Trouble keeping information in mind? Could be sleep, mood

You’re heading to the market. You need to pick up eggs, cheese, milk, bread, tomatoes, carrots, and string beans. Can you keep those items in mind by repeating them to yourself? You arrive at your usual market, but it is unexpectedly closed. A passerby gives you verbal directions to a new market. Can you close your eyes and visualize the route? Both activities tap working memory — that is, your memory for information that you need to actively keep “in mind” and manipulate often.

We use this type of memory every day. For example, when we are comparing two or more options — whether dinner entrees, health plans, or mutual funds — we are using our working memory to keep the details of the different options in mind.

The frontal lobes direct the components of working memory

The two frontal lobes of the brain play important roles in certain types of memory. Working memory is typically divided into two components, plus an executive system that shifts attention between them. One component helps you keep verbal information in your head by silently repeating it to yourself. Another component processes spatial information, such as mentally planning the route you will drive to avoid rush hour traffic.

Virtually all tasks involving working memory activate the prefrontal cortex, the part of your frontal lobes right behind your forehead. The left hemisphere of your brain is more involved when you are repeating verbal information to yourself. The right hemisphere is more involved when you are mentally following a route. Interestingly, as a working memory task becomes more difficult, both hemispheres become engaged regardless of whether the task is verbal or spatial.

New research shows sleep and mood affect working memory

Recently, researchers from California and Michigan conducted a pair of studies to understand the effects of sleep, mood, and age on working memory. Two aspects of these studies are novel. First, although each of these effects has previously been looked at separately, this research examined their combined effects and how they interact with each other. Second, the researchers examined a community sample of adults aged 21 to 77. This adds to the real-world generalizability of the results.

The first study found that poor sleep quality and depressed mood each independently reduce the capacity of working memory — the number of items that can be kept in mind. The second study confirmed the results of the first. It also found that greater age reduced the precision of working memory — the details of each item, such as whether the cheese you need to pick up is swiss or cheddar.

Improving mood may help

The implications of this research are clear. Although we cannot stop getting older, we can work to improve our sleep quality and mood. Depressed mood may be due to external life events (such as retirement, a new diagnosis, or the death of a friend), or to biological factors (such as alterations in our brain chemistry). Regardless of its cause, depression can be treated by medications or talk therapy. Studies show that combining these approaches provides the greatest benefit. Not interested in taking medications or talking with someone about your mood? Aerobic exercise, meditation, and relaxation therapy have each been shown to improve mood.

Better sleep may improve working memory

Poor sleep quality may be due to a sleep disorder, such as obstructive sleep apnea (not getting enough oxygen during sleep). Or, it could be secondary to a medical problem, such as heart failure.

Sleep disturbances may also result from habits, such as doing wakeful activities in bed. Sleep experts note that the feeling of being in bed should signal the body that it is time to go to sleep. It is best to use your bed only for sleeping and sexual activity. If you spend hours in bed talking on the phone, eating meals, or doing other activities, you are sending the wrong signals to your body about the purpose of being in bed. Learning about healthy sleep habits can help.

People may also get into a bad sleep cycle by repeatedly staying up too late at night or sleeping too long in the morning. Most people need about eight hours of sleep each night, with the average range between seven and nine. Many people think that they need more sleep as they get older, but that actually isn’t true. On average, older adults need the same amount of sleep as when they were younger — or maybe even 30 minutes less. If you sleep too long one day, you’ll often have difficulty falling asleep the following night.