Stage Two Consolidation - How We Remember: Improving Memory Understanding Age Related Memory Loss

Content provided by the Faculty of the Harvard Medical School

Stage two: Consolidation

Let's say that you were paying close attention to the information you just heard and that it was effectively encoded in your brain. How does it become stored as a memory that you can recall in the future? For the information to become a long-term memory, its initial neuronal pathways must be strengthened. The strengthening process, typically referred to as consolidation, occurs over a period of time.

Consolidation of declarative memories

The hippocampus plays a major role in consolidating declarative memories. Several factors influence whether the hippocampus responds to the newly acquired information and gives the signal to store it as long-term memory. For example, you're more likely to retain new information if it relates to long-term memories you already have. It's easier to remember the names of the players on your local football team if you know something about football than if you don't follow the game at all. Another factor is the information's emotional impact (see Figure 3). You're far more likely to remember a disturbing photograph than a bland one. You can probably remember the images of the World Trade Center falling far more vividly than you can, say, a photo of a hotel where you attended a business conference. The part of the brain that reacts to emotionally powerful information is the amygdala, which is situated near the hippocampus. Some research using PET scans suggests that information that activates the amygdala is most likely to be retained long-term.

Figure 3: Remember grandma's cookies? An experience that stimulates many parts of the brain is more likely to be remembered, particularly if it has an emotional component.

Consolidation of procedural memories

In contrast to declarative memory, the consolidation of procedural memories is less dependent on the hippocampus. Even people with amnesia, who have damage to the hippocampus, can form new procedural memories — that is to say, they can learn new skills through practice. Procedural memories, such as riding a bicycle and playing a musical instrument, also tend to remain intact with aging. They even persist during the early stages of Alzheimer's disease, which damages the hippocampus. However, acquiring new procedural memories becomes more difficult with age because we process information more slowly.

Procedural memory is stored throughout the brain in regions that are important for coordinating movement or sequential processing, such as the frontal lobes, the cerebellum, and the basal ganglia. Studies also show that sleep is vital for consolidating procedural memory. In an experiment at Harvard University, students who learned a computer game were better able to remember it and play it the next day if they'd had more than six hours of sleep than if they'd had less. Even two days to a week later, students who were consistently well-rested outperformed those who didn't sleep as well.

Last updated:	January 23, 2007