We hold on to different kinds of memories.
<ul>
<li>Short-term memories last seconds to hours and long-term memories last for years.</li>
<li>We also have a working memory, which allows us to keep something in mind for a limited time by repeating it.</li>
<li>Declarative memories are memories you experience consciously, like facts or "common knowledge."</li>
<li>Nondeclaritive memory unconsciously builds up. These include procedural memories, such as riding a bicycle or playing the piano.</li>
</ul>

The different kinds of memories

Health

By studying people with amnesia, it seems that short-term and long-term memories don't form in precisely the same way, nor do declarative and procedural memories. 
<ul>
<li>Emotional responses such as fear occur in a brain region called the amygdala.</li>
<li>Memories of learned skills are associated with the region called the striatum.</li>
<li>The hippocampus is essential for forming, retaining, and recalling declarative memories.</li>
<li>The temporal lobes play a critical role in forming and recalling memories.</li>
</ul>

Where your brain keeps memories

Memories are held within groups of neurons called cell assemblies. They fire as a group in response to a specific stimulus, such as recognising your friend's face. 
The more neurons fire together, the more the interconnection of the cells strengthen. We experience the nerves' collective activity as a memory.

How we experience memories

For a short-term memory to become a long-term memory, it must be strengthened for long-term storage. The process is called memory consolidation and occurs using several processes.
Long-term potentiation consists of individual nerves changing themselves to grow and talk to their neighboring nerves differently. The remodeling modifies the nerve's connections, which makes the memory stable.

Memory consolidation

When we recall a memory, many parts of the brain share information, including regions that do high-level information processing, regions that deal with our senses' new inputs, and the region that help coordinate the process, the medial temporal lobe.

Recalling a memory

<figure><picture><source srcset="https://www.nationalgeographic.com/content/dam/science/2019/03/04/reference-memory/02-nationalgeographic_1763764.adapt.133.1.jpg 133w, https://www.nationalgeographic.com/content/dam/science/2019/03/04/reference-memory/02-nationalgeographic_1763764.adapt.152.1.jpg 152w, https://www.nationalgeographic.com/content/dam/science/2019/03/04/reference-memory/02-nationalgeographic_1763764.adapt.162.1.jpg 162w, https://www.nationalgeographic.com/content/dam/science/2019/03/04/reference-memory/02-nationalgeographic_1763764.adapt.210.1.jpg 210w, https://www.nationalgeographic.com/content/dam/science/2019/03/04/reference-memory/02-nationalgeographic_1763764.adapt.224.1.jpg 224w, https://www.nationalgeographic.com/content/dam/science/2019/03/04/reference-memory/02-nationalgeographic_1763764.adapt.225.1.jpg 225w, https://www.nationalgeographic.com/content/dam/science/2019/03/04/reference-memory/02-nationalgeographic_1763764.adapt.280.1.jpg 280w, https://www.nationalgeographic.com/content/dam/science/2019/03/04/reference-memory/02-nationalgeographic_1763764.adapt.352.1.jpg 352w, https://www.nationalgeographic.com/content/dam/science/2019/03/04/reference-memory/02-nationalgeographic_1763764.adapt.470.1.jpg 470w, https://www.nationalgeographic.com/content/dam/science/2019/03/04/reference-memory/02-nationalgeographic_1763764.adapt.536.1.jpg 536w, https://www.nationalgeographic.com/content/dam/science/2019/03/04/reference-memory/02-nationalgeographic_1763764.adapt.590.1.jpg 590w, https://www.nationalgeographic.com/content/dam/science/2019/03/04/reference-memory/02-nationalgeographic_1763764.adapt.676.1.jpg 676w, https://www.nationalgeographic.com/content/dam/science/2019/03/04/reference-memory/02-nationalgeographic_1763764.adapt.710.1.jpg 710w, https://www.nationalgeographic.com/content/dam/science/2019/03/04/reference-memory/02-nationalgeographic_1763764.adapt.768.1.jpg 768w, https://www.nationalgeographic.com/content/dam/science/2019/03/04/reference-memory/02-nationalgeographic_1763764.adapt.885.1.jpg 885w, https://www.nationalgeographic.com/content/dam/science/2019/03/04/reference-memory/02-nationalgeographic_1763764.adapt.945.1.jpg 945w, https://www.nationalgeographic.com/content/dam/science/2019/03/04/reference-memory/02-nationalgeographic_1763764.adapt.1190.1.jpg 1190w, https://www.nationalgeographic.com/content/dam/science/2019/03/04/reference-memory/02-nationalgeographic_1763764.adapt.1900.1.jpg 1900w" sizes="784px"><img width="784" height="523"></picture></figure><h2>Human memory happens in many parts of the brain at once, and some types of memories stick around longer than others.</h2><div dir="ltr">4 Minute Read</div>From the moment we are born, our brains are bombarded by an immense amount of information about ourselves and the world around us. So, how do we hold on to everything we've learned and experienced? Memories.Humans <a href="https://www.nationalgeographic.com/science/phenomena/2011/08/05/five-myths-about-memory-and-why-they-matter-in-court/" dir="ltr">retain different types of memories for different lengths of time</a>. Short-term memories last seconds to hours, while long-term memories last for years. We also have a working memory, which lets us keep something in our minds for a limited time by repeating it. Whenever you say a phone number to yourself over and over to remember it, you're using your working memory.Another way to categorize memories is by the subject of the memory itself, and whether you are consciously aware of it. Declarative memory, also called explicit memory, consists of the sorts of memories you experience consciously. Some of these memories are facts or “common knowledge”: things like the capital of Portugal (Lisbon), or the number of cards in a standard deck of playing cards (52). Others consist of past events you've experienced, such as a childhood birthday.Nondeclarative memory, also called implicit memory, unconsciously builds up. These include procedural memories, which your body uses to remember the skills you've learned. Do you play an instrument or ride a bicycle? Those are your procedural memories at work. Nondeclarative memories also can shape your body's unthinking responses, like salivating at the sight of your favorite food or tensing up when you see something you fear.<div class="caption">Your Memory Under Stress</div><div class="caption" dir="ltr">
 
 
 A memory matching game pits your ability to remember ... against some added stressors.
 
 
 </div>In general, declarative memories are easier to form than nondeclarative memories. It takes less time to memorize a country's capital than it does to learn how to play the violin. But nondeclarative memories stick around more easily. Once you've learned to ride a bicycle, you're not likely to forget.<div>Coronavirus in the U.S.: Where cases are growing and declining</div>To understand how we remember things, it's incredibly helpful to study how we forget—<a href="https://news.nationalgeographic.com/2017/03/brain-memory-amnesia-perpetual-now-lemonick/" dir="ltr">which is why neuroscientists study amnesia, the loss of memories or the ability to learn</a>. Amnesia is usually the result of some kind of trauma to the brain, such as a head injury, a stroke, a brain tumor, or chronic alcoholism.There are two main types of amnesia. The first, retrograde amnesia, occurs where you forget things you knew before the brain trauma. Anterograde amnesia is when brain trauma curtails or stops someone's ability to form new memories.The most famous case study of anterograde amnesia is <a href="https://www.nytimes.com/2010/12/07/science/07memory.html?ref=health" dir="ltr">Henry Molaison</a>, who in 1953 had parts of his brain removed as a last-ditch treatment for severe seizures. While Molaison—known when he was alive as H.M.—remembered much of his childhood, he was unable to form new declarative memories. People who worked with him for decades had to re-introduce themselves with every visit.By studying people such as H.M., as well as animals with different types of brain damage, scientists can trace where and how different kinds of memories form in the brain. It seems that short-term and long-term memories don't form in exactly the same way, nor do declarative and procedural memories.There's no one place within the brain that holds all of your memories; different areas of the brain form and store different kinds of memories, and different processes may be at play for each. For instance, emotional responses such as fear reside in a brain region called the amygdala. Memories of the skills you've learned are associated with a different region called the striatum. A region called the hippocampus is crucial for forming, retaining, and recalling declarative memories. The temporal lobes, the brain regions that H.M. was partially missing, play a crucial role in forming and recalling memories.<h2>How memories are formed, stored, and recalled</h2>Since the 1940s scientists have surmised that memories are held within groups of neurons, or nerve cells, called cell assemblies. Those interconnected cells fire as a group in response to a specific stimulus, whether it's your friend's face or the smell of freshly baked bread. <a href="https://news.nationalgeographic.com/2015/11/151113-ramirez-memory-mice-erase-ptsd-science0/" dir="ltr">The more the neurons fire together, the more the cells' interconnections strengthen</a>. That way, when a future stimulus triggers the cells, it's more likely that the whole assembly fires. The nerves' collective activity transcribes what we experience as a memory. Scientists are still working through the details of how it works.For a short-term memory to become a long-term memory, it must be strengthened for long-term storage, a process called memory consolidation. Consolidation is thought to take place by several processes. One, called long-term potentiation, consists of individual nerves modifying themselves to grow and talk to their neighboring nerves differently. That remodeling alters the nerves' connections in the long term, which stabilizes the memory. All animals that have long-term memories use this same basic cellular machinery; scientists worked out the details of long-term potentiation <a href="http://science.sciencemag.org/content/278/5337/467" dir="ltr">by studying California sea slugs</a>. However, not all long-term memories necessarily have to start as short-term memories.<div class="caption">Could Tweaking Our Memories Help Us Feel Better?</div><div class="caption" dir="ltr">
 
 
 Can we replace bad memories with good memories or even erase certain memories to improve our mental health? Neuroscientist and 2015 National Geographic Emerging Explorer Steve Ramirez is… Read More
 
 
 </div>As we recall a memory, many parts of our brain rapidly talk to each other, including regions in the brain's cortex that do high-level information processing, regions that handle our senses' raw inputs, and a region called the medial temporal lobe that seems to help coordinate the process. One recent study found that at the moment when patients recalled newly formed memories, ripples of nerve activity in the medial temporal lobe synced up with ripples in the brain's cortex.Many mysteries of memory remain. How precisely are memories encoded within groups of neurons? How widely distributed in the brain are the cells that encode a given memory? How does our brain activity correspond to how we experience memories? These active areas of research may one day provide new insight into brain function and <a href="https://news.nationalgeographic.com/2018/03/snails-memory-molecules-spd/" dir="ltr">how to treat memory-related conditions</a>.For instance, recent work has demonstrated that some memories must be “reconsolidated” each time they're recalled. If so, the act of remembering something makes that memory temporarily malleable—letting it be strengthened, weakened, or otherwise altered. Memories may be more easily targeted by medications during reconsolidation, <a href="https://www.nationalgeographic.com/science/2018/07/news-memory-manipulation-research-neuroscience/" dir="ltr">which could help treat conditions such as post-traumatic stress disorder, or PTSD</a>.

Human memory happens in many parts of the brain at once, and some types of memories stick around longer than others.

From the moment we are born, our brains are bombarded by an immense amount of information about ourselves and the world around us. So, how do we hold on to everything we've learned and experienced? Memories.

Humans <a dir="ltr" href="https://www.nationalgeographic.com/science/phenomena/2011/08/05/five-myths-about-memory-and-why-they-matter-in-court/">retain different types of memories for different lengths of time </a>. Short-term memories last seconds to hours, while long-term memories last for years. We also have a working memory, which lets us keep something in our minds for a limited time by repeating it. Whenever you say a phone number to yourself over and over to remember it, you're using your working memory.

Another way to categorize memories is by the subject of the memory itself, and whether you are consciously aware of it. Declarative memory, also called explicit memory, consists of the sorts of memories you experience consciously. Some of these memories are facts or “common knowledge”: things like the capital of Portugal (Lisbon), or the number of cards in a standard deck of playing cards (52). Others consist of past events you've experienced, such as a childhood birthday.

Nondeclarative memory, also called implicit memory, unconsciously builds up. These include procedural memories, which your body uses to remember the skills you've learned. Do you play an instrument or ride a bicycle? Those are your procedural memories at work. Nondeclarative memories also can shape your body's unthinking responses, like salivating at the sight of your favorite food or tensing up when you see something you fear.

In general, declarative memories are easier to form than nondeclarative memories. It takes less time to memorize a country's capital than it does to learn how to play the violin. But nondeclarative memories stick around more easily. Once you've learned to ride a bicycle, you're not likely to forget.

To understand how we remember things, it's incredibly helpful to study how we forget—<a dir="ltr" href="https://news.nationalgeographic.com/2017/03/brain-memory-amnesia-perpetual-now-lemonick/">which is why neuroscientists study amnesia, the loss of memories or the ability to learn </a>. Amnesia is usually the result of some kind of trauma to the brain, such as a head injury, a stroke, a brain tumor, or chronic alcoholism.

There are two main types of amnesia. The first, retrograde amnesia, occurs where you forget things you knew before the brain trauma. Anterograde amnesia is when brain trauma curtails or stops someone's ability to form new memories.

The most famous case study of anterograde amnesia is <a dir="ltr" href="https://www.nytimes.com/2010/12/07/science/07memory.html?ref=health">Henry Molaison </a>, who in 1953 had parts of his brain removed as a last-ditch treatment for severe seizures. While Molaison—known when he was alive as H.M.—remembered much of his childhood, he was unable to form new declarative memories. People who worked with him for decades had to re-introduce themselves with every visit.

By studying people such as H.M., as well as animals with different types of brain damage, scientists can trace where and how different kinds of memories form in the brain. It seems that short-term and long-term memories don't form in exactly the same way, nor do declarative and procedural memories.

There's no one place within the brain that holds all of your memories; different areas of the brain form and store different kinds of memories, and different processes may be at play for each. For instance, emotional responses such as fear reside in a brain region called the amygdala. Memories of the skills you've learned are associated with a different region called the striatum. A region called the hippocampus is crucial for forming, retaining, and recalling declarative memories. The temporal lobes, the brain regions that H.M. was partially missing, play a crucial role in forming and recalling memories.

How memories are formed, stored, and recalled

Since the 1940s scientists have surmised that memories are held within groups of neurons, or nerve cells, called cell assemblies. Those interconnected cells fire as a group in response to a specific stimulus, whether it's your friend's face or the smell of freshly baked bread. <a dir="ltr" href="https://news.nationalgeographic.com/2015/11/151113-ramirez-memory-mice-erase-ptsd-science0/">The more the neurons fire together, the more the cells' interconnections strengthen </a>. That way, when a future stimulus triggers the cells, it's more likely that the whole assembly fires. The nerves' collective activity transcribes what we experience as a memory. Scientists are still working through the details of how it works.

For a short-term memory to become a long-term memory, it must be strengthened for long-term storage, a process called memory consolidation. Consolidation is thought to take place by several processes. One, called long-term potentiation, consists of individual nerves modifying themselves to grow and talk to their neighboring nerves differently. That remodeling alters the nerves' connections in the long term, which stabilizes the memory. All animals that have long-term memories use this same basic cellular machinery; scientists worked out the details of long-term potentiation <a dir="ltr" href="http://science.sciencemag.org/content/278/5337/467">by studying California sea slugs </a>. However, not all long-term memories necessarily have to start as short-term memories.

As we recall a memory, many parts of our brain rapidly talk to each other, including regions in the brain's cortex that do high-level information processing, regions that handle our senses' raw inputs, and a region called the medial temporal lobe that seems to help coordinate the process. One recent study found that at the moment when patients recalled newly formed memories, ripples of nerve activity in the medial temporal lobe synced up with ripples in the brain's cortex.

Many mysteries of memory remain. How precisely are memories encoded within groups of neurons? How widely distributed in the brain are the cells that encode a given memory? How does our brain activity correspond to how we experience memories? These active areas of research may one day provide new insight into brain function and <a dir="ltr" href="https://news.nationalgeographic.com/2018/03/snails-memory-molecules-spd/">how to treat memory-related conditions </a>.

For instance, recent work has demonstrated that some memories must be “reconsolidated” each time they're recalled. If so, the act of remembering something makes that memory temporarily malleable—letting it be strengthened, weakened, or otherwise altered. Memories may be more easily targeted by medications during reconsolidation, <a dir="ltr" href="https://www.nationalgeographic.com/science/2018/07/news-memory-manipulation-research-neuroscience/">which could help treat conditions such as post-traumatic stress disorder, or PTSD </a>.

Bite-sized knowledge
to upgrade
your career

Human memory: How we make, remember, and forget memories

The different kinds of memories

Where your brain keeps memories

How we experience memories

Memory consolidation

Recalling a memory

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Why Don’t We Forget How to Ride a Bike?

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How you perceive time may depend on your income

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Bite-sized knowledgeto upgradeyour career

Human memory: How we make, remember, and forget memories

The different kinds of memories

Where your brain keeps memories

How we experience memories

Memory consolidation

Recalling a memory

IDEAS ABOUT

MORE LIKE THIS

Why Don’t We Forget How to Ride a Bike?

Do You Have Stellar Memory? It May Be Your Hippocampus

How you perceive time may depend on your income

It's time to

READ

LIKE

A PRO!

Bite-sized knowledge
to upgrade
your career