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Physiological measurement methods

Read about the different types of physiological measurements and the protocols we use. For more information, contact SOLO Research and Lab Support.

An electrocardiogram measures the electrical activity of the heart muscle by using electrodes placed on the skin. These electrodes detect the small electrical changes that are a consequence of cardiac muscle depolarization followed by repolarization during each cardiac cycle (heartbeat).

When you measure electrodermal activity (EDA - also known as galvinic skin response (GSR) or skin conductance level (SCL)), you are measuring how ‘well’ the skin conducts electricity. Often the skin will conduct electricity better during states of high arousal.

EEG measures the electrical activity in the brain. More specifically, it measures the sum of all post-synaptic potentials of the neurons in the cerebral cortex. This signal is very weak and is therefore measured in microvolt (µV). 

Facial electromyography (EMG) is a psychophysiological technique used to measure electrical potential generated by facial muscles. As the activity of certain facial muscles has been associated with emotional expression, facial EMG can be used to index variance in the valance of emotional expression.

ICG measures the electrical impedance (resistance) of the blood in the thorax (chest), specifically in the aorta. This impedance depends on the blood levels in the aorta. Every heartbeat shows a change in impedance. When blood levels are high (directly after the opening of the aorta valve in the heart) the impedance is low. The ICG signal (Z(t)), as well as its derivative (dZ/dt) are used to calculate various hemodynamic parameters, such as stroke volume, cardiac output, and the pre-ejection period. 

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