Research News Summer 2018 Issue 45

Research News

Mouse neurons visualized using nontoxic rabies viral vectors. Image: Ian Wickersham
Mouse neurons visualized using nontoxic rabies viral vectors. Image: Ian Wickersham

The Jasanoff lab has developed a new MRI sensor that monitors neural activity deep within the brain by tracking calcium ions. Because calcium ions are directly linked to neuronal firing—unlike the changes in blood flow detected by other types of MRI—this new sensor will allow researchers to link specific brain functions to neural activity, and help determine how distant brain regions communicate during particular tasks.

Humans use an ability known as Theory of Mind (ToM) whenever they infer someone else’s mental state. Children begin succeeding at a key behavioral measure of this ability around age 4. A new fMRI study out of the Saxe lab has found that the relevant ToM brain network forms earlier than previously expected, in children as young as 3.

Catching a bouncing ball or hitting a ball with a racket requires estimating when the ball will arrive. Neuroscientists have long thought that the brain does this by calculating the speed of the moving object. However, a new study by Mehrdad Jazayeri shows that the brain’s approach is more complex, tracking speed and integrating this with additional temporal information that reflects the pattern of an object’s movement (for example, how the ball moves around a bounce, or even the timing of an object’s movement before and after traveling behind an opaque obstacle). In a separate study, Jazayeri applied a mathematical framework, known as dynamical systems analysis, to model and identify a strategy that the brain uses to rapidly select and flexibly perform different mental operations.

For the past decade, neuroscientists have been using a modified rabies virus to label neurons and trace the connections between them. Although this technique has proven very useful, it is toxic to cells and can’t be used for longer-term studies. McGovern principal research scientist Ian Wickersham has developed a version of this virus that stops replicating once it infects a cell, allowing it to deliver its genetic cargo without harming the cell, enabling longer-term studies of neural functions and connections.

Studies of amyotrophic lateral sclerosis (ALS) patients have shown that an abnormally expanded region of DNA in a specific region of a specific gene accounts for up to 40 percent of all familial cases of ALS. The Horvitz lab used the microscopic worm Caenorhabditis elegans to examine the function of this gene, discovering that it plays a key role in helping cells remove waste products via structures known as lysosomes. When the gene is mutated, these unwanted substances build up inside cells. If this also happens in neurons of human ALS patients, it could account for some of their symptoms.

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