ISSN:
1432-1351
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Medicine
Notes:
Summary 1. The large segmental auditory neuron (LSAN) was identified both morphologically and physiologically in experiments with extracellular recording of spike potentials by electrodes filled with 2–3 M CoCl2. 2. The LSAN connects left and right auditory neuropiles of the prothoracic ganglion and has no branches outside them (Fig. 3). Soma-ipsilateral arborizations are physiologically interpreted as dendritic, receiving information from different primary tympanal organ fibres. The axon crosses the midline of the ganglion via an antero-ventral commissural bridge and gives off 2 main branches, medial and lateral, projecting into all 3 parts of the contralateral auditory neuropile. There they form terminal arborizations with characteristic large (1–1.5 μm) synaptic boutons (Fig. 1B, C). 3. The LSAN is a tonic unit working in the frequency range of 2–3 kHz to 20–45 kHz with a narrow sensitivity maximum at 5 kHz, and moderate sensitivity at high frequencies above 8 kHz. The exact form of the tuning curves depends on the direction of sound incidence and absolute intensity (Fig. 6). 4. The LSAN has sharp directional sensitivity only within a limited frequency range very close to the 5 kHz optimum (Fig. 5), corresponding to the peak frequency of the conspecific calling song. At 5 kHz it is most sensitive to frontal stimulation, at high frequencies above 18 kHz — to caudal stimulation. 5. The LSAN precisely reproduces the time-pattern of the calling song and accurately codes the absolute intensity of such signals (Fig. 7, 8). 6. It is suggested that the LSAN plays an important role in the location of singing conspecifics in the field.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00666372
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