credit: A. Ajifo

Welcome to Brain Bits, where I highlight important or interesting recent news in the world of neuroscience. This week: why you get hangry, how flies fly without getting lost, kicking old professors out of the lab, and more!

Deep in the brain, within a region called the hypothalamus, there are neurons that control eating. These cells, called AGRP neurons, fire when mice are hungry and drive them to eat. You might think that the AGRP neurons directly control the act of food consumption, driving the mice to physically put food into their little mouths like automatons. But a new paper in Nature shows that the AGRP neurons do something more complicated: they induce a negative emotional state (like being hangry) which the mice know they can overcome by eating. This negative emotional state was demonstrated by showing that mice avoid foods or places that are associated with the firing of AGRP neurons—they remember that they felt crappy there and don’t want to go back. These results help us understand how our brains translate physical needs into emotional states.

In order to navigate in the world, we need to know where things are located and how we’re moving among them. To make sure we don’t get lost, our brains contain an internal map of the world and keep track of which direction we’re facing relative to known landmarks. A new paper published in Nature shows that the brains of fruit flies contain a similar internal navigation system as mammals. Their internal compass is even shaped like a circle: it’s contained within a doughnut-shaped brain structure called the ellipsoid body, whose function has never been well understood. At any given time neurons in just one wedge of the doughnut are firing, depending on which way the fly is facing; as the fly turns left or right, the active wedge of doughnut also moves left or right. Pretty cool, right? But now I want a doughnut. Paper here; non-technical summary here; doughnuts here.

Figure from Seelig and Jayaraman showing the wedges of the ellipsoid body. Different wedges are active (colored red) when the fly is facing different directions.

The New Yorker published an in-depth profile of Karl Deisseroth, a renowned neuroscientist at Stanford. Deisseroth is largely credited with developing the field of optogenetics, which has revolutionized neuroscience by allowing us to use light to manipulate the activity of specific cells in the brain. The piece also recounts neuroscience’s long history of manipulating brain activity, starting with experiments on dead frogs in the 1700s.

Is it just me or does Deisseroth look exactly like new Spock in the New Yorker photo?

Neuroscientist Eve Marder wrote a perspective in PLoS Biology highlighting some of the problems that are arising in this era of “big data”. Her main point is that collecting vast quantities of data means that complicated statistical analyses are required to analyze it, and the more complicated the analysis, the more likely it is to contain inappropriate assumptions and lead to erroneous conclusions. “Different from today, many of the findings in the past were instantly recognizable once the experiment was done and were not hidden in model-dependent analyses.”

Nature published an article describing the debate over whether older lab heads should be forced to retire to make room for younger scientists. As shown in the graph below, the past couple of decades have witnessed a striking and ongoing trend of older scientists receiving a greater proportion of NIH grants at the expense of young scientists trying to start their careers. But certainly some older scientists are still productive, so should they really be forced out? On a related note, I had no idea that so many other countries currently enforce mandatory retirement at age 65, even when it means shutting down someone’s entire 70-member department.

Graph from the Nature article showing that the proportion of NIH grants received by younger scientists is declining, while the proportion received by older scientists is rising.

Did you see any recent neuroscience news that you’d like to share? Leave a comment below!