Causes of Memory Loss -
Memory Defined

By M. CHRIS WOLF, PH.D.
Founder & Editor-in-Chief

There are many causes of memory loss and types of memory. However, it is first helpful to define what we mean by memory, types of memory and thus causes of memory loss.

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Memory has been defined as the attainment and preservation of information. BUT… Memory defined above can be refined in different ways. It is possible do be very good at one type of memory process and do poorly in another. In fact, this is more often the case than not. So, let’s take a look at the different kinds of memory that can be involved in the causes of memory loss.

The ability to learn or encode and then to recall new information is calledAnterograde Memory. So you have an experience and are later able to remember it if needed. Memory defined in this ways asks, does the person remember a new recent experience? So, if a person has a concussion, a doctor may wish to discover if the person is laying down new memories. Memory defined this way becomes an important part of a mental status examination and causes of memory loss following a head injury.

Of course, learning about the person’s level of Anterograde memory is important to any memory evaluation.

What is Autobiographical Memory? This is the person’s ability to recall PERSONAL experience. Here is an example of memory defined in this way. For example, yesterday I met with my boss at work to discuss plans for a project. Do I remember meeting with her? What did we discuss? What details do I remember from the meeting? Obviously, this is an important part of what makes me who I am.

Memory defined as Explicit Memory or sometimes referred to asDeclarative Memory can be described in this way. Often times this is what people think of when they define memory or examine causes of memory loss.

Explicit memory is the recollection of facts, experiences or events. Who is the president of the United States? How old are you? What is the date today? What did you have for breakfast today? Thus, Declarative Memory can contain autobiographical memory or recent personal experiences as well as facts.

Echoic Memory refers to the capacity to remember things through your ears for a short duration. This is an area often examined when exploring causes of memory loss.

For example, a doctor may ask the person to repeat a series of numbers in a sequence. Usually this kind of memory is brief, perhaps 2-3 seconds. This is sometimes used as a measure of immediate attention as well.

The kind of memory that involves recalling a specific context or personal experience in terms of time and space is called Episodic Memory. There is no special significance to this type of memory but it is usually autobiographical. This is the “what”, “when” and “where of your experience. This would be like recalling the experience of being at your wedding.

Being able to remember a visual image for a very short period of time is called Iconic Memory. For example, if I were to show you a picture of my Labrador Retriever Bambi and then you closed your eyes, you would be able to see her briefly in your mind’s eye if your Iconic memory was working properly.

There is a memory called Immediate Memory which refers to being able to hold information in your conscious awareness for a brief period of time. When examining causes of memory loss in brain injury we often examine immediate memory.

For example, recalling a phone number which you intend to dial immediately or remembering a road sign immediately. Generally, if you are interrupted in the seconds following encoding of the information you may have trouble recalling it. Immediate memory is very useful in our daily living.

If you are recalling something that happened during last holiday season you are using Long-term Memory. Long-term memories are the last to be affected by an injury or illness.

However, we examine long-term memory when looking at causes of memory loss such as Alzheimer's Disease (AD).

Thus, if a person is suffering from Dementia or Alzheimer’s disease and they do not remember the name of their child this would be considered a serious disruption of Long-term Memory. Mild or Moderate Traumatic Brain Injuries rarely disrupt long-term memory.

A memory that we gain and reproduce without really thinking is calledNondeclarative Memory or Implicit Memory. Examples of this kind of memory would be remembering how to brush your teeth, singing part of a familiar song or riding a bicycle. We really don’t think much about how to do these actions. Once we acquire these memories they seem almost automatic.

Procedural Memory is a kind of Implicit Memory that involves our actions-like bringing a spoonful of soup to our mouth. We do not need to self-talk this kind of memory. It is a kind of motor learning.

If we are remembering something that we plan to do in the future that is calledProspective Memory. For example, you plan to go to your daughters play on Thursday evening. This is an action you intend to do in the future that you have remembered.

Recent Memory refers to your ability to form a new memory. Above we mentioned Immediate Memory or memory that we hold briefly. Recent Memory starts where Immediate Memory ends. Thus, if a doctor asks a person for the time, date and place that they are at she is attempting to measure Recent Memory.

This can often be a concern with causes of memory loss. Recent memory is often very important to assess in the initial examination

If you remember an event from childhood, we considered that to beRemote Memory. This really is another term used to indicate Long-term Memory which we is a memory defined above.

Retrograde Memory refers to information that you have encoded and stored before. Doctors often talk about Retrograde Amnesia when they are examining a person who has experienced a Traumatic Brain Injury (TBI). Basically they are looking to determine whether the person is able to lay down new memories.

Above we defined Episodic Memory when referring to specific information about situations we have learned. Semantic Memoryis concerned with general knowledge or concepts and may be a concern we we examine causes of memory loss.

For example, a screw driver is used with screws to hold objects together and George Washington was the first U.S. president.

In Sensory Memory we are concerned with the first part of encoding a sound or vision in our brain. It refers to both Echoic Memory and Iconic Memory which is memory defined above.

When we are referring to Short-term Memory we mean information that we have retained over seconds to hours. Neuroscientists debate when memory defined as short-term memory ends and long-term memory begins. But for our purposes Short-term Memory refers to information that we have processed very recently. Short-term Memory is what often is affected first in aging, injury or illness as opposed to Long-Term Memory which is more resistant to Memory Loss.

Source Memory refers to when an Episodic Memory defined above was first learned. In other words, where and when did an event that I remember happen? Neuroscientists have found that this type of memory is more affected by aging and is often due to decline in the Frontal Lobes (front part of the brain).

Finally, in Working Memory doctors are referring to temporary storage of information when we are using information to perform a task of some sort. Doctors might ask person to repeat numbers or spell a word backward to assess this capacity. This type of memory is in some ways like RAM memory in a computer.

So... now that we have explored the many memory types, let’s move on to how to improve memory.

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