The early years of parenthood involve so many rewarding firsts—when your infant cracks a toothless grin, when he crawls and later walks, and, of course, when he utters a real, nonbabble word. A mother once told me she found it sad that if she were to pass away suddenly, her toddler wouldn't remember her or these exciting years. It is true that most of us don't remember much, if anything, from our infancy. So at what point do children start making long-term memories?
I must first explain the different types of memory we possess. As I type this, I am using procedural memory—a form of motor memory in which my fingers just know how to type. In contrast, declarative memories represent two types of long-term recall—semantic and episodic. Semantic memory allows us to remember general facts—for example, that Alfred Hitchcock directed the film Vertigo; episodic memory encompasses our ability to recall personal experiences or facts—that Vertigo is my favorite film. Episodic memories are most relevant for understanding our childhood recollections.
Making an episodic memory requires binding together different details of an event—when it happened and where, how we felt and who was there—and retrieving that information later. The processes involve the medial temporal lobes, most notably the hippocampus, and portions of the parietal and prefrontal cortices, which are very important in memory retrieval. Imaging studies often show that the same regions that encode an episode—for example, the visual cortex for vivid visual experiences—are active when we recall that memory, allowing for a kind of “mental time travel” or replay of the event.
Some evidence suggests that young children do have episodic memories of their infancy but lose them later. A six-year-old, for instance, can remember events from before her first birthday, but by adolescence, she has probably forgotten that celebration. In other words, young children can likely make long-term-like memories, but these memories typically fade after a certain age or stage of brain development. Memories made in later childhood and beyond are more likely to stick because the young brain, especially the hippocampus and the frontoparietal regions, undergoes important developmental changes that improve our ability to bind, store and recall events.
There is good news, however, for that mother and any other parent who worries that their toddler will not remember their special early years together. A memory is essentially a unit of experience, and every experience shapes the brain in meaningful ways. Specific memories may be forgotten, but because those memories form the fabric of our identities, knowledge and experiences, they are never truly or completely gone.
Question submitted by Red Smucker-Green, Atlanta
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