In the latest issue of this monthly series digest you can learn how to transplant neurons, how dance and music training affect the brain, how dominance and aggressiveness are regulated in the female and male brain, and much more.
Social differences are regulated differently in males and females
A team of researchers led by Dr. Elliott Albers, director of the Center for Behavioral Neuroscience and Regents’ Professor of Neuroscience at Georgia State University, has discovered that serotonin (5-HT) and arginine-vasopressin (AVP) act in opposite ways in males and females to influence aggression and dominance. Because dominance and aggressiveness have been linked to stress resistance, these findings may influence the development of more effective gender-specific treatment strategies for stress-related neuropsychiatric disorders.
Prominent sex differences occur in the incidence, development and clinical course of many neuropsychiatric disorders. Women, for example, have higher rates of depression and anxiety disorders such as posttraumatic stress disorder (PTSD), while men more frequently suffer from autism and attention deficit disorder. However, little is known about the brain mechanisms underlying these phenomena differ in females and males.
In this study conducted in hamsters, the researchers investigated the hypothesis that 5-HT promotes and AVP inhibits aggression and dominance in females and that 5-HT inhibits and AVP promotes aggression and dominance in males. Their data show strong support for this hypothesis with the discovery that 5-HT and AVP act in opposite ways within the hypothalamus to regulate dominance and aggression in females and males. Their study also found that administration of the 5-HT re-uptake inhibitor fluoxetine, one of the most commonly prescribed drugs for psychiatric disorders, increased aggression in females and inhibited aggression in males. These studies raise the possibility that stress-related neuropsychiatric disorders such as PTSD may be more effectively treated with 5-HT-targeted drugs in women and with AVP-targeted drugs in men.
The next step will be to investigate whether there are sex differences in the efficacy of 5-HT- and AVP-active drugs in reducing social stress.
How to transplant neurons
Neuronal transplants (blue) connect with host neurons (yellow) in the adult mouse brain in a highly specific manner, rebuilding neural networks lost upon injury.
© Sofia Grade at NeuroscienceNews.
Researchers at the Max Planck Institute of Neurobiology in Martinsried, the Ludwig Maximilians University Munich and the Helmholtz Zentrum Munich have demonstrated that, in mice, transplanted embryonic nerve cells can be incorporated into an existing network and correctly carry out the tasks of damaged cells originally found in that region.
In their experiments, the team transplanted embryonic nerve cells from the cerebral cortex into lesioned areas of the visual cortex of adult mice. Over the course of the following weeks and months, they monitored the behavior of the implanted, immature neurons by means of two-photon microscopy to ascertain whether they differentiated into so-called pyramidal cells, a cell type normally found in the area of interest. “The fact that the cells survived and continued to develop was already very encouraging,” said Mark Hübener, joint leader of the study together with Magdalena Götz. But things got really exciting when the scientists took a closer look at the electrical signals of the transplanted cells. They were able to show that the new cells formed the synaptic connections that neurons in their position in the network would normally make, and that they responded to visual stimuli.
The team then went on to characterize, for the first time, the precise pattern of connections made by the transplanted neurons. Astonishingly, they found that pyramidal cells derived from the transplanted immature neurons formed functional connections with the appropriate nerve cells all over the brain. In other words, they received precisely the same inputs as their predecessors in the network. In addition, the cells were able to process that information and pass it on to the correct downstream neurons. “These findings demonstrate that the implanted nerve cells have integrated with high precision into a neuronal network into which, under normal conditions, new nerve cells would never have been incorporated,” explained Götz. The transplantation of young nerve cells into an affected network of patients for example with Parkinson’s disease, allow for the possibility of a medical improvement of clinical symptoms.
After Blindness, The Adult Brain Can Learn to See Again
More than 40 million people worldwide are blind, and many of them reach this condition after many years of slow and progressive retinal degeneration. The development of sophisticated prostheses or new light-responsive elements, aiming to replace the disrupted retinal function and to feed restored visual signals to the brain, has provided new hope. However, very little is known about whether the brain of blind people retains residual capacity to process restored or artificial visual inputs.
A new study published in the open-access journal PLOS Biology by Elisa Castaldi and Maria Concetta Morrone from the University of Pisa, Italy, and colleagues investigates the brain’s capability to process visual information after many years of total blindness, by studying patients affected by Retinitis Pigmentosa, a hereditary illness of the retina that gradually leads to complete blindness. Using functional magnetic resonance imaging (fMRI), the researchers found that patients were able to learn to recognize simple visual stimuli, such as flashes of light, and that this ability correlated with increased brain activity in visual cortex.
However, these results could only be achieved after extensive and prolonged training, which lead to only moderate improvements in patients' performance. It's a good sign that the more prolonged exposure to artificial vision lead to stronger responses in early visual cortex, suggesting that the brain is capable of learning to interpret the very crude, artificial vision that current retinal prostheses provide. On the other hand, there was no increase of BOLD activity in areas beyond the early visual cortex, such as the visual motion area hMT+ and associative cortices (e.g., intraparietal, superior temporal, and precuneus), suggesting that plasticity in late blind subjects might be limited to early sensory cortices.
In other neural prosthetics news, Second Sight Medical Products, Inc. announced the first successful implant of a cortical prosthesis ("Orion I") in an animal model. The Orion I technology is based on the FDA-approved Argus II Retinal Prosthesis System ("Argus II"), but with updates to the electrode neural interface—moving from the retina to the visual cortex. Implanted on the surface of the visual cortex located within the occipital lobe of the brain, Orion will bypass the retina and optic nerve altogether—offering hope for sight restoration in people with glaucoma, diabetic retinopathy, retinal detachments, and others. Fully functional prototypes are expected to be completed later this year with active animal implants scheduled to begin by Q1 2016; the first human clinical trials are planned to commence by Q1 2017. (SecondSight)
Researchers from the Life and Health Sciences Research Institute (ICVS) at the University of Minho (Braga, Portugal) found that a protein originally known to promote the growth of breast cancer cells is essential for the production of new neurons in the adult brain. (Molecular Psychiatry via NeuroscienceNews)
Researchers from the Allen Institute for Brain Science have completed the 3D mapping of the mouse cortex as part of the Allen Mouse Common Coordinate Framework (CCF): a standardized spatial coordinate system for comparing many types of data on the brain from the suite of Allen Brain Atlas resources. The CCF enables quantification and comparison of many types of data, including gene expression, connectivity, single cell characterization and functional imaging—across 1,675 specimens and 43 regions of the cortex. The end result is a template brain rendered faithfully in three dimensions, which serves as a useful guide to mouse brain anatomy as well as a platform for comparing data across many Allen Brain Atlas resources. (Allen Institute via NeuroscienceNews)
The reproducibility crisis continues. Previous research found that a patient with cortical blindness (homonymous hemianopia) was able to successfully avoid an obstacle placed in his blind field, despite reporting no conscious awareness of it. This finding led to the suggestion that normal obstacle avoidance behavior can proceed without input from the primary visual cortex. However, a new study tried to replicate this finding in a group of patients (N=6) and failed. As expected, all patients successfully avoided obstacles placed in their intact visual field. However, none of them showed reliable avoidance behavior—as indicated by adjustments in the hand trajectory in response to obstacle position—for obstacles placed in their blind visual field. These findings suggest that behavior in complex visuomotor tasks relies on visual input from occipital areas. (Cortex)
New research published in The FASEB Journal suggests that omega-3 polyunsaturated fatty acids, which are found in fish oil, could improve the function of the glymphatic system, which facilitates the clearance of waste from the brain, and promote the clearance of metabolites including amyloid-β peptides, a primary culprit in Alzheimer’s disease. (FASEB via NeuroscienceNews)
A new study published in NeuroImage by a team of researchers from the the International Laboratory for Brain, Music and Sound Research, proves that dance and music training have even stronger effects on the brain than previously understood—but in markedly different ways. They found that dancers and musicians differed in many white matter regions, including sensory and motor pathways, both at the primary and higher cognitive levels of processing. In particular, dancers showed broader connections of fiber bundles linking the sensory and motor brain regions themselves, as well as broader fiber bundles connecting the brain’s two hemispheres (in the regions that process sensory and motor information). In contrast, musicians had stronger and more coherent fiber bundles in those same pathways. (NeuroImage via NeuroscienceNews)