Does Grey Matter?

Aug. 8, 2014

By Medical Discovery News

The brain

What do brain scientists and fans of E. L. James have in common? They are both passionate about shades of grey. Results from a recent study in the scientific journal “Molecular Psychiatry” indicate that grey matter really does, well, matter. This study shows that the thickness of grey matter in the brain may be linked to intelligence and may also explain why some people have learning difficulties.

Grey matter is the outermost region of the brain, a layer of tissue two to four millimeters thick covering the brain on both sides with a wrinkled surface. Underneath the grey matter, also called the cerebral cortex, is the white matter of the brain, the cerebrum.

Grey matter is responsible for some major human functions including awareness, attention, consciousness, language, thought, and memory. Previous studies have shown that animals with bigger brains generally have thicker cortexes, but there has not been a strict link between intelligence and the thickness of the grey matter until now. 

For this new study, researchers at King’s College London’s Institute of Psychiatry obtained brain scans and DNA samples from 1,583 14-year-olds. They also tested the verbal and nonverbal intelligence of these subjects. Using DNA analysis, scientists looked for gene variants that could be responsible for the intelligence differences of this group. This proved to be a daunting task as they discovered more than 50,000 gene variants associated with brain development. However, with the help of computation biology, researchers uncovered some astounding results. Those with one particular gene variant caused by a single nucleotide polymorphism (or change) had thinner grey matter on the left side of their brains. And, these same individuals tested lower on the intelligence tests. 

Called NPTN, this gene encodes a protein that works in brain cells called neurons. The variant of NPTN affects communication between neurons in the brain, thereby explaining its impact on important functions of grey matter. Additional experiments suggest the NPTN variant may have more of an effect in the left side of the brain than the right side. This may correlate to lower intelligence due to the function of this important gene and its encoded protein in the left brain. 

While important, NPTN is not the only thing that determines intelligence – a multitude of other genes and environmental influences are clearly involved as well. However, this gene may provide new clues as to how intelligence is built in humans. Also, it will be interesting to see if this gene variant is associated with cognitive diseases like autism or psychological disorders like schizophrenia. 

Thanks to the new B.R.A.I.N. initiative that funds basic and translational research, we look forward to better understanding the human brain, arguably one of the most important human organs we know the least about. 

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Do We Smell the Same Thing?

Feb. 7, 2014

By Medical Discovery News

Do We Smell the Same Thing?

Have you ever wondered if we all sense the world in the same way? Evidence suggests that the sense of smell is highly individualized, based on genetic differences. This could revolutionize scents and food flavors into custom-designed creations for individuals.

Humans have specialized neuronal cells within the lining the nasal cavities, part of what’s called the olfactory epithelium. The surface of these cells, like much of the nasal cavity, is covered with mucus. Odor molecules dissolve into this layer and are detected when they bind to receptors on the neurons. This sets off a string of biochemical events that produces a signal, which travels along the olfactory nerve to the olfactory bulb of the brain. Then that signal is transferred to different regions of the brain’s cerebrum. Here odors can be distinguished and characterized. These signals are stored in long-term memory, which is linked to emotional memory. That’s why particular smells can evoke memories. This process is quite complex due to the highly evolved sense of smell in humans.

The genes that are involved in olfactory or smell sensations are not well understood. People do perceive odors differently, but researchers have only identified genes for certain odors. For example, human perception of cilantro has been linked to the olfactory receptor OR6A2 and grassy odors have been linked to receptor OR2J3.

New Zealand scientist Dr. Richard Newcomb tested the ability of almost 200 people to smell 10 different chemicals associated with the key odors of things like apples and blue cheese. Then these individuals’ genomes were completely sequenced, and genetic variances that could account for these olfactory differences were determined. For four of the chemicals tested, clusters of genes were identified as being able to detect these odors. Interestingly, these genes were located on different chromosomes. Newcomb’s work almost doubled the number of genes known to be connected with the sense of smell. For beta-ionone, a chemical associated with the smell of violets, a single gene was shown to allow people to sense that fragrant flower’s scent. Overall, the result of this study was that people are capable of experiencing chemical smells in different ways.

This opens the door for scientists to define an individual’s olfactory profile. If it’s understood how an individual perceives smells, a chef could personalize food just for their senses. Imagine walking into a restaurant and handing your server a card with your olfactory profile based on your genes. And violá! A dinner prepared with the seasonings and flavors you find most pleasing. With continued research, our sense of smell may be able to experience this scenario and more. 

For a link to this story, click here.