The purpose of this study is to investigate possible neural correlates of electrodermal activity.
Electrodermal activity (EDA) is a broad term describing the changes in the electrical properties of the skin. Activation of the sympathetic nervous system (SNS) – the part of the nervous system responsible for your “fight or flight” response – induces microscopic changes in the sweat glands beneath the skin. More simply, “you sweat when you’re stressed.” Clammy hands, “sweating bullets” when nervous, and other euphemisms aptly describe this phenomenon. However, one does not have to be sweating bullets for sensors to pick up the tiny changes induced by the SNS. As a person sweats, even subtly, the electrical resistance of the skin lowers, causing a corresponding increase in the conductance across the skin. By placing two electrodes on the skin, we can measure this skin conductance or electrodermal activity. It is a measure of the body’s physiological arousal.
Studies have shown that increased EDA correlates strongly to feelings of stress, anxiety, fear, high cognitive load (i.e., thinking hard), and physical activity, but exactly how EDA is driven by brain activity remains unknown.
The participants in this study are patients diagnosed with intractable epilepsy – that is, medicine or other interventions have been unsuccessful at controlling their epilepsy. In order to manage their seizures, these patients have had thin electrodes inserted deep into their brains. These deep brain probes are able to both passively record the patient’s neural activity and, in the event of a seizure, deliver tiny bursts of electrical stimulation with the hopes of off-setting the seizure’s intensity and duration. This stimulation can also be delivered in a controlled setting under the supervision of a doctor.
For this study, we intend to concurrently measure each patient’s neural activity while measuring their EDA at several sites on their body.. We will measure the brain signals passively, while they perform various activities, and we will also actively stimulate their brain under the supervision of a doctor in order precisely map the neural stimulation to skin conductance. In doing so, we hope to better understand how brain activity drives EDA.
Then, since EDA is easy to measure non-invasively using wrist-worn and other wearable sensors, this study will help us use EDA as a more effective tool to understand underlying brain activity and both cognitive and affective processes in the wild. The naturalistic and longitudinal measurement of cognitive and affective processes could help inform prediction and treatment modalities for individuals with epilepsy, PTSD, anxiety, depression, and autism, with future implications for digital health and personalized medicine.