Remember: The Science of Memory and the Art of Forgetting

by Lisa Genova

we often forget not because it’s efficient for our brains to do so but because we haven’t supplied our brains with the kinds of input needed to support memory creation and retrieval.

you don’t pay attention to where you park your car in the mall garage, you’ll struggle to find it later, but not because you’ve forgotten where you parked. You have forgotten nothing. Without adding your attention, you never formed a memory for where you parked in the first place.

Creating a memory takes place in four basic steps: Encoding. Your brain captures the sights, sounds, information, emotion, and meaning of what you perceived and paid attention to and translates all this into neurological language. Consolidation. Your brain links the previously unrelated collection of neural activity into a single pattern of associated connections. Storage. This pattern of activity is maintained over time through persistent structural and chemical changes in those neurons. Retrieval. You can now, through the activation of these associated connections, revisit, recall, know, and recognize what you learned and experienced.

The hippocampus, a seahorse-shaped structure deep in the middle of your brain, is essential for memory consolidation.

Alzheimer’s disease begins its rampage in the hippocampus. As a result, the first symptoms of this disease are typically forgetting what happened earlier today or what someone just said a few minutes ago and repeating the same story or question over and over. With an impaired hippocampus, people with Alzheimer’s have trouble creating new memories.

Memory is stored throughout your brain in the pattern of neural activity that was stimulated when the event or information was first experienced.

Psychologists call working memory for what you see your visuospatial scratchpad. Imagine words on a sticky note hastily written in disappearing ink. Working memory for what you hear is called your phonological loop, the auditory version of the visual scratchpad.

We have three basic types of long-term memories: memory for information, memory for what happened, and memory for how to do things. I

Popular culture calls this ability to perform a previously learned skill muscle memory. With repetition and focused practice, complex sequences of previously unrelated physical movements can be bound together and executed as a single action instead of as a series of separate, labored steps.

Muscle memory is unconscious, remembered below your awareness. Driving a car, riding a bicycle, eating with chopsticks, hitting a fastball, brushing your teeth, and typing are all muscle memories.

While semantic and episodic memories are consolidated via the hippocampus, muscle memories are bound together by a part of the brain called the basal ganglia.

The stuff you know, so-called semantic memory, is memory for the knowledge you’ve learned, the facts you know about your life and the world—the Wikipedia of your brain.

Memories for what happened, for information that is attached to a where and when are called episodic.

Which is better for long-term retention—cramming the night before or studying the material spaced out over the seven days? If the total number of study hours is equal, distributed practice beats out cramming. Called the spacing effect, rehearsing the information to be remembered spaced out over time gives your hippocampus more time to fully consolidate what you’re learning.

Regular use of these tools—repetition, spaced learning, self-testing, meaning, and visual and spatial imagery—will no doubt strengthen your semantic memory.

Episodic memory, your memory for what happened in your life, is the history of you remembered by you. It is memory tethered to a place and time, the where and when recollections of your life’s experiences.

Strung together, your most meaningful episodic memories create your life story and are collectively called your autobiographical memory.

Why do we retain so few memories for what happened when we were young? The development of language in our brains corresponds with our ability to consolidate, store, and retrieve episodic memories. We need the anatomical structures and circuitry of language to tell the story of what happened, to organize the details of our experiences into a coherent narrative that can then be revisited and shared later. So as adults, we only have access to memories of what happened when we owned the language skills to describe them.