See an example of how lateral line excitation patterns are
modeled.
A computer program for modeling the flow field about a vibratory source has been developed
by Dr. Mardi Hastings and her students in the Engineering Department at Ohio State in
collaboration with Parmly faculty member Sheryl Coombs. This program is based on the flow
field equations for a dipole source and is a collection of Matlab files designed to
calculate and display the pressure, intensity, and flow (velocity) lines generated by a
dipole source in a single plane at a time. The orientation and distance of the plane re:
the source and its axis of vibration can be specified with user-defined inputs, as can
source size, frequency and amplitude of vibration. Thus, multiple views can be used to
build a 3D view of the flow field for different source parameters. This program has been
used in the analysis of behavioral results to map the step-by-step approach positions of
mottled sculpin into the computed map of the flowfield. In addition, it has been used to
predict the spatial distributions of pressure gradients, the effective stimulus to the
lateral line system, along different subcomponents of the lateral line system, for example
the trunk lateral line canal. In these cases, the canal is modeled as a simple straight
tube with a series of pressure sampling points, or pores leading into the canal. Since
there is generally one neuromast between every two pores, the response of the neuromast to
fluid flow inside the canal will be proportional to the pressure gradient across the two
pores. Thus, by knowing the spatial separation between pores on the canal (this can be
obtained from simple anatomical measurements on real fish), one can compute the pressure
difference between each consecutive pair of pores to generate the pressure gradient
pattern along the canal. Recent modifications of the Matlab program by Ruth Conley have
allowed pressure gradient patterns along fish to be displayed as a visual spectrum, so
that one can easily visualize how these patterns change as mottled sculpin approach
vibratory sources. This strategy has enabled us to determine the sensory cues and approach
strategies used by mottled sculpin in locating dipole sources (Coombs & Conley 1994,
1995; Conley & Coombs 1996) and has led to new theories about how source distance
might be encoded by both the amplitude and phase pattern of pressure gradients along the
spatially-distributed lateral line system (Coombs, Hastings & Finneran 1995).
See an example of how lateral line excitation patterns are
modeled.