Two forms of Pavlovian conditioning, fear and eyeblink conditioning,
have been the most frequently examined in the field of
neuroscience. During fear conditioning, the cue and/or context
becomes associated with an aversive stimulus. When, a subject is
re-exposed to a fear associated CS, the CS elicits a fear response
that can be measured by startle magnitude, heart rate, or freezing
behavior. Similarly, eyeblink conditioning involves an association
between a US that elicits an eyeblink reflex and a CS, leading to
eyeblink CR. Both fear and eyeblink conditioning have allowed
for detailed analysis of underlying learning circuitry in animal
models, while providing useful translational value in human
studies.