Stress, Sex, and the Generalization of Fear

Peak eyeblink startle responses 20-200 ms following presentation of a startle probe were measured. Startle responses were assessed for each of 3 trial types: (1) following the startle probe alone [noise alone (NA) trials], (2) following the CS+ and startle probe (CS+ trials), and (3) following the CS- and startle probe (CS- trials). Participants were exposed to 16 blocks of trials, and each block included 1 presentation of each trial type. During the last 12 blocks, CS+ trials also included the presentation of an aversive US. For each block, startle responses to NA trials were subtracted from startle responses to CS+ trials and from startle responses to CS- trials to create 2 separate fear-potentiated startle response measures: 1 for the CS+ and 1 for the CS-. Average fear-potentiated startle responses to the CS+ and CS- during the last 4 blocks of trials were used as an indicator of fear learning (greater responses to the CS+, relative to the CS-, indicated greater learning).

Peak eyeblink startle responses 20-200 ms following the presentation of a startle probe were measured. Startle responses were assessed for each of 10 trial types: (1) following the startle probe alone [noise alone (NA) trials], (2) following the CS+ and startle probe (CS+ trials), (3) following each of 7 generalization stimuli and startle probe (GS trials), and (4) following the CS- and startle probe (CS- trials). Participants were exposed to 3 blocks of trials, and each block included 1 presentation of each trial type. For each block, startle responses to the NA trials were subtracted from startle responses to the CS+, GSs, and CS- trials to create separate fear-potentiated startle response measures for each of the 9 different stimuli. Average fear-potentiated startle responses to each stimulus across all 3 blocks were used as an indicator of fear expression. Greater scores for the generalization stimuli (GS) indicated a greater generalization of fear.

Electrodermal activity was measured following presentation of the CS+ and CS- during acquisition on Day 1. Participants were exposed to 16 blocks of trials, with each block including a single presentation of each stimulus. During the last 12 blocks, CS+ trials included the presentation of an aversive US. For each block, skin conductance responses were quantified by calculating the average increase in electrodermal activity (from a 1 s pre-stimulus baseline) 3-6 s after CS+ or CS- onset. Average skin conductance responses to the CS+ and CS- during the last 4 blocks of trials were used as an indicator of fear learning (greater responses to the CS+, relative to the CS-, indicated greater learning).

Electrodermal activity was measured following presentation of the CS+, 7 generalization stimuli (GSs), and CS- during generalization testing on Day 2. Participants were exposed to 3 blocks of trials, with each block including a single presentation of each stimulus. For each block, skin conductance responses were quantified by calculating the average increase in electrodermal activity (from a 1 s pre-stimulus baseline) 3-6 s after onset of the CS+, 7 GSs, or CS- onset.. Average skin conductance responses to each stimulus across all 3 blocks were used as an indicator of fear expression. Greater scores for the generalization stimuli (GS) indicated a greater generalization of fear.

Participants were exposed to 16 blocks of trials, and each block included 1 presentation of the CS+ and one presentation of the CS-. During the last 12 blocks, CS+ trials included the presentation of an aversive US. During each trial, participants pressed, within 3 seconds of stimulus onset, a button marked "+" if they expected the stimulus to be followed by the US, a button marked "-" if they did not expect the stimulus to be followed by the US, or a button marked "0" if they were uncertain. For the purpose of data analysis, + was scored as +1, - were scored as -1, and 0 was scored as 0. Average expectancy ratings during the last 4 blocks of trials were used as an indicator of fear learning (greater responses to the CS+, relative to the CS-, indicated greater learning).

Participants were exposed to 3 blocks of trials, and each block included 1 presentation of the CS+, one presentation of each of 7 generalization stimuli (GSs), and one presentation of the CS-. Participants were instructed to press, within 3 seconds of stimulus onset, a button marked "+" if they expected the stimulus to be followed by the US, a button marked "-" if they did not expect the stimulus to be followed by the US, or a button marked "0" if they were uncertain. For the purpose of data analysis, + was scored as +1, - was scored as -1, and 0 was scored as 0. Average expectancy ratings for each stimulus across all 3 blocks were used as an indicator of fear. Greater scores for the generalization stimuli (GS) indicated a greater generalization of fear.

Saliva samples were collected from participants prior to undergoing the stress or sham control condition (baseline) and then 25 min later. The change in salivary cortisol levels was analyzed. Greater levels indicated greater cortisol responses to stress.

Saliva samples were collected from participants prior to undergoing the stress or sham control condition (baseline) and then immediately after the manipulation. The change in salivary alpha-amylase levels was analyzed. Greater levels indicated greater alpha-amylase responses to stress.

During the stress or sham control manipulation, participants rated the painfulness of the water bath at 1-minute intervals on an 11-point scale ranging from 0-10, with 0 = lack of pain and 10 = unbearable pain. The obtained ratings were averaged and analyzed. Greater ratings indicated greater subjective pain during the stressor.

During the stress or sham control manipulation, participants rated the stressfulness of the water bath at 1-minute intervals on an 11-point scale ranging from 0-10, with 0 = lack of stress and 10 = unbearable stress. The obtained ratings were averaged and analyzed. Greater ratings indicated greater subjective stress during the stressor.

Heart rate (bpm) measurements were aken via the PPG module of the Biopac MP150 system from participants prior to undergoing the stress or sham control condition (baseline) and then halfway through the manipulation.The change in heart rate was analyzed.

Saliva samples were collected from female participants prior to undergoing the stress or sham control condition (baseline) and then 25 min later. The change in salivary progesterone levels were analyzed.

Salivary estradiol (pg/ml) was measured by enzyme immunoassay (Salimetrics LLC) performed on saliva samples collected from female participants on Days 1 and 2.

The Spielberger State-Trait Anxiety Inventory (STAI) was administered following generalization testing on Day 2. The STAI provides scores (20-80) for state and trait anxiety. State anxiety was used for this measure and was a sum of 20 items from the STAI. The minimum score for state anxiety was 20, and the maximum score was 80. Higher scores represented higher levels of state anxiety.

The Childhood Trauma Questionnaire (CTQ) was administered following generalization testing on Day 2. The questionnaire consists of 25 items and yields a score between 25 and 125. Higher scores represent greater levels of childhood trauma exposure.

The Anxiety Sensitivity Index (ASI) was administered following generalization testing on Day 2. The ASI consists of 18 items and yields a score that reflects an individual's dispositional anxiety sensitivity. The minimum score is 0, and the maximum score is 72. Greater scores reflect a greater sensitivity to anxiety.

The Center for Epidemiological Studies Depression Scale (CES-D) was administered following generalization testing on Day 2. The CES-D is a 20-item measure of symptoms of depression. The possible range for scores is 0-60 with higher scores suggesting more severe symptoms of depression.

The PTSD Checklist - Civilian Version was administered following generalization testing on Day 2. The checklist is a 17-item measure of symptoms of post-traumatic stress disorder (PTSD). The minimum score is 0, and the maximum score is 80. Greater scores reflect greater symptoms related to PTSD.