Memory is a complex process, and understanding how memory works is quite a hot topic in the research of such processes. It may help us to understand, though, why certain types of memory are more available to us than others, particularly in the area of traumatic memory, and how they can cause such difficulty (often in seemingly unrelated ways). What follows here in Part 1 of this article will be an attempt to explain in as simple terms as possible a little about what researchers are finding out about memory processes.

In order to understand how memory (or the lack of it) occurs in a survivor of trauma, we must have at least a basic concept of how trauma affects the mind and what information the brain is able to retain or store. Trauma is not merely a psychological event; it is also a physiological one (and visa versa). In fact, actual bodily harm (bruising, broken bones, etc.) does not necessarily have to occur in order for an event to be traumatic. Psychological trauma (witnessing a death, violence, fear for life and limb) exacts a heavy toll on the body as well as it does on the mind because the two are intricately interconnected and will, of course, affect one another. We need to understand, then, how the brain processes and “remembers” traumatic events and the consequences of those memory-storing processes.

In earlier articles, we have discussed some of the dynamics of how traumatic stress can be a factor in, and contribute to, such conditions as DID and PTSD. Because more and more research is being done, in the area of PTSD at least, researchers are becoming more aware of what occurs in this condition. According to Rothschild (2000), many of the experts in the field recognize PTSD as a “complex psychobiological condition.” How the mind stores traumatic memory is also more understood than it was in the past. “In PTSD a traumatic event is not remembered and relegated to one’s past in the same way as other life events. Trauma continues to intrude with visual, auditory, and/or other somatic reality on the lives of its victims.”

Somatic memory (“body memories”) will be discussed in a later article. For now, though, let us think about the questions how and why this is the case, at least on a very introductory level. First, we need to know what memory is. Memory generally has to do with the way the brain records, stores, and remembers information. It can be measured by recall, reproduction, recognition, and relearning (Chaplin, 1985). In order for information from our external world to be “memorized,” it must be encoded (transformed into appropriate signals so that it can be recorded in the brain). Not all information is stored and recorded so that it becomes a memory, but some types of information are more likely to be recorded or stored in long-term memory than others. “The greater the significance, and the higher the emotional charge – both positive and negative – the more likely a piece of information (or an event made up of multiple pieces of information) will be stored” (Schacter, 1996). When it comes to traumatic memories, all of this comes into play.

There are two main systems of memory – long-term memory and short-term memory. Memory can either be stored in the brain as explicit (also called declarative memory) or implicit (procedural memory). Which type of memory it is determines where it is stored in the brain and how the memory is retrieved. “Explicit memory depends on language and involves facts, descriptions, and operations that are based on thought,” says Rothschild, while implicit memory involves “procedures and internal states that are automatic. It operates unconsciously, unless made conscious through a bridging to explicit memory that narrates or makes sense of the remembered operation, emotion, sensation, etc.” Many times, only images remain, there simply are not words to describe or explain or make sense of the trauma; thus the memory cannot be stored as an explicit (declarative) one, but rather as an implicit memory process. Van der Kolk (1987) tells us that trauma and memory of trauma interrupts normal developmental processes. He explains:

“When habitual and previously adaptive actions and strategies fail, the autonomic nervous system is activated and a search through the memory systems of different domains begins. In children, this search is heavily weighted toward visual memory…. Numbing, denial, and constriction of personality functioning follow traumatization in adults.”

When you think of how the brain stores information and what kind of information becomes memory, the difficulty in retrieving certain types of memory (especially traumatic memories) makes more sense. Because traumatic memories are stored differently than other types of memory, retrieval can be a huge problem. One reason for this is that traumatic memories are often stored as implicit rather than explicit memories, which is why the sense of “not having words to describe” a trauma is such a common experience for survivors. It also makes sense, then, that extremely overwhelming events would send someone into “defense mode” in order to cope with the unbearable and find alternate ways to deal with the memory of those events. DID is the result of one such coping mechanism. On the subject of dissociation, for example, Bessel van der Kolk (1995) says this:

"People have a range of capacities to deal with overwhelming experience. Some people, some kids particularly, are able to disappear into a fantasy world, to dissociate, to pretend like it isn’t happening, and are able to go on with their lives. And sometimes it comes back to haunt them."

This is most certainly the nature of DID and PTSD. In our next article, we will look at what physiologically occurs in the brain and attempt to explain how somatic or “body memories” result from trauma.

A Short Introduction to Memory Processes Part II

Let us continue our discussion on memory processes. In Part One of this article, we talked about how memory processes are affected by trauma and how that can determine what information the brain is able to retain or store. We talked about the autonomic nervous system (the part of the central nervous system responsible for automatic functions we don’t usually think about, such as breathing or the heart beating) and how traumatic memories can affect those functions. We also talked about how traumatic memories are stored differently than other types of memory, as well as the difference between implicit and explicit memory.

Now we will look at memory processes from a physiological perspective. We’ll begin by looking at the physical brain, beginning with some very basic terms that will aid us in understanding which parts of the anatomy are involved in the functions of memory, learning, and emotion.

The human brain is an extremely complex organ. For the sake of this discussion, we will mention only those areas of the brain that play the greatest part in the processes and formation of memory. For a picture view and short glossary of some of these terms, please see the website at http://www.ahaf.org/alzdis/about/Anatomy...

Our main focus here will involve the area of the brain called the Limbic System, which is located deep within the center of the brain. This “system” consists of several structures, including the hippocampus (important in memory formation), the amygdala (center of major emotional activity), the thalamus (a “switching station” through which signals travel to various parts of the brain), and several other structures. Also part of the limbic system are those areas that are directly affected or closely connected to it, such as the olfactory system (smells can definitely trigger strong emotions) and the hypothalamus (center for the regulation of several body systems including hunger, thirst, respiration, body temperature, and the regulation of complex emotions such as anger and fatigue).

The limbic system controls mood and attitude. Its functions include setting the emotional tone of the mind, filtering and deciding the importance of events, storing highly charged emotional memories, moderating motivation, controlling appetite and sleep cycles, and processing the sense of smell. It is the part of the brain that determines our mood, is involved in clinical depression, perception of events, motivation, and how we view things from an emotional perspective (see website for BrainPlace.com listed below). According to one of the leading experts in the field of trauma and its treatment, Dr. Bessell van der Kolk (1994), the limbic system plays a major part in traumatic memory processes. “The limbic system is thought to be the part of the CNS (central nervous system) that maintains and guides the emotions and behavior necessary for self-preservation and survival of the species, and that is critically involved in the storage and retrieval of memory.”

When we have a least a basic concept of these areas of the brain and their functions we can better understand how external influences affect them. It helps us to make sense of why trauma related memories can trigger such strong physiological (physical) arousal. Van der Kolk explains that when a signal travels through the thalamus to the limbic system, the emotional significance of that input is determined. “Most of this occurs outside of conscious awareness, and only novel, significant or threatening information is selectively passed on to the neocortex (outer surface of the brain) for further attention.” Once meaning is assigned to information, emotional behavior is guided by the amygdala to the hypothalamus, hippocampus and other parts of the brain. Obviously, this has strong implications for behavior, especially when a trauma survivor is faced with exposure to “strong reminders of the traumatic past” (van der Kolk).

When we are in danger or are under attack, the limbic system is where fear and rage occur. Fear energizes the body so we can run (flight), and the rage response is the signal to prepare the body to fight in order to protect ourselves or others. Rothschild (2000) refers to the limbic system as “survival central.” An apt description. “It responds to extreme stress/trauma/threat by setting the HPA axis (the system that responds to stress) in motion, releasing hormones that tell the body to prepare for defensive action.” The autonomic nervous system goes into a state of heightened arousal that readies the body for fight or flight, epinephrine (adrenaline) is released into the brain, respiration and heart rate quicken, the skin pales, and the body prepares for quick movement. “When neither fight nor flight is perceived as possible,” continues Rothschild, “the limbic system commands the parasympathetic branch of the autonomic nervous system (ANS) to cause the body to freeze” (called tonic immobility).

Why does the survivor of trauma continue to react to certain stimuli (triggers)? “The limbic system continues to command the hypothalamus to activate the ANS, persisting in preparing the body for fight/flight/freeze, even though the actual traumatic event has ended – perhaps years before.” In PTSD, the brain persists in calling and recalling the same alert. “Symptoms can become chronic as objects, sounds, colors, movements, etc., that might otherwise be insignificant… become associated with past traumas, causing traumatic hyperarousal” (Rothschild).

The good news is that this cycle can be broken, the symptoms can abate, and healing can take place. With the help of those who understand such processes, recovery is possible. In the meantime, if we can gain at least a basic understanding of what takes place within the brain as a result of trauma we are one step closer to making sense of how these things relate to those struggling with PTSD and DID.