Tag Archives: cerebral cortex

Detailed new map of human brain reveals almost 100 new regions

The human brain is one of the most complex phenomena known to man and despite extensive research, scientists have yet to fully understand it. Although a complete grasp of the nature of the human brain is still far-off, a new study by researchers from the Washington University School of Medicine brings us closer to this goal in the form of a detailed new map of the outermost layer of the brain, revealing almost 100 new regions.

The detailed new map of the human brain's cerebral cortex. Credit: Matthew Glasser and Eric Young

The detailed new map of the human brain’s cerebral cortex. Credit: Matthew Glasser and Eric Young

The outermost layer of the brain, referred to as the cerebral cortex, is a layer of neural tissue that encases that rest of the brain. It is the primary structure involved in sensory perception, attention, and numerous functions that are uniquely human, including language and abstract thinking.

In the new study, the team divided the cortex of the left and right cerebral hemispheres into 180 areas based on physical differences such as cortical thickness, functional differences and neural connectivity.

“The brain is not like a computer that can support any operating system and run any software,” said David Van Essen of the Washington University School of Medicine and senior author of the paper. “Instead, the software – how the brain works – is intimately correlated with the brain’s structure—its hardware, so to speak. If you want to find out what the brain can do, you have to understand how it is organized and wired.”

Matthew Glasser, lead author of the study, spearheaded the research after he realized that the current map of the human cortex – created by German neuroanatomist Korbinian Brodmann in the first decade of the 20th century – just wasn’t cutting it for modern research.

“My early work on language connectivity involved taking that 100-year-old map and trying to guess where Brodmann’s areas were in relation to the pathways underneath them,” Glasser said. “It quickly became obvious to me that we needed a better way to map the areas in the living brains that we were studying.”

Using data from 210 healthy young adults, both male and female, the team took measures of cortical thickness and neuronal cable insulation and combined them with magnetic resonance imaging (MRI) scans of the brain at rest as well as during simple tasks.

“We ended up with 180 areas in each hemisphere, but we don’t expect that to be the final number,” Glasser said. “In some cases, we identified a patch of cortex that probably could be subdivided, but we couldn’t confidently draw borders with our current data and techniques. In the future, researchers with better methods will subdivide that area. We focused on borders we are confident will stand the test of time.”

In the future, such cortical maps could be created on an individual basis and help in the diagnosis and treatment of neurological or psychiatric illnesses such as dementia and schizophrenia.

Journal Reference: A multi-modal parcellation of human cerebral cortex. 20 July 2016. 10.1038/nature18933

Smoking thins vital part of the brain – quitting reverses the effect

If you’re a smoker, I’ve got some (more) bad news for you – long term smoking thins the cerebral cortex, the outer layer of the brain, responsible among others for memory, perception and language. The good news is that if you quit smoking, then the effect is reversible.

The cerebral cortex is the outer layer
depicted in dark violet. Image via Wiki Commons.

The history of smoking can be dated to as early as 5000 BC, but it wasn’t until the 19th and 20th century that the practice became widespread throughout the globe. Today, smoking (mainly tobacco smoking) is practiced by some 1.1 billion people; in other words, every 1 in 3 adults in the world smokes. This is a huge issue, because smoking is known  to cause a number of major health issues (including lung cancer and cardiovascular diseases). Now, you can add another problem to that long list: smoking thins the cerebral cortex.

This study involved 244 male and 260 female subjects. While this is not the first study to look at the link between tobacco and cortical thickness, it’s 5 times bigger than previous studies. All of the subjects were examined as children in 1947 as part of the Scottish Mental Survey, and then reexamined in recent times.

“We found that current and ex-smokers had, at age 73, many areas of thinner brain cortex than those that never smoked. Subjects who stopped smoking seem to partially recover their cortical thickness for each year without smoking,” says the study’s lead author Dr. Sherif Karama, assistant professor of psychiatry at McGill University, psychiatrist at the Douglas Mental Health University Institute and an affiliate of the Montreal Neurological Institute.

However, the recovery process is slow and incomplete. Even after quitting for 25 years, the cortex isn’t back to its full thickness, but the improvement is significant.

Annual per capita cigarette consumption rates. Gray countries have no data available. (Max Fisher / Washington Post)

It’s noteworthy that  the cortex tends to get thinner as you age as well, but smoking accelerates the process.

“Smokers should be informed that cigarettes could hasten the thinning of the brain’s cortex, which could lead to cognitive deterioration. Cortical thinning seems to persist for many years after someone stops smoking,” says Dr. Karama.

Journal Reference: S. Karama, S. Ducharme, J. Corley, F. Chouinard-Decorte, J.M. Starr, J.M. Wardlaw, M.E. Bastin, I.J. Deary. BTBD3 Controls Dendrite Orientation Toward Active Axons in Mammalian Neocortex.  Molecular Psychiatry, Published Online February 10 2015. doi: 10.1038/mp.2014.187