How human memory works?

Memory is essential to all our lives. Without a memory of the past, we could not operate in the present or think about the future. We would not be able to remember what we did yesterday, what we have done today or what we plan to do tomorrow. Without memory, we could not learn anything.

“Memory is the process of maintaining information over time” (Matlin, 2005).

In the past, many experts were fond of describing memory as a sort of tiny filing cabinet full of individual memory folders in which information is stored away. Others linked memory to a neural supercomputer wedged under the human scalp. But today, experts believe that memory is far more complex and elusive than that and that it is located not in one particular place in the brain but is instead a brain-wide process.

Do you remember what you had for breakfast this morning? If the image of a big toast with avocado popped into your mind, you didn’t dredge it up from some out-of-the-way neural alleyway. Instead, that memory was the result of an incredibly complex constructive power that reassembled disparate memory impressions from a web-like pattern of cells scattered throughout the brain. Your “memory” is really made up of a group of systems that each play a different role in creating, storing, and recalling your memories. When the brain processes information normally, all of these different systems work together perfectly to provide cohesive thought.

What seems to be a single memory is actually a complex construction that involves the processing of a vast amount of information. If you think of an object (e.g. a pen) your brain retrieves the object’s name, its shape, its function, the sound when it scratches across the page… Each part of the memory of what a “pen” is comes from a different region of the brain. The entire image of “pen” is actively reconstructed by the brain from many different areas. Neurologists are only beginning to understand how the parts are reassembled into a coherent whole.

If you’re riding a bike, the memory of how to operate the bike comes from one set of brain cells; the memory of how to get from here to the end of the street comes from another; the memory of biking safety rules from another; and that nervous feeling you get when a car veers dangerously close, from still another. Yet you’re never aware of these separate mental experiences, nor that they’re coming from all different parts of your brain because they all work together so well. In fact, experts tell us there is no firm distinction between how you remember and how you think.

This doesn’t mean that scientists have figured out exactly how the system works. They still don’t fully understand exactly how you remember or what occurs during recall. The search for how the brain organizes memories and where those memories are acquired and stored has been a never-ending quest among brain researchers for decades. Still, there is enough information to make some educated guesses. The process of memory begins with encoding, then proceeds to storage and, eventually, retrieval.

Memory encoding

Encoding is the first step in creating a memory. It’s a biological phenomenon, rooted in the senses, that begins with perception. Experts believe that the hippocampus, along with the frontal part of the brain, is responsible for analyzing the various sensory inputs occurring into one single experience and deciding if they’re worth remembering. If they are, they may become part of your long-term memory. as indicated earlier, these various bits of information are then stored in different parts of the brain. How these bits and pieces are later identified and retrieved to form a cohesive memory, however, is not yet known.

When information comes into our memory system from sensory input, it needs to be encoded into a form that the system can cope with, so that it can be stored.  Think of this as similar to changing your money into a different currency when you travel from one country to another. If you are willing to know more about this process, please read the “How Human memory works” article (see References).

To properly encode a memory, you must first be paying attention. Since you cannot pay attention to everything all the time, most of what you encounter every day is simply filtered out, and only a few stimuli pass into your conscious awareness. If you remembered every single thing that you noticed, your memory would be full before you even left the house in the morning. What scientists aren’t sure about is whether stimuli are screened out during the sensory input stage or only after the brain processes its significance. What we do know is that how you pay attention to information may be the most important factor in how much of it you actually remember.

Short and long-term memory

Once a memory is created, it must be stored (no matter how briefly). Many experts think there are three ways we store memories: first in the sensory stage; then in short-term memory; and ultimately, for some memories, in long-term memory. Because there is no need for us to maintain everything in our brain, the different stages of human memory function as a sort of filter that helps to protect us from the flood of information that we’re confronted with on a daily basis.

 

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Figure 1. The model that explains how human memory works. There are three ways humans store memories: in the sensory stage, then in the short-term memory stage, and ultimately, for some memories, in the long-term memory.

The creation of a memory begins with its perception: The registration of information during perception occurs in the brief sensory stage that usually lasts only a fraction of a second. It’s your sensory memory that allows a perception such as a visual pattern, a sound, or a touch to linger for a brief moment after the stimulation is over.

After that first flicker, the sensation is stored in short-term memory (STM). Short-term memory has a fairly limited capacity; it can hold about seven items for no more than 20 or 30 seconds at a time. You may be able to increase this capacity somewhat by using various memory strategies. For example, a ten-digit number such as 8005840392 may be too much for your short-term memory to hold. But divided into chunks, as in a telephone number, 800-584-0392 may actually stay in your short-term memory long enough for you to dial the telephone. Likewise, by repeating the number to yourself, you can keep resetting the short-term memory clock.

Important information is gradually transferred from short-term memory into long-term memory (LTM). The more the information is repeated or used, the more likely it is to eventually end up in long-term memory, or to be “retained.” (That’s why studying helps people to perform better on tests.) Unlike sensory and short-term memory, which are limited and decay rapidly, long-term memory can store unlimited amounts of information indefinitely.

People tend to more easily store material on subjects that they already know something about, since the information has more meaning to them and can be mentally connected to related information that is already stored in their long-term memory. That’s why someone who has an average memory may be able to remember a greater depth of information about one particular subject.

Most people think of long-term memory when they think of “memory” itself but most experts believe information must first pass through sensory and short-term memory before it can be stored as a long-term memory.

Memory retrieval

When you want to remember something, you retrieve the information on an unconscious level, bringing it into your conscious mind at will. While most people think they have either a “bad” or a “good” memory, in fact, most people are fairly good at remembering some types of things and not so good at remembering others. If you do have trouble remembering something (assuming you don’t have a physical disease) it’s usually not the fault of your entire memory system but an inefficient component of one part of your memory system.

Let’s look at how you remember where you put your keys. When you arrive at home, you must register where you place your keys: you must pay attention while you set them in the hall, in your bedroom, inside your purse… You must be aware of where you are putting them, or you won’t be able to remember their location the next time you leave home. This information is retained, ready to be retrieved at a later time. If the system is working properly, when you leave home to go to work you will remember exactly where you left your keys.

If you’ve forgotten where they are, one of several things could have happened:

  • You may not have registered clearly where you put them down to begin with.
  • You may not have retained what you registered.
  • You may not be able to retrieve the memory accurately.

Therefore, if you want to stop forgetting where you left your keys, you will have to work on making sure that all three stages of the remembering process are working properly.

If you’ve forgotten something, it may be because you didn’t encode it very effectively, because you were distracted while encoding should have taken place, or because you’re having trouble retrieving it. If you’ve “forgotten” where you put your keys, you may not have really forgotten at all — instead, the location of your keys may never have gotten into your memory in the first place. For example, you probably would say that you know what a five-euro bill looks like, but most of the times that you’ve seen one, you’ve not really encoded its appearance, so that if you tried to describe it, you probably couldn’t.

Distractions that occur while you’re trying to remember something can really get in the way of encoding memories. If you’re trying to read a business report in the middle of a busy airport, you may think you’re remembering what you read, but you may not have effectively saved it in your memory.

Finally, you may forget because you’re simply having trouble retrieving the memory. If you’ve ever tried to remember something one time and couldn’t, but then later you remember that same item, it could be that there was a mismatch between retrieval cues and the encoding of the information you were searching for.

References

How human memory works by Richard C. Mohs at Science – How stuff works?

Storage and Retrieval by Saul McLeoad at Simply Psychology in 2013

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