Crickets provide a useful model system to study how animals analyze sound frequency. While much is known about how sound frequency is represented by central neurons and in behavior, little is yet known about auditory receptor neurons. I investigated physiological and anatomical properties of auditory receptor fibers (ARFs) and functional organization of their axon terminals, using single-unit recording and staining techniques. Behavioral experiments suggest that crickets are sensitive to two broad frequency ranges, centered at 4--5 kHz for acoustic communication and at 25--50 kHz for predator detection. However, cricket ARFs fall into three distinct populations, based on characteristic frequency (CF; low frequency, ∼3--5.5 kHz; mid frequency, 9--12 kHz; ultrasound, ≥18 kHz). One striking characteristic of single ARFs is the occurrence of multiple sensitivity peaks at different frequencies, which implies that the wide audible range of crickets is mediated by these multiple sensitivity peaks, even though CFs of ARFs are clustered at the three small ranges. To understand how populations of ARFs code sound intensity, level-response functions are examined. Physiological parameters derived from level-response functions are diverse, and are systematically related to threshold within each population. Low-frequency ARFs comprise two distinct anatomical types, based on the distributions of axon terminals, which also differ physiologically. Thus, based on CF and anatomy, cricket ARFs can be classified into four distinct populations. To understand how information flows from peripheral to central neurons, the positions of varicosities, i.e. output sites, of ARF axon terminals are mapped on a two-dimensional coordinate system. In crickets, the ARF axon terminals are functionally organized with respect to frequency and intensity. Anatomical organization with respect to threshold is related to physiological organization, which may reduce non-linear effects in postsynaptic
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.36956 |
| Date | January 2000 |
| Creators | Imaizumi, Kazuo. |
| Contributors | Pollack, Gerald S. (advisor) |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Department of Biology.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001810432, proquestno: NQ70047, Theses scanned by UMI/ProQuest. |
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