Just 20 minutes of contact with nature will lower stress hormone levels

Taking at least twenty minutes out of your day to stroll or sit in a place that makes you feel in contact with nature will significantly lower your stress hormone levels. That’s the finding of a study that has established for the first time the most effective dose of an urban nature experience. Healthcare practitioners can use this discovery, published in Frontiers in Psychology, to prescribe ‘nature-pills’ in the knowledge that they have a real measurable effect.

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Nature pills could be a low-cost solution to reduce the negative health impacts stemming from growing urbanization and indoor lifestyles dominated by screen viewing. To assist healthcare practitioners looking for evidence-based guidelines on what exactly to dispense, Hunter and her colleagues designed an experiment that would give a realistic estimate of an effective dose.

Over an 8-week period, participants were asked to take a nature pill with a duration of 10 minutes or more, at least 3 times a week. Levels of cortisol, a stress hormone, were measured from saliva samples taken before and after a nature pill, once every two weeks.

“Participants were free to choose the time of day, duration, and the place of their nature experience, which was defined as anywhere outside that in the opinion of the participant, made them feel like they’ve interacted with nature. There were a few constraints to minimize factors known to influence stress: take the nature pill in daylight, no aerobic exercise, and avoid the use of social media, internet, phone calls, conversations and reading,” Hunter explains.

She continues, “Building personal flexibility into the experiment, allowed us to identify the optimal duration of a nature pill, no matter when or where it is taken, and under the normal circumstances of modern life, with its unpredictability and hectic scheduling.”

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Trippy images designed by AI to super-stimulate monkey neurons

To find out which sights specific neurons in monkeys “like” best, researchers designed an algorithm, called XDREAM, that generated images that made neurons fire more than any natural images the researchers tested. As the images evolved, they started to look like distorted versions of real-world stimuli.

Researchers have known that neurons in the visual cortex of primate brains respond to complex images, like faces, and that most neurons are quite selective in their image preference. Earlier studies on neuronal preference used many natural images to see which images caused neurons to fire most. However, this approach is limited by the fact that one cannot present all possible images to understand what exactly will best stimulate the cell.

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The XDREAM algorithm uses the firing rate of a neuron to guide the evolution of a novel, synthetic image. It goes through a series of images over the course of minutes, mutates them, combines them, and then shows a new series of images. At first, the images looked like noise, but gradually they changed into shapes that resembled faces or something recognizable in the animal’s environment, like the food hopper in the animals’ room or familiar people wearing surgical scrubs. The algorithm was developed by Will Xiao in the laboratory of Gabriel Kreiman at Children’s Hospital and tested on real neurons at Harvard Medical School.

From this study, the researchers believe they are seeing that the brain learns to abstract statistically relevant features of its world. “We are seeing that the brain is analyzing the visual scene, and driven by experience, extracting information that is important to the individual over time,” says Ponce. “The brain is adapting to its environment and encoding ecologically significant information in unpredictable ways.”

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Organ Bioprinting

The goal of bioprinting healthy, functional organs is driven by the need for organ transplants. More than 100,000 people are on transplant waiting lists in the United States alone, and those who do eventually receive donor organs still face a lifetime of immune-suppressing drugs to prevent organ rejection. Bioprinting has attracted intense interest over the past decade because it could theoretically address both problems by allowing doctors to print replacement organs from a patient’s own cells. A ready supply of functional organs could one day be deployed to treat millions of patients worldwide.

 

The new innovation allows scientists to create exquisitely entangled vascular networks that mimic the body’s natural passageways for blood, air, lymph and other vital fluids. The research presented in the video is featured on the cover of this week’s issue of Science. It includes a visually stunning proof-of-principle — a hydrogel model of a lung-mimicking air sac in which airways deliver oxygen to surrounding blood vessels. Also reported are experiments to implant bioprinted constructs containing liver cells into mice.

The work was led by bioengineers Jordan Miller of Rice University and Kelly Stevens of the University of Washington (UW) and included 15 collaborators from Rice, UW, Duke University, Rowan University and Nervous System, a design firm in Somerville, Massachusetts.

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