Chapter 8 Summary

The generally accepted taxonomy of memory systems distinguishes three major systems: declarative memory, nondeclarative memory, and working memory. Damage to the medial temporal lobe impairs declarative memory but spares working memory. Other types of lesions can impair working memory without disrupting declarative memory.
Nondeclarative memory depends on brain regions other than medial temporal lobes, which vary for different forms of nondeclarative memory: priming, skill learning, and conditioning.
Priming is defined as a change in processing of a stimulus due to a previous encounter with the same or a related stimulus in the absence of conscious awareness of the original encounter. The neural correlates of priming include neocortical regions that vary with the type of priming: visual perceptual priming is associated with altered activity in the visual sensory areas in occipitotemporal cortex; conceptual priming, with anterior left inferior prefrontal areas; and semantic priming, with left anterior temporal areas. In functional neuroimaging studies of priming, these regions typically show a reduction in activity, known as repetition suppression, which may reflect a dropping out of noncritical neurons across repetitions.
Skill learning depends on the basal ganglia and is associated with cortical regions that depend on the type of skill learning (motor regions for motor learning, temporal fusiform regions for perceptual learning, and so on).
Conditioning is the altered probability of a behavioral response engendered by associating the response with a reward. Eyeblink conditioning has been linked to circuits in the cerebellum. Operant conditioning (instrumental learning) has been associated with the basal ganglia.
All varieties of memory appear to depend on the same cellular and molecular mechanisms of neural plasticity. At the cellular level, memories are transiently stored as changes in the efficacy of existing synaptic connections between neurons within particular neuronal assemblies. Longer-lasting memories require more permanent changes in gene expression, protein synthesis, and morphology, including the formation of new synaptic connections.