The jamming avoidance response of African electric fish, Gymnarchus, offers an excellent model system where computational algorithms for a behavior is well understood and neuronal elements are accessible for neurophysiological studies. Temporal modulations of two stimulus parameters, amplitude and phase of the electrosensory signal, carry essential information for the behavior. We are currently entering an exciting phase of the investigation where we examine the interaction of postsynaptic potentials generated by these two parameters in neurons that are sensitive to behaviorally relevant combination of signal components. This project is currently funded by National Science Foundation.
References:
Kawasaki M (1993) Independently evolved jamming avoidance responses employ identical computational algorithms: a behavioral study of the African electric fish, Gymnarchus niloticus. J Comp Physiol 173: 9-22
Kawasaki M, Guo Y (1998) Parallel projection of amplitude and phase information from the hindbrain to the midbrain of the African electric fish, Gymnarchus niloticus. J Neurosci 18: 7599-7611
Kawasaki M, Guo Y-X (1996) Neuronal circuitry for comparison of timing in the electrosensory lateral line lobe of an African wave-type electric fish, Gymnarchus niloticus. J Neurosci 16: 380-391
Matsushita A, Kawasaki M (2002) A novel cell type for phase computation in the electrosensory lateral line lobe of Gymnarchus niloticus. Program No 87.2. Abstract Viewer and Itinerary Planner. Washington, DC: Society for Neuroscience Online
Kawasaki M, Guo Y-X (in press) Emergence of temporal-pattern sensitive neurons in the midbrain of weakly electric fish Gymnarchus niloticus. J. Physiol. Paris
Wave-type electric fishes are capable of detecting a small time difference in the nanosecond range in sensory signals when performing the jamming avoidance response. This temporal hyperacuity behavior was first discovered in Eigenmannia by Rose and Heiligenberg (1985). We have found later that an independently evolved electric fish, Gymnarchus, also exhibit the same level of behavioral acuity. In Gymnarchus, the neuronal mechanisms that detect small time differences are more accessible. Thus, we investigate how these neurons detect small time disparities in this fish. This project is supported by the Japan Science and Technology Corporation (PRESTO).
References:
Rose GJ, Heiligenberg W (1985) Temporal hyperacuity in the electric sense of fish. Nature 318: 178-180
Kawasaki M, Rose GJ, Heiligenberg W (1988) Temporal hyperacuity in single neurons of electric fish. Nature 336: 173-176
Guo Y-X, Kawasaki M (1997) Representation of accurate temporal information in the electrosensory system of the African electric fish, Gymnarchus niloticus. J Neurosci 17: 1761-1768
Kawasaki M (1997) Sensory hyperacuity in the jamming avoidance response of weakly electric fish. Curr Opin Neurobiol 7: 473-479
Kawasaki M, Takagi H (in press) Modeling of time disparity detection by the Hodgkin-Huxley equations. J. Comp. Physiol.
We have recently discovered that some neurons in the midbrain of Gymnarchus respond specifically to a specific temporal combination of stimulus parameters that is relevant for jamming avoidance responses. These neurons send a long axon to a previously unknown area in the medulla. We plan to record from this new area (medullary prepacemaker nucleus) and investigate neuronal connection between this area and the final output structure, the pacemaker nucleus. This project in the motor system will complete the tracking of the information flow from electroreceptor afferents to the final output for the jamming avoidance response in Gymnarchus.
References:
Kawasaki M (1994) The African wave-type electric fish, Gymnarchus niloticus, lacks corollary discharge mechanisms for electrosensory gating. J Comp Physiol 174: 133-144
Kawasaki M (1996) Comparative analysis of the jamming avoidance response in African and South American wave-type fishes. Biol Bull 191: 103-108
Kawasaki M, Heiligenberg W (1990) Different classes of glutamate receptors and GABA mediate distinct modulations in the firing pattern of a neuronal oscillator, the medullary pacemaker of gymnotiform electric fish. J Neurosci 10: 3896-3904
Kawasaki M, Maler L, Rose GJ et al. (1988) Anatomical and functional organization of the prepacemaker nucleus in gymnotiform electric fish: The accommodation of two behaviors in one nucleus. J Comp Neurol 276: 113-131
The frequency of electric organ discharges in a wave-type electric fish, Eigenmannia, has been recently found to decelerate in response to amplitude modulation of electrosensory feedback in immobilized preparations. We are currently exploring naturally behaving individuals for this new type of electrical behavior.
Reference:
Takizawa Y, Rose G, Kawasaki M (1999) Resolving competing theories for control of the jamming avoidance response: the role of decelerations to amplitude modulations. J Exp Biol 202: 1377-1386
