IVAN PAVLOV, the Nobel prize-winning Russian physiologist, laid the groundwork for understanding how bad memories can disrupt the memory process when they become incorporated into the brain's menu of powerful conditioned reflexes. Pavlov's experiments with dogs involved the ringing of a bell plus the presentation of a piece of meat to a dog, and measuring the increase in the amount of saliva produced. When the bell ringing and meat presentation were combined often enough to cause the same volume of increased saliva flow -- that is, the classic conditioned reflex.
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At the beginning of this chapter we described the establishment of powerful conditioned reflexes in the dog. What isn't so well realized is that the establishment of a reflex with its associated memory is actually accomplished more easily in human beings than it is in dogs. Over a period of time, we humans develop thousands of conditioned reflexes and the associated memories that go along with them.
Most conditioning is helpful and is the basis of all new learning. Some conditioning, however, is harmful or negative, particularly when the conditioning is inappropriate. For example, when we have become conditioned to a danger or the threat of a danger, various internal systems in our bodies respond to an impending emergency. Our hearts begin to race, blood vessels constrict, more sugar and oxygen are delivered to vital tissues, and we are prepared to fight or run away. If the danger is not real, however, if it is something that we just imagine, there will be no one to fight and no place to run. Yet all the internal changes of the body still take place. Those changes can make us feel frightened, full of panic, and filled with somatic complaints of the heart and gut. And the memory of the perceived danger, if repeated often enough, may make us profoundly depressed.
The stress from bad conditioned reflexes, as well as stress induced under experimental conditions, if often associated with increased levels of the steroid hormone cortisol in the body and especially in parts of the brain associated with memory, such as the hippocampus. There is strong reason to believe that cortisol adversely affects not only the function of the hippocampus but also its structure. It is not surprising, therefore, to find that stress and the resulting increase in cortisol levels are often associated with an impairment in certain memory faculties. At times this impairment can be quite severe. This is particularly true if the stress is chronic and results in a dysregulation of the hypothalamic-pituitary-adrenal axis, resulting in chronically raised cortisol levels.
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Most people encounter stress at some point in their lives, but not everyone reacts the same way. People who are depressed and have bad conditioned reflexes (along with the bad memories that are part of those bad conditioned reflexes) are much more susceptible to the effects of stress than healthy individuals. The former group has a longer period of stress anticipation, higher cortisol levels, and more deterioration of memory than healthier individuals. The combination of bad conditioned reflexes with bad memories, stress, and some degree of depression are so intertwined in most people complaining of memory problems that I often regard them as part of the same syndrome. All of these factors have to be taken into account in diagnosing and treating people with this, the most common form of memory disorder.
As was described in Chapter 2, there are three basic mechanisms of memory. The first is encoding, namely, laying down new memories in the brain. The mechanisms of concentration and focusing attention are essential to insuring that encoding is done properly. The second is storage, the storage of memories in the memory banks of the brain. The third is retrieval, the retrieval of memories from the memory bank for our use.
Panic and depression interfere with the encoding of new memories. They interfere with concentration and focusing of attention. If new memories are not properly encoded, they will not be stored properly in the memory bank. Finally, the retrieval of deficient memories from the widespread memory bank is also going to be seriously impaired.
Unfortunately, bad conditioned reflexes, particularly those that are associated with strong emotions like fear and anger, are easily remembered and are very ease to retrieve. In a paradoxical way, these bad memories, which are so easily accessible to us even when we don't want them, have a particularly noxious effect on the laying down of new memories, good memories that we need and that may be vital to us.
Source:
Vernon H. Mark, M.D., with Jeffrey P. Mark, M.SC., Reversing Memory Loss: (New York: Houghton Mifflin Company, 1999), 51, 63-65.
IN CLINICAL practice, people who experience chronic pain often report problems with memory functioning. A clinical study completed in 1995 of self-reported memory problems was based on two groups of chronic pain patients. Fifty-six patients had pain secondary to automobile accidents; twenty-seven patients suffered pain from various work-related accidents. They were compared to control groups, including twenty-four patients with medical-dental problems and twenty receiving psychotherapy.
The findings of this study indicated that memory complaints were higher in patients with chronic pain than in the medical-dental group or in the psychotherapy patients. No differences were found between patients suffering pain from an automobile accident as compared to patients suffering pain from an industrial accident.
On a questionnaire designed to be specific to memory complaints in chronic pain patients, differences in memory complaints for pain patientsx as contrasted to controls were found, even after the effects due to depression were statistically removed. There was no report of memory problems attributable to medication.
This study was not unique or really that surprising. People with chronic pain find it difficult to concentrate. They are easily distracted and, as a result, the encoding of messages in the memory center is interfered with. The treatment of this kind of memory disorder has to bbe directed toward relieving the chronic pain.
Unfortunately, in some people, this is more easily said than done. The important point to remember, however, is that chronic pain can interfere with the memory process. People who suffer chronic pain and who have difficulty functioning efficiently in the workplace may have a memory problem that reduces their functional abilities. This does not mean, however, that they have a structural defect or serious disease of the brain.
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Impaired memory test performance related to post-traumatic stress can reflect a host of factors, such as head injury/post-concussion syndrome, involvement in litigation, malingering, psychological distress, and the use of certain medications. The claim of memory loss in litigation always has to be verified by scrupulous investigation. However, there are certain litigation claims regarding memory loss associated with post-traumatic stress disorder that may have merit.
Attention and memory performances were studied in Persian Gulf war veterans, with and without the diagnosis of post-traumatic stress disorder. Veterens diagnosed with post-traumatic stress disorder showed relative performance deficiences on tasks of sustained attention, mental manipulation, initial acquisition of information, and retroactive interference.
The patterns of intellectual and memory loss in veterens with post-traumatic stress disorder suggests that the intrusive memories of the traumatic events themselves may be augmented over a period of time by conditioning. Finally, a number of seemingly unrelated environmental stimuli may trigger the flashbacks that produce a disorganization of memory and other intellectual functions.
Another study of post-traumatic stress disorder focused on rape victims. Fifteen rape victims with and sixteen rape victims without post-traumatic stress disorder were tested for learning and memory abilities. The subjects with post=traumatic stress disorder performed significantly worse than the other group. Their performance could be improved to some extent by cues and recognition testing. The memory deficits described in this study were mild and were not attributable to depression, anxiety, or substance abuse.
Obvioulsy, the best way to treat memory deficiency in people with post-traumatic stress disorder is to treat the disorder itself. This is sometimes difficult and tedious, but there are established psychotherapeutic techniques for it.
Source:
Vernon H. Mark, M.D., with Jeffrey P. Mark, M.SC., Reversing Memory Loss: (New York: Houghton Mifflin Company, 1999), 106-107, 109-110.