Can you distinguish the taste of a red wine from a rosé? What about the appearance of a muscle car from the 60s versus a foreign import? Do you prefer to grow lilies or tulips? Do you prefer to listen to Dark Side of the Moon or “Fly Me to the Moon”? To answer one of these questions, you must use your semantic memory.
Your semantic memory is your supply of factual knowledge of the world and the meaning of words. It is how you know that a fork is for eating (not turning your hair) and what color a lion is. It is both the source of your vocabulary and how you know what something is doing, even if you don’t know its name – such as that little piece of plastic that covers the end of a shoelace (an aglet).
Use episodic memory to increase your semantic memory
To form new semantic memories, you must use your episodic memory to learn new information. For a week, month, or year, you may remember where you were and what you did when you discovered a new fact. Over time, however, you forget the context and you just remember the fact. If only the fact remains, it is part of your semantic memory.
The left temporal lobe: the dictionary of your brain
Several milestones have been investigated where semantic memory is stored in the brain. Two related studies were published in an article in Nature in 1996.
For the first, the researchers took over 100 patients with strokes and other brain injuries in their left temporal lobe. (Put your finger on your left temple, just behind your eye – that’s where the left temporal lobe is located.) They asked these patients to name famous people, animals, and tools that were man-made objects. They discovered that the location of brain injuries can be influenced. Patients with the most anterior lesions (close to their eyes) had the greatest difficulty appointing people. Patients with the most posterior lesions (against the back of the head) had the greatest difficulty in naming tools. And those with lesions between these areas had the most trouble naming animals.
In the second study, the researchers had healthy adults who named famous people, animals, and devices while undergoing a PET (positron emission tomography) scan that showed brain activity. As expected, naming people yielded the most prior activity, tools the most posterior activity, and for animals, the activity was in between.
Dementia can erase words from the dictionary
More recent research links deterioration of the anterior temporal lobe to the difficulty of understanding what a word means shown by people with some types of dementia. Although people with Alzheimer’s disease usually show this disorder, it is most prominent in a type of aphasia known as semantic dementia. When you talk to these people, they may start to sound normal, but you will notice that they refer to all kinds of different items such as the “thing” or a similar word. If you continue to talk to them, you will discover that they don’t know what certain words mean, such as “medicine” or “shoe” – two examples of one of my patients.
Semantic memory in other areas of the brain
Just as our knowledge is not limited to words, our semantic memory is not limited to the left temporal lobe. The correct temporal lobe is linked to knowledge of non-verbal information (such as the weight of a golf ball versus a ping-pong ball) and face recognition. Other parts of the brain also participate in semantic memory. For example, how Frank Sinatra sings ‘Fly Me to the Moon’ is stored in your auditory association cortex in your superior temporal lobe. Your image of a Chevrolet Camaro is stored in your visual association cortex in your occipital lobes. And the feeling of tulip petals resting on your cheek is stored in your sensory association cortex in your parietal lobe.
Semantic memory does not decrease with age
Can improving your semantic memory help you create a crossword puzzle? Yes. Semantic memory not only stores the meaning of words, but also non-verbal concepts, it also stores the relationships between and between words and concepts. For example, your semantic memory of the Pink Floyd band can be linked to the President of the United States in the following way: Pink Floyd’s Dark Side of the Moon album can be connected to moon landings in your semantic memory, then connected to astronauts , John Glenn, senators, politicians and presidents.
Finally, a bit of good news: research suggests that semantic memory does not deteriorate with normal aging. As you continue to learn new information throughout your life, your vocabulary and your ability to solve crossword puzzles can improve with age.