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Thursday, October 27, 2016

Overgeneral autobiographical memory and its relation to depression and trauma



Williams, J. M. G., Barnhofer, T., Crane, C., Hermans, D., Raes, F., Watkins, E., & Dalgleish, T. (2007). Autobiographical Memory Specificity and Emotional Disorder. Psychological Bulletin, 133(1), 122-148.  http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.721.1249&rep=rep1&type=pdf

What is OGM – overgeneral autobiographical memory?

When certain people are asked to retrieve specific autobiographical memories (memories of specific events that happened at a specific time and place) related to key words, they tend to retrieve categorical, overgeneral memories – memories that group similar events together (for example, "I used to walk the dog every morning") instead of specific memories.

This phenomenon was first found by researchers Willians and Broadbent (1986) in suicidal patients.  Later it was found as a consistent characteristic of patients with a diagnosis of depression, postnatal depression and people with sub clinical levels of depression.  The phenomenon is also found in people with a tendency for rumination (passive and repetitive thinking about the depressive symptoms, and the possible causes and consequences of these symptoms.  For example, "What did I do wrong?" "Why am I not getting over this?").  Memory remains overgeneral in those with a history of emotional disorder, even if not currently in an episode.

The phenomenon of overgeneral autobiographical memory is also found in people with a history of trauma, like sexual abuse, physical abuse, traffic accidents, war trauma, cancer diagnosis etc.  OGM is found in these people even when they are not asked to retrieve memories related to their trauma, but rather memories that are related to certain key words.  OGM doesn't occur in every person who has gone through trauma.  It tends to occur more in people who reacted with post traumatic stress disorder and in people who experienced trauma in childhood.

The OGM phenomenon was assessed mainly by various versions of the AMT – autobiographical memory test.  This test usually uses emotional key words, for instance "excited", "happy", "relaxed ", "bored", "helpless", "lonely" and so on.  The person is asked to retrieve a specific event (that occurred at a specific time and place, lasting no more than one day) that is related to this key word. 

People with depression or post trauma tend to have OGM in response to both positive and negative key words.  People with depression or post trauma tend to respond with OGM even when the stimuli are not key words but situations (for example, " Recall a time when a neighbour helped you with a practical problem"), a general instruction ("Recall as many episodes from your life as you can in ten minutes") or actions ("Try to recall going to a concert").


How do researchers explain OGM?

There are three kinds of explanations:  Functional Avoidance, "capture" and executive dysfunction.

Functional Avoidance

The explanation is related to the structure of autobiographical memory.  According to Conway – Pleydell- Pearce model (2000), autobiographical memory has three hierarchical levels:

The highest level is the level of representations of life periods with clear beginning and end points (for example, being in high school, military service, the time when I lived in Tel Aviv etc.). 

The middle level has general event descriptions:  event that repeat themselves (for example, driving to work each morning) or singular events (for example, my vacation in South Korea).  The events are represented at this level as conceptualized and abstract summaries of experiences.

The lowest level has specific event knowledge.  In this level concrete, sensory and perceptual aspects of events are represented.  They can take the form of visual, auditory, tactile or other images of the event – what the surrounding looked like, who was present at the event, how I felt during the event etc.

When people receive a key word and are asked to recall a specific event related to this word, they create associations for the word that become the basis for memory search.  For example, for the word "calm" I can think about "my dog Jane".  Now people access the level of representation of life periods ("when I lived in Tel Aviv") or the level of general events ("I used to take her for walks") and from here they go on to the specific event level ("one day we went on a walk to "Ben Shemen" forest and she was frightened by a wild boar that suddenly appeared on the path"). 

For post traumatic people, this kind of memory search may lead to emotionally difficult placesConsider the following protocol from a patient in response to the cue summer. She was thinking back of summer holidays and found “hot summer evenings” coming to mind. Further specifying on this theme, she began to retrieve a specific summer evening when, although already after 10:00 p.m., the temperature was still agreeable, and she was sitting outside with friends talking about the new puppy she had bought. Subsequently, however, this triggered another memory from that same summer when she was assaulted when walking the dog in the neighborhood park.

As a result of these kinds of experiences people with PTSD and people with depression tend to avoid memories which are too specific,  Conway and Pleydell – Pearce  argue that these people stop their search in memory at the level of general event description and tend to avoid reaching the level of specific events.

Capture

Individuals suffering from depression and people with a tendency for rumination may get "caught at the middle level (the general event level).  When such people receive, for example, the key word "happy", they may ruminate:  "why can't I be more happy?"  These thoughts "capture" them and prevent them from retrieving specific events from autobiographical memory.  These people move across the middle level of autobiographical memory instead of moving downward towards the more specific level.

Executive functions

Searching in memory according to a cue requires effort, strategy, control and monitoring – that is, executive functions.  During the search a person has to inhibit irrelevant autobiographical knowledge (and also ruminative thoughts that disturb the search for a specific event). 

People with depression and post trauma have depleted attention resources and executive control.  Their difficulties are especially salient in the aspects of initiating and managing the search and inhibiting irrelevant information during the search.

Thus, functional avoidance, "capture" at the middle level of autobiographical memory and poor executive functions cause the overgeneral memory phenomenon.  These factors also work together and interact and thus exacerbate the problem. 

Overgeneral autobiographical memory may lead to slow recovery from depression or traumatic events.  OGM may also lead to difficulties in problem solving, because OGM makes it harder for us to lean on past experience when we deal with new situations.

Fortunately, training people with depression or PTSD to retrieve specific memories can lead to improved emotional state and can prevent the development of another episode of depression.  This can be done, for example, by creating a list of specific memories that the patient wants to remember.  Each item on the list is linked via visual imagery to a specific location on a "mental trail".  The person takes a mental hike and retrieves the memories along the trail.  This technique prevents the development of depression.

Another way is to train depressed people to focus on concrete images which are not self centered and have aspects of perceptual processing/mental imagery (“Think about the face of the Mona Lisa,” “a raindrop falling down a window pane”).  This leads to retrieval of much more specific autobiographical memories.  Retrieval of specific memories alleviates depression.

One of the authors of this paper, Dalgleish, elaborates on this subject in this interview:


Clinical depression and memory: Professor Tim Dalgleish



1 comment:

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