Understanding the Role of Forgetting in Memory

Most of us paint forgetting as our mortal adversary, but it isn’t always an obstacle to overcome. Effective remembering often requires forgetting. And just because memory sometimes fails doesn’t mean it’s in any way broken. While admittedly frustrating, forgetting is a normal part of being human.

By understanding how memory functions, we can take these inconvenient gaffes in stride. We can also learn to prevent many episodes of forgetting by eliminating or artfully navigating around common errors and bad assumptions.

Not all memories are created equal. There are many flavors-memories for the present moment, for how to do things, for the stuff you know, for what just happened, for what you intend to do later—and each memory is processed and organized in your brain in distinctly different ways. Some memories are built to exist for only a few seconds (a temporary passcode), whereas others can last a lifetime (your wedding day). Some are easier to create (your to-do list), others are easier to retrieve (what your daughter looks like), and still others are more likely to be forgotten (last Thursday’s com-mute). You can depend on some kinds of memory to be highly accurate and reliable (how to drive your car). Others, much less so (everything that has happened).

Making a memory literally changes your brain. Every memory you have is a result of a lasting physical alteration in your brain in response to what you experienced. You went from not knowing something to knowing something, from never before having experienced today to having lived another day. And to be able to remember tomorrow what happened today means that your brain has to change.

How does it change? First, the sensory, emotional, and factual elements of what you experience are perceived through the portals of your senses. You see, hear, smell, taste, and feel.

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.

All four steps have to work for you to create a long-term memory that can be consciously retrieved. You have to put the information into your brain. You have to weave the information together. You have to store that woven information via stable changes in your brain. And then you have to fetch the woven information when you want to access it.

The information contained within an experience that is collected by your brain—the sensory perceptions, the language, the who, what, where, when, and why—is linked by a part of your brain called the hippocampus.

The hippocampus, a seahorse-shaped structure deep in the middle of your brain, is essential for memory consolidation. What does that mean? The hippocampus binds your memo-ries. It is your memory weaver. What happened? Where and when did it happen? What does it mean? How did I feel about it? The hippocampus links all these separate pieces of information from disparate parts of the brain together, knitting them into a retrievable unit of associated data, a neural network that, when stimulated, is experienced as a memory.

So your hippocampus is necessary for the formation of any new memories that you can later consciously retrieve. If your hippocampus is damaged, your ability to create new memories will be impaired. 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.

Moreover, the consolidation mediated by the hippocampus is a time-dependent process that can be disrupted. The formation of a memory that can be retrieved tomorrow, next week, or twenty years from now requires a series of molecular events that take time. During that time, if something interferes with the processing of a nascent memory in the hippocampus, the memory can be degraded and possibly lost.

Say you’re a boxer, a rugby player, or a football player, and you sustain a blow to the head. If I were to interview you immediately after you got clocked, you would be able to tell me about the punch, the play, the details of what was hap-pening. But if I were to ask you the next day, you might have no memory of what happened. The information that was in the process of becoming linked by your hippocampus to form a new, lasting memory was disrupted and was never fully consolidated. The blow to your head caused amnesia. Those memories are gone.

So any new information from today that you perceive and attend to, that you find interesting, special, surprising, useful, meaningful, or, well, memorable, will be processed by your hippocampus for consolidation into memory. The hippocampus continues to repeatedly activate the parts of the brain involved in what-is-to-be-remembered until those parts of the brain become a stable, connected pattern of activity, essentially wired together.

While you need a hippocampus to form new memories, once they are made, they don’t reside there. So where are memories stored? In no one place. They are distributed throughout the parts of the brain that registered the initial experience. Unlike perception and movement, which reside in specific addresses in our brains, we don’t have specialized memory-storage neurons or a memory cortex. Vision, hearing, smell, touch, and movement can all be mapped to discrete geographic regions in the brain. At the back of the brain, we have a visual cortex, where neurons process what we see. We have an auditory cortex where we hear and an olfactory cortex where we perceive odor. Pain, temperature, and touch are housed in the somatosensory cortex on the top of your head. Wiggling your big toe can be mapped to the activation of a specific set of neurons in your motor cortex.

Source – Remember: The Science of Memory and the Art of Forgetting by Lisa Genova

Goodreads – https://www.goodreads.com/book/show/54895704-remember

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