The Hippocampus And Long
A short-term memory can be consolidated into an enduring long-term memory. This involves a system of brain structures within the medial temporal lobe that are essential for forming declarative memories. The hippocampus is a key region in the medial temporal lobe, and processing information through the hippocampus is necessary for the short-term memory to be encoded into a long-term memory.
The long-term memory does not remain stored permanently in the hippocampus. These long-term memories are important and having them stored in only one brain location is risky damage to that area would result in the loss of all of our memories.
Instead, it is proposed that long-term memories become integrated into the cerebral cortex . This process is referred to as cortical integration; it protects the information stored in the brain.
However, damage to areas of the brain, particularly the hippocampus, results in loss of declarative memories, which is known as amnesia.
The famous case study of H.M. – Henry Molaison – demonstrated the hippocampus is vital to the formation of long-term memories. H.M. had his hippocampus removed as a 23-year-old in an attempt to treat epileptic seizures that originated in his medial temporal lobe.
Long Term Vs Short Term Memories
If we try to look into the depth of what memories are there can be two types. Based on the time limit, memories can be broadly classified into long and short-termed memories.
Short Term Memory
A short-term memory has the time span ranging from seconds to a few minutes. They are stored temporarily and then either get to the long-term memory storage, or they are discarded. Let us say someone gives us the mobile number. As the number is new so our memory will retain it for the short term. There are the possible chances that we are going to forget about this number after few moments.
Long Term Memory
These are the memories stored in the brain over a more extended period. They are several short-term memories organized to form a long memory that is stored permanently. ;Depending upon the importance and number of recalls, it can fade or be remembered forever. For example, you can recall your 18th birthday but not what you ate on Monday three weeks ago.
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In 2017, researchers at the Massachusetts Institute of Technology, led by Takashi Kitamura, showed that short- and long-term memories are actually formed simultaneously.
Kitamuras team used new techniques that involved optogenetics, which is a way of turning cells on and off using light, together with labelling individual memory cells. The team trained mice to fear a particular chamber by giving them a small electric shock when they entered it.
Immediately after the training, the researchers were able to see memories of the shock forming in both the hippocampus and the prefrontal cortex, an area just behind the forehead.
Such sophisticated methods for analysing the human brain will continue to help us understand healthy memory, as well as what happens when it is ravaged by disease.
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Finding A Home For Your Memories
Coding a memory is all well and good, but it is useless if it has nowhere to go. Finding a storage place is the next step.
Newer memories, onceconsolidated, appear to reside in the hippocampus for a while. But as more memories are formed, the neurons that represent a specific memory migrate further into the cortex. As a result, memories are stored throughout the brain. Its a bit like the internet, which is made of information spread all across the planet and accessed via countless connections.
Similar memories tend to clump together spoken memories near the language centres, visual memories near the visual cortex and theres a lot of redundancy too; you can have several memories for the same thing. Every time they are activated they are strengthened. Human memories arent stored like books in a library; theyre constantly being updated and tweaked.
How Are Memories Stored In The Brain
31 August 2010
Because memories underlie so much of our rich life as humans our ability to learn, to tell stories, even to recognize each other it’s unsettling to think that it all hinges on the mass of flesh and goo between our ears.
Researchers have been able to trace memory down to the structural and even the molecular level in recent years, showing that memories are stored throughout many brain structures in the connections between neurons, and can even depend on a single molecule for their long-term stability.
How it works
The brain stores memories in two ways. Short-term memories like a possible chess move, or a hotel room number are processed in the front of the brain in a highly developed area called the pre-frontal lobe, according to McGill University and the Canadian Institute of Neurosciences, Mental Health and Addiction.
Short-term recollection is translated into long-term memory in the hippocampus, an area in the deeper brain. According to McGills , the hippocampus takes simultaneous memories from different sensory regions of the brain and connects them into a single “episode” of memory, for example, you may haveone memory of a dinner party rather than multiple separate memories of how the party looked, sounded , and smelled.
Images of the brain
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How Are Memories Formed
The brain simmers with activity. Different groups of neurons , responsible for different thoughts or perceptions, drift in and out of action.;
Memory is;the reactivation of a specific group of neurons,;formed from persistent changes in the strength of connections between;neurons. But what allows a specific combination of neurons to be reactivated over any other combination of neurons?;
The answer is synaptic plasticity. This term describes the persistent changes in the strength of connections called synapses between brain cells. These connections can be made stronger or weaker depending on when and how often they have been activated in the past. Active connections tend;to get stronger, whereas those that arent used get weaker and can eventually disappear entirely.
A connection between two neurons becomes stronger when neuron A consistently activates neuron B, making it fire an;action potential;, and the connection gets weaker if neuron A consistently;fails;to make neuron B fire a spike. Lasting increases and decreases in synaptic strength are called long-term potentiation and long-term depression .
A Molecular Account Of Long
Eric Kandel is best known for his work on the physical basis of learning and memory in the marine snail Aplysia. This animal, simple as its nervous system is , nevertheless provides an excellent model for the study of learning and memory, through its “gill withdrawal” reflex. When Aplysia perceives something touching its skin, it quickly withdraws both the siphon and the gill, much as a person withdraws a hand from a hot stove without thinking about it. Although this withdrawal is a reflex, it is not completely hard-wired but can be modified by various forms of learning. One such form is sensitization, in which the animal becomes aware of a threatening factor in the environment and to protect itself learns to augment its reflex. The augmented version of the withdrawal reflex can also be maintained in short-term or long-term memory, depending on whether researchers administer the noxious stimulus only once or twice, or many times within a short period. The two forms of memory can be distinguished not only by their durationthe difference between minutes and daysbut also at a molecular level, because it is possible to treat the snail with a chemical compound that interferes with long-term memory but leaves short-term memory unimpaired.
Anatomy Of The Hippocampus
The anatomy of the hippocampus is of chief importance to its function. The hippocampus receives input from and sends output to the rest of the brain via a structure known as the entorhinal cortex, which is located beneath the anterior region of the hippocampus. The hippocampal formation itself is composed of several subregions, which include the cornu ammonis , the dentate gyrus, and the subiculum.
Sleep Is Important For Memory Formation
Sleep is another important factor for memory storage. During sleep, the hippocampus and neocortex take part in a carefully choreographed dialogue in which the hippocampus replays recent events: the same hippocampal neurons active during an experience become activated again during slow-wave sleep, over and over in a time-compressed manner, helping to update the neocortex as to what needs to be stored. This replay only occurs during sleep, so if; youre skimping on sleep, you arent letting your brain consolidate memories.
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What Is The Gray Matter And White Matter
Gray and white matter are two different regions of the central nervous system. In the brain, gray matter refers to the darker, outer portion, while white matter describes the lighter, inner section underneath. In the spinal cord, this order is reversed: The white matter is on the outside, and the gray matter sits within.
Gray matter is primarily composed of neuron somas , and white matter is mostly made of axons wrapped in myelin . The different composition of neuron parts is why the two appear as separate shades on certain scans.
Each region serves a different role. Gray matter is primarily responsible for processing and interpreting information, while white matter transmits that information to other parts of the nervous system.
The Architecture Of The Brain
The brain is like a committee of experts. All the parts of the brain work together, but each part has its own special properties. The brain can be divided into three basic units: the;forebrain, the;midbrain, and the;hindbrain.
The hindbrain includes the upper part of the spinal cord, the brain stem, and a wrinkled ball of tissue called the cerebellum;. The hindbrain controls the bodys vital functions such as respiration and heart rate. The cerebellum coordinates movement and is involved in learned rote movements. When you play the piano or hit a tennis ball you are activating the cerebellum. The uppermost part of the brainstem is the midbrain, which controls some reflex actions and is part of the circuit involved in the control of eye movements and other voluntary movements. The forebrain is the largest and most highly developed part of the human brain: it consists primarily of the;cerebrum; and the structures hidden beneath it .
When people see pictures of the brain it is usually the cerebrum that they notice. The cerebrum sits at the topmost part of the brain and is the source of intellectual activities. It holds your memories, allows you to plan, enables you to imagine and think. It allows you to recognize friends, read books, and play games.
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Ventricles And Cerebrospinal Fluid
Deep in the brain are four open areas with passageways between them. They also open into the central spinal canal and the area beneath arachnoid layer of the meninges.
The ventricles manufacture cerebrospinal fluid, or CSF, a watery fluid that circulates in and around the ventricles and the spinal cord, and between the meninges. CSF surrounds and cushions the spinal cord and brain, washes out waste and impurities, and delivers nutrients.
Memories Shape Our Perception And Reality
Everything we are and everything we will ever be is all dependent on memory. Human belief systems, perceptions, and learning are all memory related. Our consciousness is the ultimate reality of us as people with personality and preferences. Memories define actions, and actions are what we become.
Suppose you think racism was not real. But you came across literature contradicting the idea. Your perception said that it was right. So, you committed the new information to your memory. Based on which you acted differently than before. Had it not because of the mind, you might have stuck to your old beliefs.
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The Long And Short Of It
The notion of human memory doesnt refer to any one thing. The term is an umbrella for an array of recollections, from the names of colors to half-remembered song lyrics to your first breakup. So, what are these different types of memory?
Over a century ago, scientists partitioned memory into short-term and long-term categories. Short-term memory, sometimes called working memory, refers to our ability to retain information or events from the recent past but only for as long as about 20 seconds ago, sometimes even less. In other words, its the stuff that youre actively holding in your head while performing other tasks for example, remembering a phone number as you scroll around to plug it into your contacts list.
In the 1990s, scientists analyzed high-resolution brain scans and found that these fleeting memories depend on neurons firing in the prefrontal cortex, the front part of the brain responsible for higher-level thinking.
They are temporary , says neuroscientist and author Dean Burnett. Its not meant to be for long-term storage, because theyre constantly changing and constantly in flux.
If you hold something in the brain long enough, you can turn it into a long-term memory, he adds. Thats why, if you recite something like a phone number, you can eventually remember it quite easily. But if too much stuff keeps coming in, your short-term memory gets overloaded and the first will get kicked out.
The Cerebellar Cortex And Ltd
Experimentally it has proved extremely difficult to determine the relative roles of the cerebellar cortex and interpositus nucleus in eyeblink conditioning using the lesion method. There is general argument that very large cortical lesions impair learning and memory of the eyeblink CR, but it is difficult to rule out damage to the interpositus nucleus; it lies immediately underneath the critical cortical tissue . A recent study made use of the mutant Purkinje cell degeneration mouse strain . In this mutant, Purkinje neurons are normal throughout pre and perinatal development. At about 24 weeks postnatal, the Purkinje neurons in the cerebellar cortex degenerate and disappear . For a period of about two months after this time, other neuronal structures appear relatively normal . Thus, during this period of young adulthood, the animals have a complete functional decortication of the cerebellum.
Appropriate lesions of the interpositus nucleus in the wild-type control mice completely prevented learning of the conditioned eyeblink response, as with all other mammals studied. So the cerebellum is completely necessary for learning in this species as well. The pcd mice learned very slowly, very poorly, and to a much lower level than wild-type controls, but showed extinction with subsequent training to the CS alone. Thus the cerebellar cortex plays a critically important role in normal learning but some degree of learning is possible without the cerebellar cortex.
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Memory Storage In Brain
Generally, we might see a similarity in storage devices or a hard drive and brain, but they are hardly alike. Unlike storage devices, memory in mind is not stored at a specific location. And brain structure is not like a hard drive. It is much more complex, and memories are stored all over it. This is evident from the brain scan. Suppose we are looking at the brain activity of a person recalling a past event. The image will show several neurons firing up located in several different parts of the brain. Let us see how it is stored.
Hippocampus that is involved in making memory comes in and takes the aggregate of several short-termed memories. Suppose the memory for the graduation party can include the food you taste, what you feel like, and what the house smells like. In short, there are several small chunks of memory involved. Hippocampus takes the whole piece and assigns them specific places in the brain center, like the smell, will go to the olfactory region, and sounds go to the auditory area. The neurons on which these are written make connections with each other. This develops a big large memory circuit. The way these connections are made forms the indexing or the flow of how you remember a particular thing.
Emotions And False Memories
; ;A;flashbulb memory;is a highly detailed, exceptionally vivid episodic memory of the circumstances surrounding a piece of surprising, consequential, or emotionally arousing news was heard. However, even flashbulb memories can have decreased accuracy with the passage of time, even with very important events. For example, on at least three occasions, when asked how he heard about the terrorist attacks of 9/11, President George W. Bush responded inaccurately. In January 2002, less than 4 months after the attacks, the then sitting President Bush was asked how he heard about the attacks. He responded:
I was sitting there, and my Chief of Staffwell, first of all, when we walked into the classroom, I had seen this plane fly into the first building. There was a TV set on. And you know, I thought it was pilot error and I was amazed that anybody could make such a terrible mistake.
Contrary to what President Bush recalled, no one saw the first plane hit, except people on the ground near the twin towers. The first plane was not videotaped because it was a normal Tuesday morning in New York City, until the first plane hit.
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