Memory and Learning

Article excerpt

So much learning, so little memory.

This is the third article in a series by Weiss on learning and the brain. See "Brain-Based Learning" (July) and "Howard Gardner Talks About Technology" (September).

We take our memory for granted-until we can't recall someone's name, a word, or where we put our keys. Then we have a moment of panic: Are we losing our memory, or our mind?

Memory is essential for going about the daily business of our lives. We need memory for everything we do: perceiving the world, synthesizing and analyzing information, and applying knowledge to new situations. In fact, learning is the making of memory, which is laid down in our brains in chemical form. Chemical changes are created at the neuron level; without them, there's no substance for our minds to work with.

According to the current model of memory, input from our senses via the environment is processed through our perceptual memory in fractions of a second. If deemed important enough, either by one's unconscious or conscious mind, the input is put into the short-term memory. From there, it's either discarded or planted in the long-term memory.

Eric Jensen, educator and author of Teaching With the Brain in Mind, notes that "learning and memory are two sides of a coin. You can't talk about one without the other." He calls learning that lasts (information stored in our long-term memory) "long-term potentiation." When LTP occurs, "a cell is electrically stimulated over and over so that it excites a nearby cell. If a weaker stimulus is then applied to the neighboring cell a short time later, the cell's ability to get excited is enhanced."

Ken Kosik, professor of neurology at the Harvard Medical School and a cofounder of the Brigham and Women's Hospital Memory and Disorders Clinic, explains that our brain changes with learning in functional ways. When we learn something that stays with us for any length of time, it goes from the short-term into our medium- or long-term memory. When that occurs, certain genes in the brain turn on. When they turn on, new proteins are made and the connections between the axons and dendrites increase in complexity. In other words, new memories create new interconnecting pathways between neurons.

As we learn something new, each chemical message is laid down as a chain of neurons called a neural network. Those connections become stronger the more often our brains access the network. Synapses, or spaces between the neurons, also become stronger, says educator Marilee Sprenger in her book, The Brain in Action. She compares the process to creating a path in the woods: "The first time you create a path, it is rough and overgrown. The next time you use it, it's easier to travel because you have previously walked over the weeds and moved the obstacles. Each time thereafter, it gets smoother and smoother. In a similar fashion, the neural networks get more efficient, and messages travel more swiftly."

Neuroscientist Joseph LeDoux, author of The Emotional Brain, says that what we are conscious of at any given moment is what's in our short-term memory-especially our working memory, a special kind of short-term memory. Furthermore, only information that's registered in a person's short-term memory can eventually go into the long-term memory.

Scientists agree that short-term memory capacity is limited to five to nine items, although it's capable of holding more information if packaged into chunks. Educator Jeb Schenck compares the short-term memory to a desktop: Once it's filled, if an additional item finds its way in, a pre-existing item will have to be pushed out. Moreover, with short-term memory, the more time that elapses between learning details and recalling them, the harder it is to access those details.

The hippocampus, a region deep within the brain, is the memory-staging area that connects stimuli and responses. It's vital for consolidation of memories. …