Best and Worst of Neuroscience and Neurology – April 2016by Viatcheslav Wlassoff, PhD | May 8, 2016
This article presents a selection of research papers on the subject of neuroscience and neurology published in April. As usual, many new interesting findings were made public this month, and the selection presented here reflects mostly my personal opinion of their importance.
In April, the scientific community marks the birthday of Italian neuroscientist Rita Levi-Montalcini. Together with Stanley Cohen, Levi-Montalcini was a recipient of the 1986 Nobel Prize in Physiology and Medicine for her discovery of nerve growth factor. Rita Levi-Montalcini died in 2012 at the age of 103. Even in the last years of her life she remained very active both professionally and in politics.
Interaction between beta-amyloid and tau proteins leads to the development of Alzheimer’s disease
For decades, there were two competing theories to explain the pathogenesis of Alzheimer’s disease. One theory claimed that the major culprit in this process is the protein called beta-amyloid that forms characteristic plaques, while the second theory linked the development of Alzheimer’s to the deposition of the protein tau. It appears that the article published this month provides a definite answer: both proteins are important. The authors have demonstrated that beta-amyloid and tau enhance each other’s toxicity and thus cause together the cognitive dysfunctions observed in this neurodegenerative condition.
Drug for hypertension might be useful for treating brain tumor
Glioblastoma is one of the deadliest cancers with very few treatment options. In an effort to find a treatment for this tumor, researchers screened the library of existing medications and found that a known drug against hypertension, prazosin, might be very useful. In the animal models, the drug was shown to shrink the tumor and extend the survival by more than 50%. Re-purposing this anti-hypertensive agent for use against cancer might improve the clinical outcomes for thousands of patients.
Stem cells may help in repairing severe spinal cord injuries
Although stem cell therapy is potentially promising for repairing spinal cord injuries, large gaps in the spinal cord remain resistant to regeneration. A new approach developed by Japanese scientists may become a game changer, however. The scientists implanted the neural progenitor cells taken from rat embryos into the severed spinal cord of rats. The procedure promoted extensive regeneration of broken nerve fibers and resulted in much improved ability of rats to move their forelimbs. The approach is potentially applicable to humans too.
The next two articles deal with the fundamental question of connection between brain and intelligence: is it the size of the brain or its organization that really matters?
Bigger brain in humans is linked to bigger body
Scientists tend to assume that body size and brain size are the results of two different evolutionary processes and are, to a certain degree, independent. This assumption, however, was recently questioned by anthropologists. Evolutionary data on human ancestors indicate that the substantial increase in the body size during human evolution was driven by the increase in the size of brain. Body size and brain size are linked on the genetic level, and the increase in brain size caused the enlargement of body size.
Crows and ravens are as clever as primates, despite having smaller brains
But the size is definitely not the whole story and not the only factor in brain evolution. Recent research on the intelligence of birds such as ravens, New Caledonian crows and jackdaws has demonstrated that they are just as capable at solving intellectual problems as chimpanzees. These birds, however, have relatively small brains. Researchers believe that differences in the organization of their brain and neuronal density might be behind the extraordinary intelligence of these birds.
“Pain signature” on brain MRI scans incorrectly interpreted
Researchers studying mechanisms of pain and pain responses in the body might have been misled by some previous assumptions regarding how to interpret the MRI scan data. The pattern of brain activity that was observed in almost all MRI studied of pain and is considered as “pain signature” was also shown to be present in patients with genetic inability to feel pain. Researchers believe that this pattern is generated not in response to pain, but in response to the attention-grabbing sensory stimuli. The discovery questions the validity of wide range of data previously obtained using this pain signature.
Parkinson’s medication may cause impulsive behavior
One rather unexpected and a bit disturbing discovery published this month with regards to some commonly used medications for treating the symptoms of Parkinson’s disease. In some patients, dopamine agonists such as pramipexole and ropinirole were linked to impulsive behavior manifesting itself in various forms such as binge eating, compulsive gambling and shopping, and even hypersexuality. At least one of the impulsive control disorders is observed in 14% of Parkinson’s patients, with males being more frequently affected. Clearly, doctors and care providers should take a notice of this potential side effect.
Painkiller can make us prone to errors
Acetaminophen is a common and efficient painkiller, but the findings from a recent study point to a possibility of rather unexpected side effect: the drug may reduce our ability to notice errors. Physical pain and evaluative responses of the brain share some neural pathways. By reducing the pain, the drug also appears to reduce our ability to evaluate our action, which manifests itself in not noticing the errors. Although the scale of this problem in real life is hard to estimate, the patients should be informed on this potential side effect.
Excessive fructose consumption might be linked to multiple brain disorders
Researchers from UCLA have identified 700 genes in the hypothalamus and more than 200 genes in the hippocampus of rats that can become altered under the influence of fructose. A very common sweetener in Western diet, the chances are that excessive consumption of fructose might be linked to a range of brain disorders that involve the above genes. The list of conditions linked to these genes includes bipolar disorder, depression, Parkinson’s disease and many others.
Hay fever drugs might be harmful
The use of anticholinergic drugs commonly administered to counter the symptoms of hay fever, such as Clarityn and Piriton, were shown to correlate with declined cognitive performance and even with the loss of brain cells and connections. The study published this month also demonstrates that people taking this drugs have reduced glucose metabolism, thus hinting to diminished brain activity. The authors could not tell if the drugs in question cause this effect, but the finding clearly point to the presence of correlation.
Grabowski, M. (2016). Bigger Brains Led to Bigger Bodies?: The Correlated Evolution of Human Brain and Body Size Current Anthropology, 57 (2), 174-196 DOI: 10.1086/685655
Kabadayi, C., Taylor, L., von Bayern, A., & Osvath, M. (2016). Ravens, New Caledonian crows and jackdaws parallel great apes in motor self-regulation despite smaller brains Royal Society Open Science, 3 (4) DOI: 10.1098/rsos.160104
Kadoya, K., Lu, P., Nguyen, K., Lee-Kubli, C., Kumamaru, H., Yao, L., Knackert, J., Poplawski, G., Dulin, J., Strobl, H., Takashima, Y., Biane, J., Conner, J., Zhang, S., & Tuszynski, M. (2016). Spinal cord reconstitution with homologous neural grafts enables robust corticospinal regeneration Nature Medicine, 22 (5), 479-487 DOI: 10.1038/nm.4066
Assad Kahn, S., Costa, S., Gholamin, S., Nitta, R., Dubois, L., Feve, M., Zeniou, M., Coelho, P., El-Habr, E., Cadusseau, J., Varlet, P., Mitra, S., Devaux, B., Kilhoffer, M., Cheshier, S., Moura-Neto, V., Haiech, J., Junier, M., & Chneiweiss, H. (2016). The anti-hypertensive drug prazosin inhibits glioblastoma growth via the PKC -dependent inhibition of the AKT pathway EMBO Molecular Medicine, 8 (5), 511-526 DOI: 10.15252/emmm.201505421
Meng, Q., Ying, Z., Noble, E., Zhao, Y., Agrawal, R., Mikhail, A., Zhuang, Y., Tyagi, E., Zhang, Q., Lee, J., Morselli, M., Orozco, L., Guo, W., Kilts, T., Zhu, J., Zhang, B., Pellegrini, M., Xiao, X., Young, M., Gomez-Pinilla, F., & Yang, X. (2016). Systems Nutrigenomics Reveals Brain Gene Networks Linking Metabolic and Brain Disorders EBioMedicine DOI: 10.1016/j.ebiom.2016.04.008
Pascoal, T., Mathotaarachchi, S., Mohades, S., Benedet, A., Chung, C., Shin, M., Wang, S., Beaudry, T., Kang, M., Soucy, J., Labbe, A., Gauthier, S., & Rosa-Neto, P. (2016). Amyloid-? and hyperphosphorylated tau synergy drives metabolic decline in preclinical Alzheimer’s disease Molecular Psychiatry DOI: 10.1038/mp.2016.37
Ramirez-Zamora, A., Gee, L., Boyd, J., & Biller, J. (2016). Treatment of impulse control disorders in Parkinson’s disease: Practical considerations and future directions Expert Review of Neurotherapeutics, 16 (4), 389-399 DOI: 10.1586/14737175.2016.1158103
Randles, D., Kam, J., Heine, S., Inzlicht, M., & Handy, T. (2016). Acetaminophen attenuates error evaluation in cortex Social Cognitive and Affective Neuroscience DOI: 10.1093/scan/nsw023
Risacher, S., McDonald, B., Tallman, E., West, J., Farlow, M., Unverzagt, F., Gao, S., Boustani, M., Crane, P., Petersen, R., Jack, C., Jagust, W., Aisen, P., Weiner, M., Saykin, A., & , . (2016). Association Between Anticholinergic Medication Use and Cognition, Brain Metabolism, and Brain Atrophy in Cognitively Normal Older Adults JAMA Neurology DOI: 10.1001/jamaneurol.2016.0580
Salomons, T., Iannetti, G., Liang, M., & Wood, J. (2016). The “Pain Matrix” in Pain-Free Individuals JAMA Neurology DOI: 10.1001/jamaneurol.2016.0653
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