William Barr, Ph.D., ABPP
NYU Comprehensive Epilepsy Center
Memory is commonly reported as a big area of concern for people with epilepsy. If you have epilepsy, your memory can be affected in several ways. In each case, the end result will be that you cannot recall an event or a piece of information when you need it.
Problems of attention and encoding
Memory disturbance often can be traced to a problem with some other function. For example, attention is commonly affected in people with epilepsy. Epilepsy can reduce your attentional speed or rate of information processing. Years of research also have shown that many forms of epilepsy are associated with impairments in sustaining attention over time. Other studies have demonstrated a reduction in attention span, defined as the amount of information you can process at any given moment. All of these deficits ultimately affect your ability to encode information into some form of memory.
Many call this the "information age." Computers and other forms of media have given us access to levels of information that were never dreamed of before. Unfortunately, the amount of available information can be overwhelming to many. People with conditions such as epilepsy have problems processing information when it is presented at a rapid rate or over extended periods. You may find yourself unable to follow the dialogue when actors in movies or plays are speaking. You may miss out on key elements when people quickly give you directions, addresses, or phone numbers. If you are a student, you may have trouble keeping up with lectures. You may "space out" when required to sit and listen to something that lasts for a long time.
In many cases, people with epilepsy are able to process the required information, but not at the rate at which it is presented. If your processing speed is reduced, you can miss out on critical facts. When faced with a message that has three major points, you might fully absorb numbers one and two but fail to process number three. In many cases, you cannot succeed with just two out of three. In other situations, you may fail to absorb information because you can't keep focused over time. Some people have their attention "burn out" on them. Others tend to be very distractible and are prone to shifting their attention to details other than the topic at hand. Some can attend only to a very specific amount of information before becoming overwhelmed. To use an analogy, the funnel they use to obtain information is narrower than the one that others use.
The person in each of these examples will report a failure of memory. But what might appear to be a difficulty with remembering is actually the result of never getting the information in the first place-not only details that they intend to remember, but also background information that may be needed in certain situations. At times, seemingly irrelevant information might become critical. For example, someone may ask you, "Did you meet the guy with the blue shirt?" You might remember meeting a man, but because your ability to focus on incidental details is restricted, you may be unable to remember anything about his clothing. Problems with attention cause many people with epilepsy to have difficulty absorbing information in general. If you are unable to recall and retain information, it may be because you have this kind of problem with memory encoding. You cannot remember what you never got to begin with.
Problems of storage
Unfortunately, even if you successfully encode a bit of information, you might not be guaranteed to remember it because difficulties with storage also may affect your memory if you have epilepsy. Research has shown that people with epilepsy are prone to forget things more quickly than others. In some situations, it may seem that information "goes in one ear and out the other." This rapid rate of forgetting is thought to be the result of impairment in the ability to store or consolidate new information. This storage problem is ultimately linked to a defect in the "hardware" required for normal memory functioning. Difficulty with this stage of memory processing is no accident; epilepsy directly affects many of the brain structures involved in memory processing.
Problems of retrieval
Sometimes you may know that the information is in there, but you just can't get it out. In this case, it has been encoded properly and it also has been stored adequately. The problem is in gaining immediate access to it. This kind of difficulty in "retrieval" is a common cause of memory failure in people with epilepsy and many other neurological disturbances. Some retrieval problems might result from deficits in speed of access. If you are asked to remember something "on the spot" you may not be able to come up with it, but a few minutes later it comes to you. It is clear that the information was always there, but access to it was delayed. At times, access might become blocked altogether. Some form of distraction, like another piece of similar information, might get in the way of remembering.
Some people have trouble recalling things out of context. For example, you might not remember attending a certain party until you hear more details about it. Then you say, "Oh, you mean that party!" This shows that it is often difficult to retrieve episodes in isolation. Similar things can happen with words. You might not be able to come up with the word until you think about it in another form or meaning. A large part of successful memory functioning involves being able to generate a context for retrieval. Unfortunately, many people with epilepsy have subtle difficulties with problem-solving that might affect the ability to generate these contexts. In some cases, these people can't initiate a plan for remembering. In other cases, they might not be able to see the relationship between various contexts.
Epilepsy has significant effects on retrieval from declarative memory, the kind that we process consciously. You may have difficulty in retrieving episodes or events that happened to you, and also have difficult in retrieving what scientists call "semantic information"-words or facts in general knowledge. Just as problems with encoding are often the result of a problem with attention, this kind of failure in retrieval also may actually be due to a difficulty with attention or can be due to higher-order cognitive deficits in areas such as organization and sequencing. The kind of problems with word retrieval (also called "word finding") that many people with epilepsy report may occur because of memory impairment, or they may occur because of a disturbance in language functions.
The important thing to remember is that what we commonly refer to as a problem with memory often is the result of problems with a number of underlying processes that can be affected by factors associated with epilepsy.