Cognitive vs. Emotional Psychopharmacological Manipulations of Fear vs. Anxiety

Phase 4

Completed

Conditions: Anxiety Disorder

Interventions: Drug: Placebo
Drug: Methylphenidate
Drug: Propranolol

Registration Number: NCT02153944

Lead Sponsor: National Institute of Mental Health (NIMH)

Brief Summary: Objective:

The overall aim of this protocol is to examine the effect of pharmacological manipulations of affective and cognitive processes on anxiety and task performance. Ultimately, the goal is 1) to provide insight into the relative influence of cognitive and affective states on anxiety, 2) generate theoretical models that can be applied to a better understanding of the interaction between cognition and emotion, 3) develop a better screening approach to candidate anxiolytics, and 4) help formulate novel therapeutic interventions for clinical anxiety.

Excessive or inappropriately sustained anxiety and fear lead to the most common group of psychiatric disorders. A number of theoretical models have been proposed to understand the mechanisms engaged in these maladaptive behaviors. Most recent emphasis has focused on the synergistic contribution of cognitive and emotional processes. Our laboratory has been instrumental in delineating aspects of behavioral and neural processes that are associated with fear and anxiety, using psychophysiological and neuroimaging measures of fear and anxiety. Evidence shows that levels of anxiety modulate cognitive performance, such as working memory or perceptual discrimination, and that, conversely, cognitive engagement influences severity of experimentally induced anxiety. The exact contribution of emotional processes vs. cognitive processes to the experience of anxiety is not clear, similarly to the neural mechanisms underlying these interactions.

In this protocol, we propose to manipulate pharmacologically separately cognitive and emotional processes to dissociate their contribution to fear/anxiety, while using state-of-the-art measures of anxiety derived from translational work. Indeed, we already developed integrative experimental models of fear and anxiety via the manipulation of predictable and unpredictable shock, respectively. We already employed successfully these models to measure anxiolytic and anxiogenic effects of various compounds such as alprazolam, citalopram, hydrocortisone, and oxytocin in healthy participants.

We propose in a first step (step-1) to start with a simple proof-of-concept study, using two pharmacological compounds in a double-blind randomized parallel design, each preferentially acting respectively on the cognitive (methylphenidate) or affective (propranolol) domain, and using a single cognitive process (working memory). In a second step (step-2), we propose to extend this work to the fMRI to examine the cognitive correlates of the effects seen in the step-1 behavioral study, specifically with methylphenidate. Whereas the comparison among three drugs is planned for the electrophysiology study, we plan to study only the drug that improves cognition in the fMRI. The reason we will focus on methylphenidate in step 2 is that our overall goal is to study the effect of improving cognitive functions on anxiety using neuroimaging. To reach this goal, we plan to use different approaches to boost cognitive functions in the coming years, including psychopharmacology, direct current stimulation, mindfulness. Methylphenidate is our first psychopharmacological study towards this objective. Future work will also expand to other compounds and cognitive processes, as well as vary the strategy to induce anxiety. Presently, anxiety will be induced using the threat of shock, while participants perform the task. We will examine in step-1 whether 1) the reduction of induced-anxiety with propranolol improves cognitive performance, and 2) the facilitation of cognitive performance with methylphenidate reduces induced-anxiety. In step-2, we will identify the neural mechanisms underlying the effects of methylphenidate, the drug having beneficial effects on cognitive function.

Study population:

Medically and psychiatrically healthy adult males and females, aged 18 to 50 years.

Design:

The study is a double-blind design. For step-1, three groups of healthy participants will come for one experimental session. During this session, they will be asked to perform a working memory task under the threat of shock, i.e., while anticipating unpleasant electric shocks. Each group will receive one drug challenge, either placebo, propranolol (40 g) or methylphenidate (20 mg). For step-2, the study tasks will be conducted in a 3T fMRI scanner. In this step, only methylphenidate and placebo will be compared. Two groups will come for one experimental session, one will receive placebo and the other one will receive methylphenidate (20 mg). In a follow-up study for the step-2 fMRI the two groups will come for one experimental fMRI session one will receive methylphenidate (60 mg).

Outcome measures:

In step-1, the primary outcome measures are the startle reflex and performance on the working memory task. In step-2, the primary outcome measures are the startle reflex and the cerebral fMRI blood-oxygen-level ...

Detailed Description: Objective:

The overall aim of this protocol is to examine the effect of pharmacological manipulations of affective and cognitive processes on anxiety and task performance. Ultimately, the goal is 1) to provide insight into the relative influence of cognitive and affective states on anxiety, 2) generate theoretical models that can be applied to a better understanding of the interaction between cognition and emotion, 3) develop a better screening approach to candidate anxiolytics, and 4) help formulate novel therapeutic interventions for clinical anxiety.

Excessive or inappropriately sustained anxiety and fear lead to the most common group of psychiatric disorders. A number of theoretical models have been proposed to understand the mechanisms engaged in these maladaptive behaviors. Most recent emphasis has focused on the synergistic contribution of cognitive and emotional processes. Our laboratory has been instrumental in delineating aspects of behavioral and neural processes that are associated with fear and anxiety, using psychophysiological and neuroimaging measures of fear and anxiety. Evidence shows that levels of anxiety modulate cognitive performance, such as working memory or perceptual discrimination, and that, conversely, cognitive engagement influences severity of experimentally induced anxiety. The exact contribution of emotional processes vs. cognitive processes to the experience of anxiety is not clear, similarly to the neural mechanisms underlying these interactions.

In this protocol, we propose to manipulate pharmacologically separately cognitive and emotional processes to dissociate their contribution to fear/anxiety, while using state-of-the-art measures of anxiety derived from translational work. Indeed, we already developed integrative experimental models of fear and anxiety via the manipulation of predictable and unpredictable shock, respectively. We already employed successfully these models to measure anxiolytic and anxiogenic effects of various compounds such as alprazolam, citalopram, hydrocortisone, and oxytocin in healthy participants.

We propose in a first step (step-1) to start with a simple proof-of-concept study, using two pharmacological compounds in a double-blind randomized parallel design, each preferentially acting respectively on the cognitive (methylphenidate) or affective (propranolol) domain, and using a single cognitive process (working memory). In a second step (step-2), we propose to extend this work to the fMRI to examine the cognitive correlates of the effects seen in the step-1 behavioral study, specifically with methylphenidate. Whereas the comparison among three drugs is planned for the electrophysiology study, we plan to study only the drug that improves cognition in the fMRI. The reason we will focus on methylphenidate in step 2 is that our overall goal is to study the effect of improving cognitive functions on anxiety using neuroimaging. To reach this goal, we plan to use different approaches to boost cognitive functions in the coming years, including psychopharmacology, direct current stimulation, mindfulness. Methylphenidate is our first psychopharmacological study towards this objective. Future work will also expand to other compounds and cognitive processes, as well as vary the strategy to induce anxiety. Presently, anxiety will be induced using the threat of shock, while participants perform the task. We will examine in step-1 whether 1) the reduction of induced-anxiety with propranolol improves cognitive performance, and 2) the facilitation of cognitive performance with methylphenidate reduces induced-anxiety. In step-2, we will identify the neural mechanisms underlying the effects of methylphenidate, the drug having beneficial effects on cognitive function.

Study population:

Medically and psychiatrically healthy adult males and females, aged 18 to 50 years.

Design:

The study is a double-blind design. For step-1, three groups of healthy participants will come for one experimental session. During this session, they will be asked to perform a working memory task under the threat of shock, i.e., while anticipating unpleasant electric shocks. Each group will receive one drug challenge, either placebo, propranolol (40 g) or methylphenidate (20 mg). For step-2, the study tasks will be conducted in a 3T fMRI scanner. In this step, only methylphenidate and placebo will be compared. Two groups will come for one experimental session, one will receive placebo and the other one will receive methylphenidate (20 mg). In a follow-up study for the step-2 fMRI the two groups will come for one experimental fMRI session one will receive methylphenidate (60 mg).

Outcome measures:

In step-1, the primary outcome measures are the startle reflex and performance on the working memory task. In step-2, the primary outcome measures are the startle reflex and the cerebral fMRI blood-oxygen-level dependent (BOLD) responses. For both step-1 and step-2, secondary measures include skin conductance, heart rate, and subjective measures of anxiety.

Recruitment & Eligibility

Status: COMPLETED

Sex: All

Target Recruitment: 142

Inclusion Criteria

Not provided

Exclusion Criteria

Not provided

Study & Design

Study Type: INTERVENTIONAL

Study Design: PARALLEL

Arm && Interventions

Group	Intervention	Description
Behavioral: Drug challenge with placebo	Placebo	Participant received placebo orally during study visit
fMRI: Drug challenge with placebo	Placebo	Participant received placebo orally during study visit
Behavioral: Drug challenge with methylphenidate	Methylphenidate	Participant received methylphenidate 20 mg orally during study visit
Behavioral: Drug challenge with propranolol	Propranolol	Participants received propranolol 40mg orally during study visit
fMRI: Drug challenge with methylphenidate	Methylphenidate	Participant received methylphenidate 20 mg orally during study visit

Primary Outcome Measures

Name	Time	Method
Magnitude of Startle Reflex During Safe Condition	20-120 milliseconds following the onset of the startle stimulus	The magnitude of the startle reflex during working memory tasks (n-back) while undergoing alternating periods of safety and threat of shock. The n-back is a paradigm used to assess working memory function by presenting sequential stimuli individually. The participant holds each stimulus in short-term memory while new stimuli are presented. For each new item presented, the participant's task is to decide if it is the same as the stimulus presented one time before (1Back), two times before (2Back) or three times before (3Back) by responding "yes" if the stimulus currently presented matches the stimulus presented earlier. Participants responded with a button press. The startle reflex was elicited with a 102 decibel (dB) white noise (40-ms duration) delivered via headphone. The eyeblink component of the startle reflex was recorded binaurally with two silver chloride (AgCl) electrodes placed under one eye.
Magnitude of Startle Reflex During Threat Condition	20-120 milliseconds following the onset of the startle stimulus	The magnitude of the startle reflex during working memory tasks (n-back) while undergoing alternating periods of safety and threat of shock. The n-back is a paradigm used to assess working memory function by presenting sequential stimuli individually. The participant holds each stimulus in short-term memory while new stimuli are presented. For each new item presented, the participant's task is to decide if it is the same as the stimulus presented one time before (1Back), two times before (2Back) or three times before (3Back) by responding "yes" if the stimulus currently presented matches the stimulus presented earlier. Participants responded with a button press. The startle reflex was elicited with a 102 decibel (dB) white noise (40-ms duration) delivered via headphone. The eyeblink component of the startle reflex was recorded binaurally with two silver chloride (AgCl) electrodes placed under one eye.
Proportion of Correct Responses in the Working Memory Task (N-back) - Safe Condition	Task started 90 minutes post drug admin up to max of 125 mins post drug admin (max total is 35 mins) during a 6-hour single day visit	Stimuli were presented one at a time on a screen. Participants were instructed to remember (working memory) one, two, or three stimuli back (N-back) from the current stimulus on the screen while undergoing alternating periods of safety and threat of shock i.e. while anticipating unpleasant electric shocks or no shock (safe). The n-back is a paradigm used to assess working memory function by presenting sequential stimuli individually. The participant holds each stimulus in short-term memory while new stimuli are presented. For each new item presented, the participant's task is to decide if it is the same as the stimulus presented one time before (1Back), two times before (2Back) or three times before (3Back)" by responding "yes" if the stimulus currently presented matches the stimulus presented earlier. Performance on working memory task (n-back) accuracy was measured across condition (threat and safe) x Load (1Back, 2Back, 3Back) using repeated measures ANOVA.
Proportion of Correct Responses in the Working Memory Task (N-back) - Threat Condition	task started 90 minutes post drug admin up to max of 125 mins post drug admin (max total is 35 mins) during a 6-hour single day visit	Stimuli were presented one at a time on a screen. Participants were instructed to remember (working memory) one, two, or three stimuli back (N-back) from the current stimulus on the screen while undergoing alternating periods of safety and threat of shock i.e. while anticipating unpleasant electric shocks or no shock (safe). The n-back is a paradigm used to assess working memory function by presenting sequential stimuli individually. The participant holds each stimulus in short-term memory while new stimuli are presented. For each new item presented, the participant's task is to decide if it is the same as the stimulus presented one time before (1Back), two times before (2Back) or three times before (3Back)" by responding "yes" if the stimulus currently presented matches the stimulus presented earlier. Performance on working memory task (n-back) accuracy was measured across condition (threat and safe) x Load (1Back, 2Back, 3Back) using repeated measures ANOVA.
Proportion of Correct Responses in the Working Memory Task (N-Back): Safe Condition - 1BACK - Run 1	90 minutes post drug admin plus zero seconds within a 6-hour study visit	Stimuli were presented one at a time on a screen. Participants were instructed to remember (working memory) one or three stimuli back (N-back) from the current stimulus on the screen while undergoing alternating periods of safety and threat of shock i.e. while anticipating unpleasant electric shocks or no shock (safe).Two levels of difficulties were tested: 1- and 3-back. The n-back is a paradigm used to assess working memory function by presenting sequential stimuli individually. Participants indicated whether the letter currently displayed was the same as the letter presented 1 or 3 letters back. The task included 3 runs, 8 blocks per run (4 safe and 4 threat presented alternatively), 18 sequential letters per block. Each block represented a given level of difficulty, i.e., 1- and 3-back. Performance on working memory task (n-back) accuracy was measured across condition (threat and safe) x Load (1-back, 3-back) using repeated measures ANOVA.
Proportion of Correct Responses in the Working Memory Task (N-back): Threat Condition - 1BACK - Run 1	90 minutes plus 90 seconds within a 6-hour study visit	Stimuli were presented one at a time on a screen. Participants were instructed to remember (working memory) one or three stimuli back (N-back) from the current stimulus on the screen while undergoing alternating periods of safety and threat of shock i.e. while anticipating unpleasant electric shocks or no shock (safe). Two levels of difficulties were tested: 1- and 3-back. The n-back is a paradigm used to assess working memory function by presenting sequential stimuli individually. Participants indicated whether the letter currently displayed was the same as the letter presented 1 or 3 letters back. The task included 3 runs, 8 blocks per run (4 safe and 4 threat presented alternatively), 18 sequential letters per block. Each block represented a given level of difficulty, i.e., 1- and 3-back. Performance on working memory task (n-back) accuracy was measured across condition (threat and safe) x Load (1-back, 3-back) using repeated measures ANOVA.
Proportion of Correct Responses in the Working Memory Task (N-back): Safe Condition - 1BACK - Run 2	90 minutes plus 180 seconds within a 6-hour study visit	Stimuli were presented one at a time on a screen. Participants were instructed to remember (working memory) one or three stimuli back (N-back) from the current stimulus on the screen while undergoing alternating periods of safety and threat of shock i.e. while anticipating unpleasant electric shocks or no shock (safe). Two levels of difficulties were tested: 1- and 3-back. The n-back is a paradigm used to assess working memory function by presenting sequential stimuli individually. Participants indicated whether the letter currently displayed was the same as the letter presented 1 or 3 letters back. The task included 3 runs, 8 blocks per run (4 safe and 4 threat presented alternatively), 18 sequential letters per block. Each block represented a given level of difficulty, i.e., 1- and 3-back. Performance on working memory task (n-back) accuracy was measured across condition (threat and safe) x Load (1-back, 3-back) using repeated measures ANOVA.
Proportion of Correct Responses in the Working Memory Task (N-back): Threat Condition - 1BACK - Run 2	90 minutes plus 260 seconds within a 6-hour study visit	Stimuli were presented one at a time on a screen. Participants were instructed to remember (working memory) one or three stimuli back (N-back) from the current stimulus on the screen while undergoing alternating periods of safety and threat of shock i.e. while anticipating unpleasant electric shocks or no shock (safe). Two levels of difficulties were tested: 1- and 3-back. The n-back is a paradigm used to assess working memory function by presenting sequential stimuli individually. Participants indicated whether the letter currently displayed was the same as the letter presented 1 or 3 letters back. The task included 3 runs, 8 blocks per run (4 safe and 4 threat presented alternatively), 18 sequential letters per block. Each block represented a given level of difficulty, i.e., 1- and 3-back. Performance on working memory task (n-back) accuracy was measured across condition (threat and safe) x Load (1-back, 3-back) using repeated measures ANOVA.
Proportion of Correct Responses in the Working Memory Task (N-back): Safe Condition - 3BACK - Run 1	90 minutes post drug admin plus 45 seconds within a 6-hour study visit	Stimuli were presented one at a time on a screen. Participants were instructed to remember (working memory) one or three stimuli back (N-back) from the current stimulus on the screen while undergoing alternating periods of safety and threat of shock i.e. while anticipating unpleasant electric shocks or no shock (safe). Two levels of difficulties were tested: 1- and 3-back. The n-back is a paradigm used to assess working memory function by presenting sequential stimuli individually. Participants indicated whether the letter currently displayed was the same as the letter presented 1 or 3 letters back. The task included 3 runs, 8 blocks per run (4 safe and 4 threat presented alternatively), 18 sequential letters per block. Each block represented a given level of difficulty, i.e., 1- and 3-back. Performance on working memory task (n-back) accuracy was measured across condition (threat and safe) x Load (1-back, 3-back) using repeated measures ANOVA.
Proportion of Correct Responses in the Working Memory Task (N-back): Threat Condition - 3BACK - Run 1	90 minutes plus 135 seconds within a 6-hour study visit	Stimuli were presented one at a time on a screen. Participants were instructed to remember (working memory) one or three stimuli back (N-back) from the current stimulus on the screen while undergoing alternating periods of safety and threat of shock i.e. while anticipating unpleasant electric shocks or no shock (safe). Two levels of difficulties were tested: 1- and 3-back. The n-back is a paradigm used to assess working memory function by presenting sequential stimuli individually. Participants indicated whether the letter currently displayed was the same as the letter presented 1 or 3 letters back. The task included 3 runs, 8 blocks per run (4 safe and 4 threat presented alternatively), 18 sequential letters per block. Each block represented a given level of difficulty, i.e., 1- and 3-back. Performance on working memory task (n-back) accuracy was measured across condition (threat and safe) x Load (1-back, 3-back) using repeated measures ANOVA.
Proportion of Correct Responses in the Working Memory Task (N-back): Safe Condition - 3BACK - Run 2	90 minutes plus 215 seconds within a 6-hour study visit	Stimuli were presented one at a time on a screen. Participants were instructed to remember (working memory) one or three stimuli back (N-back) from the current stimulus on the screen while undergoing alternating periods of safety and threat of shock i.e. while anticipating unpleasant electric shocks or no shock (safe). Two levels of difficulties were tested: 1- and 3-back. The n-back is a paradigm used to assess working memory function by presenting sequential stimuli individually. Participants indicated whether the letter currently displayed was the same as the letter presented 1 or 3 letters back. The task included 3 runs, 8 blocks per run (4 safe and 4 threat presented alternatively), 18 sequential letters per block. Each block represented a given level of difficulty, i.e., 1- and 3-back. Performance on working memory task (n-back) accuracy was measured across condition (threat and safe) x Load (1-back, 3-back) using repeated measures ANOVA.
Proportion of Correct Responses in the Working Memory Task (N-back): Threat Condition - 3BACK - Run 2	90 minutes plus 305 seconds within a 6-hour study visit	Stimuli were presented one at a time on a screen. Participants were instructed to remember (working memory) one or three stimuli back (N-back) from the current stimulus on the screen while undergoing alternating periods of safety and threat of shock i.e. while anticipating unpleasant electric shocks or no shock (safe). Two levels of difficulties were tested: 1- and 3-back. The n-back is a paradigm used to assess working memory function by presenting sequential stimuli individually. Participants indicated whether the letter currently displayed was the same as the letter presented 1 or 3 letters back. The task included 3 runs, 8 blocks per run (4 safe and 4 threat presented alternatively), 18 sequential letters per block. Each block represented a given level of difficulty, i.e., 1- and 3-back. Performance on working memory task (n-back) accuracy was measured across condition (threat and safe) x Load (1-back, 3-back) using repeated measures ANOVA.
Reaction Time to Stimuli: Safe Condition - 1BACK - Run 1	90 minutes post drug admin plus zero seconds within a 6-hour study visit	Reaction time (RT) is the time it takes to respond to stimuli. Participants RTs were measured while undergoing alternating periods of safety and shock threat conditions i.e. while anticipating unpleasant electric shocks (threat) or no shock (safe) during the n-back paradigm task. The n-back is a paradigm used to assess working memory function by presenting sequential stimuli individually. Two levels of difficulties were tested: 1Back and 3Back (n-back). Participants were instructed to indicate whether the letter currently displayed was the same as the letter presented 1 or 3 letters back. The task was organized in 2 runs, 8 blocks per run (4 safe and 4 threat presented alternatively), 18 sequential letters per block. Each block (threat or safe) corresponded to 2 tasks, 1- and 3-back tasks. RT was analyzed using condition( threat, safe) x Load (1Back, 3Back) repeated-measures ANOVA.
Reaction Time to Stimuli: Threat Condition - 1BACK - Run 1	90 minutes plus 90 seconds within a 6-hour study visit	Reaction time (RT) is the time it takes to respond to stimuli. Participants RTs were measured while undergoing alternating periods of safety and shock threat conditions i.e. while anticipating unpleasant electric shocks (threat) or no shock (safe) during the n-back paradigm task. The n-back is a paradigm used to assess working memory function by presenting sequential stimuli individually. Two levels of difficulties were tested: 1Back and 3Back (n-back). Participants were instructed to indicate whether the letter currently displayed was the same as the letter presented 1 or 3 letters back. The task was organized in 2 runs, 8 blocks per run (4 safe and 4 threat presented alternatively), 18 sequential letters per block. Each block (threat or safe) corresponded to 2 tasks, 1- and 3-back tasks. RT was analyzed using condition (threat, safe) x Load (1Back, 3Back) repeated-measures ANOVA.
Reaction Time to Stimuli: Safe Condition - 1BACK - Run 2	90 minutes plus 180 seconds within a 6-hour study visit	Reaction time (RT) is the time it takes to respond to stimuli. Participants RTs were measured while undergoing alternating periods of safety and shock threat conditions i.e. while anticipating unpleasant electric shocks (threat) or no shock (safe) during the n-back paradigm task. The n-back is a paradigm used to assess working memory function by presenting sequential stimuli individually. Two levels of difficulties were tested: 1Back and 3Back (n-back). Participants were instructed to indicate whether the letter currently displayed was the same as the letter presented 1 or 3 letters back. The task was organized in 2 runs, 8 blocks per run (4 safe and 4 threat presented alternatively), 18 sequential letters per block. Each block (threat or safe) corresponded to 2 tasks, 1- and 3-back tasks. RT was analyzed using condition (threat, safe) x Load (1Back, 3Back) repeated-measures ANOVA.
Reaction Time to Stimuli: Threat Condition - 1BACK - Run 2	90 minutes plus 260 seconds within a 6-hour study visit	Reaction time (RT) is the time it takes to respond to stimuli. Participants RTs were measured while undergoing alternating periods of safety and shock threat conditions i.e. while anticipating unpleasant electric shocks (threat) or no shock (safe) during the n-back paradigm task. The n-back is a paradigm used to assess working memory function by presenting sequential stimuli individually. Two levels of difficulties were tested: 1Back and 3Back (n-back). Participants were instructed to indicate whether the letter currently displayed was the same as the letter presented 1 or 3 letters back. The task was organized in 2 runs, 8 blocks per run (4 safe and 4 threat presented alternatively), 18 sequential letters per block. Each block (threat or safe) corresponded to 2 tasks, 1- and 3-back tasks. RT was analyzed using condition (threat, safe) x Load (1Back, 3Back) repeated-measures ANOVA.
Reaction Time to Stimuli: Safe Condition - 3BACK - Run 1	90 minutes post drug admin plus 45 seconds within a 6-hour study visit	Reaction time (RT) is the time it takes to respond to stimuli. Participants RTs were measured while undergoing alternating periods of safety and shock threat conditions i.e. while anticipating unpleasant electric shocks (threat) or no shock (safe) during the n-back paradigm task. The n-back is a paradigm used to assess working memory function by presenting sequential stimuli individually. Two levels of difficulties were tested: 1Back and 3Back (n-back). Participants were instructed to indicate whether the letter currently displayed was the same as the letter presented 1 or 3 letters back. The task was organized in 2 runs, 8 blocks per run (4 safe and 4 threat presented alternatively), 18 sequential letters per block. Each block (threat or safe) corresponded to 2 tasks, 1- and 3-back tasks. RT was analyzed using condition (threat, safe) x Load (1Back, 3Back) repeated-measures ANOVA.
Reaction Time to Stimuli: Threat Condition - 3BACK - Run 1	90 minutes plus 135 seconds within a 6-hour study visit	Reaction time (RT) is the time it takes to respond to stimuli. Participants RTs were measured while undergoing alternating periods of safety and shock threat conditions i.e. while anticipating unpleasant electric shocks (threat) or no shock (safe) during the n-back paradigm task. The n-back is a paradigm used to assess working memory function by presenting sequential stimuli individually. Two levels of difficulties were tested: 1Back and 3Back (n-back). Participants were instructed to indicate whether the letter currently displayed was the same as the letter presented 1 or 3 letters back. The task was organized in 2 runs, 8 blocks per run (4 safe and 4 threat presented alternatively), 18 sequential letters per block. Each block (threat or safe) corresponded to 2 tasks, 1- and 3-back tasks. RT was analyzed using condition (threat, safe) x Load (1Back, 3Back) repeated-measures ANOVA.
Reaction Time to Stimuli: Safe Condition - 3BACK - Run 2	90 minutes plus 215 seconds within a 6-hour study visit	Reaction time (RT) is the time it takes to respond to stimuli. Participants RTs were measured while undergoing alternating periods of safety and shock threat conditions i.e. while anticipating unpleasant electric shocks (threat) or no shock (safe) during the n-back paradigm task. The n-back is a paradigm used to assess working memory function by presenting sequential stimuli individually. Two levels of difficulties were tested: 1Back and 3Back (n-back). Participants were instructed to indicate whether the letter currently displayed was the same as the letter presented 1 or 3 letters back. The task was organized in 2 runs, 8 blocks per run (4 safe and 4 threat presented alternatively), 18 sequential letters per block. Each block (threat or safe) corresponded to 2 tasks, 1- and 3-back tasks. RT was analyzed using condition (threat, safe) x Load (1Back, 3Back) repeated-measures ANOVA.
Measure of BOLD Response in Brain Cluster - Threat Condition - 3BACK	started 90 minutes post drug administration plus up to 450 seconds within a 6-hour study visit	The blood-oxygen-level dependent (BOLD) responses were measured using an fMRI scanner. The cerebral fMRI BOLD uses magnetic fields to measure localized changes in brain blood flow and blood oxygenation in activated regions-of-interest (ROI). Participants BOLD responses were measured while undergoing alternating periods of safety and shock threat conditions i.e. while anticipating unpleasant electric shocks or no shock (safe) during the n-back task. The n-back is a paradigm used to assess working memory function by presenting sequential stimuli individually. Two levels of difficulties were tested: 1Back and 3Back (n-back). Participants were instructed to indicate whether the letter currently displayed was the same as the letter presented 1 or 3 letters back.
Reaction Time to Stimuli: Threat Condition - 3BACK - Run 2	90 minutes plus 305 seconds within a 6-hour study visit	Reaction time (RT) is the time it takes to respond to stimuli. Participants RTs were measured while undergoing alternating periods of safety and shock threat conditions i.e. while anticipating unpleasant electric shocks (threat) or no shock (safe) during the n-back paradigm task. The n-back is a paradigm used to assess working memory function by presenting sequential stimuli individually. Two levels of difficulties were tested: 1Back and 3Back (n-back). Participants were instructed to indicate whether the letter currently displayed was the same as the letter presented 1 or 3 letters back. The task was organized in 2 runs, 8 blocks per run (4 safe and 4 threat presented alternatively), 18 sequential letters per block. Each block (threat or safe) corresponded to 2 tasks, 1- and 3-back tasks. RT was analyzed using condition (threat, safe) x Load (1Back, 3Back) repeated-measures ANOVA.
Measure of BOLD Response in Brain Clusters - Safe Condition - 1BACK	started 90 minutes post drug administration plus 90 seconds within a 6-hour study visit	The blood-oxygen-level dependent (BOLD) responses were measured using an fMRI scanner. The cerebral fMRI BOLD uses magnetic fields to measure localized changes in brain blood flow and blood oxygenation in activated regions-of-interest (ROI). Participants BOLD responses were measured while undergoing alternating periods of safety and shock threat conditions i.e. while anticipating unpleasant electric shocks or no shock (safe) during the n-back task. The n-back is a paradigm used to assess working memory function by presenting sequential stimuli individually. Two levels of difficulties were tested: 1Back and 3Back (n-back). Participants were instructed to indicate whether the letter currently displayed was the same as the letter presented 1 or 3 letters back.
Measure of BOLD Response in Brain Cluster - Threat Condition - 1BACK	started 90 minutes post drug administration plus up to 360 seconds within a 6-hour study visit	The blood-oxygen-level dependent (BOLD) responses were measured using an fMRI scanner. The cerebral fMRI BOLD uses magnetic fields to measure localized changes in brain blood flow and blood oxygenation in activated regions-of-interest (ROI). Participants BOLD responses were measured while undergoing alternating periods of safety and shock threat conditions i.e. while anticipating unpleasant electric shocks or no shock (safe) during the n-back task. The n-back is a paradigm used to assess working memory function by presenting sequential stimuli individually. Two levels of difficulties were tested: 1Back and 3Back (n-back). Participants were instructed to indicate whether the letter currently displayed was the same as the letter presented 1 or 3 letters back.
Measure of BOLD Response in Brain Clusters - Safe Condition - 3BACK	started 90 minutes post drug administration plus up to 270 seconds within a 6-hour study visit	The blood-oxygen-level dependent (BOLD) responses were measured using an fMRI scanner. The cerebral fMRI BOLD uses magnetic fields to measure localized changes in brain The blood-oxygen-level dependent (BOLD) responses were measured using an fMRI scanner. The cerebral fMRI BOLD uses magnetic fields to measure localized changes in brain blood flow and blood oxygenation in activated regions-of-interest (ROI). Participants BOLD responses were measured while undergoing alternating periods of safety and shock threat conditions i.e. while anticipating unpleasant electric shocks or no shock (safe) during the n-back task. The n-back is a paradigm used to assess working memory function by presenting sequential stimuli individually. Two levels of difficulties were tested: 1Back and 3Back (n-back). Participants were instructed to indicate whether the letter currently displayed was the same as the letter presented 1 or 3 letters back.

Secondary Outcome Measures

Name	Time	Method
Measure of Level of Anxiety	20 minutes after arrival for study; 10 minutes & 145 minutes post drug administration	The level of anxiety was assessed using the State Anxiety Inventory questionnaire. The State Anxiety Scale (S-Anxiety) evaluates the current state of anxiety. The State Anxiety Scale has 20 items. All items are rated on a 4-point scale ranging from "1 = not at all" to "4 = very much so". The scale has a minimum score of 20 and a maximum score of 80. Higher score indicates greater anxiety. State Anxiety score was measured at different time points during the study.
Measure of Heart Rate	20 minutes after arrival for study; 10 minutes & 145 minutes post drug administration	The heart rate was monitored with two disposable electrodes on the ribcage midway between the waist and the armpit.