Lorazepam dose-dependently decreases risk-taking related activation in limbic areas

The anti-anxiety drug lorazepam changes implicit behaviors but not explicit evaluations of sense of agency under authoritative pressure: A functional magnetic resonance imaging study

Previous research on coercion has neglected the fact that agents under authoritative pressure may also suffer from coercive power, which can trigger anxiety-like emotional negativity on its victims. Furthermore, high levels of neuroticism and/or anxiety have been found to be associated with the compliance of various forms of social pressure. In this study, we investigate the effects of the anxiolytic GABA A (gamma-Aminobutyric acid) modulator, lorazepam, on behavioral and neural responses to coercive power. Here, we applied a virtual obedience to authority paradigm alongside lorazepam administration (versus placebo), and during functional magnetic resonance imaging scanning. Our results show that lorazepam administration exerted differential effects on the reaction times (RTs) when initiating harming versus helping behaviors, with longer harming RTs compared to helping RTs, despite comparable subjective ratings regarding perceived coercion. Coercive harming significantly increased activity in the amygdala, hippocampus, orbitofrontal cortex, and dorsolateral prefrontal cortex (dlPFC). Lorazepam administration decreased amygdala and hippocampus activity, but increased dlPFC and right temporoparietal junction activations. The lower activity in the hippocampus predicted higher ratings for perceived coercion. Furthermore, lorazepam significantly decreased the functional connectivity of the hippocampus with the dlPFC during coercive harming. In conclusion, we provide evidence -by incorporating multimodal indices, including neuroimaging, neuropharmacological interventions, and behavioral assessments- to posit that the GABA A agonist, lorazepam, might aid as a possible intervention in service of coping strategies against coercion.

GABAA receptor subtypes and benzodiazepine use, misuse, and abuse

Benzodiazepines have been in use for over half a century. While they remain highly prescribed, their unfavorable side-effect profile and abuse liability motivated a search for alternatives. Most of these efforts focused on the development of benzodiazepine-like drugs that are selective for specific GABA_A receptor subtypes. While there is ample evidence that subtype-selective GABA_A receptor ligands have great potential for providing symptom relief without typical benzodiazepine side-effects, it is less clear whether subtype-selective targeting strategies can also reduce misuse and abuse potential. This review focuses on the three benzodiazepine properties that are relevant to the DSM-5-TR criteria for Sedative, Hypnotic, or Anxiolytic Use Disorder, namely, reinforcing properties of benzodiazepines, maladaptive behaviors related to benzodiazepine use, and benzodiazepine tolerance and dependence. We review existing evidence regarding the involvement of different GABA_A receptor subtypes in each of these areas. The reviewed studies suggest that α1-containing GABA_A receptors play an integral role in benzodiazepine-induced plasticity in reward-related brain areas and might be involved in the development of tolerance and dependence to benzodiazepines. However, a systematic comparison of the contributions of all benzodiazepine-sensitive GABA_A receptors to these processes, a mechanistic understanding of how the positive modulation of each receptor subtype might contribute to the brain mechanisms underlying each of these processes, and a definitive answer to the question of whether specific chronic modulation of any given subtype would result in some or all of the benzodiazepine effects are currently lacking from the literature. Moreover, how non-selective benzodiazepines might lead to the maladaptive behaviors listed in DSM and how different GABA_A receptor subtypes might be involved in the development of these behaviors remains unexplored. Considering the increasing burden of benzodiazepine abuse, the common practice of benzodiazepine misuse that leads to severe dependence, and the current efforts to generate side-effect free benzodiazepine alternatives, there is an urgent need for systematic, mechanistic research that provides a better understanding of the brain mechanisms of benzodiazepine misuse and abuse, including the involvement of specific GABA_A receptor subtypes in these processes, to establish an informed foundation for preclinical and clinical efforts.

Doubling down: increased risk-taking behavior following a loss by individuals with cocaine use disorder is associated with striatal and anterior cingulate dysfunction

BACKGROUND

Cocaine use disorders (CUDs) have been associated with increased risk-taking behavior. Neuroimaging studies have suggested that altered activity in reward and decision-making circuitry may underlie cocaine user's heightened risk-taking. It remains unclear if this behavior is driven by greater reward salience, lack of appreciation of danger, or another deficit in risk-related processing.

METHODS

Twenty-nine CUD participants and forty healthy comparison participants completed the Risky Gains Task during a functional magnetic resonance imaging scan. During the Risky Gains Task, participants choose between a safe option for a small, guaranteed monetary reward and risky options with larger rewards but also the chance to lose money. Frequency of risky choice overall and following a win versus a loss were compared. Neural activity during the decision and outcome phase were examined using linear mixed effects models.

RESULTS

Although the groups did not differ in overall risk-taking frequency, the CUD group chose a risky option more often following a loss. Neuroimaging analyses revealed that the comparison group showed increasing activity in the bilateral ventral striatum as they chose higher-value, risky options, but the CUD group failed to show this increase. During the outcome phase, the CUD group showed a greater decrease in bilateral striatal activity relative to the comparison group when losing the large amount, and this response was correlated with risk-taking frequency after a loss.

CONCLUSIONS

The brains of CUD individuals are hypersensitive to losses, leading to increased risk-taking behaviors, and this may help explain why these individuals take drugs despite aversive outcomes.

Attenuated Neural Processing of Risk in Young Adults at Risk for Stimulant Dependence

Objective

Approximately 10% of young adults report non-medical use of stimulants (cocaine, amphetamine, methylphenidate), which puts them at risk for the development of dependence. This fMRI study investigates whether subjects at early stages of stimulant use show altered decision making processing.

Methods

158 occasional stimulants users (OSU) and 50 comparison subjects (CS) performed a “risky gains” decision making task during which they could select safe options (cash in 20 cents) or gamble them for double or nothing in two consecutive gambles (win or lose 40 or 80 cents, “risky decisions”). The primary analysis focused on risky versus safe decisions. Three secondary analyses were conducted: First, a robust regression examined the effect of lifetime exposure to stimulants and marijuana; second, subgroups of OSU with >1000 (n = 42), or <50 lifetime marijuana uses (n = 32), were compared to CS with <50 lifetime uses (n = 46) to examine potential marijuana effects; third, brain activation associated with behavioral adjustment following monetary losses was probed.

Results

There were no behavioral differences between groups. OSU showed attenuated activation across risky and safe decisions in prefrontal cortex, insula, and dorsal striatum, exhibited lower anterior cingulate cortex (ACC) and dorsal striatum activation for risky decisions and greater inferior frontal gyrus activation for safe decisions. Those OSU with relatively more stimulant use showed greater dorsal ACC and posterior insula attenuation. In comparison, greater lifetime marijuana use was associated with less neural differentiation between risky and safe decisions. OSU who chose more safe responses after losses exhibited similarities with CS relative to those preferring risky options.

Discussion

Individuals at risk for the development of stimulant use disorders presented less differentiated neural processing of risky and safe options. Specifically, OSU show attenuated brain response in regions critical for performance monitoring, reward processing and interoceptive awareness. Marijuana had additive effects by diminishing neural risk differentiation.

Antihistamine induced blood oxygenation level dependent response changes related to visual processes during sensori-motor performance

The histaminergic involvement in selective processes underlying its role in human sensori-motor performance is largely unknown. Recently, selective effects of central H₁-inverse agonism on sensory visual processes were observed in electrophysiological--but not behavioral data; a discrepancy suggested to result from speeded response-choice related processes. This study attempts to establish the effects on visual processes and identify putative compensatory mechanisms related to increased visual and response-choice task demands by assessing H₁-inverse agonism induced changes in blood oxygenation level dependent (BOLD) response. Twelve participants received oral doses of dexchlorpheniramine 4 mg, lorazepam 1 mg, and placebo in a three-way crossover designed study. Brain activity was assessed for choice reaction time task performance in a 3 T magnetic resonance scanner 2 h after drug administration. Participants responded with their left or right hand and index or middle finger as indicated by the laterality of stimulus presentation and identity of the stimulus, respectively. Stimuli were intact or visually degraded and responses were compatible or incompatible with the laterality of stimulus presentation. Both dexchlorpheniramine and lorazepam affected the BOLD response in the occipital cortex indicating affected visual information processing. Dexchlorpheniramine decreased BOLD response in the dorsal precuneus and left precentral gyrus as part of a motor network, which however might not be interpreted as a compensatory mechanism, but may be the upstream consequence of impaired visual processing.

Alcohol attenuates amygdala-frontal connectivity during processing social signals in heavy social drinkers: a preliminary pharmaco-fMRI study

RATIONALE

Convergent evidence shows that alcohol exerts its effects on social behavior via modulation of amygdala reactivity to affective stimuli. Given that affective processing involves dynamic interactions between the amygdala and the prefrontal cortex (PFC), alcohol's effects are likely to extend beyond regional changes in brain activity to changes that manifest on a broader functional circuit level.

OBJECTIVE

The current study examines alcohol's effects on functional connectivity (i.e., "coupling") between the amygdala and the PFC during the processing of socio-emotional stimuli using functional magnetic resonance imaging (fMRI).

METHODS

In a randomized, double blind, placebo-controlled, within-subjects cross-over design, 12 heavy, social drinkers performed an fMRI task designed to probe amygdala response to socio-emotional stimuli (angry, fearful, and happy faces) following acute ingestion of alcohol or placebo. Functional connectivity between the amygdala and PFC was examined and compared between alcohol and placebo sessions using a conventional generalized psychophysiological interaction (gPPI) analysis.

RESULTS

Relative to placebo, alcohol reduced functional coupling between the amygdala and the right orbitofrontal cortex (OFC) during processing of both angry and fearful faces. Alcohol also reduced functional coupling between the amygdala and left OFC during processing of happy faces.

CONCLUSIONS

These preliminary findings suggest that alcohol's effects on social behavior may be mediated by alternations in functional connectivity between the amygdala and OFC during processing of emotional faces.

Red brain, blue brain: evaluative processes differ in Democrats and Republicans

Liberals and conservatives exhibit different cognitive styles and converging lines of evidence suggest that biology influences differences in their political attitudes and beliefs. In particular, a recent study of young adults suggests that liberals and conservatives have significantly different brain structure, with liberals showing increased gray matter volume in the anterior cingulate cortex, and conservatives showing increased gray matter volume in the in the amygdala. Here, we explore differences in brain function in liberals and conservatives by matching publicly-available voter records to 82 subjects who performed a risk-taking task during functional imaging. Although the risk-taking behavior of Democrats (liberals) and Republicans (conservatives) did not differ, their brain activity did. Democrats showed significantly greater activity in the left insula, while Republicans showed significantly greater activity in the right amygdala. In fact, a two parameter model of partisanship based on amygdala and insula activations yields a better fitting model of partisanship than a well-established model based on parental socialization of party identification long thought to be one of the core findings of political science. These results suggest that liberals and conservatives engage different cognitive processes when they think about risk, and they support recent evidence that conservatives show greater sensitivity to threatening stimuli.

Establishing the neurobiologic basis of treatment in children and adolescents with generalized anxiety disorder

Generalized anxiety disorder (GAD) is associated with significant morbidity in children and adolescents, yet only recently have the neuropharmacology and neurophysiology of this condition been studied in youth. Accumulating data suggest structural and functional abnormalities within the brain's fear networks in youth with GAD. Additionally, seven studies examined the efficacy of medications that modulate this system and, in some cases, the direct effects of these medications on structures within these networks (e.g. amygdala, ventrolateral prefrontal cortex [VLPFC]). In this review, we summarize the extant functional, functional connectivity, and structural neuroimaging data in children and adolescents with GAD. In addition, data concerning selective serotonin reuptake inhibitors (SSRIs), selective serotonin norepinephrine reuptake inhibitors (SSNRIs), atypical anxiolytics, benzodiazepines, and psychotherapy are reviewed in the context of the neurophysiology of pediatric GAD. The existing data suggest abnormal activity within the amygdala, VLPFC, and anterior cingulate cortex, as well as the possibility of impaired connectivity among these brain regions. In addition to numerous cognitive behavioral therapy (CBT) trials, five randomized, controlled psychopharmacologic trials primarily in youth with GAD suggest that SSRIs and SSNRIs are effective for this condition. These findings also raise the possibility that functional activity within the amygdala and VLPFC may be altered following successful treatment.

Pregabalin effects on neural response to emotional faces

Pregabalin has shown promise in the treatment of anxiety disorders. Previous functional magnetic resonance imaging (fMRI) studies indicate agents used to treat anxiety, e.g., SSRIs and benzodiazepines, attenuate amygdala, insula, and medial prefrontal cortex (mPFC) activation during emotional processing. Our prior study has shown that during anticipation of an emotional stimulus, pregabalin attenuates amygdala and insula activation but increases medial PFC activation. In this study, we examined whether, similar to SSRIs and benzodiazepines, pregabalin attenuates amygdala, insula, and medial PFC during emotional face processing. Sixteen healthy volunteers underwent a double-blind within-subjects fMRI study investigating effects of placebo, 50 mg, and 200 mg pregabalin on neural activation during an emotional face-matching task. Linear mixed model analysis revealed that pregabalin dose-dependently attenuated left amygdala activation during fearful face-matching and left anterior insula activation during angry face-matching. The 50 mg dose exhibited more robust effects than the 200 mg dose in the right anterior insula and ventral ACC. Thus, pregabalin shares some similarity to SSRIs and benzodiazepines in attenuating anger and fear-related insula and amygdala activation during emotional face processing. However, there is evidence that a subclinical 50 mg dose of pregabalin produced more robust and widespread effects on neural responses in this paradigm than the more clinically relevant 200 mg dose. Taken together, pregabalin has a slightly different effect on brain activation as it relates to anticipation and emotional face processing, which may account for its unique characteristic as an agent for the treatment of anxiety disorders.

Anxiolytic-like effect of pregabalin on unconditioned fear in the rat: an autoradiographic brain perfusion mapping and functional connectivity study

Clinical and preclinical evidence suggests anxiolytic-like efficacy of pregabalin (PGB, Lyrica). However, its mechanism of action remains under investigation. The current study applied [(14)C]-iodoantipyrine cerebral blood flow (CBF) mapping to examine the effect of PGB on neural substrates underlying unconditioned fear in a rat model of footshock-induced fear. Regional CBF (rCBF) was analyzed by statistical parametric mapping. Functional connectivity and graph theoretical analysis were used to investigate how footshock and PGB affect brain activation at the network level. Pregabalin significantly attenuated footshock-induced ultrasonic vocalization, but showed no significant effect on freezing behavior. Footshock compared to no-shock controls elicited significant increases in rCBF in limbic/paralimbic regions implicated in the processing of unconditioned fear and ultrasonic vocalization, including the amygdala, hypothalamus, lateral septum, dorsal periaqueductal gray, the anterior insular (aINS) and medial prefrontal cortex (mPFC). The activation pattern was similar in vehicle- and PGB-treated subjects, with PGB significantly attenuating activation in the amygdala, hypothalamus, and aINS. The vehicle/no-shock group showed strong, positive intra-structural correlations within the cortex, hypothalamus, amygdala, thalamus, and brainstem. The cortex was negatively correlated with the hypothalamus and brainstem. Footshock reduced the total number of significant correlations, but induced greater intra-cortical connectivity of the aINS and mPFC, and new positive correlations between the hypothalamus and amygdala. In no-shock controls, PGB significantly reduced the positive intra-structural correlations within the cortex and amygdala, as well as the negative cortico-subcortical correlations. Following footshocks, PGB disrupted both the network recruitment of aINS and mPFC, and the positive hypothalamic-amygdaloid correlations. Our findings suggest that PGB may exert anxiolytic effect by attenuating cortico-cortical and cortico-subcortical communication and inhibiting network recruitment of the aINS, mPFC, amygdala, and hypothalamus following a fear-inducing stimulus. Functional brain mapping in rodents may provide new endpoints for preclinical evaluation of anxiolytic drug candidates with potentially improved translational power compared to behavioral measurements alone.

Pregabalin influences insula and amygdala activation during anticipation of emotional images

Pregabalin (PGB) has shown potential as an anxiolytic for treatment of generalized and social anxiety disorder. PGB binds to voltage-dependent calcium channels, leading to upregulation of GABA inhibitory activity and reduction in the release of various neurotransmitters. Previous functional magnetic resonance imaging (fMRI) studies indicate that selective serotonin reuptake inhibitors and benzodiazepines attenuate amygdala, insula, and medial prefrontal cortex activation during anticipation and emotional processing in healthy controls. The aim of this study was to examine whether acute PGB administration would attenuate activation in these regions during emotional anticipation. In this double-blind, placebo-controlled, randomized crossover study, 16 healthy controls completed a paradigm involving anticipation of negative and positive affective images during fMRI approximately 1 h after administration of placebo, 50, or 200 mg PGB. Linear mixed model analysis revealed that PGB was associated with (1) decreases in left amygdala and anterior insula activation and (2) increases in anterior cingulate (ACC) activation, during anticipation of positive and negative stimuli. There was also a region of the anterior amygdala in which PGB dose was associated with increased activation during anticipation of negative and decreased activation during anticipation of positive stimuli. Attenuation of amygdala and insula activation during anticipatory or emotional processing may represent a common regional brain mechanism for anxiolytics across drug classes. PGB induced increases in ACC activation could be a unique effect related to top-down modulation of affective processing. These results provide further support for the viability of using pharmaco-fMRI to determine the anxiolytic potential of pharmacologic agents.

Limbic justice--amygdala involvement in immediate rejection in the Ultimatum Game

Imaging studies have revealed a putative neural account of emotional bias in decision making. However, it has been difficult in previous studies to identify the causal role of the different sub-regions involved in decision making. The Ultimatum Game (UG) is a game to study the punishment of norm-violating behavior. In a previous influential paper on UG it was suggested that frontal insular cortex has a pivotal role in the rejection response. This view has not been reconciled with a vast literature that attributes a crucial role in emotional decision making to a subcortical structure (i.e., amygdala). In this study we propose an anatomy-informed model that may join these views. We also present a design that detects the functional anatomical response to unfair proposals in a subcortical network that mediates rapid reactive responses. We used a functional MRI paradigm to study the early components of decision making and challenged our paradigm with the introduction of a pharmacological intervention to perturb the elicited behavioral and neural response. Benzodiazepine treatment decreased the rejection rate (from 37.6% to 19.0%) concomitantly with a diminished amygdala response to unfair proposals, and this in spite of an unchanged feeling of unfairness and unchanged insular response. In the control group, rejection was directly linked to an increase in amygdala activity. These results allow a functional anatomical detection of the early neural components of rejection associated with the initial reactive emotional response. Thus, the act of immediate rejection seems to be mediated by the limbic system and is not solely driven by cortical processes, as previously suggested. Our results also prompt an ethical discussion as we demonstrated that a commonly used drug influences core functions in the human brain that underlie individual autonomy and economic decision making.

It is well-established that emotions influence decision making. One way of studying this relationship is the Ultimatum Game, which has revealed that subjects punish unfair behavior in others in spite of receiving a concomitant economic loss. Previous brain imaging studies have suggested that this decision to punish involves complex cortical processing. However, punishment also involves an instant aggressive emotional response, a behavior often linked to subcortical structures such as the amygdala. In this study, we present a model that joins these views. We designed a paradigm that allows us to measure the activity of subcortical brain regions during decision making in the Ultimatum Game, while at the same time using a pharmacological approach that can suppress emotional responses and amygdala activity. The pharmacological treatment made subjects punish unfair behavior less, and decreased brain activity in the amygdala in response to unfair proposals, without changing the subjects' feeling of unfairness. In the control group, punishment was directly linked to an increase in amygdala activity. Thus, immediate punishment of unfair behavior involves the amygdala and is not solely driven by cortical processes, as previously suggested. Our results show that a commonly used drug influences autonomy and decision making, which may have ethical implications for its use.

One milligram of lorazepam does not decrease anxiety induced by CCK-4 in healthy volunteers: investigation of neural correlates with BOLD MRI

Benzodiazepine effects on cholecystokinin tetrapeptide (CCK-4)-induced panic attack (PA) in humans are incompletely characterized, in particular on the neurofunctional level. This work explores the effects of lorazepam on brain activity and behavioral and physiological symptoms related to CCK-4-induced PA in healthy volunteers. Twenty-one male volunteers received 1 mg of lorazepam or placebo orally, 2 hours before an injection of 0.9% saline solution followed by 50 µg of CCK-4 during functional magnetic resonance imaging (fMRI) and heart rate recording. Panic attacks were defined using the panic symptom scale (PSS). In addition, the Y1-STAI (state anxiety) and the Bond & Lader Visual Analogue Scale (VAS) were used. Eleven subjects were classified as panickers. CCK-4 induced behavioral anxiety and cardiovascular effects along with cerebral activation in anxiety-related brain regions. Overall, lorazepam did not significantly modify the anxiogenic and cardiovascular effects of CCK-4. Regarding CCK-4-induced brain activation, lorazepam did not reduce activity in the insulae and cingulate gyrus of panickers. One milligram of lorazepam was not sufficient to reverse strong panicogenic effects, but decreased brain activity in the case of mild anxiety.

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.

Effects of lorazepam on brain activity pattern during an anxiety symptom provocation challenge

Human models of anxiety are useful to develop new effective anxiolytics. The objective of this study was to use functional magnetic resonance imaging (fMRI) to test the hypothesis that a single dose of lorazepam modifies brain activation during an anxiety challenge. Eighteen healthy male subjects underwent fMRI associated with a challenge based on the anticipation of aversive electrical stimulations after pretreatment, either with placebo or with 1.0 mg of oral lorazepam. Anxiety was rated before fMRI and after, referring to the threat condition periods, using State Trait Anxiety Inventory (STAI) and Hamilton scales. The conditioning procedure induced anxiety, as indicated by clinical rating score changes. Lorazepam did not modify anxiety rating as compared to placebo. Lorazepam reduced cerebral activity in superior frontal gyrus, anterior insula/inferior frontal gyrus and cingulate gyrus. The current finding provides the first evidence of the modulatory effects of an established anxiolytic agent on brain activation related to anticipatory anxiety.

Subchronic SSRI administration reduces insula response during affective anticipation in healthy volunteers

The anterior cingulate cortex (ACC) and insula are important neural substrates for the integration of cognitive, emotional, and physiological information, as well as the coordination of responses to anticipated stimuli. Increased neural activation within these structures has been observed in individuals with anxiety and depressive disorders. Selective serotonin reuptake inhibitors (SSRIs) are among the most effective and frequently prescribed anxiolytic agents, yet it is not known whether ACC or insula underlie the effects of these drugs. We examined whether subchronic administration of a SSRI to healthy volunteers attenuates activation in ACC or insula during anticipation, an important emotional process underlying anxiety. Support for this hypothesis would help to understand where and by what process SSRIs may exert beneficial effects as anxiolytics and would provide further mechanistic evidence for functional magnetic resonance imaging (fMRI) as a biomarker for the development of anxiolytics. Fifteen volunteers participated in a double-blind, placebo-controlled, randomized cross-over study. Participants completed a pleasant and aversive picture-cued anticipation task during fMRI after taking either escitalopram (10 mg) or placebo for 21 d. We found that escitalopram significantly decreased activation in bilateral posterior and middle insula during the anticipation condition irrespective of stimulus valence and in medial prefrontal and ACC during anticipation of aversive vs. pleasant images. Reduced insular and ACC activation in healthy controls during anticipation may be integral to the therapeutic efficacy of SSRIs and may provide a mechanistic approach for the use of pharmaco-fMRI in the identification of novel pharmacotherapeutic agents in patient populations.

A link between serotonin-related gene polymorphisms, amygdala activity, and placebo-induced relief from social anxiety

Placebo may yield beneficial effects that are indistinguishable from those of active medication, but the factors underlying proneness to respond to placebo are widely unknown. Here, we used functional neuroimaging to examine neural correlates of anxiety reduction resulting from sustained placebo treatment under randomized double-blind conditions, in patients with social anxiety disorder. Brain activity was assessed during a stressful public speaking task by means of positron emission tomography before and after an 8 week treatment period. Patients were genotyped with respect to the serotonin transporter-linked polymorphic region (5-HTTLPR) and the G-703T polymorphism in the tryptophan hydroxylase-2 (TPH2) gene promoter. Results showed that placebo response was accompanied by reduced stress-related activity in the amygdala, a brain region crucial for emotional processing. However, attenuated amygdala activity was demonstrable only in subjects who were homozygous for the long allele of the 5-HTTLPR or the G variant of the TPH2 G-703T polymorphism, and not in carriers of short or T alleles. Moreover, the TPH2 polymorphism was a significant predictor of clinical placebo response, homozygosity for the G allele being associated with greater improvement in anxiety symptoms. Path analysis supported that the genetic effect on symptomatic improvement with placebo is mediated by its effect on amygdala activity. Hence, our study shows, for the first time, evidence of a link between genetically controlled serotonergic modulation of amygdala activity and placebo-induced anxiety relief.

Sex-related differences in neural activity during risk taking: an fMRI study

This study explored sex effects on the process of risk-taking. We observed that the female participants (n = 10) showed stronger activation in the right insula and bilateral orbitofrontal cortex (OFC) than did the male participants (n = 12) while they were performing in the Risky-Gains task. The female participants also showed stronger activations in the precentral, postcentral, and paracentral regions after receiving punishment feedback. In addition, the strength of neural activity in the insula correlated with the rate of risky behaviors for the female participants but not for the male participants. Similarly, the percent signal changes in the right OFC correlated negatively with the rate of selecting risky choices for the female group. These findings strongly suggest a sex-related influence modulating brain activity during risk-taking tasks. When taking the same level of risk, relative to men, women tend to engage in more neural processing involving the insula and the OFC to update and valuate possible uncertainty associated with risk-taking decision making. These results are consistent with the value-based decision-making model and offer insights into the possible neural mechanisms underlying the different risk-taking attitudes of men and women.

An event-related fMRI study on risk taking by healthy individuals of high or low impulsiveness

This event-related functional Magnetic Resonance Imaging study examined the differential neural activities associated with a Risky-Gains task in 18 healthy individuals of high (n=9) or low (n=9) impulsiveness, according to their scores on the Barratt Impulsiveness Scale (BIS). The neural activities of people belonging to the high and low impulsiveness groups were monitored by a 3T MRI scanner while they were performing the Risky-Gains task. We demonstrated that a stronger activation in the insula-orbitofrontal-parietal regions was found in the high impulsiveness group compared to the low impulsiveness group. However, the levels of activation in the lateral prefrontal and anterior cingulate regions did not differ between the two groups. The findings suggest that the neural substrates of comprehension of cognitive and affective information associated with risk-taking decision making may vary according to the impulsiveness among healthy individuals.

Escitalopram effects on insula and amygdala BOLD activation during emotional processing

RATIONALE

The amygdala and insular cortex are integral to the processing of emotionally salient stimuli. We have shown in healthy volunteers that an anxiolytic agent, lorazepam, dose-dependently attenuates activation of limbic structures.

OBJECTIVE

The current study investigated whether administration of a selective serotonin reuptake inhibitor (SSRI), escitalopram, alters the activation of limbic structures. We hypothesized that subchronic (21 days) SSRI treatment attenuates the activation of the amygdala and insula during processing of emotional faces.

MATERIALS AND METHODS

Thirteen healthy volunteers participated in a double-blind, placebo-controlled, crossover, randomized study. After 21 days of treatment with either escitalopram or placebo, participants underwent functional magnetic resonance imaging (fMRI) during which all subjects completed an emotion face assessment task, which has been shown to elicit amygdala and insula activation.

RESULTS

Subjects activated the bilateral insula and amygdala after treatment with both escitalopram and placebo. In subjects who were adherent to the protocol (as evidenced by sufficiently high urine concentrations of escitalopram), a reduction in amygdala activation was seen in the escitalopram condition compared to placebo.

CONCLUSION

The current investigation provides further evidence for the mechanism of action of SSRIs through the attenuation of activation in brain regions responsible for emotion processing and provides support for the use of blood oxygenation level-dependent fMRI with pharmacological probes to help identify the specific therapeutic effect of these agents in patients with anxiety and mood disorders.

Amygdala activation modulated by levodopa during emotional recognition processing in healthy volunteers: a double-blind, placebo-controlled study

A critical role of dopaminergic systems in emotional processing has been revealed by several animal and clinical studies in Parkinson disease and schizophrenia. We conducted a study with functional magnetic resonance imaging (fMRI) in 13 healthy volunteers to test the dopaminergic modulation on amygdala response to emotional processing and to evaluate if it was the result of a direct action on amygdalar nuclei or indirect modulation via medial prefrontal cortex projecting on amygdala.A placebo-controlled crossover experimental design was used. Subjects received either levodopa (100 mg) or placebo in 2 fMRI sessions. Amygdala activation was evaluated during a facial emotion recognition test.The statistical comparison between placebo versus levodopa situations revealed a significant reduction in activation of right amygdala during the levodopa fMRI session. The functional connectivity analysis revealed only a change of correlated activations between right and left amygdala, and not medial prefrontal cortex, after levodopa administration. Our results suggest that administration of levodopa to healthy volunteers impairs the amygdalar activation. It supports the hypothesis that amygdala activation follows an inverted U-shaped curve in relation to dopamine (DA) concentration. The results of the functional connectivity seem to suggest a dopaminergic action on amygdalar nuclei rather than a modulation of medial prefrontal cortex on amygdala.

Increased amygdala activation is related to heart rate during emotion processing in adolescent subjects

Emotions have been conceptualized as representations of bodily responses to a stimulus that critically involves the autonomic nervous system (ANS). An association between amygdala activation and ANS activity has been shown in adults. However, to date, no studies have demonstrated this association in adolescents. Examining the interaction between the ANS and amygdala in healthy adolescents may provide information about age-related changes in the association between amygdala activation and ANS measures. Therefore, the aim of this study was to examine the relationship between amygdala activation and heart rate in normal adolescents. Eighteen 12- to 17-year old adolescents participated. Heart rate data was collected during functional magnetic resonance imaging while subjects performed a facial expression matching task that reliably activates the amygdala. Adolescents showed significant amygdala activation for all facial expressions relative to the shape-matching, control task. Moreover, the degree of activation in the right amygdala for Fearful faces was significantly correlated with heart rate (Spearman's rho=0.55, p=0.018, two-tailed). This study shows that amygdala activity is related to heart rate in healthy adolescents. Thus, similar to adults, adolescents show a coupling between processing emotional events and adjusting the ANS accordingly. Furthermore, this study confirms previous adolescent studies showing amygdala activation to Fearful, Angry, and Happy faces. Finally, the results of the present study lay the foundation for future research to investigate whether adolescents with mood or anxiety disorders show an altered coupling between processing emotionally salient events and ANS activity.

Age-related differences in neural activities during risk taking as revealed by functional MRI

Previous research has clearly documented that risky decision making is different in young and older adults. Yet, there has been a relative dearth of research that seeks to understand such age-related changes in the neural activities associated with risk taking. To address this research issue, 21 men (12 young men, mean age 29.9 ± 6.2 years and 9 older men, mean age 65.2 ± 4.2 years) performed a risky-gains task while their brain activities were monitored by an fMRI scanner. The older adults, relative to their younger peers, presented with contralateral prefrontal activity, particularly at the orbitofrontal cortex. Furthermore, stronger activation of the right insula was observed for the older-aged participants compared to the younger-aged adults. The findings of this study are consistent with the a priori speculations established in accordance with the HAROLD model as well as previous findings. Findings of this study suggest that when making risky decisions, there may be possible neuropsychological mechanisms underlying the change in impulsive and risk-taking behaviors during the course of natural ageing.

Affect recognition deficits in schizophrenia: neural substrates and psychopharmacological implications

Impaired emotional functioning is a prominent feature of schizophrenia that includes significant deficits in the ability to accurately recognize facial expressions of emotion. Recent work demonstrates that deficits in affect perception are related to functional outcome and negative symptoms, suggesting that remediation of these deficits may contribute to symptomatic and functional improvements. Thus far, antipsychotic drug treatments appear to be relatively ineffective as a remedial tool. However, investigations into the neurobiology of affective dysfunction show abnormal amygdala activation in schizophrenia during affect recognition tasks. Such findings indicate that regulation of amygdala responses may aid in more accurate emotion processing. Both serotonergic and anxiolytic GABAergic agents that modulate activation of the limbic system offer promising avenues for remediation efforts.

Role of functional magnetic resonance imaging in drug discovery

In this review, we survey the state of the field of functional magnetic resonance imaging (fMRI) as it relates to drug discovery and drug development. We highlight the advantages and limitations of fMRI for this purpose and suggest ways to improve the use of fMRI for developing new therapeutics, with emphasis on treatments for anxiety disorders. Fundamentally, pharmacological studies with standard psychiatric treatments using standardized behavioral probes during fMRI will need to be carried out to determine characteristic brain signatures that could be used to predict whether novel compounds are likely to have specific therapeutic effects.