Biomedical subjects

Sheryl Coombs

Publications and source records attributed to Sheryl Coombs.

4 recordsLinked to original sources

PubMed2006

Distant touch hydrodynamic imaging with an artificial lateral line.

Nearly all underwater vehicles and surface ships today use sonar and vision for imaging and navigation. However, sonar and vision systems face various limitations, e.g., sonar blind zones, dark or murky environments, etc. Evolved over millions of years, fish use the lateral line, a distributed linear array of flow sensing organs, for underwater hydrodynamic imaging and information extraction. We demonstrate here a proof-of-concept artificial lateral line system. It enables a distant touch hydrodynamic imaging capability to critically augment sonar and vision systems. We show that the artificial lateral line can successfully perform dipole source localization and hydrodynamic wake detection. The development of the artificial lateral line is aimed at fundamentally enhancing human ability to detect, navigate, and survive in the underwater environment.

Animals↗

PubMed2003

Rheotaxis and prey detection in uniform currents by Lake Michigan mottled sculpin (Cottus bairdi).

Lake Michigan mottled sculpin, Cottus bairdi, exhibit a lateral-line mediated, unconditioned orienting response, which is part of the overall prey capture behavior of this species and can be triggered in visually deprived animals by both live (e.g. Daphnia magna) and artificial (e.g. chemically inert vibrating sphere) prey. However, the extent to which background water motions (e.g. currents) might mask the detection of biologically significant stimuli like these is almost entirely unknown, despite the fundamental nature and importance of this question. To examine this question, the orienting response of mottled sculpin was used to measure threshold sensitivity to a nearby artificial prey (a 50 Hz vibrating sphere) as a function of background noise level (unidirectional currents of different flow velocities). Because many fish show unconditioned rheotaxis to uniform currents, we also measured the fish's angular heading relative to the oncoming flow in the absence of the signal. Frequency distributions of fish headings revealed positive rheotaxis to flows as low as 4 cm s(-1) and an increasing degree of alignment with the oncoming flow as a function of increasing flow velocity. Sculpin positioned in the upstream direction were able to detect relatively weak signals (estimated to be approx. 0.001-0.0001 peak-peak cm s(-1) at the location of the fish) in the presence of strong background flows (2-8 cm s(-1)), and signal levels at threshold increased by less than twofold for a fourfold increase in flow velocity. These results are consistent with the idea that lateral line canals behave as high-pass filters to effectively reject low frequency noises such as those caused by slow d.c. currents.

Animals↗

PubMed2002

Modeling electrosensory and mechanosensory images during the predatory behavior of weakly electric fish.

Black ghost knifefish (Apteronotus albifrons) are nocturnal, weakly electric fish that feed on insect larvae and small crustaceans in the freshwater rivers of South America. In the absence of visual cues, prey detection and localization in this species is likely to rely on weak electrosensory and mechanosensory cues generated by the prey. In this paper, a modeling approach is used to estimate contributions to prey capture behavior from three octavolateralis modalities: the high- (tuberous) and low- (ampullary) frequency components of the electric sense and the high-frequency (canal neuromast) component of the lateral line mechanosensory system. For each of these modalities, the physical stimulus generated by the prey is approximated using a simple dipole model. Model parameters are constrained using previously published data as well as new empirical data on the electrical impedance characteristics of Daphnia magna. Models of electrosensory and mechanosensory stimuli are combined with actual prey strike trajectories from infrared video recordings to reconstruct spatial images of the prey along the sensory surface of the fish during the behavior. Modeling results suggest that all three modalities might contribute and that the relative contributions may change as a function of environmental conditions (e.g., water conductivity) and as a function of time over the course of the prey capture event.

Animals↗

PubMedDate not supplied

Information-processing demands in electrosensory and mechanosensory lateral line systems.

The electrosensory and mechanosensory lateral line systems of fish exhibit many common features in their structural and functional organization, both at the sensory periphery as well as in central processing pathways. These two sensory systems also appear to play similar roles in many behavioral tasks such as prey capture, orientation with respect to external environmental cues, navigation in low-light conditions, and mediation of interactions with nearby animals. In this paper, we briefly review key morphological, physiological, and behavioral aspects of these two closely related sensory systems. We present arguments that the information processing demands associated with spatial processing are likely to be quite similar, due largely to the spatial organization of both systems and the predominantly dipolar nature of many electrosensory and mechanosensory stimulus fields. Demands associated with temporal processing may be quite different, however, due primarily to differences in the physical bases of electrosensory and mechanosensory stimuli (e.g. speed of transmission). With a better sense of the information processing requirements, we turn our attention to an analysis of the functional organization of the associated first-order sensory nuclei in the hindbrain, including the medial octavolateral nucleus (MON), dorsal octavolateral nucleus (DON), and electrosensory lateral line lobe (ELL). One common feature of these systems is a set of neural mechanisms for improving signal-to-noise ratios, including mechanisms for adaptive suppression of reafferent signals. This comparative analysis provides new insights into how the nervous system extracts biologically significant information from dipolar stimulus fields in order to solve a variety of behaviorally relevant problems faced by aquatic animals.

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