September 11, 2011

Flashbulb Memories: Real or Rehearsed?

http://www.spring.org.uk/images/flashbulb.jpg
I have put off working on my new post relating to hippocampal connectivity to write this.  It just occurred to me that tomorrow is 9/11 and would make for a nice post on memory.  I tried to get this out before 9/11, but I failed by about 1.5 hours.  When I realized this at around 8:30 or 9 PM, I naturally started thinking about flashbulb memories, and then it led to writing a post on them.  Hopefully it's somewhat informative.

Flashbulb memories are those that contain vivid details, more so than regular memories, and they are also accompanied by an enhanced confidence in reporting these details.  Flashbulb memories are reported to 'occur' after striking events that are highly dramatic, either for good or bad.  Most individuals can recall with enhanced detail where they were/time they heard about it/specific location when you heard it/what you were wearing/etc. (although, not flawlessly!).  These are often reported after large stories, like presidential assassinations, 9/11, or the space shuttle Challenger explosion.

after the jump, are emotional memories different from flashbulb memories or other episodic memories?  Also, a video clip on flashbulb memories of 9/11.





Psychologists and neuroscientists are not at a consensus as to whether flashbulb memories have their own distinct neural mechanism for encoding and/or recall or if it is only the case of increased attention given to the event.

Flashbulb memories started to be researched more heavily after President Kennedy's assassination.  Brown & Kulik (1977) first termed this phrase after findings of an enhancement of details recalled from asking about the assassination of JFK.  They suspected that these memories have distinct neural mechanisms for the encoding of the event, which is 'triggered' by surprise, perceived emotional valence, distinctness, and others (picture below). However,  McCloskey et al. (1988) state that flashbulb memories are not special and are just like 'ordinary' memories in terms of neural machinery involved.  These memories decay at the same rate that regular memories do, are susceptible to forgetting of details, and are no more accurate than other ordinary, control memories.

What is strikingly different is the confidence reported in the recall between flashbulb memories and ordinary memories.  Even if the details have been shown to be wrong, people that have had flashbulb memories still claim them to be completely accurate, whereas with other memories that are proclaimed not to be flashbulbs, confidence in the reported recall is lower.  It appears that if the person thinks they should remember based on the distinctiveness of the event, this boosts confidence ratings but does not increase accuracy upon recall.   

Logically, the flashbulb-memories-are-special stance is easily argued, as that the memories that we remember the most are events that have had national media coverage, generated much talk amongst others discussing the event, and hence has been given more attention (Water-cooler Effect).  Even if you have a flashbulb memory that is not covered by the media, you often find yourself rehearsing it in your head, talking about it with others, writing it -- interacting with the memory, as you normally do not with 'normal' memories.



Finkenauer et al. (1998)
Neurally, can we identify whether these memories are just caused from more attention through frequent rehearsal mechanisms or do they carry specific encoding mechanisms that create perma-memories (permanent storage of the memory)?  Not a whole heck of a lot is known, because, due to ethical restrictions, we cannot induce highly emotional memories that would likely constitute a flashbulb memory.  Therefore, the study of the encoding of these memories is untenable.  However, you can study emotional encoding of memories, which is the closest to trying to induce a FBM.


The encoding of emotional memories in humans has largely followed in the foot-steps of rodent research, only to a higher cognitive degree.  We have learned that the amygdala is the primary mover at the encoding of emotional memories. The amygdala also affects the explicit memory recall by enhancing the activation of other cortical and subcortical areas that are involved.  Stress hormones are also release in response to emotional stimuli, which interacts with the hippocampus and, more indirectly, the amygdala.  The modulatory mechanisms of the amygdala act directly on the consolidation process of memory storage.

(left) Emotions modulatory effect on encoding and consolidation.
(right) fMRI activity (a) correlation map with positive stimuli;
  (b) correlation map with negative stimuli. 
Correlated activity is in yellow.
Imaging studies have provided us with a window in to the encoding process of emotional memories.  Hamann et al. (1999) has shown that the amount of bilateral amygdalar activity at the time of encoding is predictive of the accuracy at the time of recognition one month later (right picture), but not at recall right after scanning.  This was not the case for non-arousing stimuli.







 Sharot et al. (2007) scanned the brains of people that were either in Downtown NYC, closer to the scene of the World Trade Center crashes on 9/11, or Midtown NYC.  They found that there was stronger amygdalar activity upon recalling details of that day for the Downtown group than those in the other group.  This finding suggests that personal experience (e.g closer to the scene) may reflect the psychological mechanism by which the amygdala modulates memory.  To check out more about memory and one of the researchers involved in the consortium of 9/11 researchers, check out Brain, n. An apparatus with which we think that we think by Jon Simons (Cambridge).




However, the fact still remains whether we have special neural circuitry dedicated to the encoding and/or recall of flashbulb memories as opposed to regular, emotional memories but that lack in details.  In terms of the psychology of memory, it may make sense to have a term for this enhancement of recall/recognition.  In terms of the neuroscience of memory and the neural activity and connectivity thereof, it may be a non-sequitur in trying to assign special circuitry to these types of memories.  A memory encoded is always going to engage different regions.  If an event is highly emotional, it only makes sense that it would engage other areas.



 Tell me what you think: are FBM psychologically or neurally special?

Happy Birthday, Blog!  You are one-month old today.  You survived another day.

References:

Brown, R. & Kulik, J. (1977). Flashbulb memories.  Cognition, 5(1), 73-99. 

McCloskey, M., Wible, C. G., & Cohen, N. J. (1988).  Is there a special flashbulb-memory mechanism?  Journal of Experimental Psychology: General, 117(2), 171-181.
Finkenauer, C., et al. (1998).  Flashbulb memories and the underlying mechanisms of their formation: Toward an emotional-integrative model.  Memory & Cognition, 26(3), 516-531.

Hamann, S.B. et al. (1999) Amygdala activity related to enhanced memory for pleasant and aversive stimuli. Nat. Neurosci., 2, 289–293.

Sharot, T., Martorella, E. A., Delgado, M. R. & Phelps, E. A. (2007).  How personal experience modulates the neural circuitry of memories on September 11.  PNAS, 104(1), 389-394.

 



2 comments :

  1. Your blog is interesting, has left a great impression.
    Best wishes
    Jonas

    ReplyDelete
  2. Very interesting, good references also, gets the basics down in a easy format! Glad I found this the morning of a psychology exam.
    Best wishes,

    ReplyDelete