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Neuronal pathways for the lingual reflex in the Japanese toad
T Matsushima1, M Satou, K Ueda
1Zoological Institute, Faculty of Science, University of Tokyo, Japan.
Journal of Comparative Physiology. A, Sensory, Neural, and Behavioral Physiology
|December 1, 1988
Summary
This study reveals distinct neural pathways controlling anuran tongue movements, differentiating between protractor and retractor motoneurons based on glossopharyngeal nerve afferent signals.
Area of Science:
- Neuroscience
- Comparative Physiology
- Motor Control
Background:
- Anuran tongue movements, crucial for prey capture and feeding, are modulated by both visual and intra-oral stimuli.
- Understanding the neural circuitry underlying these complex motor behaviors is essential for comprehending vertebrate motor control.
Purpose of the Study:
- To investigate the neuronal pathways connecting glossopharyngeal (IX) afferents to hypoglossal (XII) tongue motoneurons in anurans.
- To differentiate the neural responses elicited in tongue-protractor motoneurons (PMNs) and tongue-retractor motoneurons (RMNs).
Main Methods:
- Recording of field potentials on the bulbar dorsal surface following ipsilateral IX nerve stimulation.
- Intra-axonal recording of orthodromic action potentials from IX afferent fibers.
- Electrophysiological analysis of excitatory postsynaptic potentials (EPSPs) in PMNs and RMNs.
Main Results:
- Two distinct groups of IX afferent fibers (S1 and S2 waves) with different conduction velocities were identified.
- IX nerve stimulation elicited EPSPs in both PMNs and RMNs, with no observed inhibitory postsynaptic potentials.
- EPSPs in RMNs exhibited shorter onset latencies and distinct early/late components compared to PMNs.
Conclusions:
- The study elucidates specific neural pathways mediating tongue movements in anurans, involving distinct afferent fiber groups and differential motoneuron responses.
- Findings contribute to understanding the neural basis of feeding behaviors and motor control in vertebrates.