Modulation de l'adaptation anxieuse

On one study day, participants will complete experimental tasks during functional magnetic resonance imaging. On two other study days, participants will complete tasks before and after receiving repetitive transcranial magnetic stimulation (rTMS). All participants will receive rTMS to ventromedial prefrontal cortex on one study day, and to pre-supplementary motor area on another study day.

Two stimulation procedures will be used, one for ventromedial prefrontal cortex and one for pre-supplementary motor area. For both targets, 3 sessions of 600 pulses at 110% of resting motor threshold will be presented over 30 minutes. For ventromedial cortex, a session will involve intermittent theta burst triplets at 50 Hz for 2 seconds and repeated every 10 seconds for a total of 190 seconds. For pre-supplementary motor area, a session will involve continuous theta burst presented in 3-pulse bursts with 15 pulses/ sec.

A repetitive Transcranial Magnetic Stimulation (rTMS) MagVenture MagPro TMS System will be used to deliver intermittent theta burst to ventromedial prefrontal cortex, and continuous theta burst to pre-supplementary motor area.

Fear-potentiated startle is measured during an experimental task in which participants prepare to avoid, escape, or simply be exposed to aversive pictures. Fear-potentiated startle measures motivational activation during the preparation period.

Reaction time to initiate flight is measured in an experimental task in which participants can win money but also must evade a slow, moderate, or fast virtual predator. Reaction time measures behavioral tendency to approach or avoid.

Electroencephalography (EEG) is measured during an experimental task in which participants prepare to avoid, escape, or simply be exposed to aversive pictures. An event-related potential, the stimulus-preceding negativity, will be derived from the EEG to index action preparation processing.

Electroencephalography (EEG) is measured during an experimental task in which participants can win money but also must evade a slow, moderate, or fast virtual predator. A frequency signature, power in the theta frequency band, will be derived from the EEG to index cognitive control processes.

Heart rate is measured during experimental tasks in which: 1) participants prepare to avoid, escape, or simply be exposed to aversive pictures; 2) participants can win money but also must evade a slow, moderate, or fast virtual predator. Heart rate slowing measures task-related engagement of attention, while heart rate increase indicates defensive activation.

Skin conductance is measured during experimental tasks in which: 1) participants prepare to avoid, escape, or simply be exposed to aversive pictures; 2) participants can win money but also must evade a slow, moderate, or fast virtual predator. Skin conductance increases indicate task-related sympathetic arousal.

Perceived control over aversive stimuli is queried after an experimental task in which participants prepare to avoid, escape, or simply be exposed to aversive pictures. Perceived control for each condition is queried using self-report Likert-type scales for each condition.

Difficulty of avoiding exposure to aversive stimulation is queried after each trial during a task in which participants can win money but also must evade a slow, moderate, or fast virtual predator. Avoidance difficulty is queried using a Likert-type scale delivered after each trial. The scale ranges from 1 to 5, with higher scores indicating greater perceived difficulty of avoiding capture by the virtual predator.

State-level anxiety is measured throughout the experimental session using the State-Trait Anxiety Inventory - State Form. The State-Trait Anxiety Inventory - State Form uses 20 items querying anxiety symptom experience in the present moment to measure how anxiety fluctuates across the experimental session. The scale ranges from 20 to 80, with higher scores indicating higher state anxiety.

Blood flow in the brain will be measured during completion of two experimental tasks using functional magnetic resonance imaging (fMRI). Blood flow in the brain can be used to measure what brain areas are being activated during the performance of a task.