at 10-14 days.

CONCLUSIONS

Despite significant impairment in neuropsychological functioning in the depression group, most measures failed to differentiate between treatment responders and non-responders at 10-14 days or at 6 weeks. Simple reaction time, verbal working memory and recognition of angry facial expressions may be useful in assessing response in severe depression but probably not at an early stage.

Chlorpheniramine exerts anxiolytic-like effects and activates prefrontal 5-HT systems in mice

RATIONALE

The traditional antihistamine chlorpheniramine ameliorates panic attacks, phobias, and lowered mood, and this therapeutic effect is independent of the blockade of histamine H(1) receptors. Since chlorpheniramine inhibits the reuptake of serotonin (5-HT), the anxiolytic-like effect of chlorpheniramine may be produced by an increase in serotonergic function.

OBJECTIVE

To elucidate the mechanisms underlying the anxiolytic-like effects of chlorpheniramine in mice, we examined the involvement of 5-HT systems in the prefrontal cortex that is a crucial region in the regulation of emotional function.

RESULTS

Chlorpheniramine (0.05-5 mg/kg, i.p.) dose-dependently and significantly decreased the duration of freezing behavior in both the elevated open-platform and conditioned fear tests. The anti-freezing effects of chlorpheniramine (5 mg/kg, i.p.) in these tests were inhibited by pretreatment with the non-selective antagonist at 5-HT receptors, methiothepin (0.01 mg/kg, s.c.). In addition, the local injection of chlorpheniramine (10-100 ng/mouse) and 5-HT (1-10 μg/mouse) into the medial part of the prefrontal cortex (mPFC) dose-dependently and significantly decreased the duration of freezing behavior in the elevated open-platform test. In a microdialysis study, chlorpheniramine (0.5 and 5 mg/kg, i.p.) dose-dependently and significantly increased the extracellular 5-HT level in the mPFC. In addition, the local perfusion of chlorpheniramine (10 and 30 μM), but not of the selective H1 receptor antagonist, cetirizine, into the mPFC markedly increased the extracellular 5-HT level in the mPFC.

CONCLUSION

The anxiolytic-like effect of chlorpheniramine is produced, at least in part, by the facilitation of serotonergic neurotransmission in the PFC.

Major depression is associated with impaired processing of emotion in music as well as in facial and vocal stimuli

BACKGROUND

The processing of emotional stimuli is thought to be negatively biased in major depression. This study investigates this issue using musical, vocal and facial affective stimuli.

METHODS

23 depressed in-patients and 23 matched healthy controls were recruited. Affective information processing was assessed through musical, vocal and facial emotion recognition tasks. Depression, anxiety level and attention capacity were controlled.

RESULTS

The depressed participants demonstrated less accurate identification of emotions than the control group in all three sorts of emotion-recognition tasks. The depressed group also gave higher intensity ratings than the controls when scoring negative emotions, and they were more likely to attribute negative emotions to neutral voices and faces.

LIMITATIONS

Our in-patient group might differ from the more general population of depressed adults. They were all taking anti-depressant medication, which may have had an influence on their emotional information processing.

CONCLUSIONS

Major depression is associated with a general negative bias in the processing of emotional stimuli. Emotional processing impairment in depression is not confined to interpersonal stimuli (faces and voices), being also present in the ability to feel music accurately.

Biases in emotional processing are associated with vulnerability to eating disorders over time

Biases in emotional processing are thought to play a role in the maintenance of eating disorders (EDs). In a previous study (Pringle et al., 2010), we were able to demonstrate that biases in the processing of negative self beliefs (a self-schema processing task), facial expressions of emotion (a facial expression recognition task) and information relating to eating, shape and weight (an emotional Stroop) were all predictive of the level of subclinical ED symptoms (used here as a measure of risk) cross-sectionally in a vulnerable sample of dieters. The present study was a 12-month follow up of the participants from Pringle et al. (2010). Longitudinally, greater endorsement of ED relevant and depression relevant negative self beliefs in the self-schema processing task at time 1 was related to subclinical ED systems (level of risk) 12 months later at time 2. Compared to the cross-sectional study, there was no clear relationship between performance on the facial expression recognition task, emotional Stroop task and level of risk 12 months later. Although these findings are preliminary, one tentative interpretation may be that whilst biases in the processing of ED specific stimuli are predictive of level of risk at a given moment, over time less specific stimuli relating to beliefs about the self, including mood related variables, are more closely related to level of risk.

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.

The HTR1A and HTR1B receptor genes influence stress-related information processing

The serotonergic system has been widely implicated in stress related psychiatric disorders such as depression and anxiety. We investigated the possible association between depression and anxiety scores and SNPs within the HTR1A and HTR1B genes in a population sample (n=1387). There was no direct SNP-phenotype association, but in interaction with recent stressful life events rs6295 G, rs878567 T alleles and rs6296 C alleles were associated with significantly higher symptom scores. A subset of control subjects (n=101) took part in a computerised face emotion processing task. Healthy rs6295 GG carriers did not show an affective bias to perceive more negative emotions but reacted more quickly to fearful faces. Thus we conclude that the serotonin-1A receptor conveys vulnerability to these psychiatric disorders by modulating threat-related information processing. Our results extend previous findings of an interaction between stressful life events and the serotonin transporter gene to two other genes in the serotonergic pathway and emphasise the possible role of increased threat-related information processing as an intermediate phenotype.

Impaired attribution of emotion to facial expressions in anxiety and major depression

Background

Recognition of others' emotions is an important aspect of interpersonal communication. In major depression, a significant emotion recognition impairment has been reported. It remains unclear whether the ability to recognize emotion from facial expressions is also impaired in anxiety disorders. There is a need to review and integrate the published literature on emotional expression recognition in anxiety disorders and major depression.

Methodology/Principal Findings

A detailed literature search was used to identify studies on explicit emotion recognition in patients with anxiety disorders and major depression compared to healthy participants. Eighteen studies provided sufficient information to be included. The differences on emotion recognition impairment between patients and controls (Cohen's d) with corresponding confidence intervals were computed for each study. Over all studies, adults with anxiety disorders had a significant impairment in emotion recognition (d = −0.35). In children with anxiety disorders no significant impairment of emotion recognition was found (d = −0.03). Major depression was associated with an even larger impairment in recognition of facial expressions of emotion (d = −0.58).

Conclusions/Significance

Results from the current analysis support the hypothesis that adults with anxiety disorders or major depression both have a deficit in recognizing facial expression of emotions, and that this deficit is more pronounced in major depression than in anxiety.

A single dose of mirtazapine modulates neural responses to emotional faces in healthy people

RATIONALE

Single-dose administration of selective serotonin and noradrenaline reuptake blockers has been shown to alter emotional processing in both behavioral and fMRI studies in healthy volunteers. Mirtazapine is a clinically established antidepressant with different pharmacological actions from monoamine reuptake inhibitors, involving blockade of noradrenaline α(2)-adrenoceptors and multiple 5-HT receptor subtypes. The aim of this study was to investigate the effect of a single dose of mirtazapine on the neural processing of emotional faces in healthy volunteers.

METHODS

Twenty-eight participants were randomized to receive either a single dose of mirtazapine (15 mg) or placebo. Two hours later, participants underwent an fMRI scan, in which they classified fearful and happy faces on the basis of gender. Mood and subjective experience were also measured.

RESULTS

Whole-brain analysis showed significant group × emotion interactions in a right amygdala-hippocampal region and left fronto-striatal cortex. Post hoc analyses revealed significantly reduced activation to fear and greater activation to happy faces in both regions under mirtazapine.

CONCLUSIONS

Our findings indicate that a single dose of mirtazapine modulates neural activity to affective stimuli. Mirtazapine was found to decrease neural responses to fear and increase responses to happy facial expressions in regions implicated in the processing of emotional faces. These effects may be important for our understanding of the neural mechanisms of antidepressant action in anxiety and depression.

Effects of alcohol on brain responses to social signals of threat in humans

Alcohol is a known exogenous modulator of negative affect (anxiety, tension) in both animals and humans. It has been proposed that the anxiolytic effects of alcohol are mediated via the amygdala, an area critical to fear perception and responding. However, little is known about the acute effects of alcohol on amygdala reactivity to threatening information in humans. We used functional magnetic resonance imaging and a validated task to probe amygdala responses to social signals of threat in 12 healthy, social drinkers after a double-blind crossover administration of alcohol or placebo. We found that alcohol significantly reduced amygdala reactivity to threat signals. The current findings fit well with the notion that alcohol may attenuate threat-based responding and provide a potential brain-based mechanism for the link between alcohol and anxiety and/or social threat perception.

A new strategy for antidepressant prescription

From our research and literature search we propose an understanding of the mechanism of action of antidepressants treatments (ADTs) that should lead to increase efficacy and tolerance. We understand that ADTs promote synaptic plasticity and neurogenesis. This promotion is linked with stimulation of dopaminergic receptors. Previous evidence shows that all ADTs (chemical, electroconvulsive therapy, repetitive transcranial magnetic stimulation, sleep deprivation) increase at least one monoamine neurotransmitter serotonin (5-HT), noradrenaline (NA) or dopamine (DA); this article focuses on DA release or turn-over in the frontal cortex. DA increased dopaminergic activation promotes synaptic plasticity with an inverted U shape dose–response curve. Specific interaction between DA and glutamate is mediated by D1 receptor subtypes and Glutamate (NMDA) receptors with neurotrophic factors likely to play a modulatory role. With the understanding that all ADTs have a common, final, DA-ergic stimulation that promotes synaptic plasticity we can predict that (1) AD efficiency is related to the compound strength for inducing DA-ergic stimulation. (2) ADT efficiency presents a therapeutic window that coincides with the inverted U shape DA response curve. (3) ADT delay of action is related to a “synaptogenesis and neurogenesis delay of action.” (4) The minimum efficient dose can be found by starting at a low dosage and increasing up to the patient response. (5) An increased tolerance requires a concomitant prescription of a few ADTs, with different or opposite adverse effects, at a very low dose. (6) ADTs could improve all diseases with cognitive impairments and synaptic depression by increasing synaptic plasticity and neurogenesis.

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.

Serotonin selectively influences moral judgment and behavior through effects on harm aversion

Aversive emotional reactions to real or imagined social harms infuse moral judgment and motivate prosocial behavior. Here, we show that the neurotransmitter serotonin directly alters both moral judgment and behavior through increasing subjects' aversion to personally harming others. We enhanced serotonin in healthy volunteers with citalopram (a selective serotonin reuptake inhibitor) and contrasted its effects with both a pharmacological control treatment and a placebo on tests of moral judgment and behavior. We measured the drugs' effects on moral judgment in a set of moral 'dilemmas' pitting utilitarian outcomes (e.g., saving five lives) against highly aversive harmful actions (e.g., killing an innocent person). Enhancing serotonin made subjects more likely to judge harmful actions as forbidden, but only in cases where harms were emotionally salient. This harm-avoidant bias after citalopram was also evident in behavior during the ultimatum game, in which subjects decide to accept or reject fair or unfair monetary offers from another player. Rejecting unfair offers enforces a fairness norm but also harms the other player financially. Enhancing serotonin made subjects less likely to reject unfair offers. Furthermore, the prosocial effects of citalopram varied as a function of trait empathy. Individuals high in trait empathy showed stronger effects of citalopram on moral judgment and behavior than individuals low in trait empathy. Together, these findings provide unique evidence that serotonin could promote prosocial behavior by enhancing harm aversion, a prosocial sentiment that directly affects both moral judgment and moral behavior.

Stable expression recognition abnormalities in unipolar depression

Although abnormalities in emotion recognition during a depressed episode have frequently been reported in patients with depression, less is known about the stability of these abnormalities. To examine the stability of emotion recognition abnormalities, this longitudinal study assessed patients with unipolar depression on three separate occasions at 3-monthly intervals. Recognition of sad, angry, fearful, disgusted, happy and neutral facial expressions was assessed in a matching task and a labelling task. Patients performed as well as matched healthy controls on the matching task. On the labelling task, patients showed higher accuracy and higher response bias than controls for sad expressions only, which remained stable over a 6-month interval. Over the same period, symptom severity, as measured with the Beck Depression Inventory and the Hamilton Depression Rating Scale, decreased significantly in the patient group. Furthermore, labelling performance for sad expressions was not associated with symptom severity or with changes in severity over time. This stable bias for sad expressions might signal a vulnerability factor for depression, as proposed by cognitive theories of depression.

Neural activity changes to emotional stimuli in healthy individuals under chronic use of clomipramine

Previous functional magnetic resonance imaging (fMRI) studies examined neural activity responses to emotive stimuli in healthy individuals after acute/subacute administration of antidepressants. We now report the effects of repeated use of the antidepressant clomipramine on fMRI data acquired during presentation of emotion-provoking and neutral stimuli on healthy volunteers. A total of 12 volunteers were evaluated with fMRI after receiving low doses of clomipramine for 4 weeks and again after 4 weeks of washout. Fear-, happiness-, anger-provoking and neutral pictures from the International Affective Picture System (IAPS) were used. Data analysis was performed with statistical parametric mapping (P < 0.05). Paired t-test comparisons for each condition between medicated and unmedicated states showed, to negative valence paradigms, decrease in brain activity in the amygdala when participants were medicated. We also demonstrated, across both positive and negative valence paradigms, consistent decreases in brain activity in the medicated state in the anterior cingulate gyrus and insula. This is the first report of modulatory effects of repeated antidepressant use on the central representation of somatic states in response to emotions of both negative and positive valences in healthy individuals. Also, our results corroborate findings of antidepressant-induced temporolimbic activity changes to emotion-provoking stimuli obtained in studies of subjects treated acutely with such agents.

Recognition of disgusted facial expressions in severe depression

Facial emotion processing was examined in patients with severe depression (n = 68) and a healthy control group (n = 50), using the Facial Expression Recognition Task. A negative interpretation bias was observed in the depression group: neutral faces were more likely to be interpreted as sad and less likely to be interpreted as happy, compared with controls. The depression group also displayed a specific deficit in the recognition of facial expressions of disgust, compared with controls. This may relate to impaired functioning of frontostriatal structures, particularly the basal ganglia.

Augmenting serotonin neurotransmission with citalopram modulates emotional expression decoding but not structural encoding of moderate intensity sad facial emotional stimuli: an event-related potential (ERP) investigation

Antidepressants targeting the serotonergic system have been shown to modulate biases in emotional processing. The effects of serotonergic modulation on the temporal course of emotional processing (accruing within milliseconds) are unknown. Furthermore, it is unknown how serotonin affects different stages of facial emotional processing. The current study investigated the effects of acute serotonin augmentation on event-related potential (ERP) measures associated with 'structural encoding' (N170) and emotion 'expression decoding' (N250 and a late slow-wave positive potential [LPP]) of happy and sad facial stimuli, relative to neutral facial stimuli. The study was a double-blind, placebo-controlled, cross-over design, in which 14 healthy male participants completed a facial recognition task under two acute treatment conditions: 1) placebo (PLB) and 2) 20 mg citalopram (CIT). ERP recording were conducted while subjects viewed neutral, happy and sad facial stimuli. Findings indicated that under PLB, the N170 was not modulated by valence (happy or sad versus neutral), but the N250 and LPP were enhanced for processing happy (relative to neutral) faces. Citalopram had no effect on the N170, but it enhanced the LPP for processing sad (relative to neutral) faces. These findings suggest that serotonin enhancement has selective and temporal effects on emotional face processing, with evidence for modulating processes associated with 'expression decoding' but not 'structural encoding'. The enhanced cortical response to perception of moderately intense sad facial expressions following citalopram administration may relate to the cognitive processing of the social relevance or significance of such ambiguous stimuli.

Antidepressants in healthy subjects: what are the psychotropic/psychological effects?

A wide debate is ongoing regarding whether antidepressant effects should be considered a general property of these agents or whether they exclusively belong to the context of target symptoms. The aim of the present review is to summarize findings on antidepressant influences on healthy volunteers, focusing on changes in psychological and cognitive functions. Differences have been detected between acute and chronic treatments. Acute treatment has been found to lead to positive bias in emotion processing and facilitation in negative emotion recognition. Chronic treatments have been found to stabilise some changes induced by acute treatment, such as increased social behaviours. Regarding antidepressant modulation of affective symptomatology contrasting results have been reported suggesting that the link between action on cognitive processes and mood may be not direct. In fact, meta-analyzing data on mood and anxiety symptoms no difference was detected between subjects receiving placebo and SSRIs. However, meta-analyzing data on negative affects, a significant decrease was detected in subjects receiving SSRIs in comparison with subjects receiving placebo. In summary, antidepressants seem to exert a detectable influence also in healthy subjects.

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.