Itskovits, Eyal et al. (2015) International Worm Meeting "A new multi-worm tracker reveals unprecedented insights on worm chemotaxis."

Itskovits, Eyal, Zaslaver, Alon

[International Worm Meeting, 2015]

We have developed a novel Multi Worm Tracker (MWT) that is capable of tracking over a hundred worms simultaneously. The tracker employs a machine learning classification approach to identify the behaving worms. The system produces a long informative track for each individual worm, and generally maintains tracking despite frequent animal collision events. This MWT provides unprecedented statistical power revealing subtle, yet significant, behavioral features. Here we present results that challenge the prevalent "biased random walk" strategy of worms' chemotaxis. Moreover, we readily obtain data with satisfactory statistical significance following a single chemotaxis assay. Our system includes a suite of solutions for acquisition, tracking, and statistical analyses via a friendly user interface that is easy to operate with minimal programming skills.

Bokman, Eduard et al. (2019) International Worm Meeting "Encoding principles of a compact sensory system."

Ruach, Rotem, Zaslaver, Alon, Itskovits, Eyal, Bokman, Eduard, Pritz, Christian

[International Worm Meeting, 2019]

Animals critically depend on accurate sensation and processing of environmental cues. This task becomes particularly challenging for animals with a small and highly interconnected sensory system. Here, we used Caenorhabditis elegans nematodes to investigate how information is encoded within a compact sensory system. For this, we generated a new strain expressing the genetically encoded calcium indicator GCaMP in all 60 ciliated neurons, and used a fast-scanning confocal system to measure activity simultaneously from all chemosensory neurons while subjecting the worms to various stimuli. We found that the sensory system responds with small, unique, and mostly bi-laterally symmetrical subsets of neurons. Moreover, analysis of mutants, defective in neuro-transmitter or neuro-peptide release, revealed that the number of primary neurons, which directly respond to the cue, is minimal, typically comprised of 2-3 neuron types. Interestingly, these neurons exhibit a range of response dynamics that is both stimulus and circuitry-dependent, effectively increasing encoding capacity of the compact sensory system. Finally, exposing animals to combinations of stimuli revealed that the sensory system integrates information using a simple weighted sum strategy. These findings elucidate the principles that allow a small and compact sensory system to expand its encoding repertoire and to efficiently extract information from the environment.

Deshe, Noa et al. (2021) International Worm Meeting "Inheritance of associative memories in C. elegans"

Eliezer,, Yifat, Itskovits,, Eyal, Hoch,, Lihi, Zaslaver*, Alon, Ben-Ezra, Shachaf, Deshe, Noa

[International Worm Meeting, 2021]

Organisms often face changing environments; hence, the ability to predict future conditions is essential for survival. Associative memories play a central role in this regard, as memory reactivation generates fast physiological responses that aid in coping with impending developments. But could these valuable associative memories be transferred to subsequent generations? We show that parental associative memories of traumatic experiences are indeed inheritable. We trained worms to associate a naturally favorable odor with starvation. Subsequent odor-evoked memory reactivation induced stress. Surprisingly, the stressful associative memory was also transmitted to the F1 and F2 generations, even though these animals were never exposed to the odorant before. Moreover, the stress responses provided both the parents and the offspring with a fitness advantage. The sperm, but not the oocytes, transmitted the associative memory, and a candidate-gene screen revealed that H3K9 methylation and the RNAi machinery underlie these heritable responses. Furthermore, activation of a single chemosensory neuron (AWCOFF) sufficed to induce a systemic stress response in both the parents and their progeny, suggesting that this neuron is part of the memory engram. Our findings provide an important evidence, to the yet debatable idea, that associative memories can be inherited

Pritz, Christian et al. (2021) International Worm Meeting "Principles for coding associative memories in a compact neural network"

Itskovits, Eyal, Menasherof, Mai, Zaslaver, Alon, Nelken, Tal, Pritz, Christian, Ruach, Rotem, Bokman, Eduard, Gritsenko, Vladimir, Azulay, Aharon

[International Worm Meeting, 2021]

A major goal in neuroscience is to elucidate the principles by which memories are stored in a neural network. Here, we have systematically studied how the four types of olfactory associative memories (short- and long-term memories, each as positive and negative associations) are encoded within the compact neural network of C. elegans worms. By combining these robust training paradigms with fast confocal calcium imaging using multi-neuron and whole-brain imaging approaches, we systematically traced experience-dependent activity changes down to the level of individual neurites. Interestingly, short-term, but not long-term, memory broadly altered memory-evoked responses of chemosensory neurons. Modulated activity in three neurons, namely AWA, AWC, and ASE, sufficed to discriminate between the different memory states. This economy in memory-coding neurons increases memory capacity and limits non-innate behavioral responses. In contrast, long-term memory was relegated to deeper layers of the network. Primary interneurons, AIY and AIA, exhibit memory-state-dependent activation signatures, allowing the sensory system to resume innate functionality. In conclusion, olfactory associative memory appears to follow a hierarchical and temporally structured encoding logic.