In this review, I’m presenting a selection of research articles published in October. As usual, many new interesting findings were made public this month, and the small selection in this article reflects mostly my personal opinion of their importance.

On the 9th of October, scientific community marked the birthday of Sir Peter Mansfield. Peter Mansfield received the 2003 Nobel Prize in Physiology or Medicine for his works on magnetic resonance imaging.

The research of Professor Mansfield laid both theoretical and technical foundation for acquisition of internal body images with the use of MRI and the development of methods of functional MRI. These days, fMRI is one of the most commonly used techniques in both neuroscience research and in clinical settings. In fact, around half of the studies listed below used MRI to get the experimental data.

THE BEST

Brains of young people and physically active elderly men function similarly

It is well established that physical activity and mental fitness are linked, and physically active older adults perform better in mental tests. But what exactly happens in the brain of older individuals with different levels of physical activity remained unknown.

In a new landmark study published this month, Japanese researchers have provided the answer to this question. It is known that younger people predominantly use the left side of their prefrontal cortex (PFC) while performing mental tasks. As we age, we start using both left and right PFCs – this broadening of brain area involved in the task performance is viewed as a compensation for the age-related reduced brain capacity. However, in physically active older people the left side PFC remains much more active during mental tasks. Apparently, their brains retain the youth-like mechanisms of mental activity for tasks involving memory and attention.

Cancer drug shown to be a promising memory enhancer

Nootropics, memory-enhancing compounds, have always fascinated both scientists and non-scientists alike. And yet another promising compound has appeared from a rather unexpected corner.

In the recently published study on animals, a drug currently called as RGFP966 and developed as a cancer therapeutic was demonstrated to enhance memory and facilitate making the connections between neurons. Scientists think that this compound might be developed into treatment for Alzheimer’s patients, helping them to better retain memories.

Simple test for Lewy Body disease suggested

Although Lewy Body Dementia (LBD) is the second most common neurodegenerative disorder, few people have ever heard of this condition. LBD is often diagnosed very late or, even worse, misdiagnosed and treated as a different condition. The lack of neurologists skilled in recognizing LBD worsens the problem further.

A newly developed simple and fast test called “Lewy Body Composite Risk Score” (LBCRS) will help greatly in addressing this problem. The test is a one-page questionnaire that can be filled in three minutes. Despite its apparent simplicity, its accuracy in diagnosing early-stage LBD is almost 97%. Such accuracy and simplicity have a potential to make a huge difference for millions of affected patients.

Rehearsal helps to store memories

Most of our memories are short-lived. The mechanism of forming long-term memories is different from the one involved in the short-term retention of the current flow of information. Although we still don’t know the details of how long-term memories are formed and stored, we know that the crucial part of brain in this process is the posterior cingulate.

New findings by British scientists published this month demonstrate that this region of brain becomes activated when we actively try to remember important information by rehearsing it. Researchers have shown that simple rehearsal of information immediately, or as soon as possible after obtaining it, helps to integrate new memories into the brain and allows one to successfully recall them 1-2 weeks after the event. Information that is not rehearsed becomes largely forgotten after this period of time.

Surprisingly high mutation rates in neurons

One interesting and rather unexpected discovery was published this month in Science. Using the new technology of single-cell genome sequencing, researchers from Howard Hughes Medical Institute were studying mutations in individual neurons from the human brain. It turned out that an average neuron contains more than 1,000 different mutations, mostly in the actively expressed parts of their DNA. This rate of mutations is significantly higher than in other somatic cells, but neither its mechanisms nor functional significance is clear at the moment.

The discovery adds yet another dimension to the complexity of brain organization and poses more questions that need to be answered. In the meantime, the scientists have demonstrated that the mutation data can be successfully used to trace the history and origin of individual neurons. This will help us to attain a better picture of brain development.

THE WORST

Diet high in fructose detrimental for recovery after brain injury

The consumption of high amounts of fructose is linked to a range of chronic and serious conditions such as diabetes, cancer, fatty liver disease and obesity.

New research data show that excessive fructose consumption can also slow down the recovery from traumatic brain injury and concussion. In the animal study published this month, the efficiency of recovery from TBI was reduced by 30% in mice kept on high-fructose diet. Unfortunately, fructose is plentiful in Western diet, with average American consuming almost 8 teaspoons of fructose daily.

Mechanism of forgetting memories discovered

Neuroscientists are naturally interested in mechanisms of memory formations. The mechanisms for forgetting memories, however, receives relatively little attention. The working assumption was that the memories naturally disappear when they are not evoked or used on a regular basis. Swedish researchers took a closer look to the phenomenon of forgetting, with rather surprising results.

It turned out that our brain has a specific dedicated mechanism for forgetting memories, in which memories considered less important get actively erased. Scientists believe that this is done to conserve energy since maintaining association pathways is an energetically costly process.

Male and female brains are not as different as previously thought

In the last few years we have witnessed a significant number of publications pointing to various differences in male and female brain. With clearly different behavioral traits between sexes, it is tempting to explain them by gender-related differences in brain structure. Many research publications claimed that the size of hippocampus, a part of brain involved in consolidating our memories, which appears to be larger in females. However, the results of new meta-analysis published this month do not confirm this view.

Researchers combined and analyzed data from 76 studies involving more than 6,000 individuals. Although some smaller studies observed gender-related differences in the size of hippocampus, large statistical data demonstrate that these differences are either very small or trivial.

No clear link between IQ and brain size

Another recent meta-analysis of large statistical data helped to debunk a long-held view that our intellectual abilities are linked to the absolute size of our brain.

Combined together with various published data on the brain size and IQ of 8,000 individuals, scientists found that the connection between the two is small and statistically insignificant. Clearly, many opinions in neuroscience are still based on popular beliefs rather than firm data!

Smoking is an overdose/addiction risk factor in the use of painkiller codeine

Codeine, a commonly prescribed painkiller, is known to cause its pain-relieving effect by converting into morphine in the liver. The extent of pain-relieving effect of the compound, however, varies significantly among patients, even when the blood level of morphine is the same.

New research data demonstrate that codeine can get converted to morphine not only in the liver but also in the brain, and the level of morphine in brain determines the strength of codeine’s effect. Alarmingly, the level of codeine-converting enzyme in the brain is significantly elevated in smokers, apparently under the influence of nicotine. This may lead to generation of much higher level of morphine in response to a standard codeine dose, and thus may lead to overdose and even addiction, with prolonged drug administration. Although the exact dose-effect relationship in smokers is not yet established, this is something healthcare professionals should take into consideration when prescribing codeine.

References

Agrawal R et al. Dietary fructose aggravates the pathobiology of traumatic brain injury by influencing energy homeostasis and plasticity. J Cereb Blood Flow Metab, 2015. doi: 10.1177/0271678X15606719

Bieszczad, K., Bechay, K., Rusche, J., Jacques, V., Kudugunti, S., Miao, W., Weinberger, N., McGaugh, J., & Wood, M. (2015). Histone Deacetylase Inhibition via RGFP966 Releases the Brakes on Sensory Cortical Plasticity and the Specificity of Memory Formation Journal of Neuroscience, 35 (38), 13124-13132 DOI: 10.1523/JNEUROSCI.0914-15.2015

Bird, C., Keidel, J., Ing, L., Horner, A., & Burgess, N. (2015). Consolidation of Complex Events via Reinstatement in Posterior Cingulate Cortex Journal of Neuroscience, 35 (43), 14426-14434 DOI: 10.1523/JNEUROSCI.1774-15.2015

Galvin JE (2015). IMPROVING THE CLINICAL DETECTION OF LEWY BODY DEMENTIA WITH THE LEWY BODY COMPOSITE RISK SCORE. Alzheimer’s & dementia (Amsterdam, Netherlands), 1 (3), 316-324 PMID: 26405688

Hyodo, K., Dan, I., Kyutoku, Y., Suwabe, K., Byun, K., Ochi, G., Kato, M., & Soya, H. (2015). The association between aerobic fitness and cognitive function in older men mediated by frontal lateralization NeuroImage DOI: 10.1016/j.neuroimage.2015.09.062

Lodato, M., Woodworth, M., Lee, S., Evrony, G., Mehta, B., Karger, A., Lee, S., Chittenden, T., D’Gama, A., Cai, X., Luquette, L., Lee, E., Park, P., & Walsh, C. (2015). Somatic mutation in single human neurons tracks developmental and transcriptional history Science, 350 (6256), 94-98 DOI: 10.1126/science.aab1785

McMillan, D., & Tyndale, R. (2015). Nicotine Increases Codeine Analgesia Through the Induction of Brain CYP2D and Central Activation of Codeine to Morphine Neuropsychopharmacology, 40 (7), 1804-1812 DOI: 10.1038/npp.2015.32

Pietschnig, J., Penke, L., Wicherts, J., Zeiler, M., & Voracek, M. (2015). Meta-analysis of associations between human brain volume and intelligence differences: How strong are they and what do they mean? Neuroscience & Biobehavioral Reviews, 57, 411-432 DOI: 10.1016/j.neubiorev.2015.09.017

Rasmussen, A., Zucca, R., Johansson, F., Jirenhed, D., & Hesslow, G. (2015). Purkinje cell activity during classical conditioning with different conditional stimulus explains central tenet of Rescorla–Wagner model Proceedings of the National Academy of Sciences DOI: 10.1073/pnas.1516986112

Tan, A., Ma, W., Vira, A., Marwha, D., & Eliot, L. (2016). The human hippocampus is not sexually-dimorphic: Meta-analysis of structural MRI volumes NeuroImage, 124, 350-366 DOI: 10.1016/j.neuroimage.2015.08.050

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