Every month, hundreds of research articles are published in the field of neuroscience. Obviously, this short review cannot cover them all. Here I highlight some new research data that I found particularly interesting and important. Some of them were publicized in popular media while others received very little attention.

Two particularly interesting articles related to our perception of emotions and pain were published this month.

The level of our stress hormones is surprisingly sensitive to our surroundings. It can rise, for instance, even from being in the same room as a complete stranger. Apparently, this almost unnoticeable rise in stress level makes us significantly less empathic. Researchers asked student volunteers to rate the pain of a stranger or a friend whose hand was immersed in the bucket of ice-cold water. Invariably, the pain of a friend was rated higher. Another group of students took a drug blocking the stress hormone before the test. This group, being not stressed any more, felt the pain of stranger more deeply. This observations may give some clues to the apparent lack of empathy towards other people during times of social upheaval. Elevated stress level appears to block the neuronal pathways involved in considering the feelings of others.

A second study looked at emotional support and pain during childbirth. Medical professionals often encourage the presence of a partner at the delivery to alleviate the pain of the woman. But does it really work this way? New research data obtained in a small study performed by British scientists cast serious doubts on the wisdom of having a romantic partner around during a painful medical treatment. In their experiments, researchers subjected female volunteers to painful, but tolerable, laser pulses to their finger in the presence and absence of their significant others. Women were asked to rate the level of pain, which was also monitored via measuring brain activity by electroencephalography (EEG). A significant proportion of women reported stronger pain in the presence of their partners. EEG confirmed that the level of pain in these cases was indeed higher. Obviously, pain in a finger and pain during child birth are two rather different things. However, this is a wake-up call to have a serious look into the issue and not leave it to the matter of opinion alone.

Continuing with the medical theme, the four articles below are definitely worth mentioning.

Our body weight is not a simple balance of calories in and calories out – the level of fat burning is also regulated by the brain. Two hormones, leptin and insulin, work together to inform the brain about the level of body fat. More specifically, the hormones interact with proopiomelanocortin (POMC) neurons in the hypothalamus. In the situations when the hormones signal excessive level of fat deposits, POMC neurons send signals instructing some cells of fat tissues to burn fat. The molecular mechanisms behind this process are still being investigated, but researchers believe that there is a good possibility to develop a drug that will be able to interfere in this neuronal signalling and increase the rate of fat burning.

Brain-acting fat-burning pills might be still many years away. In the meantime, lots of people take pills that help prevent the build-up of cholesterol, a common problem associated with the excessive body weight. Cholesterol-controlling statins are probably the most commercially successful modern medicines, and their use is on the rise. However, a number of reports suggest that the drugs from this class may cause cognitive problems. Since 2012, FDA requests that statin labels must show this warning of potential harm. A group of researchers from Brown University has re-examined this claim by performing a meta-analysis of available information which included the data from 27,643 patients. They found no evidences that statins affect mental abilities of people with normal brain or worsen the mental state of people with neurodegenerative diseases. Scientists assume that previously reported harmful effects of statins might have been associated with overdose or the presence of some other medical conditions. Clearly, further studies are needed to reach the final verdict on this issue.

Brain injuries such as concussions are not often easy to detect and diagnose. Readily visible symptoms do not reflect the extent of brain trauma. As a result, scientists tried to find a reliable blood marker, an easily detectable compound generated in the course of brain injury that can be used for diagnostic purposes. Multiple markers are used to this end in the detection of various diseases such as cardiovascular problems and cancers. However, in case of brain injuries the issue is complicated by the existence of brain’s own waste removal system, which can also be affected by the injury. This results in unreliable and fluctuating levels of potential blood markers. Researchers from the University of Rochester concluded that the whole biomarker approach might not be useful in the diagnostic of traumatic brain injuries. This is disappointing, particularly taking into account how many millions of dollars were spent to search for such markers.

Parkinson’s disease affects growing number of people worldwide. For patients with this severe progressing neurodegenerative disorder that affects motor neurons, the risk of falls is a serious problem associated with large number of injuries, pain and limitation of activity. Australian researchers checked if an exercise program of moderate intensity would help in improving the conditions of Parkinson’s patients. It turned out that six month-long program of balance and leg strengthening exercise (30-40 minutes, three times per week) helped to reduce the frequency of falls by 70% among the patients with mild form of disease. In people with more advance condition, the exercise program did not reduce the risk of falls, but still helped in improving the physical and psychological well-being. This is yet another confirmation that exercise is good for our health, whatever is our age and medical history.

It is sometimes really surprising how little we know about the basic brain functions. Two perfect illustration of this come in the January issue of Nature magazine.

In one article, scientists from Howard Hughes Medical Institute published their findings on the neural mechanisms involved in the regulation of thirst. The general assumption was that this basic system must be really simple – dehydration should activate certain brain circuits thus triggering water-seeking behavior. Well, it turned out that the brain has two separate centers, one of which triggers the thirst and the other depresses it. Activation of the first center makes even fully hydrated animals to drink much more, while activation of the second center represses the thirst even in extremely thirsty animals. This makes sense from the evolutionary point of view – the existence of thirst-suppressing center may not only help animals to adapt to the inhospitable conditions in deserts but also give them clear survival advantage in evolution.

The second article investigates the mechanisms of fear. Fear is vital for our survival – we all have to be able to recognize dangers and avoid them. But the question how the alarm is triggered in the brain was never properly investigated. Scientists from Cold Spring Harbour Laboratory and Stony Brook University found that this life-preserving neural circuit is located in the paraventricular nucleus of the thalamus (PVT). The PVT is responsible for recognizing and forming the memories of threats, and for activating of other brain regions in the appropriate response. Chemical signalling in this circuit involves brain-derived neurotrophic factor (BDNF) as a messenger. Genetically modified mice with absent BDNF had impaired ability to recognize danger even after conditioning. On the other hand, infusion of animals’ brains with excess of BDNF caused excessive response to dangers. Scientists believe that in humans this newly discovered circuit is also involved in the formation of phobias and anxiety.

Continuing with the subject of how our brain works, two articles below will certainly be interesting for many readers.

If you spend lots of time pondering rather trivial questions before making your decisions, you might be relieved to learn that such strategy appears to be evolutionary programmed in our brain. “Degree of certainty” is rather subjective category, especially when evidences are not abundant. In the absence of clear evidence, we tend to hesitate before making a decision. You may argue that this hesitation allows brain to better analyze the existing evidences, but new research study suggest that the amount of time spent on the decision-making is in itself a confidence-improving factor. Researchers subjected human volunteers to a test where they needed to figure out the direction of the dots movements on a very noisy computer screen. After various periods of time watching the screen the subjects were reported both their conclusion and the level of confidence. Obviously, the level of confidence was higher when the movement of dots was better visible. In those cases when the answer was less than obvious, increased amount of time spent on decision-making improved the level of confidence, even when the final answers were wrong. Researchers concluded that deliberation time informs certainty because it serves as a proxy for task difficulty.

The questions “what makes us smarter than other primates?” and “what makes some of us much smarter than the rest of us?” still wait to be answered. A correlation between the area of cortical surface and intellectual ability in both evolution and childhood development was noticed long ago. Now scientists have shown that higher intellectual abilities, such as better visuospatial reasoning abilities, are particularly strongly linked to certain highly expanded cortical regions, especially anterior cingulate. Individuals whose brain features larger expansion of these regions have better cognitive functions. Obviously, these findings themselves do not explain why some people have higher IQ, but it points to the areas of the brain where further research on our intellectual capabilities should be focused.

References

Martin LJ, Hathaway G, Isbester K, Mirali S, Acland EL, Niederstrasser N, Slepian PM, Trost Z, Bartz JA, Sapolsky RM, Sternberg WF, Levitin DJ, & Mogil JS (2015). Reducing Social Stress Elicits Emotional Contagion of Pain in Mouse and Human Strangers. Current biology : CB PMID: 25601547

Krahe, C., Paloyelis, Y., Condon, H., Jenkinson, P., Williams, S., & Fotopoulou, A. (2015). Attachment style moderates partner presence effects on pain: a laser-evoked potentials study Social Cognitive and Affective Neuroscience DOI: 10.1093/scan/nsu156

Dodd, G., Decherf, S., Loh, K., Simonds, S., Wiede, F., Balland, E., Merry, T., Münzberg, H., Zhang, Z., Kahn, B., Neel, B., Bence, K., Andrews, Z., Cowley, M., & Tiganis, T. (2015). Leptin and Insulin Act on POMC Neurons to Promote the Browning of White Fat Cell, 160 (1-2), 88-104 DOI: 10.1016/j.cell.2014.12.022

Ott, B., Daiello, L., Dahabreh, I., Springate, B., Bixby, K., Murali, M., & Trikalinos, T. (2015). Do Statins Impair Cognition? A Systematic Review and Meta-Analysis of Randomized Controlled Trials Journal of General Internal Medicine DOI: 10.1007/s11606-014-3115-3

Plog, B., Dashnaw, M., Hitomi, E., Peng, W., Liao, Y., Lou, N., Deane, R., & Nedergaard, M. (2015). Biomarkers of Traumatic Injury Are Transported from Brain to Blood via the Glymphatic System Journal of Neuroscience, 35 (2), 518-526 DOI: 10.1523/JNEUROSCI.3742-14.2015

Canning, C., Sherrington, C., Lord, S., Close, J., Heritier, S., Heller, G., Howard, K., Allen, N., Latt, M., Murray, S., O’Rourke, S., Paul, S., Song, J., & Fung, V. (2014). Exercise for falls prevention in Parkinson disease: A randomized controlled trial Neurology, 84 (3), 304-312 DOI: 10.1212/WNL.0000000000001155

Oka, Y., Ye, M., & Zuker, C. (2015). Thirst driving and suppressing signals encoded by distinct neural populations in the brain Nature DOI: 10.1038/nature14108

Penzo, M., Robert, V., Tucciarone, J., De Bundel, D., Wang, M., Van Aelst, L., Darvas, M., Parada, L., Palmiter, R., He, M., Huang, Z., & Li, B. (2015). The paraventricular thalamus controls a central amygdala fear circuit Nature DOI: 10.1038/nature13978

Kiani, R., Corthell, L., & Shadlen, M. (2014). Choice Certainty Is Informed by Both Evidence and Decision Time Neuron, 84 (6), 1329-1342 DOI: 10.1016/j.neuron.2014.12.015

Fjell, A., Westlye, L., Amlien, I., Tamnes, C., Grydeland, H., Engvig, A., Espeseth, T., Reinvang, I., Lundervold, A., Lundervold, A., & Walhovd, K. (2013). High-Expanding Cortical Regions in Human Development and Evolution Are Related to Higher Intellectual Abilities Cerebral Cortex, 25 (1), 26-34 DOI: 10.1093/cercor/bht201

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