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Disasters and dementia: from earthquakes to flash bulb memories

disaster

 

The “International Federation of Red Cross and Red Crescent Societies” definition of a ‘disaster’ is:

“ .. a sudden, calamitous event that seriously disrupts the functioning of a community or society and causes human, material, and economic or environmental losses that exceed the community’s or society’s ability to cope using its own resources. Though often caused by nature, disasters can have human origins.”

Disasters offer potentially valuable information about risks of dementia, as well as insights into wider brain function.

On 11 March 2011, in the early afternoon (14:46 local time), Japan was rocked by 9.0-magnitude earthquake that caused widespread damage to the country’s eastern coastal region. It lasted approximately six minutes, occurred with an epicentre of approximately 130 km (80 miles) east of Sendai City, Tohoku region.

The earthquake was so powerful it moved Honshu, Japan’s largest island, 2.4 metres east and shifted the Earth on its axis by an estimated 10 to 25 centimetres.

Hikichi and colleagues examined whether people experienced cognitive decline in the aftermath of the 2011 Great East Japan Earthquake and Tsunami, in a survey of older community-dwelling adults who lived 80 km west of the epicenter 7 mo before the earthquake and tsunami (Hikichi et al., 2016).

Approximately 2.5 years after this natural disaster, their follow-up survey gathered information from 3,594 survivors.  The association between housing damage and cognitive decline remained statistically significant in the instrumental variable analysis. Housing damage appears to be an important risk factor for cognitive decline among older survivors in natural disasters.

Dementia is a progressive condition which can affect any part of the brain. It therefore offers academics, practitioners and professionals valuable insights into how the brain functions.

But where were you when you first learned about the assassination of John F. Kennedy, the Challenger explosion, or the attack of September 11, 2001?

Variants of this question are often asked, and, usually with great enthusiasm, people reply with vivid, elaborate, and confidently held memories, memories that they claim they will never forget. These so-called “flashbulb memories” are detailed and vivid memories of attributes of the reception context of surprising and emotionally arousing public events.

Brown and Kulik (1977) showed that such autobiographical memories flashbulb memories in order to capture their impression that people had taken a photograph of themselves while learning of a public, emotionally charged event such as the Kennedy assassination.

Research on flashbulb memories that followed their now classic paper occurred, in part, because the “flashbulb nature” of FBMs seemed distinctly different from the character of other autobiographical memories.

One recent event has provided an intriguing account of memory in a person living with mild dementia. It demonstrates for me graphically the enormous complexity with which the human brain handles memory ordinarily. This person with mild dementia had been experiencing difficulties in short term memory, for recent names, lists and events. It also provides yet further evidence how the human brain handles emotion and memory through distinct neural substrates.

The attacks in Paris on the night of Friday 13 November 2015 by gunmen and suicide bombers hit a concert hall, a major stadium, restaurants and bars, almost simultaneously – and left 130 people dead and hundreds wounded.

A person living with mild Alzheimer’s disease underwent a directed interview about these “Paris attacks” (El Haj et al., 2016).

Unlike her memory about the date and month of the attacks, she provided accurate information about the year, time and places they occurred.

She also provided accurate information about how she first became aware of the attacks, where she was, with whom, what she was doing, and what time it was when she learned about them. As for the emotional characteristics of these memories, she tended to have high ratings of vividness and rehearsal. Negative emotional states and great surprise and novelty were also reported.

One reason for an interest in flash bulb memories is that their study may help psychologists understand traumatic memories. Their relevance can be seen in two further different lines of research.

First, epidemiological studies after the attack of 9/11 established that many people in the New York City area who did not directly experience the events at Ground Zero nevertheless experienced symptoms of post-traumatic stress disorder (Galea et al., 2002).

There’s currently some evidence that the part of the brain which might be implicated in vivid flashbacks in post-traumatic stress disorder may be the part of the brain which is one of the first places to shrink in Alzheimer’s disease.

(Neuroimaging research on the neurobiology of chronic post-traumatic stress disorder) has revealed structural and functional alterations in a distinct network of interconnected brain regions, see Flatten et al., 2004.)

This part of the brain is the hippocampus.

Second, brain-imaging studies showed enhanced activity levels of the amygdala after three years for those close to, but not at, Ground Zero (Sharot, Martorella, Delgado, & Phelps, 2007)

Therefore, disasters, man-made or otherwise, offer unique insights into the human brain, and are very relevant to our understanding of dementia.

 

 

Suggested reading

 

Brown R, Kulik J. Flashbulb memories. Cognition. 1977;5:73–79.

El Haj M, Gandolphe MC, Wawrziczny E, Antoine P. Flashbulb memories of Paris attacks: Recall of these events and subjective reliving of these memories in a case with Alzheimer disease. Medicine (Baltimore). 2016 Nov;95(46):e5448.

Flatten G, Perlitz V, Pestinger M, Arin T, Kohl B, Kastrau F, Schnitker R, Vohn R, Weber J, Ohnhaus M, Petzold ER, Erli HJ. Neural processing of traumatic events in subjects suffering PTSD – a case study of two surgical patients with severe accident trauma. Psychosoc Med. 2004 Jul 15;1:Doc06.

Galea S, Ahern J, Resnick H, Kilpatrick D, Bucuvalas M, Gold J, Vlahov D. Psychological sequelae of the September 11 terrorist attacks in New York City. New England Journal of Medicine. 2002;346:982–987.

Hikichi H, Aida J, Kondo K, Tsuboya T, Matsuyama Y, Subramanian SV, Kawachi I. Increased risk of dementia in the aftermath of the 2011 Great East Japan Earthquake and Tsunami. Proc Natl Acad Sci U S A. 2016 Oct 24. pii: 201607793. [Epub ahead of print]

Sharot T, Martorella EA, Delgado MR, Phelps EA. How personal experience modulates the neural circuitry of memories of September 11. Proceedings of the National Academy of Science. 2007;104:389–394.

 

@dr_shibley

 

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