Fear Conditioning Under Social Stress

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Introduction

In the study of psychology, research has always looked at emotions and the role they play in everyday behaviour as well as in pathological behaviour. Several studies have shown that emotionally charged stimuli attract human attention quicker and have an advantage in information processing. Stimuli that are emotionally negative in nature tend to grab attention automatically and more quickly (Wieser, 2010). When studying emotions in social situations, more often than not researchers tend to use facial expressions. Facial expressions allegedly tend to be significant in an evolutionary sense and are also distinctively processed and one of the advantages is that they represent universally identifiable emotions. This makes facial expressions a strong tool to study emotions. Past research has shown that angry facial expressions are perceived as threating stimuli and have the ability to activate the human fear system (Ohman, 1986; Ekman, 1976).

Neuroscientific models assume that emotion driven responses like anxiety and fear are based in a motivational defence circuit (Duits, 2015). The amygdala has a very central position and is closely connected to the subcortical structures like the thalamus and hippocampus and cortical structures like the temporal, prefrontal and orbito cortices, all of which are crucial for fear conditioning (LeDoux, 2000). The amygdala plays an important role in fear conditioning processes and shows increased activity for conditioned stimulus paired with aversive stimulus (CS+) compared to conditioned stimulus not paired with any aversive stimuli (CS-) (LaBar, 1998). Most fear conditioning studies use a fear condition paradigm that consists of phases. The acquisition phase is when the conditioned stimulus is paired with the aversive or fearful stimulus (CS+), this is also known as the fear acquisition training. A result of this is that fear learning takes place and a conditioned response (CR) is derived to the conditioned stimulus. When the aversive stimuli are no longer presented with the conditioned stimulus the process of extinction training begins (Lonsdorf, 2017). Few studies have looked at the main characteristics of learning mechanisms with patients diagnosed with social anxiety disorder (Ahrens, 2014). A functional magnetic resonance imaging study found increased activity in the amygdala and hippocampus in patients with social anxiety disorder (SAD) when shown neutral faces paired with an aversive odor (Schneider, 1999). A study conducted used faces and audiovisual stimuli, the researchers paired angry faces with insults, happy faces with compliments and neutral faces with neutral comments. They found that when compared to healthy controls, subjects with social anxiety disorder had an increased fear startle response to the angry faces paired with insults compared to the other two pairings (Lissek 2008).

Using angry faces in a fear conditioning model has its advantages wherein, angry faces elicit larger attentional resources much more quickly (Fox, 2000). Theoretically, anxiety and fear are linked to an increased preferred processing of angry facial expressions, especially in individuals who have social anxiety (Weiser, 2010).

Differences in local brain activation have been the focus in most fear conditioning studies done in the past. More recent studies look at the changes in cortical processing due to the acquired fear. The steady state visual evoked (ssVEP) is one such method that looks at response in cortical changes to visual stimuli (Vialette, 2010). These signals are usually generated in the occipital lobe as well as other higher order cortices. These signals can be accurately detached from noise and are study to movement artefacts as well as eye-blinks (DiRusso, 2007; Regan, 1989; Perlstein, 2003). Various studies have shown that ssVEPs are conscious towards emotional and attentional processes. They have also shown increased amplitude for stimulus that is attended to compared to stimulus unattended to as well as stimulus that are emotional in nature compared to neutral stimuli (Muller, 1997). For fear conditioning studies the ssVEP smplitudes are shown to increase for conditioned stimulus paired with aversive stimulus (CS+) compared to conditioned stimulus not paired with any aversive stimuli (CS-) (Moratti, 2005). This technique is very useful while researching visual cognition (Wieser, 2014; Wieser, 2016).

Prior research studies on social anxiety have used a public speaking task to help induce state anxiety. This task is proven to be reliable in inducing state-anxiety and enhanced physiological arousal (Wieser, 2010). Past research conducted by Weiser et al showed that fear of public speaking has an influence on individual’s early perceptual processing of faces, specifically angry faces. (Weiser, 2010). Does anxiety play a role in fear association? Does it take longer to dissociate fear in individuals who are anxious compared to controls?

The present research aims to investigate if participants under social stress show stronger fear learning in a fear conditioning paradigm with angry faces as compared to individuals who are not stressed. We expect that participants in the social stress group will show quicker fear learning for the angry faces, they will have increased ssVEP amplitude during acquisition for CS+. Individuals in the social stress group, their reaction to the CS+ will take longer to be extinct compared to the control group , that is their ssVEP amplitude for the CS+ face will be higher even in the extinction phase. Participants in the stress group will have higher subjective arousal ratings and lower subjective valence ratings for the CS+ face compared to the CS- face.

Methodology

Participants

The participants of the study will be first year bachelor’s students recruited from the Erasmus Behavioral Lab Research Administration System. They will receive course credit for participation. The subjects will be matched on age and gender. The estimated sample size will be sixty, with the control group and stress group having thirty participants each. Participants will be assigned to the groups randomly. Participants will be screened for any psychiatric illness or neurological illness especially epilepsy prior to being inducted into the study. If the participant reports the presence of any of these, they will not be included in the study.

Material

Participants will fill in the Leibowitz Social Anxiety Scale(Heimberg, 1999) that measures social anxiety. The Spielberger State and Trait Anxiety Scale etzger, that measures state and trait anxiety. The Beck Depression Inventory Beck, 1988) that measures depression and the Intolerance of Uncertainty Scale(Dugas, 1997). The questionnaires will be filled out online via the tool Qualtrics. There are two versions of the questionnaires English and Dutch and the versions will be given based on the participant’s first language. The participants will watch pictures of two angry faces on a computer screen. One angry face is always paired with a loud aversive sound (human scream plus white noise at 85dB which is played for 500ms). The faces are presented on the screen for 3 seconds flickering at 15Hz. The participants are then asked to rate these faces based on their emotional valence after every face trial. This response is recorded via the visual Self-Assessment Manikin (SAM). The EEG is recorded using BioSemi Active-Two system from 64 pin-type active Ag/AgCl electrodes placed on an elastic cap. There were 4 electrodes used placed above the eye (1), below the eye (2) to record eye blinks, on both temples (3 & 4) to record horizontal eye movements. The recording frequency was used 512 Hz.

Research Design

The main research question aims to investigate if individuals under social stress show stronger fear learning in a fear conditioning paradigm with angry faces as compared to individuals who are not stressed. We expect that individuals in the social stress group will show quicker fear learning for the angry faces, they will have increased ssVEP amplitude during acquisition for CS+. Individuals in the social stress group, their reaction to the CS+ will take longer to be extinct compared to the control group. Individuals in the stress group will have higher subjective arousal and lower subjective valence ratings for the CS+ face compared to the CS- face. The research design for this study is a 2×2 mixed factorial design. There is one within subject factor which is type of conditioned stimulus (CS+ vs. CS-) and one between subjects factor, the stress group vs control group.

Procedure

The participants will be brought in, they will be first given an informed consent form to read and sign. The participants will be then told to fill in the questionnaires online in the lab. The questionnaires will act as a manipulation check to record if there are any changes in the participant’s state anxiety. After this they will be randomly assigned to the group (social stress or no social stress). The subjects in the social stress group will be told that after they finish the experiment, they will be asked to choose a topic from 3 given envelopes, they will have one minute to prepare and will have to speak on the topic in front of a camera that is recording (they will be shown the placement of the camera specifically). They will be evaluated on thought content, argumentation, vocabulary, posture and talking style. The participants in the no social stress group will be told that they have to pick one of 3 envelopes, they will have a minute to prepare and five minutes to write on the topic chosen. They would be evaluated on thought content and argumentation. After these they have to fill in another questionnaire online. They will then be taken into the EEB chamber, the electrodes will be attached. The experiment will then begin and will consist of three phases. The first phase is the habituation phase where subjects will see the two angry faces randomly presented 20 times each for 3 seconds flickering at 15Hz. The next phase is the conditioning phase where again the two faces are presented randomly 20 times each for 3 seconds flickering at 15Hz. This time one angry face is always paired with a loud aversive noise (human scream). The third phase of the experiment if the extinction phase where once again the subjects see the two angry faces presented randomly 20 times for 3 seconds at 15Hz but without the sound. After each trial in every phase the participants are asked to rate the faces on valence and arousal using SAM which appears on the screen and the subjects need to use the keyboard that will be provided to lock in their responses. The EEG and subjective responses will be recorded. At the end of the experiment the participants will be asked to wither perform the speech or write it based on the group. The purpose of the writing or talking speech task is to induce social anxiety, for the actual experiment none of the written or spoken material will be evaluated nor recorded.

Statistical Analysis

The research design is a mixed design containing one within subjects’ factor (CS+ vs CS-) and one between subjects’ factor (social stress vs control). A mixed design ANOVA will be used to analyze the EEG data which will be the ssVEP data. For the valence and arousal ratings a mixed ANOVA will be used as well. Additional analyses for the state anxiety scores comparison will be done using an independent t-test.

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