Learning Objectives

In everyday life, the term memory is used to refer to the conscious experience of a previous event. However, when an event is repeated, there can also be behavioral effects and brain effects that occur outside of conscious experience. Implicit memory refers to a lack of conscious experience or awareness of previously learned information. This includes more efficient or fluent processing of an item when it is repeated (i.e., repetition priming) and skill learning (see Chapter 1). Section 7.1 of this chapter considers the brain regions that have been associated with implicit memory, which include the dorsolateral prefrontal cortex and sensory processing regions (a subset of the regions associated with long-term memory; see Chapters 1 and 3). In section 7.2, the frequency bands of activity associated with implicit memory are discussed, which include gamma activity and alpha activity (a subset of the frequency bands of activity associated with long-term memory; see Chapter 4). Although there is some overlap between implicit memory and long-term memory with regard to the associated regions and frequency bands of activity, there are many notable differences that will be highlighted in this chapter. For instance, in direct opposition to the increases in cortical activity associated with long-term memory, implicit memory is typically associated with decreases in cortical activity. Section 7.3 details theoretical models of neural activity that underlie implicit memory effects and discusses ways in which these models can be distinguished from one another. In the fourth section, 7.4, evidence is considered that has claimed to link the hippocampus to implicit memory, which if true would contradict the evidence that this region is associated with only long-term memory.