High-throughput optical quantification of mechanosensory habituation reveals neurons encoding memory in Caenorhabditis elegans

Takuma Sugi; Yasuko Ohtani; Yuta Kumiya; Ryuji Igarashi; Masahiro Shirakawa

doi:10.1073/pnas.1414867111

Edited by Martin Chalfie, Columbia University, New York, NY, and approved October 21, 2014 (received for review August 18, 2014)

Significance

A central aim of neuroscience studies is to locate physical substrates of memory, namely neurons and molecules encoding memory. Achieving this goal requires cell-specific interrogations of neural circuitry. However, it has remained difficult to rapidly and accurately quantify the memory of animals expressing a transgene in a cell-specific manner. Our study presents a powerful optical system to perform cell-specific behavioral genetic analysis in a high-throughput manner, and demonstrates its utility by identifying two interneurons as the neural substrates of mechanosensory memory in C. elegans. We propose that our identified interneurons can be novel targets for cell-specific exploration of the molecular substrates of memory.

Abstract

A major goal of neuroscience studies is to identify the neurons and molecules responsible for memory. Mechanosensory habituation in Caenorhabditis elegans is a simple form of learning and memory, in which a circuit of several sensory neurons and interneurons governs behavior. However, despite the usefulness of this paradigm, there are hardly any systems for rapid and accurate behavioral genetic analysis. Here, we developed a multiplexed optical system to genetically analyze C. elegans mechanosensory habituation, and identified two interneurons involved in memory formation. The system automatically trains large populations of animals and simultaneously quantifies the behaviors of various strains by optically discriminating between transgenic and nontransgenic animals. Biochemical and cell-specific behavioral analyses indicated that phosphorylation of cyclic AMP response element-binding protein (CREB), a factor known to regulate memory allocation, was facilitated during training and this phosphorylation in AVA and AVD interneurons was required for habituation. These interneurons are a potential target for cell-specific exploration of the molecular substrates of memory.

Footnotes

↵¹To whom correspondence should be addressed. Email: tsugi{at}icems.kyoto-u.ac.jp.

Author contributions: T.S. designed research; T.S. and Y.O. performed research; T.S., Y.K., and R.I. contributed new reagents/analytic tools; T.S. analyzed data; and T.S. and M.S. wrote the paper.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission.
This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1414867111/-/DCSupplemental.