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Unexplored neural circuit modulates memory strength -- ScienceDaily

"We know with flies, just like in mammals, there are neurons involved in positive reinforcement, there are neurons involved in negative reinforcement -- the valence neurons -- and then there are this third set," Tomchik says. "Nobody really knew what they did." The fruit fly brain contains eight groups of neurons that produce dopamine. Three of them can be found in what's known as the fly brain's "mushroom body." Humans don't have an exact analogous brain section, but other brain regions perform similar functions. In Drosophila melanogaster, aka the fruit fly, the mushroom body is an area highly responsive to odors. Past fly brain studies have shown that one of the dopamine-producing groups projecting into the mushroom body handles desire-inducing memories connected to odors. ("Mmmm, rotten bananas!") while another guides avoidant behavior related to negative experiences. ("Yikes, dangerous banana smell!") To find out the role of the third group, referred to as PPL2, research associate and first author Tamara Boto, PhD, trained the flies with an experiment that involved exposing them to fruit-like odors while simultaneously giving them a mild electric shock. Their conditioned response could be visualized under a microscope by adding a green fluorescent protein that releases light upon reacting to calcium. Calcium ions are released when neurons communicate. Stimulating the PPL2 neurons during the odor experiments changed the brightness of the fluorescence when presented with the odor, an indication that the structures involved in learning and memory had altered the degree of response. "When we activated this PPL2 set of neurons, it would actually modulate the strength of that memory," Tomchik says. "So we see there are dopaminergic neurons that encode the aversive stimulus itself, and then there is this additional set that can turn the volume up or down on that memory."

Four Rules To Guide Expectations Of Artificial Intelligence

"Our unstated contract with the universe has been if we work hard enough and think clearly enough, the universe will yield its secrets, for the universe is knowable, and thus at least somewhat pliable to our will," Weinberger writes in Everyday Chaos: Technology, Complexity, and How We're Thriving in a New World of Possibility. "But now that our tools, especially machine learning and the internet, are bringing home to us the immensity of the data and information around us, we're beginning to accept that the true complexity of the world far outstrips the laws and models we devise to explain it."

Fireflies, Heart Beats, and the Science of Sync – Neuroscience News

“The perplexing feature of these particular states is that the Rockettes in our metaphor can only see their nearest neighbor, yet manage to be coordinating with their neighbor’s neighbor,” says lead author Matthew Matheny, a research scientist at Caltech and member of the Kavli Nanoscience Institute. “We didn’t know what we were going to see,” says Matheny. “But what these experiments are telling us is that you can get complexity out of a very simple system. This was something that was hinted at before but not shown experimentally until now.” “These exotic states arising from a simple system are what we call emergent,” says Roukes. “The whole is greater than the sum of the parts.”

Fireflies, Heart Beats, and the Science of Sync – Neuroscience News

But it has also been observed since the early 2000s that these networks, even when consisting of identical oscillators, can spontaneously flip out of sync and evolve into complex patterns. To better understand what is going on, Roukes and colleagues began to develop networks of oscillating nanomechanical devices. They started by just connecting two, and now, in the new study, have developed an interconnected system of eight. To the team’s surprise, the eight-node system spontaneously evolved into various exotic, complex states. “This is the first experimental demonstration that these many distinct, complex states can occur in the same simple system,” says co-author James Crutchfield, a visiting associate in physics at Caltech and a professor of physics at UC Davis.

Applying a network perspective to human physiology: Physicist describes 'network physiology,' which looks at different organ systems and how they relate to each other -- ScienceDaily

"We need to show how the different systems communicate with each other and adjust, coordinate and stay in sync," said Ivanov. The human body, according to this view, can be thought of as a network, with each organ serving as a node connected to other organs and other nodes. "The nodes are not just dots," he said. "They're dynamical systems, constantly changing in time, as are the connections between them." Today's best hospitals aren't equipped to monitor the inter-organ interactions. "Separate devices keep track of separate functions, but no single monitor can observe a multitude of functions," he said. To improve health monitoring techniques, Ivanov and his colleagues have spent the past decade developing the computational tools and biomedical devices needed to capture data streams from different organ systems and see how they relate to each other.

An Expanded View of Complex Traits: From Polygenic to Omnigenic: Cell

In summary, many complex traits are driven by enormously large numbers of variants of small effects, potentially implicating most regulatory variants that are active in disease-relevant tissues. To explain these observations, we propose that disease risk is largely driven by genes with no direct relevance to disease and is propagated through regulatory networks to a much smaller number of core genes with direct effects. If this model is correct, then it implies that detailed mapping of cell-specific regulatory networks will be an essential task for fully understanding human disease biology.

An Expanded View of Complex Traits: From Polygenic to Omnigenic: Cell

core genes generally contribute just a small part of the total heritability and how most genes expressed in relevant cell types could make non-zero contributions to heritability. To resolve this, we propose that cell regulatory networks are highly interconnected to the extent that any expressed gene is likely to affect the regulation or function of core genes.

An Expanded View of Complex Traits: From Polygenic to Omnigenic: Cell

This debate was resolved in a seminal 1918 paper by R.A. Fisher, who showed that, if many genes affect a trait, then the random sampling of alleles at each gene produces a continuous, normally distributed phenotype in the population (Fisher, 1918). As the number of genes grows very large, the contribution of each gene becomes correspondingly smaller, leading in the limit to Fisher’s famous “infinitesimal model” (Barton et al., 2016).

‘Omnigenic’ Model Suggests That All Genes Affect Every Complex Trait | Quanta Magazine

“What we realized was that the signal for height was coming from almost the whole genome,” he said. If the genome were a long string of ornamental lights, and every DNA snippet linked to height were illuminated, more than 100,000 lights would be shining all the way down the string. That result contrasted starkly with the general expectation that GWAS findings would be clustered around the most important genes for a trait.

Everything big data claims to know about you could be wrong: To understand human health and behavior, researchers would do better to study individuals, not groups -- ScienceDaily

"If you want to know what individuals feel or how they become sick, you have to conduct research on individuals, not on groups," said study lead author Aaron Fisher, an assistant professor of psychology at UC Berkeley. "Diseases, mental disorders, emotions, and behaviors are expressed within individual people, over time. A snapshot of many people at one moment in time can't capture these phenomena." Moreover, the consequences of continuing to rely on group data in the medical, social and behavioral sciences include misdiagnoses, prescribing the wrong treatments and generally perpetuating scientific theory and experimentation that is not properly calibrated to the differences between individuals, Fisher said.

Timing is everything, to our genes -- ScienceDaily

Using RNA sequencing, the research team tracked gene expression in dozens of different non-human primate tissues every 2 hours for 24 hours. The team found that each tissue contained genes that were expressed at different levels based on the time of day. However, the number of these "rhythmic" genes varied by tissue type, from around 200 in pineal, mesenteric lymph nodes, bone marrow and other tissues to more than 3,000 in prefrontal cortex, thyroid, gluteal muscle and others. In addition, genes that were expressed most often tended to show more rhythmicity, or variability by time. Of the 25,000 genes in the primate genome, nearly 11,000 were expressed in all tissues. Of those (which mostly govern routine cellular functions, such as DNA repair and energy metabolism), 96.6 percent were particularly rhythmic in at least one tissue, varying drastically by when they were sampled.

Keeping up the pressure: New neural mechanism is found to regulate the chronic stress response -- ScienceDaily

The newly discovered nerve cells express a receptor, CRFR1, on their outer walls, which enables them to take in the message of the CRF neurotransmitter. The scientists' experiments showed that, in mice, the cortisol actually increases the number of CRFR1 receptors on these nerve cells, suggesting a positive feedback loop that could be self-renewing, rather than abating.

» The Collapse of Complex Business Models Clay Shirky

When ecosystems change and inflexible institutions collapse, their members disperse, abandoning old beliefs, trying new things, making their living in different ways than they used to. It’s easy to see the ways in which collapse to simplicity wrecks the glories of old. But there is one compensating advantage for the people who escape the old system: when the ecosystem stops rewarding complexity, it is the people who figure out how to work simply in the present, rather than the people who mastered the complexities of the past, who get to say what happens in the future.

30 neurons act very differently, depending on chemical soup

Eve Marder, a prominent neuroscientist at Brandeis University, cautions against expecting too much from the connectome. She studies neurons that control the stomachs of crabs and lobsters. In these relatively simple systems of 30 or so neurons, she has shown that neuromodulators — signaling chemicals that wash across regions of the brain, omitted from Seung’s static map — can fundamentally change how a circuit functions. If this is true for the stomach of a crustacean, the mind reels to consider what may be happening in the brain of a mouse, not to mention a human.