Losing our minds in middle age

When negative stress affects our well-being, we sometimes feel like we are losing our minds...

But when in the lifespan does this really happen? When do we lose our brains?

Until age two we experience rapid growth of brain cells, or neurons. Around that age, rarely used neurons and unneeded connections between neurons (synapses) are reduced. Past research by Hedman, van Haren, Schnack, Kahn, and Hulshoff (2012) suggests that childhood is a time of brain growth, with more neurons being produced. Starting around age thirteen and continuing through adolescence we see brain volume loss as pruning reoccurs so that our brains can be more efficient. Most of young adulthood sees little change in brain volume, but starting at age 35, MRI scans demonstrate a yearly loss of about 0.2% of brain volume. This loss accelerates in older age: in our sixties this increases to a loss of about 0.5% of brain volume every year; this acceleration is often given as one of many explanations for other normal declines associated with aging.

To examine in detail the brain volume loss during the transition to midlife, Guo, Isohanni, Miettunen, Jääskeläinen, Kiviniemi, Nikklinen, Remes, Huhtaniska, Veijola, Jones, and Murray (2016) examined MRI scans of 43 men and 23 women as they aged from their 30s (33-35 years) to their 40s (42-44 years). The participants in this longitudinal study were part of the Northern Finland 1966 Birth Cohort so they should have had similar experiences in their lives as they grew up at the same time. The researchers' goals were to measure overall brain volume at both ages, to identify the locations of any loss as observed in the second MRI performed when the participants were in their 40s, and to clarify any sex differences that emerged.

Total brain volume decline was higher than predicted by past research: on average men lost 3.21% and women lost 4.03%. This sex difference was very small but it reached statistical significance, meaning that the difference was unlikely to be due to chance.

The location of loss also showed a sex difference. After taking into account percentage of total brain loss, Guo et al. found that men lost most of their neurons in the midline areas (specifically: bilateral precentral gyri; bilateral paracingulate gyri; and bilateral supplementary motor cortices). Most of these areas relate to motor skills and one may be involved in decoding certain emotions.

Women's loss was more spread out with most of it occurring in the outer brain (specifically: bilateral frontal parietal; temporal lobe; occipital cortex; cerebellum). These areas relate to language, motor skills, sensory interpretation, vision and visual memories, and emotion association.

Guo et al. did not make guesses beyond a quick mention of hormones as to what caused the sex differences in overall brain loss or the sex differences in loss locations. They also speculated that these differences may translate into differences in midlife men's and women's health or behavior, yet they did not offer any examples.

That leaves us all free to speculate. One bit of demographic information that caught my eye was that the researchers coded participants on "parental leave" as working full-time, because it meant that the participants usually worked full-time but were absent from that work to take care of a newborn child. This made me think about other research related to brain volume and parenting. For example, when women are pregnant their brain volumes can shrink an average 4% and not return to normal volume until about six months after birth. First, that makes the 4.03% decline found in Guo et al.'s female participants sound less ominous: this sort of decline is a normal experience for many women in young adulthood. Second, although most Finnish women in the 1980s usually started having babies at age 29, is it possible that some of the 23 women in this study gave birth just before the second MRI scan? Or is the location of brain loss during pregnancy similar to the location of women's brain loss in the transition to middle age?

Starting in the 80s, Finland offered parental leave to fathers as well as mothers. So it is possible that some of the male participants may have also identified themselves as being on parental leave. However, we know that fathers and mothers often take on different roles in parenting. For example, women are more likely to report that they get up to feed or care for babies in the middle of the night; mothers report more sleep loss than fathers even as children grow older. Poor sleep is associated with brain volume loss in the frontal, temporal, and parietal lobes. Different parental roles and related sleep loss may contribute to women's additional 1% of brain loss; brain volume loss related to poor sleep and brain volume loss related to women's transition to midlife are located in similar areas.

In the end we do not know what is causing these declines or sex differences, and even if we did, at this point we cannot know if these are related to any changes in men's and women's behavior or health as they age. The one thing you can know for sure is that if you are middle aged, pregnant, a new mother, or are sleep-deprived, you ARE losing your mind.

FURTHER READING:

The Guo et al. (2016) article can be accessed online or through your local college library.

Loss of brain cells does not always relate to loss of cognitive functioning. Read an APA Monitor on Psychology article by Melissa Phillips on the strengths of the middle-aged mind.

Childhood trauma can also reduce brain volume. Read a report on trauma's effects on brain development from the Child Welfare Information Gateway (U.S. Dept. of Health and Human Services).

BONUS:

Watch a video from Brown University on Synaptic Pruning:

Tryptophan saves the day?

This week in the United States we will celebrate Thanksgiving. In addition to feelings of gratitude, family gatherings can also stir up heated arguments about political issues and other differences between family members. Today's meme suggests that the neurotransmitter found in turkey meat, the centerpiece of most Thanksgiving feasts, may be an antidote to this problem:

Tryptophan naturally occurs in turkey meat and other common foods (including beans for vegetarians). Its presence in the brain has been linked to an increase in Serotonin, another neurotransmitter associated with positive mood and decreased aggression. Could eating Tryptophan-rich foods decrease fighting? An experiment with non-human subjects suggests that a touch of Tryptophan might help.

Walz, Stertz, Fijtman, dos Santos, and de Almeida (2013) divided male mice into five groups: four groups received a dose of Tryptophan that was 1%, 2%, 3%, or 10% of 30 ml of a carrier liquid; the last group was the control group so they did not get any Tryptophan in their liquid. Immediately after dosing, the mice were individually exposed to an intruder: a stranger male mouse. This encounter lasted for five minutes as the test mouse's behaviors were recorded. This experience occurred eight times for all male mice from the five groups.

When the animals' reactions were coded across these trials, Walz et al. found that the mice dosed with a 1% and 2% Tryptophan solution were less likely than the control group to aggressively bite or to threaten the stranger mouse from the side. The other doses did not show a significant reduction in these aggressive behaviors, and none of the doses was related to changes in non-aggressive behaviors, such as activity levels or grooming. At a low dose, Tryptophan is speculated to raise Serotonin levels enough to take the edge off this stressful experience; at larger doses it may be that Serotonin rises so high that it sends a feedback signal to the mouse's body to decrease Serotonin production thereby undoing any good effect of supplementation.

The authors concluded, "...that low doses of [Tryptophan] are able to reduce aggressive behavior in male mice....Tryptophan supplementation may be an alternative treatment for aggression in groups that exhibit such behavior" (p. 400). Of course, we can't be sure that the same dose of Tryptophan (especially if it is combined with cranberry sauce, mashed potatoes, and stuffing) would have the same effect on humans or that it would diminish verbal aggression as it did physical aggression. Walz et al. encouraged further research: "To control aggressiveness, a person's diet may be an important factor" (p. 397).

Until then, when discussions get heated at your next family gathering, try changing the subject to something that everyone can agree on. Until we know the details about Tryptophan we will apparently have to rely on Adele.

Further Reading:

The Walz et al. (2013) article is available online and the Psychology and Neuroscience journal article can be accessed through your local college library.

People used to think that the Tryptophan in turkey was responsible for that sleepy feeling so many of us have after the big meal. Find out what is more likely to blame in this Live Science piece by Tanya Lewis.

Why do family celebrations so often turn into family fights? Read Olga Khazan's article in The Atlantic:  "Why families fight during the holidays."

The creepy-crawlies: spiders and itching

Trigger warning: spiders; itching; psychology.

The creepy-crawlies. The heeby-jeebies. Makes my skin crawl. Many of us have these reactions when we see spiders:

Logically we know that spiders are unlikely to hurt us - in fact we can kill them quite easily - and that spiders are important parts of the ecosystem. Illogically we fear them and may be gripped with an illusory sensation that they are crawling upon us...producing itching that is very real. Why is this?

Some suggest that we may be evolutionarily wired to notice spiders and perceive them as a threat. New and German (2015) asked undergraduate students to perform a perceptual task: indicate if two crossed lines were equal or unequal in size each time they were briefly flashed on a screen. For most of the trials all that appeared on the screen were two lines in a cross shape, but for one trial another image was sneaked in next to the cross. This other image was either: a spider or a spider-like shape; a housefly or a fly-like shape; a hypodermic needle or a shape that was similar to a hypodermic needle. This is an "inattentional blindness" test because the participants have not been instructed to look for these things: their attention has only been directed to the lines so they should be "blind" or not notice other things. If participants do notice the other images, we can know that those images really stood out to grab their attention.

New and German found that the participants were much more likely to notice the spider or spider-like shapes than the other options. This was true even of participants who reported low fear of spiders and participants who reported high fear of needles. The authors believe that this represents an evolutionary wariness of spiders that has been passed down from our earliest ancestors in Africa where venomous spiders likely posed daily threats. In our modern world we are more likely to feel pain from an injection than truly be at risk from a dangerous spider bite - yet, spiders grab our attention more than needles.

If spiders grab our attention and make our skin crawl, when are we most likely to start scratching that imaginary itch? Llyod, Hall, Hall, and McGlone (2012) showed female undergraduates images related to itching, such as insects and skin rashes, and itch-neutral images, such as flying birds. As predicted, when participants viewed the itch-related images their self-reported levels of itchiness were significantly higher.

In addition to the self-reports, Lloyd et al. observed the participants' own scratching behavior and noted any scratching movement that lasted for more than one second. Out of all of the itch-related images, the photographs that included a person scratching him- or herself were associated with the most scratching from the participants. The authors suggest that feeling itch may be automatic but a scratching response may be triggered by a social situation that activates mirror neurons: brain cells that react the same to doing or watching a behavior.

When we put this all together, we know that your eyes are likely to be drawn to this guy if he is hanging out in your living room:

If your skin starts to crawl, you are normal: seeing insects and spiders makes us feel itchy. But you are most likely to scratch if you see your friends start scratching.

Further reading:

The New and German (2015) article is published in the journal Evolution and Human Behavior but is available online in draft form; the Lloyd et al. (2012) article can be accessed through your local college library.

Some individuals suffer from chronic, not just creepy-crawlies-induced itching. You can read more about recent findings related to this debilitating condition in this National Institute of Health article.

If you are thoroughly creeped out and itchy from reading this post, here is a totally unrelated video of a baby laughing to cleanse your palate. You are welcome.

Your right prefrontal cortex is working SO well today!

A quick way to annoy a professor is to miss a class, come back the next day and ask this teacher, "Did I miss anything important?" Out of anger or to be funny your professor might smile and answer sarcastically, "Oh, NOOOOOO...we NEVER do anything IMPORTANT in here. All we did was waste our time so you didn't miss ANYTHING important."  If you understand that this is sarcasm you will a) understand that you did miss something important and b) your professor is probably annoyed with you.

On the other hand, if you don't understand that this is sarcasm you would believe that you did not miss anything important and also not catch that your professor is irritated by your question. This latter situation is frustrating for everyone involved and it is also the topic of today's memes:

Sarcasm is a form of irony that requires some sophisticated cognitive processes to understand it. Most children do not understand sarcasm until their pre-teen years (and then it is SO fun for the parents when their kids say sarcastic things to them) and people with autism struggle with this throughout their lives. We also see that people with Alzheimer's Disease and individuals with certain types of brain damage may not catch when something is said sarcastically.

Shamay-Tsoory, Tomer, and Aharon-Peretz (2005) conducted a neuroscience study to pinpoint locations in the brain that are associated with the understanding of sarcasm. They compared 17 healthy people to 41 people who had brain lesions in very specific areas. The lesions were mostly the result of head injuries but a few were due to tumors or stroke, but none of the affected individuals had problems with speech or "general intellectual functioning" (reasoning ability and verbal fluency).

All participants were tested on their abilities to identify emotions communicated by vocal tone and facial expression, to recognize mistakes in social situations (faux pas), and to interpret sarcasm. Reading people's emotions from their tones and facial expressions is a necessary part of understanding sarcastic statements in which those things conflict with the literal meaning of what is said. Recognizing when a person has committed a faux pas is considered to be a good test of Theory of Mind. Theory of Mind is the ability to understand what another person is thinking - a skill that is required to decode sarcasm. 

The sarcasm task consisted of four stories that were always told in two ways: one that depicted a sarcastic remark and one that depicted a literal remark. For example (Shamay-Tsoory et al., 2005, p. 300):

             Joe came to work, and instead of beginning to work, he sat down to rest. His boss 

             noticed his behavior and said, "Joe, don't work, too hard!"

            Joe came to work and immediately began to work. His boss noticed his behavior and

            said, "Joe, don't work, too hard!"

The participants listened to the stories and after each version they were asked comprehension questions ["Did Joe work hard (p. 300)?"] and questions to assess sarcasm understanding ["Did the manager believe that Joe worked hard (p. 300)?"].

Shamay-Tsoory et al. reported small but statistically significant results: specifically, the participants who had the worst problem understanding sarcasm tended to have lesions in their right side prefrontal cortices. This was especially true for participants whose lesions went into the ventromedial portions of this area. Participants whose lesions were located in the posterior part of their brains did not have problems understanding sarcasm: they scored the same as the healthy individuals.

The authors state that these findings make sense in relation to the functions of these locations. The entire prefrontal cortex is associated with understanding language pragmatics or the social aspects of language. The right prefrontal cortex in particular helps us to: decode the parts of language related to feelings; to understand the parts of language that are not literal; to recognize faux pas; and to "get it" when somebody is being funny. The ventromedial area adds to our experience of empathy: being able to feel the emotions of other people. These cognitive skills are necessary to understand that a speaker is saying one thing but trying to communicate another - often angry or humorous - message.

This relationship was further reinforced because the participants with right prefrontal lesions also struggled with Theory of Mind (problems recognizing faux pas) and emotion identification (problems matching tone and facial expression to particular feelings). In past research these two skills were required to understand sarcasm.

So the next time an adult (who does not have autism or brain damage) does not understand your sarcasm...

instead of getting annoyed you can smile and simply remark, "Your right prefrontal cortex is working SO well today."

Further Reading:

You can access a pdf of the Shamay-Tsoory et al. (2005) article here thanks to the American Psychological Association.

A blogpost from the Gottman Institute: sarcasm might be fun when you are joking and having a good time, but if you are sarcastic when arguing with your partner this may predict the end of your relationship.

National Geographic Channel's "Brain Games" offers an online, interactive experience of the brain and language.