The detection of specific temporal patterns in communication signals may be of vital importance for certain organisms. In crickets, for instance, a female will move towards a singing male only if she can recognize the appropriate pulse rate characteristic to its own species' song. Additionally, in order to evade predatory insectivorous bats, flying crickets must be able to track the predator's ultrasonic echolocation signals, which are emitted at a variety of pulse rates. In this thesis, the temporal processing, or the integration of stimulus through time, in the peripheral1 auditory system of the cricket will be investigated. / The ON1 interneuron temporal processing was first examined and compared at high (bat-like) and low carrier (cricket-like) frequencies in three different experimental paradigms. First, integration time, which corresponds to the time it takes for a neuron to reach threshold when stimulated at the minimum effective intensity, was found to be significantly shorter at high carrier frequency than at low carrier frequency. Second, phase locking to sinusoidally amplitude modulated (SAM) signals was more efficient at high frequency, especially at high modulation rates and low modulation depths. Finally, we examined the efficiency with which ON1 detects gaps in a constant tone. As reflected by the decrease in firing rate in the vicinity of the gap, ON1 is better at detecting gaps at low carrier frequency. Following a gap, firing rate increases beyond the pre-gap level. This "rebound" phenomenon is similar for low and high carrier frequencies. / To determine the source of this differential temporal processing, the sensory afferents making synapses with ON1 were investigated. Low frequency (MT-type) and ultrasound auditory receptors were compared on the basis of latency, maximum firing rate, adaptation, information transmission, bursting and feature detection. Ultrasound receptors (HFs) were found to have a shorter latency, a higher maximum firing rate and stronger adaptation than low-frequency receptors (LFs). Individual HFs transmitted more linear (lower-bound) information than LFs. However, HFs' responses were more correlated than LFs' (i.e. they had larger mutual information), so that when superposing the spike trains of LFs, information transmission in the lowest amplitude modulation rates was greatly improved, and, in some cases, reached the level of HFs. Feature detection by spike in HFs was better than in LFs. Feature detection by bursts was better than for spikes, but equivalent in both types of receptors. The level of bursting in HFs, however, was much higher than in LFs, making them better feature detectors in general. / 1Because it lies in the prothoracic ganglion, ON1 is technically part of the central nervous system. For the purpose of this thesis, however, because ON1 receives direct input from the receptors, it will be considered to be part of the peripheral auditory systems.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.112360 |
| Date | January 2008 |
| Creators | Sabourin, Patrick. |
| 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 | Master of Science (Department of Biology.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 002770478, proquestno: AAIMR51338, Theses scanned by UMI/ProQuest. |
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