We study how neural circuits enable animals to interact with the environment. Our goal is to unravel the mechanisms of temperature sensation, learning and memory. We aim to elucidate these mechanisms at the molecular, cellular, neural circuit and behavioral levels, utilizing the nematode Caenorhabditis elegans (C. elegans).
Animals need to interact with the changing environment to survive and reproduce. External stimuli are sensed, memorized, and processed into appropriate behavior by dedicated neural circuits. We study the memory-driven behavior of C. elegans called thermotaxis (from Greek: Oriented movement in response to a temperature stimulus), to elucidate how these neural circuits employ sensory information to generate behavior.
Thermotaxis: A behavioral paradigm for learning and memory
Thermotaxis of C. elegans is an excellent example of memory-based behavior. Well-fed animals cultivated at a certain temperature (between 15 and 25℃) and placed on a thermal gradient without food, migrate towards the cultivation temperature, where they move in straight lines along a single isotherm (isothermal tracking). In contrast, animals on a thermal gradient move away from temperatures at which they previously experienced starvation. This behavioral plasticity suggests that C. elegans can sense environmental conditions, memorize (cultivation) temperature, associate temperature with a particular feeding state, and integrate this information to generate behavior. However, the mechanisms by which neural circuits generate behavior remain largely unidentified. We use C. elegans thermotaxis as the behavioral output to reveal underlying molecular, neuronal and circuit mechanisms.
The merits of a small nematode
The nervous system of C. elegans consists of merely 302 neurons. The neural anatomy is stereotyped between animals, allowing each neuron to be identified and studied in great detail. Combined with the high level of behavioral plasticity, these characteristics allow us to use C. elegans in our study to reveal the neural circuits required for thermotaxis. Simultaneous analysis of neuronal activity and behavior can be achieved through non-invasive imaging techniques on the transparent body of C. elegans. Each neuron can be genetically targeted, to reveal its function within the neural circuits. Genetic tools and the short life cycle of C. elegans further enable precise and rapid screening for molecular regulators. Finally, there are numerous assays to analyze specific behavioral strategies, both in individuals and populations of worms.
Research objective and approach
We aim to understand the mechanisms of sensation, learning and memory, by analyzing various aspects of thermotaxis. We study the molecular, cellular, neural circuit and behavioral levels of temperature-driven behavior, using a wide range of experimental techniques. These include genetic screens, neuronal imaging (calcium imaging, optogenetics), single-worm and population-based thermotaxis assays, as well as recorded tracking of nematode behavior.
Ongoing projects focus on:
1. Neural circuits and behavioral traits generating thermotaxis
2. Genetic regulators of thermotaxis
3. Physiological analysis of thermotaxis
4. Molecular mechanisms for starvation-induced thermotactic plasticity