Some 380,000 brain surgeries are performed every year in the United States, mostly by opening a flap on the head, removing a portion of skull, and burrowing down through healthy brain tissue to create a “surgical corridor” to reach the desired location—say a tumor to be removed. Because of the sensitivity of the overall tissue, invasive surgeries like these are by definition complicated. Damage to the brain can cause neurological deficits, create the need for rehab, lengthen hospital stays, and increase the overall cost of the operation. Endoscopic approaches to neurosurgery are attractive because they limit surgical tissue damage to a small burr hole, but endoscopes typically have only a single tool channel, which basically forces surgeons to work one-handed. Now doctors at Boston Children’s Hospital and Harvard Medical School have developed a robotic endoscope with a “bimanual” design. It’s controlled by a two-armed joystick, which allows surgeons to use both hands while operating, and in laboratory studies they demonstrated that it allowed surgeons to move faster and with greater control. “These results suggest that robotics has the potential to substantially reduce the invasiveness of brain surgery,” the researchers write. Science Robotics

More than a century ago, Sigmund Freud enshrined the belief that suppressing negative thoughts is maladaptive and bad. Forgetting trauma, he held, simply causes it to resurface, cropping up in our unconscious minds, lingering in our dreams, and leading to classic psychiatric symptoms like anxiety, post-traumatic stress, and depression. Was Freud wrong? A new study from Cambridge University in England challenges his wisdom. Training 120 adults from 16 countries on techniques for suppressing fearful thoughts, researchers found, rendered those thoughts less vivid and less likely to provoke anxiety. People who had the most anxiety and stress benefited the most from the training, which suggests a valid approach to improving mental health could be, as the late, great Jim Morrison sang: Learn to forget. Science Advances

In what may be the ultimate stamp collection exercise in the history of biology, researchers at the Max Planck Institute for Mathematics in the Sciences in Leipzig, Germany, and McGill University in Montreal, Quebec, have estimated the count, sizes, and masses of all the cells in a human body, from the tiniest red blood cells to the biggest muscle fibers. They estimate a typical adult male carries about 36 trillion cells, an adult female ~28 trillion, and a child some 17 trillion. “Our data serve to establish a holistic quantitative framework for the cells of the human body, and highlight large-scale patterns in cell biology,” they write. PNAS

A “cell treemap” depiction showing the relative count and biomass of cells of the human body. Ian A. Hatton

The at-home testing market is large and growing, expected to pass $8 billion in value by 2027. A significant segment of this market are direct-to-consumer tests, also called patient-initiated tests, sales of which are expected to hit $2 billion a year by 2025. We like the liberation and promise they have for the informed consumer looking to track interventions for themselves. But these tests often fall outside FDA review, and they are commonly available without a doctor’s order. Now doctors at Baylor College of Medicine in Houston, Texas, have surveyed the terms of service included with 18 different direct-to-consumer tests from 21 companies, comparing them to marketing materials from the same companies. There is strong dissonance, they write, because the terms of service almost universally disclaim liability and state the tests are for informational purposes only—even as the marketing materials largely champion potential medical insights. Other problems also existed, such as unclear HIPAA compliance, policies over the re-use of personal data, and inconsistent follow-ups for abnormal results. JAMA Internal Medicine

Using a sophisticated type of genetic analysis known as Mendelian randomization, researchers at the Wuhan Mental Health Center and Wuhan University in China have found a causal relationship between frailty and depression that is bidirectional—frailty puts people at risk of depression and vice versa. This confirms what several earlier epidemiology studies found, and it suggests people who are depressed could benefit from routine frailty screening. “In addition, proper management of depression is also essential for downregulating the risk of frailty,” the researchers write. Science Advances

Aside from injecting overpriced repurposed diabetes drugs directly into your stomach, there’s little in weight control that’s guaranteed—though moderate-to-vigorous physical activity comes close. Studies have shown it’s inversely associated with obesity, but does the time of day you exercise matter? Yes, according to researchers at Hong Kong Polytechnic University. In an observational study looking at the 2003–2006 exercise schedules of more than 5,000 people in the National Health and Nutrition Examination Survey, the researchers found the optimal time is 7am–9am. The study involved 642 morning exercisers, 2,456 who worked out at midday, and 2,187 people who preferred to do it in the evening. The morning group exhibited the strongest inverse association between moderate-to-vigorous physical activity and obesity, even though they tended to be less active overall. Still, the researchers write, we need placebo controlled prospective studies to firmly establish that morning exercise is best. Obesity