Multisensory processing and arousal modulation in the nematode C. elegans
Yoshinori Tanizawa, William R. Schafer
Poster
Time: 2009-06-29 11:00 AM – 12:30 PM
Last modified: 2009-06-04
Abstract
The nervous system of the nematode C.elegans, a tiny worm of 1 mm long, consists of 302 neurons, and all the synaptic connections (~ 7000 chemical and ~ 700 electrical synapses) were described by electron microscopic observation. Despite such simplicity of the nervous system, worms can sense and respond to various sensory stimuli including taste, odor, temperature, UV light and mechanical stimuli. Ease of genetic manipulation and its transparent body make it possible to control/ monitor activity of specific neurons in vivo with genetically-encoded tools. Finally, a huge repository of mutants allows us to examine the roles of genes in the nervous system. These characteristics will make C. elegans a good model to study multisensory processing in its simplest form, at multiple levels from gene to behavior.
Using C. elegans as a model, we are studying how sensory stimuli in different modalities interact each other in the nervous system. As sensory inputs, we are currently using two stimuli: actual mechanical stimuli to body and artificial activation of nociceptive neurons with light-gated ion channel channelrhodopsin-2, allowing precise control of stimulus strength and location. Analysis of behavioral response (withdrawal response) to these inputs so far indicated no sign of additive effect when the two inputs were presented simultaneously. However, when interval was given between the two stimuli, significant enhancement of response to the second stimulus with enhanced motor activity was observed. This result indicates there is ‘arousal’ change in the worm nervous system, which is also important to understand indirect interaction among different modalities. By screening available mutants, we also found that neuropeptide signaling plays a role in arousal modulation. Now we are trying to measure the activity of neurons in behaving worms using genetically-encoded activity sensors, to understand where and how this change is occurring at cellular level. Also, activity monitoring can possibly identify multisensory integration effect at cellular level despite that it was not identified behaviorally so far. We are also going to use stimuli in other modalities to discover novel interaction among them in multisensory integration and arousal modulation.
Using C. elegans as a model, we are studying how sensory stimuli in different modalities interact each other in the nervous system. As sensory inputs, we are currently using two stimuli: actual mechanical stimuli to body and artificial activation of nociceptive neurons with light-gated ion channel channelrhodopsin-2, allowing precise control of stimulus strength and location. Analysis of behavioral response (withdrawal response) to these inputs so far indicated no sign of additive effect when the two inputs were presented simultaneously. However, when interval was given between the two stimuli, significant enhancement of response to the second stimulus with enhanced motor activity was observed. This result indicates there is ‘arousal’ change in the worm nervous system, which is also important to understand indirect interaction among different modalities. By screening available mutants, we also found that neuropeptide signaling plays a role in arousal modulation. Now we are trying to measure the activity of neurons in behaving worms using genetically-encoded activity sensors, to understand where and how this change is occurring at cellular level. Also, activity monitoring can possibly identify multisensory integration effect at cellular level despite that it was not identified behaviorally so far. We are also going to use stimuli in other modalities to discover novel interaction among them in multisensory integration and arousal modulation.