Biomedical subjects

Ronald R Hoy

Publications and source records attributed to Ronald R Hoy.

10 recordsLinked to original sources

PubMed2006

An inexpensive sub-millisecond system for walking measurements of small animals based on optical computer mouse technology.

Stimuli from a broad spectrum of sensory modalities, including visual, auditory, thermal, and chemical, can elicit walking responses in animals, reflecting neural activity in sensorimotor pathways. We have developed an integrated walking measurement system with sub-millisecond temporal accuracy capable of detecting position changes on the order of 100 microm. This tracking system provides the experimenter with a means by which to map out the response spectrum of a tethered animal to any number of sensory inputs on time scales relevant to propagation in the nervous system. The data acquisition system consists of a modified optical computer mouse, a microcontroller with peripheral support circuitry, a binary stimulus sync line, and a serial (RS-232) data transfer interface. The entire system is constructed of relatively inexpensive components mostly converted from commercially available peripheral devices. We have acquired walking data synchronized with auditory stimuli at rates in excess of 2100 samples per second while applying this system to the walking phonotactic response of the parasitic fly Ormia ochracea.

Acoustic Stimulation↗

PubMed2006

Flexible multielectrodes can resolve multiple muscles in an insect appendage.

Research into the neuromechanical basis of behavior, either in biomechanics, neuroethology, or neuroscience, is frequently limited by methods of data collection. Two of the most pressing needs are for methods with which to (1) record from multiple neurons or muscles simultaneously and (2) perform this recording in intact, behaving animals. In this paper we present the fabrication and testing of flexible multielectrode arrays (fMEAs) that move us significantly towards these goals. The fMEAs were used to record the activity of several distinct units in the coxa of the cockroach Blaberus discoidalis. The devices fabricated here address the first goal in two ways: (1) their flexibility allows them to be inserted into an animal and guided through internal tissues in order to access distinct groups of neurons and muscles and (2) their recording site geometry has been tuned to suit the anatomy under study, yielding multichannel spike waveforms that are easily separable under conditions of spike overlap. The flexible nature of the devices simultaneously addresses the second goal, in that it is less likely to interfere with the natural movement of the animal.

Algorithms↗

PubMed2006

Measuring and quantifying dynamic visual signals in jumping spiders.

Animals emit visual signals that involve simultaneous, sequential movements of appendages that unfold with varying dynamics in time and space. Algorithms have been recently reported (e.g. Peters et al. in Anim Behav 64:131-146, 2002) that enable quantitative characterization of movements as optical flow patterns. For decades, acoustical signals have been rendered by techniques that decompose sound into amplitude, time, and spectral components. Using an optic-flow algorithm we examined visual courtship behaviours of jumping spiders and depict their complex visual signals as "speed waveform", "speed surface", and "speed waterfall" plots analogous to acoustic waveforms, spectrograms, and waterfall plots, respectively. In addition, these "speed profiles" are compatible with analytical techniques developed for auditory analysis. Using examples from the jumping spider Habronattus pugillis we show that we can statistically differentiate displays of different "sky island" populations supporting previous work on diversification. We also examined visual displays from the jumping spider Habronattus dossenus and show that distinct seismic components of vibratory displays are produced concurrently with statistically distinct motion signals. Given that dynamic visual signals are common, from insects to birds to mammals, we propose that optical-flow algorithms and the analyses described here will be useful for many researchers.

Algorithms↗

PubMed2006

The ability of the parasitoid fly Ormia ochracea to distinguish sounds in the vertical plane.

The parasitic fly Ormia ochracea localizes its host, field crickets, by homing in on their calling song. Previous phonotactic studies indicate that their sound localization ability in azimuth is extraordinarily acute, but the fly's ability to localize the elevation of sound sources has not been tested to date. Here we show that in a freely-walking closed-loop Y-maze task elevational performance is well above chance, but slightly below the fly's performance in azimuth. Immobilizing the head or the halteres (sensory organs of balance) slightly lowered elevational discrimination, but performance was still well above chance. Because ormiine ears are thought to be symmetric and the pure-tone models of a cricket's call used in these experiments contained little to no spectral bandwidth, additional studies will be needed to elucidate the underlying cues. Nonetheless, it is clear that while walking, Ormia flies are capable of distinguishing sound sources that differ only in elevation.

Animals↗

PubMed2005

The development of a long, coiled, optic nerve in the stalk-eyed fly Cyrtodiopsis whitei.

In the stalk-eyed fly Cyrtodiopsis whitei (Diopsidae; Diptera), the relatively long optic nerve develops within the tight lumen of a very short eyestalk. Axonal growth is generally considered in terms of path finding, selective fasciculation, and towing. Physical forces that are necessary for axon lengthening are generated either by the growth cone or by the growth of surrounding tissues. Therefore, it is surprising to encounter a loosely coiled nerve apparently lacking any attachments that could allow for pull, or towing, of the nerve. In this study, we used histological sections and whole-mount preparations to confirm that the optic nerve of the stalk-eyed fly indeed elongates without the external application of tension to the nerve. Secondly, we examined the distribution of cytoskeletal elements and selected proteins that may be involved in axon extension. Staining against the vesicle fusion proteins SNAP-24 and SNAP-25 consistently results in stronger staining in the rapidly extending optic nerve than in a control nerve, suggesting a possible role of these proteins in the extension process. On a gross morphological level, SNAP-24/25 as well as the cytoskeletal elements actin and tubulin are uniformly distributed throughout the lengths of the growing nerve, suggesting that nerve elongation is distributed rather than localized. Finally, we identified glia as a possible source for tension within the nerve bundle. Glia proliferate rapidly in the optic nerve but not in the control nerve. Much work continues to focus on the growth of axons in culture, but this study is one of the few that considers the dynamics of nerve bundle extension as a whole.

Actins↗

PubMed2004

Identified auditory neurons in the cricket Gryllus rubens: temporal processing in calling song sensitive units.

This study characterizes aspects of the anatomy and physiology of auditory receptors and certain interneurons in the cricket Gryllus rubens. We identified an 'L'-shaped ascending interneuron tuned to frequencies > 15 kHz (57 dB SPL threshold at 20 kHz). Also identified were two intrasegmental 'omega'-shaped interneurons that were broadly tuned to 3-65 kHz, with best sensitivity to frequencies of the male calling song (5 kHz, 52 dB SPL). The temporal sensitivity of units excited by calling song frequencies were measured using sinusoidally amplitude modulated stimuli that varied in both modulation rate and depth, parameters that vary with song propagation distance and the number of singing males. Omega cells responded like low-pass filters with a time constant of 42 ms. In contrast, receptors significantly coded modulation rates up to the maximum rate presented (85 Hz). Whereas omegas required approximately 65% modulation depth at 45 Hz (calling song AM) to elicit significant synchrony coding, receptors tolerated a approximately 50% reduction in modulation depth up to 85 Hz. These results suggest that omega cells in G. rubens might not play a role in detecting song modulation per se at increased distances from a singing male.

Acoustic Stimulation↗

PubMed2004

The effect of substrate on the efficacy of seismic courtship signal transmission in the jumping spider Habronattus dossenus (Araneae: Salticidae).

The jumping spider Habronattus dossenus Griswold 1987 (Salticidae) communicates using seismic signals during courtship and can be found on rocks, sand and leaf litter. We examined the filtering properties of, and tested the efficacy of male courtship signals on, these natural substrates. These substrates have drastically different filtering properties at the distances at which the males court. Rocks sharply attenuated all frequencies, with considerable variability among different rocks. Desert sand showed band-pass properties, attenuating frequencies contained in the animal's signal. Leaf litter passed all frequencies and was the most favourable signalling environment. In behavioural trials, the proportion of males mating successfully was significantly higher on leaf litter than on rocks or desert sand. Males did not modify their courtship behaviour on different substrates. Therefore, the effectiveness of male courtship seismic signals appears to be strongly constrained by the available substratum resources.

Animal Communication↗

PubMed2003

Seismic signals in a courting male jumping spider (Araneae: Salticidae).

Visual displays in jumping spiders have long been known to be among the most elaborate animal communication behaviours. We now show that one species, Habronattus dossenus, also exhibits an unprecedented complexity of signalling behaviour in the vibratory (seismic) modality. We videotaped courtship behaviour and used laser vibrometry to record seismic signals and observed that each prominent visual signal is accompanied by a subsequent seismic component. Three broad categories of seismic signals were observed ('thumps', 'scrapes' and 'buzzes'). To further characterize these signals we used synchronous high-speed video and laser vibrometry and observed that only one seismic signal component was produced concurrently with visual signals. We examined the mechanisms by which seismic signals are produced through a series of signal ablation experiments. Preventing abdominal movements effectively 'silenced' seismic signals but did not affect any visual component of courtship behaviour. Preventing direct abdominal contact with the cephalothorax, while still allowing abdominal movement, only silenced thump and scrape signals but not buzz signals. Therefore, although there is a precise temporal coordination of visual and seismic signals, this is not due to a common production mechanism. Seismic signals are produced independently of visual signals, and at least three independent mechanisms are used to produce individual seismic signal components.

Abdomen↗

PubMed2002

Physiology of the auditory afferents in an acoustic parasitoid fly.

The fly, Ormia ochracea, possess a novel auditory organ, which allows it to detect airborne sounds. The mechanical coupling of its pair of tympanal membranes provides the basis for a unique means of sensing the direction of a sound source. In this study, we characterized the neuroanatomy, frequency tuning, and neurophysiological response properties of the acoustic afferents. Our experiments demonstrate that the fly's nervous system is able to encode and localize the direction of a sound source, although the binaural auditory cues available in the acoustic sound field are miniscule. Almost all of the acoustic afferents recorded in this study responded to short and long sound pulses with a phasic burst of one to four action potentials. A few afferents responded tonically for the duration of the sound stimulus. A prominent class of afferents responds to suprathreshold stimuli with only a single spike discharge, independent of stimulus level, frequency, or duration. We also tested the response of the afferents to speakers separated by 180 degrees along the azimuth of the fly. We found that the afferent responses have a shorter latency because of ipsilateral stimulation. This could be a temporal code of the direction of a sound source. The threshold frequency tuning for the afferents revealed a range of sensitivities to the frequency of the cricket host's calling song frequency. The difference in the number of afferents above threshold on either side of the animal is a population code, which can also be used for sound localization.

Acoustic Stimulation↗

PubMed2002

Two-tone suppression in the cricket, Eunemobius carolinus (Gryllidae, Nemobiinae).

Sounds with frequencies >15 kHz elicit an acoustic startle response (ASR) in flying crickets (Eunemobius carolinus). Although frequencies <15 kHz do not elicit the ASR when presented alone, when presented with ultrasound (40 kHz), low-frequency stimuli suppress the ultrasound-induced startle. Thus, using methods similar to those in masking experiments, we used two-tone suppression to assay sensitivity to frequencies in the audio band. Startle suppression was tuned to frequencies near 5 kHz, the frequency range of male calling songs. Similar to equal loudness contours measured in humans, however, equal suppression contours were not parallel, as the equivalent rectangular bandwidth of suppression tuning changed with increases in ultrasound intensity. Temporal integration of suppressor stimuli was measured using nonsimultaneous presentations of 5-ms pulses of 6 and 40 kHz. We found that no suppression occurs when the suppressing tone is >2 ms after and >5 ms before the ultrasound stimulus, suggesting that stimulus overlap is a requirement for suppression. When considered together with our finding that the intensity of low-frequency stimuli required for suppression is greater than that produced by singing males, the overlap requirement suggests that two-tone suppression functions to limit the ASR to sounds containing only ultrasound and not to broadband sounds that span the audio and ultrasound range.

Acoustic Stimulation↗