Brain Bits, 6/21/15

lightning brain2

credit: A. Ajifo

Welcome to Brain Bits, where I highlight important or interesting recent news in the world of neuroscience. This week: sexist comments that went viral, happy thoughts make mice less depressed, why broken DNA can be a good thing, and more!

 

Well, we might as well start with the story that no one could stop talking about for the last two weeks: Nobel Prize winner Tim Hunt. As I’m sure many of you know, Hunt made some sexist comments about why science labs should be gender-segregated, quipping that when “girls” work alongside men, three things happen: “You fall in love with them, they fall in love with you, and when you criticize them, they cry”. Hunt, who won the Nobel for co-discovering the basic mechanisms controlling how cells duplicate, later claimed that he was trying to be funny but also “meant to be honest”, standing by some of his comments. The ensuing backlash led to his resignation from an honorary position at University College London. Now there’s a back-backlash of people who argue that firing him was a politics-style knee-jerk reaction that compromises academics’ right to freedom of expression. Personally, I’m less concerned about this particular old dude and, like this Nature editorial, more concerned about how to address the “the dismaying extent to which sexism still pervades science”. (An aside: this link describes how Hunt has been crying because of all the criticism. Ah, irony.)

A Nature paper from Susumu Tonegawa’s lab at MIT showed that artificially stimulating happy memories in stressed mice alleviates depression-like symptoms. The researchers used genetic techniques to mark neurons in the hippocampus that responded to happy experiences—in this case, the presence of a female mouse. (The test mice were all males who don’t usually get any time with females, so you can imagine their excitement.) The researchers stressed the mice out by immobilizing them with little mouse handcuffs (I imagine…) for a few hours each day, which made them show signs of depression. But the stressed mice didn’t act so depressed anymore when researchers artificially activated the hippocampal neurons that stored happy memories of their time with females. Interestingly, trying to cheer the mice up by giving them actual females again didn’t help, suggesting that maybe they’re too depressed to enjoy happy experiences anymore—you need to directly stimulate those memories in the brain. Non-technical summary here.

tonegawa paper summary

Summary of the Tonegawa paper; see above for details. (credit: Dranovsky and Leonardo, Nature, 2015)

 

Every one of our cells contains about 20,000 genes encoded into our DNA, and each cell carefully and independently controls the level at which each gene is expressed. (I know, biology is insane.) When a neuron gets activated, many genes get expressed at higher levels. These activity-regulated genes execute the changes that enable your brain to learn and adapt. While most genes take awhile to increase their levels, there are a few special genes that respond within minutes of a neuron firing. How they respond so quickly has always been a mystery. Now a new Cell paper from Li-Huei Tsai’s lab shows that neuronal firing causes physical breaks in the DNA right next to these special genes. Usually breaking your DNA is a bad thing, just like it sounds, but in this case the breaks occur only at specific locations and allow specific proteins to bind each other, which turns on the genes. This is a pretty huge discovery: it shows that DNA breaks aren’t always a result of damage, but instead can be carefully controlled events that occur normally to regulate gene expression. Non-technical summary here.

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Cartoon of how neuronal activity “flips a switch” to cause DNA breaks, which affect gene expression. (credit: Li-Huei Tsai lab via MIT news)

 

A new study in fruit flies sheds light on why getting enough sleep helps animals remember things better. This Cell paper from Ron Davis’ lab shows that, like us, flies remember things for longer if they sleep after they learn. Conversely, getting the flies all hyped up and aroused makes them forget things sooner. Researchers identified a single dopamine-releasing neuron that’s responsible for making flies forget things: the neuron fires like crazy when flies are active and goes quiet when they’re sleeping. Strikingly, activating the neuron in sleeping flies blocked the memory-enhancing effect of sleep, while silencing it in aroused flies caused them to remember for longer. This study supports the idea is that forgetting is an active process—your brain doesn’t want to store useless or outdated memories forever, as they might conflict with newer, more relevant memories. And you might want to alter how quickly you forget based on what’s going on around you; being aroused, for example, may be a signal that your environment is rapidly changing.

 

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


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