Some great research was published in May: groundbreaking findings, paradigm shifting discoveries, and new therapies. In this article, I share the most interesting news I came across in May. These are personal opinions, presented in no particular order and we welcome your comments and suggestions. If you have come across any interesting studies, do let us know in the comment section.

THE BEST

The mechanisms of deep brain stimulation for Parkinson’s disease

Deep brain stimulation (DBS) has been showing rather promising effects in different neurological conditions. In Parkinson’s disease, DBS has been widely used with good outcomes, but its mechanisms of action remain largely unknown.

Aiming at understanding how DBS may decrease Parkinson’s disease’s symptoms, a study published in Nature Neuroscience assessed the effect of DBS in neuronal synchronization in the brain. Neuronal activity in the primary motor cortex is synchronized in the healthy brain, and this pattern is essential for proper brain function. In Parkinson’s disease, synchronization is excessively high and is associated with motor symptoms. The authors observed that DBS induced a reduction in this excessively synchronized pattern of activity and that this effect was associated with motor symptom alleviation. This is a step forward in understanding DBS’s mechanisms of action in Parkinson’s disease.

Amnesia: unattainable memories recovered through light

A pretty interesting finding has been published in Science. It (literally) sheds light on how memory and amnesia works. The discussion on whether amnesia is due to actual memory loss or to an inability to retrieve them is long-standing; this study indicates that memories may in fact be kept but be unattainable. Most importantly, this work showed that these memories can be retrieved by using light to stimulate memory engrams (the physical substrate of memories, their neurons and synapses). The formation of memory is thought to be associated with synaptic strengthening, which was blocked in this study; the authors found that the stimulation of engram neurons using blue light pulses could recover the inaccessible memories. This may be a significant contribution to the progress of clinical memory restoration.

Retinal neurovascular crosstalk

A study published in The Journal of Clinical Investigation has demonstrated that a subset of retinal neurons is required for generating and maintaining the retinal vasculature; they also showed that the dysfunction of these retinal neurons can induce visual deficits. This work reveals the close association between retinal neurons and blood vessels and how their crosstalk can manage the neuronal oxygen requirements and the blood’s capability to supply it. Understanding these mechanisms allows a better grasp of how vision deficits may arise and, consequently, of how these may be overcome.

A new type of pluripotent stem cells

Pluripotent stem cells have numerous applications because they can become any type of tissue. Therefore, research on these cells is an important and thriving field. Research published in Nature accounts for an important finding in stem cell research.

In a serendipitous finding, researchers from the Salk Institute in La Jolla, California, unveiled a new type of pluripotent stem cell. While trying to implant human pluripotent stem cells into mouse embryos, they came across a previously unknown type of these cells, with unique features. They dubbed them region-selective pluripotent stem cells (rsPSCs). They showed that by modulating cell culture parameters, rsPSCs could be efficiently obtained from mouse embryos and primate pluripotent stem cells, including humans. By being easier to grow in vitro and in an embryo when injected into the right spot, these cells may offer significant advantages for regenerative medicine applications.

The inflammatory system in depression

An increased research interest in the role of the inflammatory system in depression has been observed in the last years. Many inflammatory mediators have been suggested as key players, but, in fact, it is still not clear whether inflammation is a cause or a consequence of depression. Childhood trauma is regarded as a vulnerability factor for the development of psychiatric disorders, and it is thought to act through the modulation of inflammatory and neuroplastic mechanisms throughout life. A review published in Frontiers in Cellular Neuroscience presents an overview on the role of inflammation and neuronal plasticity in the development of depression and discusses some of the underlying mechanisms. Understanding these mechanisms could be paramount for better therapeutic approaches.

THE WORST

GDF11 is not anti-ageing after all

A molecule that could delay (or even stop) aging would obviously be a major finding. Over the years, some candidates have appeared, always with a fair amount of hype. GDF11 was one of them: it had recently been reported that the production of this molecule decreases in older animals, and that restoring its levels could rejuvenate muscles, the brain, and the heart. However, a study published in Cell Metabolism challenges these results. This work showed the opposite: GDF11 may actually have an inhibitory effect on skeletal muscle regeneration. This paper even claims that the previous findings were based on faulty methods.

Sleep deprivation and performance impairment

Sleep deprivation can lead to a neurological state wherein an awake individual’s brain activity enters a momentary and localized sleep-like state called local sleep. Work presented in The Journal of Neuroscience showed that prolonged wakefulness significantly affects the individual’s visuomotor control and impulse control, inducing performance errors.

Using electroencephalography (EEG) recordings and functional magnetic resonance imaging (fMRI), the authors showed that there is a correlation between the occurrence of local sleep events and the decline in behavioral performance, and that this performance impairment may partially depend on loss of neuronal connectivity. EEG sleep-like patterns matched times of slower movements, visual inaccuracies, and decreased impulse control. The fMRI scans showed cognitive fatigue associated with localized neuronal disconnections.

Long-term effects of cannabis use in MS patients

Many multiple sclerosis (MS) patients use cannabis due to its efficacy in relieving pain, spasticity and insomnia. However, some reports suggest that cannabis consumption in MS patients may lead to long-term deleterious effects, namely deficits in episodic memory, attention, and executive functioning, and gray matter atrophy. Cognitive impairment occurs in approximately 40–60% of patients with MS, and is associated with structural and functional brain changes. A study published in Neuroimage: Clinical indicates that cannabis use in MS results in an increased cognitive impairment which correlates with volume reductions in different brain regions.

Hormone therapy for menopause and ovarian cancer

The effects of hormone therapy for menopause on ovarian cancer risk is a matter of obvious concern. The Lancet published a large epidemiological study addressing this issue and showed that ovarian cancer risk was significantly higher in women that had at some point used hormone therapy than in never-users. They also found that this risk was strongly related to how recently they had used hormone therapy, decreasing with time after cessation. Nevertheless, women who had used hormone therapy for at least five years and then stopped still showed a significantly higher risk of developing ovarian cancer. This study highlights the fact that most guidelines about hormone therapy do not mention ovarian cancer and shows that there is a clear need to revise them.

How socioeconomic inequality affects adolescent health

An article published in The Lancet highlights a rather unfortunate reality: socioeconomic inequality’s impact on adolescent health. Data from the “Health Behaviour in School-aged Children Study” was used, which included surveys from 34 North American and European countries in 2002, 2006, and 2010. It was found that, although from 2002 to 2010 average levels of physical activity, body mass index (BMI), physical symptoms, and life satisfaction slightly increased, socioeconomic inequality also increased in many domains of adolescent health. This study highlights how the increasingly unequal distribution of wealth affects adolescent health. This aids in the prediction of future inequalities in adult health and underlines the need for urgent political intervention.

References

Bernardi G, Siclari F, Yu X, Zennig C, Bellesi M, Ricciardi E, Cirelli C, Ghilardi MF, Pietrini P, & Tononi G (2015). Neural and behavioral correlates of extended training during sleep deprivation in humans: evidence for local, task-specific effects. The Journal of neuroscience : the official journal of the Society for Neuroscience, 35 (11), 4487-500 PMID: 25788668

Cattaneo A, Macchi F, Plazzotta G, Veronica B, Bocchio-Chiavetto L, Riva MA, & Pariante CM (2015). Inflammation and neuronal plasticity: a link between childhood trauma and depression pathogenesis. Frontiers in cellular neuroscience, 9 PMID: 25873859

Collaborative Group On Epidemiological Studies Of Ovarian Cancer, Beral V, Gaitskell K, Hermon C, Moser K, Reeves G, & Peto R (2015). Menopausal hormone use and ovarian cancer risk: individual participant meta-analysis of 52 epidemiological studies. Lancet, 385 (9980), 1835-42 PMID: 25684585

de Hemptinne C, Swann NC, Ostrem JL, Ryapolova-Webb ES, San Luciano M, Galifianakis NB, & Starr PA (2015). Therapeutic deep brain stimulation reduces cortical phase-amplitude coupling in Parkinson’s disease. Nature neuroscience, 18 (5), 779-86 PMID: 25867121

Egerman MA, Cadena SM, Gilbert JA, Meyer A, Nelson HN, Swalley SE, Mallozzi C, Jacobi C, Jennings LL, Clay I, Laurent G, Ma S, Brachat S, Lach-Trifilieff E, Shavlakadze T, Trendelenburg AU, Brack AS, & Glass DJ (2015). GDF11 Increases with Age and Inhibits Skeletal Muscle Regeneration. Cell metabolism PMID: 26001423

Elgar FJ, Pförtner TK, Moor I, De Clercq B, Stevens GW, & Currie C (2015). Socioeconomic inequalities in adolescent health 2002-2010: a time-series analysis of 34 countries participating in the Health Behaviour in School-aged Children study. Lancet, 385 (9982), 2088-95 PMID: 25659283

Romero, K., Pavisian, B., Staines, W., & Feinstein, A. (2015). Multiple sclerosis, cannabis, and cognition: A structural MRI study NeuroImage: Clinical, 8, 140-147 DOI: 10.1016/j.nicl.2015.04.006

Ryan TJ, Roy DS, Pignatelli M, Arons A, & Tonegawa S (2015). Memory. Engram cells retain memory under retrograde amnesia. Science (New York, N.Y.), 348 (6238), 1007-13 PMID: 26023136

Usui Y, Westenskow PD, Kurihara T, Aguilar E, Sakimoto S, Paris LP, Wittgrove C, Feitelberg D, Friedlander MS, Moreno SK, Dorrell MI, & Friedlander M (2015). Neurovascular crosstalk between interneurons and capillaries is required for vision. The Journal of clinical investigation, 125 (6), 2335-46 PMID: 25915585

Wu J, Okamura D, Li M, Suzuki K, Luo C, Ma L, He Y, Li Z, Benner C, Tamura I, Krause MN, Nery JR, Du T, Zhang Z, Hishida T, Takahashi Y, Aizawa E, Kim NY, Lajara J, Guillen P, Campistol JM, Esteban CR, Ross PJ, Saghatelian A, Ren B, Ecker JR, & Izpisua Belmonte JC (2015). An alternative pluripotent state confers interspecies chimaeric competency. Nature, 521 (7552), 316-21 PMID: 25945737

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