Subplate Neurons Control Neuronal Migration
When excitatory cortical neurons are "born" in the developing brain, they start out multipolar and they wander aboout slowly and aimlessly. Later they suddenly change to a bipolar shape and begin to migrate rapidly through the cortical layers along the glial cell scaffold. We have just learned how this transition occurs. Among the earliest developing neurons in the cortex are the subplate neurons, which form the subplate; they disappear when initial development is completed. A research team at the Tokyo Metropolitan Institute of Medical Science found that subplate neurons make synaptic contact with the multipolar neurons and release the excitatory neurotransmitter glutamate initiating the transition. When the researchers applied additional glutamate to developing neurons, radial migration was increased. This is the first evidence of synaptic activity in immature neurons; until now it was thought that synapses became functional only after the neurons matured. Science, Vol 360, 313-317.

Improving Stroke Recovery by Reducing Sensory Input
Stroke recovery depends greatly on remapping of functions onto nearby areas of the brain; this is often unreliable and incomplete, but this could be improved if recent results with mice can be applied to humans. The researchers induced stroke in the brain area responsible for processing sensation from the right forepaw; then they trimmed the whiskers (which serve an important sensory function) of half of the mice and kept them short.
     Within five weeks the mice with trimmed whiskers were using their right forepaws normally; the mice with untrimmed whiskers had not fully recovered after eight weeks. Brain imaging showed that the whisker-sensing brain area had taken over processing of sensations from the forepaw; when the whiskers regrew, the area processed input from the whiskers and the forepaw. The remapping was mediated by the protein Arc (activity-regulated cytoskeleton-associated protein), which is important for neural plasticity; mice deficient in the Arc gene did not show remapping or recovery. Science Translational Medicine (online), Vol. 10, Issue 426, eaag1328.

Infants With Stroke Recover Language in Right Hemisphere Strokes in infants are not rare; about one in 4,000 babies are affected shortly before, during, or after birth, and a study of these individuals has reaffirmed the plasticity of the developing brain. In 12 people aged 12 to 25 who had perinatal stroke damage to the left hemisphere language areas, all used the right side of their brains for language, and their language was normal. Some did have right side motor impairment or executive function impairment, such as slower neural processing. Annual Meeting of the American Association for the Advancement of Science, Feb 15-19, 2018.

Boy Recovers Functions After Lobectomy
At the age of 4 a boy developed a tumor and began having seizures; when he was 7 doctors removed the right occipital lobe and most of the temporal lobe. Three years later his intellect, visual perception, and recognition of faces and objects were all normal for his age. His only deficiency was the inability to see anything in his left visual field, which was due to the way the eyes are connected to the brain (see Figure 10.5, along with its description). Cell Reports, DOI: 10.1016/j.celrep.2018.06.099.





The Cost of Having a Big Brain
Brains require enormous energy to run, and a couple of decades ago the idea emerged that humans and other primates can afford their larger brains only by sacrificing elsewhere. Magdalena Mchlinski studied 10 species and found that primates with larger brain volumes had less muscle mass relative to their overall body mass. Anatomical Record, DOI: 10.1002/ar.23746.
   Additional evidence of the cost of big brains comes from a study of hibernation, which is not only a response to cold but to seasonal scarcity of food. In 1104 mammalian species studied, hibernation was correlated with smaller brains relative to body size. Primates mostly live in warmer climates, or at least evolved there, and only a handful hibernate. The three orders of lemurs that do hibernate have the smallest brains relative to their body size among primates. Once a species has evolved a large brain, it may be able to use its intelligence to move into a harsher environment and survive there; in fact there is evidence that successful invasive species have larger brains. Journal of Evolutionary Biology, DOI: 10.1111/jeb.13353.

Converting Astrocytes Into Neurons
Hongkui Deng and his colleagues at Peking University Health Science Center have developed a cocktail of drugs that activate genes in astrocytes so they develop into apparently functional neurons, with a neuron-like shape and the ability to transmit electrical signals. The work was done with mice, but if the neurons prove out the technique could be used to treat human neurodegenerative diseases like Alzheimer's and Parkinson's. bioRxiv, DOI: https://doi.org/10.1101/305185.

Hyperbaric Oxygen for Treating Concussion
Although an estimated one-quarter of military personnel serving in Iraq and Afghanistan sustained head injuries and there were 244 concussions among NFL players in 2016, there is no FDA approved treatment for concussion. Evidence is beginning to accumulate that numerous sessions of breathing pure oxygen in a pressurized chamber improves cognitive functioning and quality of life. Using MRI, researchers at Tel Aviv University found that in patients treated six months to 27 years after injury hyperbaric oxygen stimulated regrowth of neural fibers by 7% and blood vessels by 5% in brain regions involved in information processing and memory. Frontiers in Human Neuroscience, DOI.org/10.3389/fnhum.2017.00508 (online).

Football, Brain Trauma, and the NFL
In an update to the Boston University study of traumatic brain injury in football players (p 73 of the text) Boston University researchers have reported chronic traumatic encephalopathy (CTE) in 177 (87%) out of 202 brains of deceased former players. CTE is a buildup of abnormal tau protein, which can disable neural pathways and is a hallmark characteristic of Alzheimer's disease. Twenty-one percent of former high school players had CTE, and the numbers rose to 91% among college players and 99% of former National Football League players. Mood symptoms (impulsivity, depression, apathy, and anxiety) were typical of those with CTE. Suicide was the most prevalent cause of death among those with mild pathology (27%), while neurodegenerative causes (dementia- and parkinsonian-related) were most prevalent among those with severe CTE (47%). It should be noted that the sample was not representative, since relatives would have been more likely to donate players' brains because of symptoms they had observed; also, most of the players with CTE had played in the 1950s through the 1990s, before more stringent safety rules were introduced. Journal of the American Medical Association, Vol 318, 360-370.