As Good As Memories In The Bank - How We Remember: Improving Memory Understanding Age Related Memory Loss

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As good as memories in the bank

One of the enduring myths about memories is that they are kept in one place in the brain, a memory bank. At first, even scientists assumed that this was the case. But, over many decades of research, they realized that this assumption was wrong. In the 1980s, when functional brain-imaging technology — such as positron emission tomography (PET) scans — became available, scientists could see people's brains at work for the first time (see "Watching the brain at work"). They could obtain images of the brain as people performed a variety of tasks, including remembering things. Researchers discovered that memories are not stored in a single location, but rather are widely distributed in networks throughout the brain, primarily in the cerebral cortex. The cerebral cortex consists of the outer covering of the two large hemispheres of the brain and is the most highly developed part of the human nervous system. The cortex contains about 20 billion neurons that collectively function to integrate sensory information, control voluntary movements, and mediate thinking processes.

We know that different areas of the brain process different kinds of information. For example, auditory information, including speech and other sounds, is processed in the temporal lobes (see Figure 2), while the registration of visual images occurs in the occipital lobe at the back of the brain. What these findings suggest is that a particular aspect of a memory will most likely be stored in a region of the cortex that specializes in processing similar information.

Figure 2: Memory map Different parts of the brain specialize in different functions. Memories are stored in many parts of the brain but some areas are more critical than others. To retrieve a memory, these areas of the brain must work in coordination with others. For example, the frontal lobe (important for planning and organization) works together with several brain regions, including the hippocampus, in acquiring and retrieving memories.

To say that each memory has a single "content slot" in the brain is simplistic. Each memory resides in a network of neuronal activation, dispersed across multiple brain regions. Sensory aspects of a memory are stored in brain regions that are specialized for processing that type of information. The words of "The Star-Spangled Banner" are stored in the left temporal lobe, which processes language, but the melody would be stored in the left parietal lobe, which processes auditory patterns. And each memory is connected to many related memories. For instance, if you associate "The Star-Spangled Banner" with the image of the American flag, that memory might be stored in your occipital lobe, which processes visual information. Your memories are thus intricately broken down and cross-referenced, making your brain less like the shelves of a library and more like the Internet. Calling up memories is like doing an Internet search, with one or two words activating many hyperlinks.

But just how does the information that you encounter on a daily basis get filed away? Memory researchers use a three-stage model to describe how the brain learns and remembers each bit of information: acquisition, consolidation, and retrieval. Impairment in any one of these three stages can result in a failure of memory.

How smoothly the process goes — which is to say, how well you remember — depends on many things. Genetics plays a major role. Studies of human intelligence suggest that approximately 50% of mental ability is genetically determined. It may be that some people are simply better at remembering than others because of a genetic predisposition for an excellent memory. But factors within your control are also important. Overall physical health, emotional well-being, stress level, sleep quality, and diet exert a huge influence on how well you learn and remember.

Last updated:	January 23, 2007