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Memory - Harvard Health Skip to main content Recent Articles Why testosterone levels drop and when to consider treatment Don't count on daily aspirin to prevent colon cancer Night owls' habits linked to worse heart health After ablation, exercise may lower atrial fibrillation recurrence What can cause an enlarged heart? Women's unique risks for heart disease Chronic kidney disease: A hidden threat to your heart Navigating your online patient portal: Best practices Treating hair loss in men: What works? Virtual cardiac rehab: Heal your heart from home / Memory April 20, 2026 Reviewed by Lindsey Crowley, MD , Contributor In many ways, our memories shape who we are. They make up our internal biographies - the stories we tell ourselves about what we've done with our lives. They tell us who we're connected to, who we've touched during our lives, and who has touched us. In short, our memories are crucial to the essence of who we are as human beings. That means memory loss can represent a loss of self. It also affects the practical side of life, like getting around the neighborhood or remembering how to contact a loved one. It's not surprising, then, that concerns about declining thinking and memory skills rank among the top fears people have as they age. What causes some people to lose their memory while others stay sharp as a tack? Genes play a role, but so do choices. Proven ways to help protect memory include following a healthy diet, exercising regularly, not smoking, and keeping blood pressure, cholesterol, and blood sugar in check. Living a mentally active life is important, too. Just as muscles grow stronger with use, mental exercise helps keep cognitive skills and memory in tone. On this page you'll discover What is memory? What causes memory loss and forgetfulness? What is mild cognitive impairment? What is dementia? What is the difference between dementia and Alzheimer's? How to improve memory and concentration? Is it possible to avoid memory loss? What is memory? As we age, it's common to worry about losing our memories - partly because a certain amount of age-related memory loss is perfectly normal. In order to preserve your memory as you age, it's important to understand how memory functions. So, what is memory? Where in the brain are memories stored, and how does the brain retrieve them? Quite simply, memory is our ability to recall information. The main two categories for memories are short-term and long-term. Short-term memories involve information that you only need to recall for a few seconds or minutes. If you're turning at an intersection, the fact that there were no cars coming when you looked to the left is important, but once you've made your turn you will quickly discard the information because it is no longer relevant. Keeping it around would unnecessarily clutter your brain. Long-term memories contain the information that makes you you - not just facts (like the capital of Kansas) or events (like your senior prom), but also skills and processes (like typing or dancing the Macarena). Long-term memory is durable yet changeable; a memory can evolve based on retelling a story or on new information learned after the event. Memories are not stored in a single location in the brain. Instead, the sensory components of a memory - sight, smell, sound, etc. - are distributed to different areas of the brain, and the act of remembering occurs as the brain pieces those bits back together. Each time a memory is created, its constituent parts are catalogued in the deep-brain structure known as the hippocampus. Next to the hippocampus sits the amygdala, the brain's emotional center. It flags certain memories as being important or emotionally powerful. The different components of the memory are then distributed mostly to sections of the cerebral cortex, which is the outer layer of the brain. When it's time to retrieve a memory, you rely on the part of the brain known as the frontal lobes, which are involved in attention and focus. The pieces of the memory are then pulled from the areas of the cerebral cortex where they're stored. For example, to remember a scene from your favorite movie might involve pulling in data from the brain's visual region to recall the backdrop and the actors' faces, but also information from the language region to remember the dialogue - and perhaps even the auditory region to remember the soundtrack or sound effects. Together, these components form a unique neuronal pattern that lies dormant until you set about remembering it, at which point it is reactivated. What causes memory loss and forgetfulness? Like the rest of our bodies, our brains change with age, meaning that most of us will find ourselves struggling to recall newly learned information or even to think of words we know well. That's usually not cause for alarm, since some memory loss in elderly people is quite normal and not indicative of memory loss diseases such as Alzheimer's. But what causes memory loss, and how and why does memory change with age? Many of the things we think of as normal memory loss with aging can actually be attributed to a slight decline in our ability to perform tasks requiring attention and so-called executive function (planning, sequencing, and regulating thought). Specific age-related changes in the brain are associated with that lower executive function. For example, to think of an acquaintance's name, you must rapidly make connections between brain cells. Each cell (called a neuron) is separated from its neighbors by a tiny gap called a synapse, and a signal from one brain cell must cross that gap to the next one via a chemical messenger called a neurotransmitter. Once across the gap, it must "unlock" a structure called a receptor on the destination cell. With age, both the brain's chemistry and the structural integrity of the neurons' wiring deteriorate (the hippocampus, crucial for memory processing, also shrinks). That doesn't mean you'll never be able to recall the bit of information that's eluding you, but it does mean it might take some time for the brain to forge a path to where the memory is stored. Thus most "memory loss" in seniors is actually just a slowing of performance. You can still learn, retain, and recall plenty of information, but it might take you longer - and require a bit more determination - than it did when you were younger. Some forms of memory loss are caused by head trauma, including brain injuries resulting from high-impact sports such as boxing, soccer, and football. Memory loss can be part of a primary brain disease. But it can also happen in people with depression, thyroid malfunction, and even vitamin deficiencies, all of which can result in improved memory with appropriate treatment. We also know that stress, fatigue, sleep deprivation , and the feeling of being overwhelmed can contribute to short-term memory loss and forgetfulness. Middle age can be a difficult period of life in which our responsibilities can extend to ourselves, our spouses, our jobs, our children, our parents, and even our grandchildren. It's not uncommon, then, to feel distracted and find it harder to concentrate on things we're trying to remember. So how do you know when to visit a doctor for memory loss? If you begin to experience difficulty completing familiar tasks, or have bouts of forgetfulness that extend beyond minor inconvenience and disrupt your day-to-day functioning, there may be something more serious going on than normal age-related memory loss. What is mild cognitive impairment? Mild cognitive impairment (MCI) occurs in nearly 20% of adults over age 65. While many people assume it is a precursor to full-blown dementia, fewer than half of people with MCI go on to develop Alzheimer's dementia within five years. MCI is marked by either memory loss, a decline in cognitive fitness, or both, that is worse than should be expected for the patient's age. When the impairment is largely memory-related, doctors refer to it as amnestic MCI. With normal age-related memory loss, people tend to forget fairly trivial things like where they put their car keys. But with amnestic MCI, the things patients forget are more important - who the presidential candidates are, what was discussed in last week's Zoom meeting, what college your granddaughter attends. Even so, the impairment is considered "mild" because it does not significantly impact day-to-day functions like preparing food, driving, and personal hygiene. The other main subtype of MCI is called non-amnestic. Rather than affecting memory, non-amnestic MCI manifests as cognitive decline in other areas such as language, spatial awareness, or the ability to focus and maintain attention. Someone with non-amnestic MCI might find it difficult to keep up with a conversation, pay their bills, make decisions, repair a faucet, or understand a speech. Again, however, the impairment is not so severe as to disrupt everyday life. People whose MCI affects both memory and other types of cognition are said to have multi-domain MCI. Amnestic MCI is the most common subtype. MCI is highly variable in terms of its severity and trajectory; it may worsen, stay the same, or even go away, depending on what's causing it. Temporary MCI can be brought on by sleep apnea, depression, or medications. Risk factors for other kinds of MCI include genetics, stroke, head injury, high cholesterol, high blood pressure, obesity, smoking, and hearing loss. What is dementia? Many people confuse mild cognitive impairment (MCI) with dementia. While MCI can be a precursor to the early stages of dementia, dementia is a separate brain disorder. The symptoms of dementia are so severe as to render the patient dependent on others to carry out the tasks of everyday living. But exactly what is dementia ? Although memory loss is one of the most common signs of dementia, the disorder often entails other forms of cognitive decline, including a drop-off in the ability to think abstractly, to