Neural mechanisms underlying spontaneous and learned behavior in larval zebrafish


April 19, 2017 - 1:00pm
Northwest Building Room 243
About the Speaker
Misha Ahrens
Speaker Title: 
Group Leader, Janelia Research Campus
Speaker Affiliation: 
Howard Hughes Medical Institute [HHMI]

An animal’s actions are dependent on its current environment as well as on its
past experiences. We sought to identify neural mechanisms underlying two types
of history dependence in behavior of larval zebrafish. First, we studied
sequences of spontaneous motor actions, where the choice of whether to swim
left or right is strongly influenced by past swim patterns. We performed
whole-brain imaging to discover groups of neurons that are necessary and
sufficient for a short-term memory of turning direction. An
excitatory-inhibitory circuit, storing heading direction in sustained activity,
enables history-dependent, non-random choices of swim direction to implement an
efficient local foraging strategy. Second, we studied a short-term form of motor
learning, in which the animals learn changes in the relationship between their
locomotor commands and the resulting distance moved, then adjust command
strength to achieve a desired travel distance. We used whole-brain neuronal
imaging and circuit manipulations to discover that the serotonergic dorsal
raphe nucleus stores a short-term memory of learned swim vigor, in persistent
activity of serotonergic neurons. This learned representation of the
“effectiveness of actions” arises from integration of the sensory feedback from
individual swim bouts, and transmission to behavior was raphe- and
serotonin-dependent. These studies reveal that experience-dependence in
spontaneous behavior and motor learning in zebrafish is implemented through
combinations of reverberating neural activity and neuromodulation, and
demonstrate how whole-brain imaging can be used to discover loci underlying
flexible behavior.