Using tools in psychophysiology to measure emotion
The Acoustic Startle Response
Through the skeletomuscular system, we measure adaptive reflexes involved in threat responding. The acoustic startle response is an integrative motor reflex to sudden auditory stimuli, observed in all mammalian species. Exaggerated startle is a predictor of emotion dysregulation and anxiety risk. We quantify electromyography (EMG) as a noninvasive measure of startle activity.
The Skin Conductance Response
Through the electrodermal system, we measure autonomic arousal via the skin conductance response (SCR). Skin conductance, which reflects changes in sweat gland activity that alters the electrical conductivity of the skin, is a direct index of sympathetic nervous system activation, and thus is an excellent measure of arousal. We quantify electrodermal activity (EDA) as a noninvasive measure of sympathetic nervous system activation.
Fear conditioning is based on a simple Pavlovian conditioning model in which a neutral conditioned stimulus (CS, i.e., a shape presented on a computer screen) is paired with an aversive unconditioned stimulus (US, i.e., a forceful airblast directed at the throat). After a number of pairings, the association is formed so that the CS alone elicits the conditioned response (CR, i.e., a fear response). This basic model is used in animal as well as human research to investigate mechanisms of fear learning and memory.
In fear-potentiated startle (FPS), the magnitude of the startle reflex increases during aversive CS presentations. We use a fear discrimination paradigm that measures startle amplitude in the presence of a reinforced conditioned stimulus (CS+) that is paired with a US, as well as during exposure to a nonreinforced conditioned stimulus (CS-) that is never paired with a US. The use of the nonreinforced CS-, which serves as a safety cue, allows us to experimentally test differences in safety signal processing (emotion regulation) between experimental groups. Hence, the FPS discrimination paradigm is an extremely powerful paradigm for studying the mechanisms of fear learning and memory. It allows for stringent experimental control over the delivery of aversive stimuli, and the fear responses can be easily quantified.
Dark-enhanced startle refers to the increase in magnitude of the acoustic startle reflex when experienced during the dark due to increased fear and anxiety. This translational model corresponds to the light-enhanced startle paradigm used in rodents. This procedure differs from fear conditioning in that it does not depend on associative learning and memory processes. Unlike fear-potentiated startle, which measures specific fear to an acute threat, dark-enhanced startle creates a state of uncertainty about a potential and unknown threat, invoking a sustained anxiety response
Neurobiological Model of Emotion Regulation
Some critical brain regions involved in fear learning in memory are the amygdala and the prefrontal cortex. The amygdala regulates the acquisition of fear memories and the expression of learned fear behaviors. Fear-potentiated startle is a direct measure of amygdala activity. The prefrontal cortex is a higher order brain region that regulates amygdala activity based on the situation or context surrounding the fear stimulus. It plays a critical role in emotion regulation by suppressing amygdala activity during perceived safe conditions.
People with anxiety disorders and/or emotion regulation deficits often show heightened amygdala activity (indicated by exaggerated startle) as well as a reduction in prefrontal activity. These deficits result in maladaptive fear behaviors during inappropriate circumstances.
We collaborate with Sharon Pearcey (Department of Psychological Science) and Doreen Wagner (School of Nursing) to collect and assay saliva for various biomarkers of interest.
Free circulating steroid hormones, 17β-Estradiol (E2) and progesterone, are major reproductive hormones that may play a role in cognition. Salivary samples are collected once at the beginning of the experiment and assayed (mean pg/mL) in duplicates with commercially available Salimetrics Enzyme Immunoassay Kits (Salimetrics, State College, PA), which are competitive immunoassays specifically designed and validated for the quantitative measurement of relevant salivary hormones.
Free circulating stress hormones are excreted by the adrenal gland and linked to the stress response system. Salivary samples of cortisol, dehydroepiandrosterone (DHEA), and dehydroepiandrosterone sulphate DHEA-S samples are collected at various time points in our experiments.
We use a variety of psychometric instruments to standardize psychological constructs related to people's thoughts, feelings, exposure to adverse experiences, and coping behaviors. We employ multiple self-report measures to assess certain clinical symptoms (e.g., stress, anxiety, depression) and levels of severity. We also assess people's attitudes and opinions surrounding social experiences.