title: Bidirectional thermotaxis in Caenorhabditis elegans is mediated by distinct sensorimotor strategies driven by the AFD thermosensory neurons.
abstract: The nematode Caenorhabditis elegans navigates toward a preferred temperature setpoint (Ts) determined by long-term temperature exposure. During thermotaxis, the worm migrates down temperature gradients at temperatures above Ts (negative thermotaxis) and performs isothermal tracking near Ts. Under some conditions, the worm migrates up temperature gradients below Ts (positive thermotaxis). Here, we analyze positive and negative thermotaxis toward Ts to study the role of specific neurons that have been proposed to be involved in thermotaxis using genetic ablation, behavioral tracking, and calcium imaging. We find differences in the strategies for positive and negative thermotaxis. Negative thermotaxis is achieved through biasing the frequency of reorientation maneuvers (turns and reversal turns) and biasing the direction of reorientation maneuvers toward colder temperatures. Positive thermotaxis, in contrast, biases only the direction of reorientation maneuvers toward warmer temperatures. We find that the AFD thermosensory neuron drives both positive and negative thermotaxis. The AIY interneuron, which is postsynaptic to AFD, may mediate the switch from negative to positive thermotaxis below Ts. We propose that multiple thermotactic behaviors, each defined by a distinct set of sensorimotor transformations, emanate from the AFD thermosensory neurons. AFD learns and stores the memory of preferred temperatures, detects temperature gradients, and drives the appropriate thermotactic behavior in each temperature regime by the flexible use of downstream circuits.
authors.affiliation: Key Laboratory of Modern Acoustics, Ministry of Education, Department of Physics, Nanjing University, Nanjing 210093, China.
authors.forename: Linjiao
authors.initials: L
authors.lastname: Luo
authors.forename: Nathan
authors.initials: N
authors.lastname: Cook
authors.forename: Vivek
authors.initials: V
authors.lastname: Venkatachalam
authors.forename: Luis A
authors.initials: LA
authors.lastname: Martinez-Velazquez
authors.forename: Xiaodong
authors.initials: X
authors.lastname: Zhang
authors.forename: Ana C
authors.initials: AC
authors.lastname: Calvo
authors.forename: Josh
authors.initials: J
authors.lastname: Hawk
authors.forename: Bronwyn L
authors.initials: BL
authors.lastname: MacInnis
authors.forename: Michelle
authors.initials: M
authors.lastname: Frank
authors.forename: Jia Hong Ray
authors.initials: JH
authors.lastname: Ng
authors.forename: Mason
authors.initials: M
authors.lastname: Klein
authors.forename: Marc
authors.initials: M
authors.lastname: Gershow
authors.forename: Marc
authors.initials: M
authors.lastname: Hammarlund
authors.forename: Miriam B
authors.initials: MB
authors.lastname: Goodman
authors.forename: Daniel A
authors.initials: DA
authors.lastname: Colón-Ramos
authors.forename: Yun
authors.initials: Y
authors.lastname: Zhang
authors.forename: Aravinthan D T
authors.initials: AD
authors.lastname: Samuel
mesh_terms: D000818:Animals; D017173:Caenorhabditis elegans / Q000502:physiology*; D057567:Memory, Long-Term / Q000502:physiology*; D008959:Models, Neurological; D009068:Movement / Q000502:physiology*; D009474:Neurons / Q000502:physiology*; D013696:Temperature; D013697:Thermosensing / Q000502:physiology*