Personal Profile

Misha Ahrens is a group leader at HHMI / Janelia Research Campus. He joined Janelia in the fall of 2012, researching systems neuroscience in zebrafish. He completed his BA in mathematics and physics at Cambridge University, and his PhD in computational neuroscience at the Gatsby Computational Neuroscience Unit, at University College London. From 2009 to 2012 he was a Sir Henry Wellcome Postdoctoral Fellow, working in the Engert Lab, at Harvard University.
His interest is to understand, on the whole-brain but single-cell level, how entire neural circuits generate adaptable behaviors and how plasticity reorganizes the functional properties of these circuits to implement learned changes in behavior.

Abstract

When a behavior repeatedly fails to achieve its goal, animals often give up and become passive, which can be strategic for preserving energy or regrouping between attempts. It is unknown how the brain identifies behavioral failures and mediates this behavioral state switch. In larval zebrafish swimming in virtual reality, visual feedback can be withheld so that swim attempts fail to trigger expected visual flow. After tens of seconds of such motor futility, animals become passive for similar durations. Whole-brain calcium imaging revealed noradrenergic neurons that responded specifically to failed swim attempts, and radial astrocytes whose calcium levels accumulated with increasing numbers of failed attempts. Using cell ablation and optogenetic or chemogenetic activation, we found that noradrenergic neurons progressively activate brainstem radial astrocytes, which then suppress swimming. Thus, radial astrocytes perform a computation critical for behavior: they accumulate evidence that current actions are ineffective and consequently drive changes in behavioral states