IN HIS MASTERFUL NOVEL One Hundred Years of Solitude, Gabriel Garcia Márquez describes a strange plague that invades a tiny village and robs people of their memories. The villagers first lose personal recollections, then the names and functions of common objects. To combat the plague, one man places written labels on every object in his home. But he soon realizes the futility of this strategy, because the plague eventually destroys even his knowledge of words and letters.
This fictional incident reminds us of how important learning and memory are in everyday life. Learning refers to a change in behavior that results from acquiring knowledge about the world, and memory refers to the processes by which that knowledge is encoded, stored, and later retrieved. Marquez’s story challenges us to imagine life without the ability to learn and remember. We would forget people and places we once knew, and no longer be able to use and understand language or execute motor skills we had once learned; we would not recall the happiest or saddest moments of our lives and would even lose our sense of personal identity. Learning and memory are essential to the full functioning and independent survival of people and animals.
In 1861, Pierre Paul Broca discovered that damage to the posterior portion of the left frontal lobe (Broca’s area) produces a specific deficit in language. Soon thereafter, it became clear that other mental functions, such as perception and voluntary movement, are also mediated by discrete parts of the brain (Chapter 1). This naturally led to the question: Are there discrete neural systems concerned with memory? If so, is there a “memory center,” or is memory processing widely distributed throughout the brain?
Contrary to the prevalent view that cognitive functions are localized in the brain, many students of learning doubted that memory is localized. In fact, until the middle of the 20th century, many psychologists doubted that memory is a discrete function, independent of perception, language, or movement. One reason for the persistent doubt is that memory storage involves many different parts of the brain. We now appreciate, however, that these regions are not all equally important. There are several fundamentally different types of memory, and certain regions of the brain are much more important for encoding some types of memory than for others.
During the past several decades, researchers have made significant progress in the analysis and understanding of learning and memory. In this chapter, we focus on studies of normal human memory behavior, its perturbations following brain lesions due to injury or surgery, and measurements of brain activity during learning and memory recall using functional magnetic resonance imaging (fMRI) and extracellular electrophysiological recordings. These studies have yielded three major insights.
First, there are several forms of learning and memory. Each form of learning and memory has distinctive cognitive and computational ...