New research from the US suggests that emotions triggered by events can endure longer than factual recollection in patients with severe amnesia; the researchers hope their findings will increase understanding of Alzheimer’s and related diseases and also bring comfort to caregivers and families in the knowledge that their loved ones may continue to feel the warmth of visits and conversations even if they can’t remember what happened.
You can read about the research by scientists at the University of Iowa (UI) in Iowa City in the 12 April early online edition of the Proceedings of the National Academy of Sciences, PNAS.
Lead author Justin Feinstein, a student in the UI graduate programs of neuroscience and psychology, told the media that:
“A simple visit or phone call from family members might have a lingering positive influence on a patient’s happiness even though the patient may quickly forget the visit or phone call.”
However, he also described the downside:
“On the other hand, routine neglect from staff at nursing homes may leave the patient feeling sad, frustrated and lonely even though the patient can’t remember why,” said Feinstein.
Feinstein and colleagues studied five patients with a rare case of memory loss due to damage to their their hippocampus that caused new memories to disappear.
The hippocampus is critical for transferring memories from short-term to long-term storage, and is one of the first regions of the brain to suffer damage in Alzheimer’s disease.
The researchers showed the patients short extracts of sad and happy films; although they couldn’t remember details of the films, they retained the emotions elicited by what they had watched.
Each patient watched 20 minutes of a sad film, underwent memory and mood tests, then on another day, they watched 20 minutes of a happy film and had the same tests.
The researchers observed that the films induced the appropriate emotion in the patients, ranging from laughing out loud while watching the happy films to tears during the sad films.
About 10 minutes after watching a film clip, Feinstein and colleagues tested the patients’ factual memories to see how much they could remember about it.
A person with a non-impaired memory would be expected to remember about 30 details from each film clip, but these patients’ memories were severely imparied: one patient couldn’t recall a single detail.
Then they asked the patients another set of questions to gauge their emotional state.
Feinstein said that they still felt the emotion, explaining that “sadness tended to last a bit longer than happiness, but both emotions lasted well beyond their memory of the films”.
“With healthy people, you see feelings decay as time goes on. In two patients, the feelings didn’t decay; in fact, their sadness lingered,” he added.
The researchers concluded that the findings suggest “both positive and negative emotional experiences can persist independent of explicit memory for the inducing event,” and provide “direct evidence that a feeling of emotion can endure beyond the conscious recollection for the events that initially triggered the emotion”.
These results appear to challenge the idea that wiping out a painful memory abolishes the associated emotional suffering, and stress the importance of attending to the needs of people with Alzheimer’s disease.
According to a 2009 report from Alzheimer’s Disease International (ADI), 35 million people worldwide will have dementia this year, and the number is set to double every 20 years, reaching 115.4 million by 2050.
The greatest risk factor for Alzheimer’s is age, and there is currently no cure, said Feinstein.
“What we’re about to face is an epidemic. We’re going to have more and more baby boomers getting older, and more and more people with Alzheimer’s disease. The burden of care for these individuals is enormous,” he added, urging that:
“… we need to start setting a scientifically-informed standard of care for patients with memory disorders. Here is clear evidence showing that the reasons for treating Alzheimer’s patients with respect and dignity go beyond simple human morals.”
The Fraternal Order of Eagles, the National Institutes of Health, the National Science Foundation and the Kiwanis International Foundation, funded the research.
“Sustained experience of emotion after loss of memory in patients with amnesia.”
Justin S. Feinstein, Melissa C. Duff and Daniel Tranel
PNAS, published ahead of print April 12, 2010.
Source: University of Iowa, ADI.
Written by: Catharine Paddock, PhD