SUMMARY Background Even though functional lateralization is a predominant feature of many nervous systems, it is poorly understood how lateralized neural function is linked to lateralized gene activity. A bilaterally symmetric pair of gustatory neurons in the nematode C. elegans, ASEL and ASER, serves as a model to study the genetic basis of functional lateralization as this pair senses a number of chemicals in a left/right asymmetric manner. The extent of functional lateralization of the ASE neurons and genes responsible for the left/right asymmetric activity of ASEL/R are unknown. Results We show here that a large panel of salt ions is sensed in a left/right asymmetric manner, as demonstrated by behavioral assays, imaging of neural activity with a genetically encoded calcium sensor and by genetic manipulations that alter the fate of either ASEL or ASER. We show that lateralized salt responses allow the worm to discriminate between distinct salt cues. To identify molecules that may be involved in sensing salt ions and/or transmitting such sensory information, we examined the chemotaxis behavior of animals harboring mutations in eight different receptor-type, transmembrane guanylyl cyclases (encoded by gcy genes), which are expressed in either ASEL (gcy-6, gcy-7, gcy-14), ASER (gcy-1, gcy-4, gcy-5, gcy-22) or ASEL and ASER (gcy-19). Disruption of a ASER-expressed gcy gene, gcy-22, resulted in a broad chemotaxis defect to nearly all salts sensed by ASER, as well as to a left/right-asymmetrically sensed amino acid. In contrast, disruption of other gcy genes resulted in highly salt ion-specific chemosensory defects. Furthermore, we show that not only the cyclase domain, but also the extracellular domain of GCY proteins is important for their activity in salt sensation. Conclusions Our findings broaden our understanding of lateralities in neural function, provide insights into how this laterality is molecularly encoded and reveal an unusually diverse spectrum of signaling molecules involved in gustatory signal transduction.

Non-invasive recording in untethered animals is arguably the ultimate step in the analysis of neuronal function, but such recordings remain elusive. To address this problem, we devised a system that tracks neuron-sized fluorescent targets in real time. The system can be used to create virtual environments by optogenetic activation of sensory neurons, or to image activity in identified neurons at high magnification. By recording activity in neurons of freely moving C. elegans, we tested the long-standing hypothesis that forward and reverse locomotion are generated by distinct neuronal circuits. Surprisingly, we found motor neurons that are active during both types of locomotion, suggesting a new model of locomotion control in C. elegans. These results emphasize the importance of recording neuronal activity in freely moving animals and significantly expand the potential of imaging techniques by providing a mean to stabilize fluorescent targets.

This article describes the fabrication and use of microfluidic devices for investigating spatial orientation behaviors in nematode worms (Caenorhabditis elegans). Until now, spatial orientation has been studied in freely moving nematodes in which the frequency and nature of encounters with the gradient are uncontrolled experimental variables. In the new devices, the nematode is held in place by a restraint that aligns the longitudinal axis of the body with the border between two laminar fluid streams, leaving the animal's head and tail free to move. The content of the fluid streams can be manipulated to deliver step gradients in space or time. We demonstrate the utility of the device by identifying previously uncharacterized aspects of the behavioral mechanisms underlying chemotaxis, osmotic avoidance, and thermotaxis in this organism. The new devices are readily adaptable to behavioral and imaging studies involving fluid borne stimuli in a wide range of sensory modalities.

In this article we describe the challenges of transdisciplinary teamwork involving four faculty members from dissimilar epistemological traditions in the process of developing a manuscript on the lessons learned in our teaching collaboration. Our difficulty originated in implicit mental models and assumptions that caused incongruence between our intent to collaborate and the (habituated) relationship structure of the partnership. The dynamics are described through the lens of Tannenbaum and Schmidt's leadership model and Aristotle's Innov High Educ (2012) 37:171-184

Higher-order projection interneurons that function in more than one behavior have been identified in a number of preparations. In this study, we document that stimulation of cell Tr1, a previously identified trigger interneuron for swimming in the medicinal leech, can also elicit the motor program for crawling in isolated nerve cords. We also show that motor choice is independent of the firing frequency of Tr1 and amount of spiking activity recorded extracellularly at three locations along the ventral nerve cord prior to Tr1 stimulation. On the other hand, during Tr1 stimulation there is a significant difference in the amount of activity elicited in the ventral nerve cord that correlates with the motor program activated. On average, Tr1 stimulation trials that lead to crawling elicit greater amounts of activity than in trials that lead to swimming.