Posts Tagged ‘medial prefrontal cortex’

The Happiness U-Curve

March 16, 2017

This post is based on a section with the same subtitle in “The Cognitive Upside of Aging” an article by Alexandra Michel in the February 2017 “Observer”, a publication of the Association of Psychological Science (APS).

Despite all the negative components of aging, researchers consistently find a happiness paradox:  As the body declines, happiness tends to increase.  Across the lifespan this “Positivity effect” follows a U-shaped pattern:  happiness starts out high in late adolescence, bottoms out in middle age, and reaches a second zenith in old age.

A 2011 Gallup analysis of 500,000 phone interviews found that “a septuagenarian is far more likely than someone in their 30s to have high emotional health.  This happiness advantage held true even after controlling for demographic factors, including gender, race, education, marital status, employment, and regional location.

This happiness U-shape appears across the world.  Economists Andrew Oswald and David G. Blanchfower documented this pattern in more than 500,000 people living in more than 70 different countries.  Their analysis concluded that from Azerbaijan to Zimbabwe, people around the world tend to be happiest in their old age regardless of their nationality.

Oswald says, “Only in their 50s do most people emerge from the low period.  But encouragingly, by the time you are 70, if you are still physically fit then on average you are as happy and mentally healthy as a 20 year old.  Perhaps realizing that such feelings are completely normal in midlife might even help individuals survive this phase better.”

This universality of happiness U-curve implies the aging may play a positive role in the brain.  A team of Australian researchers led by Leanne Williams, who is now at the Stanford University School of Medicine, argues that a combination of neurological changes and life experiences account for this phenomenon.  Using functional magnetic resonance imaging (fMRI) to monitor emotional processing as people of various ages viewed photographs of different facial expressions, the researchers found that older people were more emotionally stable and less reactive to negative emotional stimuli than younger people.

Contrary to the ubiquitous negative stereotypes of declining memory and cognitive integrity, Williams and colleagues found emotional well-being may increase with normal aging.  Their study included 242 individuals (122 males and 120 females) divided up into four major age categories:  12-19 years, 20-29 years, 30-49 years, and 50-79 years.  Participants were assessed in the scanner for the neural activation evoked by emotions of threat and happiness depicted in facial expressions.  After being shown a photograph of a face, participants had to select the best option for identifying the emotion being displayed in the photograph.  They also rated on a 1-to-5 scale, the intensity of the emotion being displayed.
Rather than showing an inevitable decline across all functions, the images displayed a linear increase in emotional stability with age, meaning that people in their 70s ultimately experience better emotional well-being than most people in their 20s.

The fMRI results suggest that as we age, the way our brains process emotional stimuli  changes in ways that favor emotional stability.  The brain scans indicated that the medial prefrontal cortex (mPFC), which is a brain area involved in the governance of emotional functions, processed stimuli differently across the lifespan, contributing to better emotional stability for older adults.  As we age, the mPFC areas become increasingly active while processing negative emotions compared with positive ones, suggesting that older people were comparatively better at controlling negative emotions.

This article ends as follows: “Ultimately Williams and colleagues argue that as we age this combination of neural processing, as well as an accumulation of life experience, provides older adults with the neural tools to take life in stride—a capability their younger counterparts will just have to wait for.”

Can You Remember Things that Never Happened?

March 24, 2016

This post is based largely on portions of the fourth chapter in Elixir J. Sternberg’s Book “Neurologic and the Brain’s idea Rationale Behind Our Irrational Behavior.” The title of this post is the same as the title of Chapter 4.  Regular readers of the health memory blog should know the answer to the question posed in the title.  The answer is “yes.”  Elizabeth Loftus and others have done extensive research in this area.  They have a variety of methodologies for implanting false memories so that they are definitely believed.  I saw an example of one of these experiments on the PBS program NOVA.  In this case the research participants were convinced of a crime that they never had committed.  To find previous posts on this topic enter “Loftus” into the search block of the healthy memory blog.

Sternberg begins the chapter with a quote from Gabriel Garcia Marquez that largely captures the workings of our memories.  “He was still too young to know that the heart’s memory eliminates the bad and magnifies the good, and that thanks to artifice we manage to endure the burden of the past.”

A research group in Israel filmed a young woman, with no history of memory problems for two days straight.  Except for the cameras they were ordinary days.  At various intervals over the next few years she filled out questionnaires that tested her memories of those days.  The researchers used fMRI while she was filling out these questionnaires.  Over time the more distorted her memory became for the details.  What was especially interesting was how her brain activity changed over time while filling out the recall questionnaires.  As time passed and the memory errors accumulated, her memory appeared to be less endless reliant on the activity of the hippocampus.  The fMRI revealed reduced activation there as her recollection became more distant.  Other regions of the brain, including the medial prefrontal cortex and associated regions, became more and more active.  The medial prefrontal cortex is associated with self-centered thinking.  Her memory was accessing not simply a record from a neurological file, but a representation stored across multiple systems.  Her memory drifted away from accurately recording the details of that time period and instead became focused on her.

“To a large extent, our memories define us.  Our personal history forges our self-image and assembles our store of knowledge.  When the unconscious system in the brain encodes our memories, it is shaping who we are.  It doesn’t record our experiences impartially as a video camera would, because it focuses on our role in the story, on the aspects that we care about.   At any given moment, there is a context of how we are feeling, our emotions at that instant, what we are expecting or dreading, and what that moment means to us.  It is on that basis that the brain begins to compose its first draft.”

Three years after 9/11, two groups of New York City residents were enrolled in an experiment to learn how their emotions at the time of the attacks might have affected their memory.  The first group of people who were in downtown Manhattan that day close to the World Trade Center, and who personally witnessed the events of that day,  The second group consisted of people who were in midtown several miles away.  As would be expected, the downtown group rated their memories as being more vivid, more complete, and more emotional instances that the midtown group did.  And they had more confidence in the accuracy of their memories, but the neurological results revealed a different story.

The hippocampus is the area key to episodic memory, of which recalling 9/11 is a conspicuous example, but depending on the type of memory being accessed, other areas of the brain may be recruited to varying degrees.  For example, the amygdala may be activated when the memory is of an emotional nature, and the posterior parahippocampal cortex will become more involved when the brain attempts to access the more meticulous spatial details surrounding the event.  The members of the midtown group showed activation of the posterior  parahippocampal cortex as they recalled the details of 9/11, but only trivial amygdala activity.  It was just the opposite for the downtown group.  They exhibited striking activity in the amygdala but not in the posterior parahippocampal cortex.  This neuroimaging suggests that the downtown group recalled the events of the day for their emotional impact at the expense of remembering peripheral details.  Studies have revealed that the more emotionally  affected people are in recalling 9/11, the better they are at consistently describing the central events of what happened to them that day, but the worse they are at providing reliable description of the emotionally  neutral details.

There is a technical difference between telling a lie and confabulation.  A person telling a lie knows that he is telling a lie.  However, a person confabulating is trying to make a coherent story where substantial memory loss has occurred.  The chapter begins and ends with a man with both severe mental and addiction problems and a faulty memory.  He continually tries to put together a coherent story from the scraps of memory he can access, because he does not want to admit that he does not know.  Although his is a clinical case, we all work to make coherent stories from what memories we can find.  The unconscious system takes a self-centered egocentric approach to construct good narratives.