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  • Storage of Implicit Memory Involves Changes in the Effectiveness of Synaptic Transmission

    • Habituation Results from an Activity-Dependent Presynaptic Depression of Synaptic Transmission

    • Sensitization Involves Presynaptic Facilitation of Synaptic Transmission

    • Classical Conditioning of Fear Involves Coordinated Pre- and Postsynaptic Facilitation of Synaptic Transmission

  • Long-Term Storage of Implicit Memory Involves Changes in Chromatin Structure and Gene Expression Mediated by the cAMP-PKA-CREB Pathway

    • Cyclic AMP Signaling Has a Role in Long-Term Sensitization

    • Long-Term Synaptic Facilitation Is Synapse Specific

    • Long-Term Facilitation Requires a Prion-Like Protein Regulator of Local Protein Synthesis for Maintenance

  • Classical Fear Conditioning in Flies Uses the cAMP-PKA-CREB Pathway

  • Memory for Learned Fear in Mammals Involves the Amygdala

  • Habit Learning and Memory Require the Striatum

  • Learning-Induced Changes in the Structure of the Brain Contribute to the Biological Basis of Individuality

  • An Overall View

Throughout this book we have emphasized that all behavior is a function of the brain and that malfunctions of the brain produce characteristic disturbances of behavior. Behavior is also shaped by experience. How does experience act on the neural circuits of the brain to change behavior? How is new information acquired by the brain and, once acquired, how is it remembered?

In the previous chapter we saw that memory is not a single process but has at least two major forms. Implicit memory operates unconsciously and automatically, as in the memory for habits and perceptual and motor skills, whereas explicit memory operates consciously, as in the memory for people, places, and objects. Long-term storage of explicit memory begins in the hippocampus and the medial temporal lobe of the neocortex, whereas long-term storage of implicit memory requires a family of structures: the neocortex for priming, the striatum for skills and habits, the amygdala for learned fear, the cerebellum for learned motor skills, and certain reflex pathways for nonassociative learning such as habituation and sensitization (Figure 66–1).

Figure 66–1
Two forms of long-term memory involve different brain systems.

Implicit memory involves the neocortex, striatum, amygdala, cerebellum, and in the simplest cases the reflex pathways themselves. Explicit memory requires the medial temporal lobe and the hippocampus, as well as certain areas of neocortex (not shown).

Over time, explicit memories are transferred to different regions of the neocortex. In addition, many cognitive, motor, and perceptual skills that we initially store in explicit memory ultimately become so ingrained with practice that they become stored as implicit memory.

The transference from explicit to implicit memory and the difference between them is dramatically demonstrated in the case of the English musician and conductor Clive Waring, who in 1985 sustained a viral infection of his brain (herpes encephalitis) that affected the hippocampus and temporal cortex. Waring was left with a devastating loss of memory for events or people he had encountered even a minute or two earlier. Yet he could ...

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