New Information On Facial Recognition and the Fusiform Gyrus

The Face is the Mirror of the Mind1

By Ajay K. Singh, MBBS, FRCP, MBA
January 9, 2017

Most people will not have heard of the fusiform gyrus. The Latin word “fusus,” meaning spindle is the origin for the area of the brain that lies within the temporal lobe (colored yellow in the illustration below).

brain illustration showing the location of the fusiform gyrus

The function of the fusiform gyrus is nicely described in this overview of the limbic system:

“If someone were to experience damage to their fusiform gyrus, they would be unable or have trouble identifying the faces of people they know. As well as face blindness, they would also have trouble processing colors. They might also have trouble reading. Complete removal of the fusiform gyrus would be a crippling blow to the way someone perceives the world and the way they interact with it. Not being able to recognize one’s own mother would be traumatic for anyone.”

A fascinating article in the January 6, 2017 issue of Science describes how children develop anatomical changes in the brain that co-occur with functional changes that expand their ability to recognize faces. In an NPR “All Things Considered” story, Jon Hamilton interviews the first author, Jesse Gomez from Stanford. According to Gomez, additional neurons are not added to the fusiform gyrus. Rather, the brain becomes more connected and denser in some areas (in their experiment, in the facial recognition but not the place recognition area). This contrasts to a 30-year old view of brain development, based on a paper by Rakic and colleagues, also published in Science, that from childhood onward “synaptic pruning” occurs in the brain – essentially molding the brain by getting rid of synapses.

According to Rakic and his colleagues, “Synaptic density increased for several months after birth before beginning to decline in all layers and areas.”

Quoting from the Jon Hamilton article: “You can imagine a 10-foot by 10-foot garden, and it has some number of flowers in there,” Gomez says. “The number of flowers isn’t changing, but their stems and branches and leaves are getting more complex.”

Gomez and colleagues examined the brains of 22 children between 5 and 12 years of age as well as 25 adults between 22 and 28 years of age. They used functional and quantitative MRI as well behavioral tests to evaluate face and place recognition.

Gomez’s data shows that children showed no significant differences in performance between the face and place recognition tests, but that adults performed significantly better at face recognition than place recognition. Their MRI tests demonstrated that the improvement in face recognition was associated with microstructural proliferation of the cortical area of the fusiform gyrus.

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So, the bottom line is that growing behavioral/functional demand for facial recognition occurs in parallel with targeted neuroanatomical changes in the fusiform gyrus of the brain. The whole brain doesn’t grow, only a specific part.

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1Quote attributed to St. Jerome

Ajay Singh, MBBS, FRCPDr. Ajay K. Singh is the Senior Associate Dean for Global and Continuing Education and Director, Master in Medical Sciences in Clinical Investigation (MMSCI) Program at Harvard Medical School. He is also Director, Continuing Medical Education, Department of Medicine and Renal Division at Brigham and Women’s Hospital in Boston.

*OPINIONS EXPRESSED BY OUR AUTHORS ARE VALUABLE TO US AT LEAN FORWARD, BUT DO NOT REPRESENT OFFICIAL POSITIONS OR STATEMENTS FROM HARVARD MEDICAL SCHOOL.

Why Do We Take Less Risk As We Age?

 

By Ajay K. Singh, MBBS, FRCP, MBA
December 19, 2016

An article on December 16 in the Washington Post about the relationship between risky behavior, age, and grey matter caught my eye.

The theoretical construct behind this body of research is as follows: with healthy aging, there is progressive loss in grey matter volume in the right posterior parietal cortex (rPPC). The less grey matter in the rPPC, the greater aversion there is to taking risk.

Several metanalyses support a relationship between aging and less risk behavior (Mata R, et al, Ann. N. Y. Acad. Sci. 2011; Mata R, et al Psychol. Sci., Best R., Psychol. Aging 2015). Yale investigators Michael Grubb and colleagues in Nature Communication, tease out the relationships between age and grey matter volume with aversion to risk.

Grubb et al designed an experiment where he asked 52 adults age 18 to 88 years old to participate in a game that required them to make a binary choice of either choosing a guaranteed monetary gain ($5) or participating in a lottery where there was a risk of losing or the opportunity of winning between $5 and $120. All choices were made while the subjects were in an MRI scanner.

The Yale investigators observed that risk tolerance decreased monotonically within the 18-88 year age range. Analysis of the data using regression models demonstrated an independent relationship between rPPC and risk tolerance that did not change when controlling for age or gender.

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The conclusion of the experiment was that grey matter volume, rather than chronological age per se, determined aversion to risk. They state: ” Though both older age and decreased rPPC GMV are associated with risk tolerance, when the independent contributions of these factors are assessed, rPPC GMV still accounts for changes in risk tolerance, whereas age does not. These results refine and extend our existing understanding of the relationship between aging and risk tolerance by attributing behavioral changes to an age-related process (that is, changes in grey matter thickness) rather than to chronological age itself.”

This research confirms something that we’ve all appreciated for many years. Younger people tend to take more risk, and this willingness to tolerate risk attenuates with age. Grubb and colleagues provide some neuroanatomical proof to back this up.

Ajay Singh, MBBS, FRCPDr. Ajay K. Singh is the Senior Associate Dean for Global and Continuing Education and Director, Master in Medical Sciences in Clinical Investigation (MMSCI) Program at Harvard Medical School. He is also Director, Continuing Medical Education, Department of Medicine and Renal Division at Brigham and Women’s Hospital in Boston.

 

*OPINIONS EXPRESSED BY OUR AUTHORS ARE VALUABLE TO US AT LEAN FORWARD, BUT DO NOT REPRESENT OFFICIAL POSITIONS OR STATEMENTS FROM HARVARD MEDICAL SCHOOL.