Psychophysiology Research
Psychophysiology Basics Skin ConductanceSkin conductance (SC) can be described simply as sweat gland activity. Using electrodes placed on two fingers of one hand, we can pick up the tiny changes in the electrical activity of the sweat gland cells located in the deepest layer of the skin. Sweat glands are activated through inputs from several areas in the brain including the frontal lobes. Skin conductance is associated with arousal, mental activity, stress, fear, and positive and negative affect, which makes it a relatively simple yet informative psychophysiological measure. The most common SC measures are the skin conductance response (SCR), the skin conductance level (SCL), and the non-specific fluctuation (NSF). The SCR indexes the net change in sweat gland activity in response to a stimulus or event (e.g., presentation of a picture or a sound). The SCL indexes the basal level of sweat gland activity. Finally, the NSF indexes changes in sweat gland activity that occur in the absence of an experimental stimulus or event. Each of these SC measures is illustrated in the hypothetic SC record depicted below. The beginning of the record illustrates SCL – a basal level of activity. At time zero a loud noise blast occurs triggering a SCR – a change in SC in response to a stimulus. After recovering to the original basal SC level, two separate increases in SC occur in the absence of any experimental stimulus or event – these are NSFs.
In our current laboratory study, we are examining each of these SC measures as they relate to the co-occurrence of substance use problems and maladaptive personality features adult men and women. Heart RateHeart rate activity represents another relatively simple yet informative psychophysiological measure. An electrocardiogram (ECG or EKG) provides information about the activity of the heart muscle. The heart rate (in beats/min.) is a common ECG measure. Changes in heart rate are associated with changes in attention, emotion, and other psychological factors. In conjunction with data on SC, we are looking at differences in heart rate activity that may relate to risk for substance abuse and other mental health problems in our current lab study. EmotionEmotional processing can be measured using non-invasive yet methodologically rigorous means. Electromyography (EMG) provides information about the activity of the tiny muscles around the eye that are engaged when people express emotions such as fear. The startle reflex is a well-documented phenomenon with associated features, including eye blink. In conjunction with data on SC and HR, we are looking at differences in magnitude of the startle-related eye blink in relation to personality disorders such as histrionic and narcissistic. |
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