Stress, Sex, and the Generalization of Fear

The impact of well-known risk factors for such disorders (stress, biological sex, anxiety-related dispositions) on fear generalization will be examined. Findings from this study may provide insight into how these risk factors influence the development and/or maintenance of psychological disorders that involve overgeneralization of fear and could facilitate future approaches to their treatment.

Many researchers approach the etiology of trauma-, stressor-, and anxiety-related mental disorders from the perspective of classical conditioning processes gone awry. According to this view, abnormal associative relationships between neutral, conditioned stimuli (CSs) and aversive, unconditioned stimuli (USs) underlie pathological anxiety and result in unusually intense fear memories or fear memories that cannot be properly extinguished. Recent work has expanded this view by showing that many psychological disorders involving pathological anxiety are associated with an exaggerated form of the commonly adaptive classical conditioning phenomenon, stimulus generalization, leading individuals with such disorders to respond with fear and anxiety to a variety of environmental contexts and cues that should not be threatening. Few studies have been conducted in humans to better understand the process of fear generalization, and factors that might influence susceptibility to overgeneralize fear have yet to be assessed. It is well-known that stress, biological sex, and anxiety-related dispositions of an individual increase one's susceptibility for pathological anxiety and significantly impact fear learning; thus, it is possible that such factors, alone or in combination, contribute to clinical anxiety by influencing fear generalization processes. Aim 1 of the present study is to determine the effects of acute stress and its physiological correlates on fear generalization in human participants. Because acute stress profoundly impacts cognitive brain areas that underlie generalization, it is predicted that acute stress will enhance or impair fear generalization, depending on when the stressor is administered relative to fear learning. Aim 2 is to assess the role of biological sex in fear generalization and acute stress-induced changes in such processes. Females are more likely than males to develop several psychological disorders that involve pathological anxiety, and research has consistently reported sex-related differences in fear learning and stress-induced alterations of fear learning, effects that have been associated with ovarian hormones. Thus, it is predicted that females will exhibit greater fear generalization than males that will be impacted differently by stress. It is also hypothesized that the observed effects will correlate with estradiol and progesterone in females. The final aim of this project (Aim 3) is to evaluate the relationship between childhood stress, dispositional anxiety, and fear generalization. Early life stress has been repeatedly associated with altered stress responses and the development of anxiety-related phenotypes, yet the influence of childhood stress and trait anxiety on fear generalization have yet to be examined. This study will be the first to examine how several factors that are known to increase susceptibility for trauma-, stressor, and anxiety-related psychological disorders impact fear generalization in human subjects. The resulting findings will provide important insight into the etiology of such disorders, which could aid future approaches to their treatment.

Male participants will be exposed to the socially evaluated cold pressor test immediately prior to fear learning. Participants will place their dominant hand in a bath of ice cold water for up to 3 minutes. The participants will also be informed that they are being videotaped for analysis of facial expressions and be asked to stare at a camera throughout the manipulation. Immediately following the acute stressor, participants will undergo the acquisition phase of fear conditioning.

Male participants will be exposed to the sham control condition (no stress) immediately prior to fear learning. Participants will place their dominant hand in a bath of lukewarm water for up to 3 minutes. Immediately following the sham control condition, participants will undergo the acquisition phase of fear conditioning.

Male participants will be exposed to the socially evaluated cold pressor test 30 minutes prior to fear learning. Participants will place their dominant hand in a bath of ice cold water for up to 3 minutes. The participants will also be informed that they are being videotaped for analysis of facial expressions and be asked to stare at a camera throughout the manipulation. Thirty minutes following the acute stressor, participants will undergo the acquisition phase of fear conditioning.

Male participants will be exposed to the sham control condition (no stress) 30 minutes prior to fear learning. Participants will place their dominant hand in a bath of lukewarm water for up to 3 minutes. Thirty minutes following the sham control condition, participants will undergo the acquisition phase of fear conditioning.

Female participants will be exposed to the socially evaluated cold pressor test immediately prior to fear learning. Participants will place their dominant hand in a bath of ice cold water for up to 3 minutes. The participants will also be informed that they are being videotaped for analysis of facial expressions and be asked to stare at a camera throughout the manipulation. Immediately following the acute stressor, participants will undergo the acquisition phase of fear conditioning.

Female participants will be exposed to the sham control condition (no stress) immediately prior to fear learning. Participants will place their dominant hand in a bath of lukewarm water for up to 3 minutes. Immediately following the sham control condition, participants will undergo the acquisition phase of fear conditioning.

Female participants will be exposed to the socially evaluated cold pressor test 30 minutes prior to fear learning. Participants will place their dominant hand in a bath of ice cold water for up to 3 minutes. The participants will also be informed that they are being videotaped for analysis of facial expressions and be asked to stare at a camera throughout the manipulation. Thirty minutes following the acute stressor, participants will undergo the acquisition phase of fear conditioning.

Female participants will be exposed to the sham control condition (no stress) 30 minutes prior to fear learning. Participants will place their dominant hand in a bath of lukewarm water for up to 3 minutes. Thirty minutes following the sham control condition, participants will undergo the acquisition phase of fear conditioning.

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).

Average of the responses from trial block 13, trial block 14, trial block 15, and trial block 16 on Day 1

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).

Average of the responses from trial block 13, trial block 14, trial block 15, and trial block 16 on Day 1

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).

Average of the ratings from trial block 13, trial block 14, trial block 15, and trial block 16 on Day 1

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.

Inclusion Criteria: 18 years of age Registered student at Ohio Northern University in Ada, Ohio Exclusion Criteria: Regular use of tobacco or recreational drugs (e.g., marijuana, cocaine, heroin, etc.) Previous diagnosis of Raynaud's disease or peripheral vascular disease Previous diagnosis of skin diseases (e.g., severe psoriasis, eczema, scleroderma) History of syncope or vasovagal response to stress History of any heart conditions or cardiovascular issues (e.g., high blood pressure) History of severe head trauma Current treatment with narcotics, beta-blockers, or steroids Previous diagnosis of substance use disorder Regular nightshift work Hearing loss Consumed alcohol in past 24 hours Engaged in strenuous exercise in past 24 hours Ate or drank anything but water in past 2 hours

Raw data and data from descriptive/raw measures were submitted on a semi-annual basis to the NIMH Data Archive