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December 2021
- Ionel Sandovici at the University of Cambridge has discovered inside the foetus a tug-of-war between genes inherited from the father and from the mother. As the fetus grows inside the belly's mother, it needs to obtain more nourishment from the mother via blood vessels in the placenta, which means that the blood vessels have to expand for more nutrients to flow to the fetus. These blood vessels expand during gestation to a total length of about 320 kms. Sandovici investigated how the foetus issues the signal that cause the expansion of such blood vessels. It turns out that the signal, known as IGF2, sent to the placenta via the umbilical cord, has to be calibrated: too much IGF2 would cause too much growth, and too little would cause little growth. This balancing of signal is achieved through the tug-of-war between the igf2 gene inherited from the father, which tries to extract as much nourishment as possible from the mother, and the igf2r inherited from the mother, which tries to limit how much is given. (paper)
November 2021
- The sponge is an animal without a nervous system, so presumably they are evolutionarily a primitive species, much older than primates. Detlev Arendt’s student Jacob Musser at the European Molecular Biology Laboratory in Germany has worked out a detailed map of sponge cells and discovered that some cells called "neuroids" look like the ancestors of neurons because they use the genes involved in nerve cell signaling. They hang out in the digestive chambers of the sponge. We may be seeing the origins of the nervous system: these neuroids may represent the first stage of "brain" when the only function was to regulate feeding. Later these neuroids evolved into modules that were incorporated into the pre- and postsynapses of the nervous systems of higher animals. (paper)
- Thomas McHugh's team at the RIKEN Center for Brain Science has shown that the CA2 region of the hippocampus plays a key role in the process that consolidates memories during sleep. Memory consolidation is known to depend on brain wave patterns in the CA1 region of the hippocampus, which selectively reactivate neural circuits associated with short-term memories until they become long-term memories. CA2 is a different hippocampal region that contributes to this brain wave patterns in CA1. (paper)
October 2021
- Guangyu Robert Yang and Peter Yiliu at Columbia University, in collaboration with Columbia neuroscientists Richard Axel and Larry Abbott, have shown that a simple neural network to classify odors develops a structure that closely resembles what happens inside the olfactory system of the brain of the fruit fly (paper)
- Friedemann Zenke's team at the Friedrich Miescher Institute for Biomedical Research in Switzerland has found out a possible solution to the dilemma of how a mechanism to the puzzle of how the “neurons that fire together wire together” process can possibly work. Proposed in 1949 by Donald Hebb, this process should generate instable states according to computational models whereas in the brain they don't. (paper)
- Erin Rich's student Feng-Kuei Chiang at Mount Sinai Hospital has discovered a neural process that could be important for advanced cognitive abilities such as planning, strategizing and problem-solving. Information is distributed from single neurons to larger populations of neurons in the prefrontal cortex, achieving the kind of real-time organization of information required for higher-level cognitive tasks. (paper)
September 2021
- Zachary Mainen's student Cindy Poo at the Champalimaud Centre for the Unknown in Portugal is studying the role of the primary olfactory cortex in encoding spatial maps and therefore spatial navigation. In 1971 John O’Keefe at University College London discovered hippocampal neurons that act as “place cells”, that becomes active at specific locations so that, together, they encode an entire area, such that one can tell where a rat is simply by checking the condition of its brain's place cells (paper). Somehow these cells are connected to the olfactory system because animals use smell to find food and, in general, for spatial navigation and memory. The mystery is how this happens, since odor molecules do not carry spatial information. Somehow the brain must combine olfactory and spatial information. It turns out that the olfactory system is unique in the brain in having reciprocal connections to the hippocampus, the brain region which is involved in memory and navigation. Poo discovered a large population of neurons in the olfactory system that behave like the hippocampal place cells: they become active at specific locations. However, the map created in the olfactory system is less comprehensive than the one created in the hippocampus: it only covers significant places associated with rewards. (paper)
- Rafael de la Torre's team at the Hospital del Mar Medical Research Institute Foundation in Barcelona found cognitive benefits from the Mediterranean diet (paper)
August 2021
- If genes cause a predisposition to self-regulation disorders like addiction and anti-social behavior (collectively known as "externalizing"), we haven't found the responsible genes. But Danielle Dick's team at Virginia Commonwealth University, in collaboration with Philipp Koellinger of Vrije Universiteit Amsterdam, Kathryn Paige Harden of University of Texas at Austin and Abraham Palmer of UC San Diego, has identified 579 locations in the genome that relate to increased risk of such disorders. This genome-wide association study studied 1.5 million people. (paper)
July 2021
- Hilary Marusak's lab at Wayne State University has discovered that exercise spurs the release of the body’s natural cannabinoids, i.e. endocannabinoids (in particular the chemical messenger anandamide, the “bliss” molecule), which are tiny molecules made of lipids that that circulate in the body to maintain homeostasis in the brain and therefore have a variety of beneficial effects, such as pain relief, stress reduction and enhanced learning and memory. Endorphins, on the other hand, are unlikely to have an effect on mental health because endorphins cannot cross blood-brain barrier. (paper)
June 2021
- Mark Bear's students Dustin Hayden and Daniel Montgomery at MIT have shown that the brainwaves related to visual memory change as the visual pattern becomes more familiar. During this process within the visual cortex one circuit of inhibitory neurons (the parvalbumin neurons) with gamma rhythms of oscillations gets replaced by another circuit of inhibitory neurons (somatostatin-expressing neurons) with "slower", lower-frequency beta rhythms. (paper)
- Neurotheology is the field of neuroscience that investigates religious and spiritual minds. Michael Ferguson of Harvard Medical School, using lesion network mapping on 88 patients who were scheduled to undergo neurosurgery to remove brain tumors, has identified a specific circuit in the brain that seems to be related to religiosity and spirituality: the periaqueductal gray, a region located in the dorsal part of the pons, deep into the brainstem, a region that is known to be involved in pain modulation, fear conditioning, and altruism. (paper). See also the work of Orrin Devinsky and George Lai at New York University, who in 2008 observed that some patients with temporal lobe epilepsy experienced intense religious phenomena (paper).
May 2021
- Lauren Aguirre, author of "The Memory Thief", writes in the Scientist about "The Overlooked Power of Inhibitory Neurons". Most attention is usually reserved to excitatory neurons, the neurons that triggers electrochemical activity in neighboring neurons. Inhibitory neurons are not as numerous but their function, which is the opposite, seems important to properly modulate brainwaves. A single inhibitory neuron can coordinate the work of thousands of excitatory neurons, switching them on and off precisely to produce the correct rhythms for memory and other functions. The result of this coordination is brainwaves that we can measure, and this brainwaves reflect the flow of information within the brain. When inhibitory neurons don't work well, it's like a feedback device that stops working well in a motor: neurons fall out of synch and the brain machine doesn't work as well. One possible result is hyperactivity in the hippocampus, which is known to be associated with Alzheimer's disease. (paper)
April 2021
- Marcia Ponce de Leon and Christoph Zollikofer at the University of Zurich have been studying the brain of primitive hominids for a long time and established that modern brain structures evolved to between 1.7 million and 1.5 million years ago. They now concluded that the first human ancestors to migrate out of Africa had much more primitive brains than previously thought (paper).
March 2021
- There is evidence that SARS-CoV-2 affects the brain, and may result in neurological and neuropsychiatric symptoms: loss of taste, seizures, headaches, dizziness, reduced cognition, depression, etc. See, for example, Victor Montalvan's review at Texas Tech University Health Science Center (paper). SARS-CoV-2 can therefore considered a neurotropic virus. A neurotropic virus is a virus that is capable of infecting the nervous system. A vast variety of viruses from different families are capable of invading the nervous system by infecting different cell types. See, for example, Hideyuki Hara's classification (paper). Most research has focused on how viruses can infect neurons but other cell types are actually more likely to get infected. Petra Tavcar at the University of Ljubljana in Slovenia studied the role of astrocytes (astroglial cells). Astrocytes are important cells of the nervous system: they support the work of neurons in several ways and provide homeostasis in the brain. Unfortunately, astrocytes provide a favorable environment to support replication of viruses, i.e. they are more easily infected than neurons (in fact, they are usually the first cell type to be infected after viruses cross the blood-brain barrier) (paper)
February 2021
- Animals are incredibly good at recognizing that something is the same thing no matter the angle from which they see it. Earl Miller's student Scott Brincat at MIT have shown that this ability has to do with the transfer of a memory from one hemisphere to the other of the brain: mental images bounce between right and left hemispheres as they are processed by the visual system. The transfer between hemispheres involves a change in neural oscillation: the synchrony across hemispheres of very low-frequency "theta" waves (approximately 4-10 hertz) and high-frequency "beta" waves (~17-40 Hz) rises and the synchrony of "alpha/beta" waves (~11-17 Hz) declines. This "push-and-pull" pattern of rhythms is fascinating because it closely resembles the pattern that Miller's team has identified in other forms of information transmission within the cortex. Encoding and recalling memories seem to depend on similar patterns that combine theta and beta rhythms. This phenomenon may also hint at the way that information is encoded in the brain. The current consensus is that it is encoded by neural groups but here it looks like the same information can be encoded by different neural groups. (paper)
January 2021
- Edward Chang's team at UC San Francisco has found evidence that speech processing takes place in parallel in different regions of the brain, rather than sequentially as previously thought. Speech is processed in the auditory cortex on the temporal lobe of the cortex. The old view of this process was that first the primary auditory cortex processes the acoustic information of speech and then the superior temporal gyrus extracts linguistic features. However, the superior temporal gyrus seems to act independently of the rest. (paper)
- Since the study of a patient named Henry Molaison in 1953 (whose hippocampus was removed) we have known that the hippocampus is important for episodic memory. In the 1970s scientists identified the hippocampus neurons that encode memories of specific locations, the "place cells". The hippocampus is able to represent not only the events and their spatial information but also the temporal information (the "sequence" of events). However, for decades it remained a mystery which neurons encode the temporal information. In 2011, Howard Eichenbaum's student Chris MacDonald at Boston University discovered cells that keep track of time in a region of the hippocampus called CA1. Now MacDonald is at MIT in Susumu Tonegawa's lab and has identified the brain circuit that encodes the timing of events, proving that spatial and timing information are encoded by different parts of the hippocampus. (paper)
- A UC Berkeley team has measured the different brainwaves related to concentration, aimless wandering and unfocused. Robert Knight's student Julia Kam (now at the University of Calgary) and Alison Gopnik's student Zachary Irving (now at the University of Virginia) found that mind wandering (when the mind jumps from one topic to another) corresponded to increased alpha waves (slow brain rhythms whose frequency ranges from 9 to 14 Hertz) in the prefrontal cortex while P3 waves (weaker waves) pop up in the parietal cortex (paper). Irving had previously studied "mind wandering" from a philosophical viewpopint (paper). After all, mind-wandering takes up about half of our waking thoughts, but it is seldom studied in philosophy of mind.
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