The Effects of Anxiety on Cognitive Functioning as Indexed by Heart Rate Variability
Anxiety is one of world’s leading mental health disorders (Vytal, Cornwell, Lekiewicz, Arkin, & Grillon, 2013). Anxiety can be described on the basis of fear response (Carnevali, Thayer, Brosschot, & Ottaviani, 2017). Trait anxiety can be described as an individualized characteristic that a person may have based on biological and/or environmental influences (Friedman, 2007). State anxiety refers to anxiety in a stress-induced circumstance (Friedman, 2007). In all its forms, anxiety has been seen as a survival instinct in the past. In Canons (1929) fight or flight model, anxiety was shown as a somatic response to threat within the environment. In the past individuals needed this type of threat induced quick response in order to survive. As the modern world has evolved and changed, the need for a fight or flight type stress response has had a different meaning from the typical “encounter a bear and run scenario.” Although in some situations anxiety may have certain psychological or physiological benefits, in other parts of the literature anxiety has been shown to have an adverse effect on multiple brain functions on both the psychological and physiological level. Anxiety has also been shown to have a negative effect on individual psychological health (Goldberger, 1991). Anxiety has been seen in the literature to have adverse effects on certain psychological functions.
Anxiety has a negative effect on the ability for individuals to regulate their emotions and/or to adapt to a new changing environment (Goldberger, 1991). In a study on the behavioral inhibition system (BIS) and behavioral activation system (BAS) scale, it was found that individuals with high anxiety had an over reactive inhibitory system, sensitive to punishment cues with a type of hypervigilance to conditioned signals of threatening environmental change (Carver & White, 1981).
In another study by Thayer and Friedman in 2002, it was found that individuals with generalized anxiety disorder (GAD) show a positive feedback loop of hyper vigilance and inhibition to seemingly stressful environmental stimuli. In this study, the authors explain how the hyper vigilance of threat can cause a perception of maladaptive emotional responses to a very wide range of environmental experiences. The perseverative cognition hypothesis (PCH) theorizes that excessive preservation, or sustained adaptive or maladaptive thinking of past events or decisions poses a threat to both the physiological and psychological well being of the individual (Williams, Feeling, Hill, Spangler, Koeing, & Thayer, 2017). In the autonomic flexibility-neurovisceral integration model, anxiety is viewed as a process of poor inhibition due to systemic inflexibility (Friedman & Thayer, 1998). Anxiety has affected working memory as well as Miyake, et al., who poised the process of three cognitive executive functions: task shifting, inhibition, and updating (Moran, 2016).
Working Memory and Executive Functions
Working memory can be described as a system that collects a limited amount of cognitive information, which encompasses three realms of executive functions, task shifting, inhibiting, and updating (Moran, 2016). Coordination of multiple different tasks at the same time is referred to as shifting (Monsell, 1996). This requires the ability to move back and forth between multiple mental tasks at the same time. Updating refers the constant monitoring of incoming information and appropriate adaption to changes in order to place new more important information at higher-level then less important information or tasks (St Clair- Thompson & Gathercole, 2006). Inhibition refers to the ability of one to hold back certain dominate automatic responses in order to focus more closely at more important tasks at hand (St Clair- Thompson & Gathercole, 2006).
Anxiety and Deficits in Working Memory
Anxiety has been shown to have a negative effect on higher cognitive functioning and productivity (Williams et al., 2017). Working memory plays a key role in cognitive functions in goal-directed tasks (Vytal et al., 2013). Individuals with anxiety can have impaired ability to perform well cognitively in a performance task (Vytal et al., 2013). It was shown that induced anxiety impaired both verbal and spatial working memory process, which showed a relationship between anxiety and disruption of working memory tasks (Vytal et al., 2013). In this study, the researchers theorize that anxiety levels are impaired due to the competition of shared cognitive resources between spatial attention and inability to inhibit hypervigilance to a perceived threat. This study also states that the increased amount of cognitive demand decreased the amount of anxiety due to the normalization of anxiety in the face of threat. When a cognitive task is increased to a level that it consumes all cognitive resources, anxiety is decreased (Vytal et al., 2013). Vytal et al. (2013) states that a facet of anxiety, anxious arousal, may specifically affect spatial working memory in that anxious arousal shares more neural circuitry with working spatial memory. This is explained due to the disruption of working spatial memory due to anxiety has been affected largely due to the competition in resources of both task accomplishment and cognitive load. There is literature of nonhuman animals, which aligns with the adverse effect of anxiety on memory and performance in the Morris water maze (Morris, 1981). But to date there is very little information on the relationship between anxiety and spatial working memory as indexed by heart rate variability.
Heart rate variability
Heart rate variability is the measure between each heartbeat as both parasympathetic and sympathetic activities affect the heart in each individual (Goldberger, 1991; Appelhans & Luecken, 2006). Heart rate variability (HRV) has become increasingly important in determining certain trait like characteristics in individuals such as the ability to effectively handle a dynamic changing environment and in turn, individual anxiety or stress levels (Applehans & Luecken, 2006) A large amount of literature has used heart rate variability as a measurement for various maladaptive emotion regulation methods. This is because HRV has been shown to be a useful measurement in assessing individual adaptive or maladaptive coping methods to a changing stressful environment. Low heart rate variability has been shown to have a relationship with higher anxiety levels. Higher variability in heart rate peaks has been shown in the literature to have a relationship with individuals that have a more adaptive way of dealing with the changing environment and in turn have lower levels of anxiety at both the state and trait level (Appelhans & Luecken, 2006). HRV has been found to be an important measure in predicting hypertension in individuals (Bigger, Fleiss, Rolnitzky, & Steinman, 1993). Low HRV has been associated with a higher risk for cardiovascular disease (Thayer & Friedman, 2002). Worry and fear, basic traits of anxiety, have been associated with an increased risk for coronary heart disease (Kubzanksy et al., 1997). In a study by Goldberger, Rigney, Mietus, Antman, & Greenwald (1988), heart rate patterns individuals were taken preceding sudden cardiac death, there was an important finding in the loss of variability in heart rate in a time period before the individuals died from sudden cardiac death.
There is a significant amount of literature on the effects of anxiety on higher cognitive functioning yet there is little to no information on the measurement of heart rate variability on individuals with anxiety and the differences in state and trait anxiety and their effects on working memory. Impairment of working memory, among other cognitive functions has shown to have an adverse effect with anxiety in many studies (Goldberger, 1991).
Cognitive Abilities and Anxiety
Many studies have shown that anxiety has a relationship with poor executive cognitive functioning (Thayer, Hansen, Saus-Rose, & Johnsen, 2009). In contrast, the relationship between higher HRV and higher cognitive function and executive function among a performance on a diverse amount of cognitive tasks was shown in the study mentioned above. Among the literature, there has been a large amount of support for the notion of cognitive functioning impairment under anxiety inducing conditions or stressful tasks. Difficult cognitive functioning has been found to change cardiac autonomic activity in one study (Gianaros, Van Der Veen, & Jennings, 2004).
The association between individuals with lower HRV and the inability to attention regulate in multiple cognitive performance tasks was also found in another study conducted in 2003 (Hansen, Johnsen, & Thayer, 2003). Individuals with high levels of anxiety have a reduced ability to inhibit cognitive behaviors such as worry and avoidance (Friedman & Thayer, 1998). A relationship between lower HRV, maladaptive rumination, and high levels of trait anxiety was found in individuals who had to complete a cognitive task (Williams et al., 2017). In this study, it was found that individuals had an inability to inhibit fear response and an inability to restrain from defensiveness. Working memory is a vital aspect of higher cognitive functions. Working memory cognitive functioning can be impaired due to anxiety. Performance will decline on a working memory task when goal directed behavior on these tasks is distracted by inability to inhibit from a state of hypervigilance to perceived threat (Vytal et al., 2013).
The Present Study
There is much information on the effects of anxiety on cognitive functioning in the literature and there is also a large amount of information on the effects of anxiety on working memory. But there seems to be a gap in the literature between the effects of anxiety on working memory as indexed by heart rate variability. The goals of the present study are to identify this relationship between spatial working memory and anxiety. Based on the surplus of literature stating that low HRV is associated with impaired cognitive functioning (Gianaros, Van Der Veen, Jennings, 2004; Ottaviania et al., 2016; Williams et al., 2017), we hypothesize (1) a strong association between decreased HRV and decreased working memory and individuals with lower resting HRV will perform more poorly on a cognitive task then individuals with higher HRV and (2) that individuals with increased HRV will be associated with decreased levels of anxiety and a higher score on cognitive tasks.
Method
Participants
Participants will be 150 male and female undergraduate college students from Towson University. Participants will be recruited through the psychology research pool. Most participants will be Introduction to Psychology students and will be given course credits for their participation. Other students may participate in the study for other extra credit in other Psychology classes or may just participate without compensation. All participants will be 18-27 years of age. Individuals with a history of cardiovascular or neurological disease, a history of smoking, and/or drug history will be excluded from the study. Individuals must abstain from alcohol for 24 hours, caffeine use for 6 hours prior to the study, and vigorous exercises for 3 hours prior to the study.
Measures
A measure of anxiety will be obtained using the trait form, STAI X-2, and state form, STAI X-1, of the State Trait Anxiety Inventory (Spielberger, Gorsuch, Lushene, Vagg & Jacobs, 1983). STAI X-1 is a 20-item state anxiety inventory that asks questions about how participants are feeling at the current moment. Examples of these questions include 1) “I feel calm” 2) “I feel secure” and 3) “I feel tense”. Ratings for each question range from 1= not at all to 4= very much so.
STAI X-2 is a 20-item trait anxiety questionnaire. Participants are given questions that describe their general feelings. Ratings for each question ranged from 1=almost never to 4=almost always. Examples of these questions include 1) “I feel pleasant”, 2) “I tire quickly”, and 3) “I feel like crying”. All participants will be given these two anxiety questionnaires.
Apparatus
Non-invasive physiological recording technology will be placed on all participants. Electrocardiography (ECG) recording with two disposable pre-gelled electrodes will be placed on the left side of the rib cage and on the right side of the sternum. Impedance cardiography (ICG) recording will be taken via four disposable electrodes, which will be placed vertically on the upper back and the lower back. Both of the ECG and ICG electrodes will be connect to lead cables, which will transmit signals to and from the recording equipment. Cardiac analysis will be assessed through Biopac Acknowledge v5.0 and Kubios HRV Analysis v3.0 systems. Individuals will be tested using three different cognitive tests including the spatial n-back task (3-back) (shifting), the stroop test (inhibition), and the letter memory task (updating). All cognitive programs will be created using E-prime v3.0 systems.
Procedures
Participants will be welcomed into the lab where a same-sex research assistant will greet them and take them to the testing room. They will be given a consent form, which they will read along with the research assistant. They will be asked if they have any questions and asked to place their belongings in a box on a desk. Four gel electrodes will be placed on the back of the participants along the spine. Two gel electrodes will be placed on the left side of the rib cage and on the right side of the sternum directly below the right shoulder bone.
The study will include three cognitive tasks as well as two questionnaires. Participants will be placed in one of two groups the emotion condition and no emotion condition. In the emotion condition group participants will be asked to place headphones on and will be interrupted by a loud burst of a sound (details of loud type and specific music TBD and added in*) every 45 seconds while they perform the cognitive tasks (details of time between loud bursts of sound TBD)*. The other group, no emotion condition will not have any music or sound playing while they perform the cognitive tasks. Participants will first be asked to complete the STAI X-2 which will be followed by a baseline physiological testing of five minutes where the participant will be asked to stay still while watching a series of neutral pictures on a computer screen. This will be followed by the spatial 3-back cognitive test, which will test task shifting. Participants will be asked to watch for a colored square three times in a row on a grid-like background. The colored square will move from location to location in the environment and individuals must locate where this colored square was three times ago. Individuals will be asked to pick the correct location of the first colored square that appeared. This will be followed by a 5-minute testing period where they will be asked to watch a series of neutral photos on the screen while sitting still. The second part of the study, the stroop test that will test inhibition, will include a series of different color words in different colors and asked to call out the color of either the word or the color that the word says. For example, a participant may be given the color “purple” written in a red color asked to give the color of the word rather then what color the word is saying. The third part of the study will include the letter memory task, which will test updating. Participants will be given a series of letters and numbers in no distinct order and asked to recall numbers in ascending or descending order and letters separately. Participants will then be asked to complete the STAI X-1 state questionnaire. Individuals will be debriefed on the reason for the study and then asked if they have any questions or concerns. Participants will then be thanked for their participation and granted credit for completion of the study.
Design
The design of the study will be a 2 (high HRV, low HRV) X 2 (emotional condition vs. no emotional conditions). The different groups emotional condition and no emotional condition will be a within subjects design. Individuals in the emotion condition will periodically hear loud bursts of sounds while performing the cognitive tasks.