Methylphenidate 20mg was given orally during study visit

Placebo was given orally during study 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.

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.

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.

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.

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.

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.

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.

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.

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 (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 (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 (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 (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 (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 (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 (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 (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.

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.

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.

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.

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.

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.

The heart rate was monitored with two disposable electrodes on the ribcage midway between the waist and the armpit.

The heart rate was monitored with two disposable electrodes on the ribcage midway between the waist and the armpit.

Participants received propranolol 40mg orally during study visit

Participant received methylphenidate 20 mg orally during study visit

Participant received placebo orally during study visit

Total of all reporting groups

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.

Analyses included subjects who completed the behavioral study arms.

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.

Analyses included subjects who completed the behavioral study arms.

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.

Analyses included subjects who completed the behavioral study arms.

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.

Analyses included subjects who completed the fMRI study arms and had data for analysis

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.

Analyses included subjects who completed the fMRI study arms and had data for analysis

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.

Analyses included subjects who completed the fMRI study arms and had data for analysis

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.

Analyses included subjects who completed the fMRI study arms and had data for analysis

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.

Analyses included subjects who completed the fMRI study arms and had data for analysis

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.

Analyses included subjects who completed the fMRI study arms and had data for analysis

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.

Analyses included subjects who completed the fMRI study arms and had data for analysis

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.

Analyses included subjects who completed the fMRI study arms and had data for analysis

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.

Analyses included subjects who completed the fMRI study arms and had data for analysis

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.

Analyses included subjects who completed the fMRI study arms and had data for analysis

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.

Analyses included subjects who completed the fMRI study arms and had data for analysis

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.

Analyses included subjects who completed the fMRI study arms and had data for analysis

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.

Analyses included subjects who completed the fMRI study arms and had data for analysis

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.

Analyses included subjects who completed the fMRI study arms and had data for analysis

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.

Analyses included subjects who completed the fMRI study arms and had data for analysis

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.

Analyses included subjects who completed the fMRI study arms and had data for analysis

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.

Analyses included subjects who completed the fMRI study arms and had data for analysis

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.

Analyses included subjects who completed the fMRI study arms and had data for analysis

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.

Analyses included subjects who completed the fMRI study arms and had data for analysis

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.

Analyses included subjects who completed the fMRI study arms and had data for analysis

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.

Analyses included subjects who completed the behavioral study arms.

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.

Analyses included subjects who completed the fMRI study arms and had data for analysis

The heart rate was monitored with two disposable electrodes on the ribcage midway between the waist and the armpit.

Analyses included subjects who completed the behavioral study arms.

The heart rate was monitored with two disposable electrodes on the ribcage midway between the waist and the armpit.

Analyses included subjects who completed the fMRI study arms and had data for analysis

Participant received placebo orally during study visit

Participants received propranolol 40mg orally during study visit

Participant received methylphenidate 20 mg orally during a single day six hour study visit

Participant received placebo orally during a single day six hour study visit