Tom Shimizu: Big mood swings in very small brains
A hallmark of living machines is their ability to harness variability. At the smallest scales, cells have evolved to tame thermal fluctuations in the form of Brownian motion and discrete chemical events – processes which span milliseconds to seconds in time, and take place on structures of nanometer scale in length. Yet understanding biological variability over longer time- and length-scales remains a formidable challenge. In this talk, I will describe our recent experiments that reveal slow and large-amplitude fluctuations (‘mood swings’) in two kinds of microscopic ‘brains’: the protein signaling network controling motility in the bacterium E. coli, and the neuronal network controlling locomotion in the nematode C. elegans. For the bacterial case, I will describe in some detail a theoretical framework that can explain the mechanistic origin of these mood swings, as well as their functional consequences. For the nematode case, the mechanism(s) driving fluctuations remains entirely open, and discussion will focus on connection to behavior and future directions for mechanistic inquiry.