1. Introduction to Neuroimaging Peripheral Measures Lecture

• Skin conductance is a measure of electrical conductivity through the skin, which can reflect autonomic nervous system activity.
• Three types of skin conductance responses: Skin conductance level (tonic), non-specific skin conductance response (phasic), and event-related skin conductance response (stimulus-locked).
• Skin conductance is often used in research on fear conditioning and economic decision making.
• Pupillometry is another measure of autonomic nervous system activity, which reflects changes in the size of the pupil in response to cognitive processes and emotional states.
• Pupillometry can be used to measure reactions to changes in luminance, arousal, surprise, mental effort, and stimulation of sympathetic and parasympathetic nervous systems.
• Pupil size can be measured using an infrared light source and an infrared-sensitive camera.
• Cardiac activity can be measured using electrocardiography (ECG), which records the electrical activity of the heart, and impedance cardiography (ICG), which measures changes in electrical conductivity in the thorax.
• Heart rate (HR) and heart rate variability (HRV) are important measures of cardiac activity.
• HR decreases with parasympathetic nervous system (PNS) influence and increases with sympathetic nervous system (SNS) influence.
• High HRV predicts better cognitive performance.
• ICG can be used to measure the pre-ejection period (PEP), which reflects the effect of the SNS on the heart.
• PEP can be used to assess effort mobilization in cognitive tasks, with shorter PEPs observed in response to sad stimuli.
• Other methods for measuring cardiac activity include photoplethysmography (PPG) and phonocardiography.
• ECG measures heart rate and heart rate variability by recording the electrical activity of the heart through surface electrodes.
• ECG does not directly measure action potentials but reflects the production and conduction of action potentials in the heart during the cardiac cycle.
• Heart rate is calculated based on the RR interval and is sensitive to emotional processes influenced by both SNS and PNS.
• Heart rate variability reflects the changes in time intervals between consecutive heartbeats and is a general measure of the influence of the PNS on the heart.
• Impedance cardiography measures changes in electrical conductivity in the thorax, with high-frequency current flowing between an electrode pair via the aorta.
• Impedance changes are picked up by a second pair and return an Impedance pulse wave (IMP) and the ICG curve (1st derivative).
• Pre-ejection period is the time interval from electrical stimulation of the ventricles to the opening of the aortic valve, reflecting the effect of the SNS on the heart.
• In affective context, PEP can be used to assess effort mobilization in a letter detection task, with shorter PEPs observed in response to sad stimuli.
• Photoplethysmography measures changes in blood volume in the microvasculature, and Phonocardiography measures heart sounds.
• All these measures are used for understanding the autonomic nervous system and cardiac activity in different contexts.

This lecture provides an introduction to neuroimaging peripheral measures, focusing on the peripheral nervous system, specifically the autonomic system. Topics covered include the sympathetic and parasympathetic divisions, their functions, and their effects on the body.