Now Where Did I Put Those Keys?

The World & I, 11-01-1998
Norbert R. Myslinski

As researchers unravel the brain's inner workings during the formation and loss of memories, we may find new ways to prevent serious memory lapses.

Along with ordering their first pair of bifocals and starting to feel the pains of arthritis, baby boomers are now worrying about their memory remember seems to be going in the opposite direction as their need to remember. Are these memory lapses a normal part of growing old, or are they the beginnings of Alzheimer's disease? How can we tell the difference? Is there anything we can do to improve our memory?

Our understanding of the neurobiology of memory has taken gigantic strides in the last five years. We have discovered genes involved in controlling memory. We are testing drugs that may enhance memory. We have scanning technology that enables us to visualize the flow of brain activity at the same time as the subject searches for a memory. And we have even seen changes in nerve cell connections (synapses) in response to learning and experience. These and other recent discoveries promise future treatments to help those having trouble with memory lapses, whether as a result of a degenerative brain disease or just normal aging.

Memories, memories

Memory is not a singular brain function. Rather, the brain processes, stores, and retrieves information in many distinct ways and in many different places. Memories have been classified according to the type of information or the time of retention.

Type of information. Memories categorized by type of information can be either declarative, procedural, or emotional. Declarative memory is the ability to remember names, faces, telephone numbers, or important events. It is material available to the conscious mind, encoded in the cerebral cortex, and expressed by language.

Procedural memory refers to motor activity and skills acquired and retrieved on a subconscious level. We utilize procedural memory during such activities as piano playing, knot tying, and bike riding, when we do not consciously direct our detailed movements. In fact, thinking about the movements may inhibit our ability to perform them. Procedural memories are stored in parts of the brain known as the basal ganglia, the cerebellum, and the premotor cortex.

Emotional memory re-creates our original emotional response. A sight, a sound, or even a smell can bring back the joy, fear, love, or hate that we once associated with it. A buzzing bee or an attractive face may mean little emotionally, until we create memories of being stung or falling in love. The anatomical correlate of emotional memory is the amygdala, located in the temporal lobes on each side of the brain. Destroying the amygdala destroys emotional memory.

If left unchecked, emotional memory can lead to chronic fear, forming the basis of anxiety disorders such as phobias, panic attacks, and post-traumatic stress disorder (PTSD). Normally, the prefrontal cortex dampens the amygdala's response and calms the fear. But for most PTSD sufferers, their prefrontal cortex does not send this message. About 25 percent of Americans have a diagnosable anxiety disorder at some point in their lives, and the collective bill for treating these disorders amounts to about $45 billion per year.

Time of retention. When viewed from the perspective of time of retention, memories may be classified as being part of either working memory or long-term memory. Working memory is the "blackboard" of the brain. It is the capacity to keep information in the conscious mind while performing tasks using that information. It maintains images "on-line" long enough to manipulate them for problem solving and planning. It is similar to a computer's RAM (random access memory). Long-term memory is filed away, stored over extended periods of time, to be retrieved later. It is similar to memory stored on a hard disk drive.

Contrary to popular belief, our brains do not record everything that happens to us. More than 99 percent of the sensory information that enters our bodies is filtered out and does not even reach our consciousness. Most of what does reach consciousness hovers briefly in working memory and then evaporates. Only meaningful experiences are preserved in long-term memory. If we were aware of every sensory message and stored every thought, there would be no room for analyzing, creating, and enjoying.