(Visited 40 times, 1 visits today)FacebookTwitterPinterestSave分享0 Your brain and eyes do things that scientists didn’t discover till recently.Retina recycling: How would you design a system that could cast off its spent parts without ceasing operation, and without changing its shape? Your photoreceptor cells have to do that every day. The process, called disc shedding, is described by PhysOrg in “A first glimpse at disc shedding in the human eye.” Here’s another system you should be glad you don’t have to consciously maintain.Photoreceptors are conic or cylindrical structures that capture and convert light into an electrical response. The light, itself, is toxic as it leads to photo-oxidative compounds that would kill the cells if left to accumulate. To remain healthy, the cells must discard the membranes that contain the toxic compounds and then renew those that were lost. The difficulty lies in the fact that the cells have to maintain a constant length as they undergo this dynamic process each day. They cannot add too many renewing bits in the assembly process that the cell becomes too big, or too few that it becomes too small to work correctly.“Shedding must be offset by renewal,” said Omer P. Kocaoglu, a biomedical engineer at Indiana University and the first author on the paper. “Dysfunction at any stage or loss in synchronization—such as loss of diurnal rhythm—can lead to photoreceptor and retinal pigment epithelium (RPE) dystrophy, and ultimately blindness.”Memory optimization: The brain’s memory is a vast but limited resource. In “How the brain makes new memories while preserving the old,” Science Daily says that neurologists at Columbia University invented a mathematical model to explain how you can continue learning new things for a lifetime but still remember things in high fidelity from your childhood. Is there an answer to the “how” question? Not exactly; “The model that we have developed finally explains why the biology and chemistry underlying memory are so complex — and how this complexity drives the brain’s ability to remember,” they boast, only to confess further down that the mathematical model collapses when realistic limits are placed on each synapse’s dial-up strength. The brain’s memory is not like computer memory. It’s not like a collection of static bins that are either empty or occupied, risking a disk-full situation down the road. Instead, the brain’s storage units—thought to reside in synapses—communicate with each other in complex ways. “Once we added the communication between components to our model, the storage capacity increased by an enormous factor, becoming far more representative of what is achieved inside the living brain.”Exactly how the synapses communicate and what they share remains to be discovered, but computer designers could sure learn something by mimicking the brain. PhysOrg says that computer makers are stuck in a rut. They are increasingly “turning to the brain to reboot computing,” inspired by the astonishing capabilities of the three-pound mass inside their own skulls that never stops learning.Stitching the left brain to the right brain: Many have heard that the two hemispheres of the brain have different functions. They are joined by the corpus callosum, a tightly-knit bundle of fibroblasts, nerve axons and other non-neural cells. Without this bridge, the hemispheres cannot communicate. Though this is not usually fatal, it leads to various disorders of development. Science Daily reports that scientists have fingered astroglia (previously thought to be unimportant brain cells) as the sewing machines for the corpus callosum. “Astroglia zip the two halves of the brain together,” the headline reads. These “main support cells of the brain” guide the fibroblasts into place. They “weave themselves between the right and left lobes, and form the bridge for axons to grow across the gap.”Automatic puzzle solver: Enjoy puzzles? The title of a paper in Nature‘s open-access journal Scientific Reports is sure to lure the curious: “How Humans Solve Complex Problems: The Case of the Knapsack Problem.” The knapsack problem is “a discrete optimisation problem commonly encountered at all levels of cognition, from attention gating to intellectual discovery.” Computers have a hard time solving it, and so do people. But some solve it without knowing they did. OK, here’s what it is. Think of deciding what to put into and take out of a knapsack before leaving on a hike. You want to take what you need without weighing yourself down.The knapsack problem (KP) is a combinatorial optimisation problem with the goal of finding, in a set of items of given values and weights, the subset of items with the highest total value, subject to a total weight constraint. It is a member of the complexity class non-deterministic polynomial-time (NP) hard. For those problems, there are no known efficient solution algorithms, that is, algorithms whose computational time only grows as a polynomial of the size of the problem’s instances. This feature obtains despite the fact that one can compute relatively fast whether a given candidate solution reaches a certain value level.Two Australian scientists explain that the KP “permeates the lives of humans” at many levels, such as deciding what stimulus to focus on, how to budget your time with a list of things to do, all the way up to managing a company’s portfolio for greatest ROI for shareholders. “It has also been argued that the KP reflects an important aspect of innovation and intellectual discovery,” as revealed by patent applications for combining technologies in novel ways. Animals, too, confront situations where they have to budget resources to obtain food or other needs. A cheetah can’t run all day; which prey animal should it target?Obviously, people differ in their ability to solve this problem. Factors like complexity of the problem, effort required, motivation, skill at arithmetic, memory, ability to concentrate and mental health will affect scoring. Some people seem to have innately better tacit knowledge, the inexplicable insight to sense the best strategy.The authors sought to identify what about the brain helps solve the KP. What they found is that humans generally solve the problem, but not like computers programmed for optimization. Some subjects, for instance, will continue to waste energy on a complex problem beyond the point of diminishing returns. “Across participants, we found little overlap in the knapsacks that they visited,” they conclude. “This implies … that there does not seem to be a ‘representative heuristic’ which captures the essence of all participants’ strategies.” This result appears to support the view that human beings are individuals, not products of a blind programming process of natural selection that all act alike. Maybe that’s why the authors didn’t mention evolution in the paper.Earth is the brain’s habitat: Experiments with rodents show that the expected amount of radiation on a long voyage to Mars would likely damage astronauts’ brains. Astrobiology Magazine says, “Mars-bound astronauts face chronic dementia risk from galactic cosmic ray exposure.” Star Trekkies take note:“This is not positive news for astronauts deployed on a two-to-three-year round trip to Mars,” said the professor of radiation oncology in UCI’s School of Medicine. “The space environment poses unique hazards to astronauts. Exposure to these particles can lead to a range of potential central nervous system complications that can occur during and persist long after actual space travel – such as various performance decrements, memory deficits, anxiety, depression and impaired decision-making. Many of these adverse consequences to cognition may continue and progress throughout life.”Indeed, the astronauts may lose the ability to return to Earth. That’s sorry news for fans of last year’s movie hit, The Martian. Outer space is a shooting gallery of solar particles and cosmic rays. A soul may imagine itself exploring the universe, but the human brain, as a physical organ in a physical body, needs a suitable habitat. That habitat may be limited to the surface of a particular blue planet orbiting a particular star.We must surely stand in awe of the equipment bequeathed to us. So much of our day is focused on things occupying our conscious attention, which is amazing enough. But to learn about all these automatic, subconscious processes that support our minds and memories should make us gasp with astonishment. What treasures inhabit our skulls! It should make us grieve when a brain is damaged or destroyed, whether by accident or intention. It should make us nourish and cherish our gifts, and treat others with the utmost respect. No one, not even the disabled or faithless, is to be despised like a piece of trash. We are all made in the image of God. We honor God by respecting the crown of His creation.