This fundamental question addresses another type of memory: the implicit memory that involves associative and nonassociative learning
. The cerebellum and the amygdala are critical for associative learning.
Viola et al., "Role of hippocampal signaling pathways in long-term memory formation of a nonassociative learning
task in the rat," Learning & Memory, vol.
Habituation to a novel environment is believed to be one of the most elementary forms of nonassociative learning
. The repeated exposure to the same environment induces a reduction in the exploratory behavior, which can be taken as an index of habituation .
We begin by focusing on sensitization, an elementary form of nonassociative learning
by which an animal learns about the properties of a single noxious stimulus and enables the formation of a learned fear response.
Such examples of nonassociative learning
mechanisms have led scientists to argue that there is no unitary learning process at the computational level of analysis.
Carew at Yale University and his co-workers have applied this developmental approach to the study of nonassociative learning
in Aplysia, a marine snail whose adult form became famous in pioneering studies of the molecular basis of memory (SN: 1/22/83, p.58).
Habituation is a form of nonassociative learning, common to all animals, in which behavioral responses to repeated stimuli decrease over time.
Nonassociative learning processes affecting swimming probability in the seaslug Tritonia diomedea: habituation, sensitization and inhibition.
Moreover, recent evidence indicates that not only associative learning, but also nonassociative learning, in Aplysia depends critically on postsynaptic changes.
The recent work on nonassociative learning in Aplysia suggests that postsynaptic processes play critical roles in both habituation and sensitization.