Broadly speaking, psychophysiology is the study of the relationship between psychological processes and physiological responses. This relationship is typically examined in human participants, in healthy controls as well as groups with physical or psychological illnesses.
There are many types of psychological processes that are examined, including orienting, arousal, sensation, perception, and higher order “executive” processes such as attention, learning, memory, emotion processing, and cognitive control. Physiological responses that may be examined span both the central and peripheral nervous systems, including the activity of the brain (EEG, ERPs, fMRI, etc.), heart, lungs, muscles, and electrodermal system.