Movement
control in
fish
My research integrates biomechanics and neurobiology to study how axial
movements are generated and coordinated to respond to the physical
properties
of an organism's environment. Of particular interest to me are the
startle
response (Figure 1) and rhythmic swimming behaviors of fishes. These
behaviors
provide excellent model systems for examining motor control and the
mechanics
of axial movement. Because the startle response involves a discrete
behavior,
large neurons and simple neural circuits, it has been important in
studies
of motor control. Because it is critical for survival and involves
maximal
performance, it has been important for work on muscle physiology and
performance.
Rhythmic axial and fin swimming has long been studied in lampreys and
tadpoles
to examine central pattern generation in spinal circuits and in a wide
diversity of fishes to understand the relationship between morphology
and
movement.
The scope of questions I am asking can be divided into three
interconnected
research initiatives. The first explores the broad question: How do
morphology,
physiology and the physics of the aquatic environment interact to
produce
swimming movement? To address this question, I examine the scaling of
locomotor
performance through development with changes in the physics of movement
such as the Reynolds number, a ratio of inertial to viscous forces. The
second area examines the generation of swimming movements. Questions I
am addressing include: How do reticulospinal and spinal neurons and
circuits
generate startle behavior? And, how are gate transitions due to the
physics
of movement mediated neurally? To address these questions I examine
reticulospinal
and spinal interneuron morphology and function in zebrafish and examine
comparatively species that differ in components of their startle neural
circuits. A third area of research examines the evolution of neural
circuits
and behaviors. Through this work I am addressing the general question:
How are neural circuits and behaviors modified evolutionarily? I
examine
the startle neural circuit in fishes comparatively within a
phylogenetic
context. In addition, mutant and transgenic zebrafish are providing new
ways of addressing evolutionary questions such as this.
My approaches to these questions include using zebrafish as a
model
as well as comparative work on actinopterygian fishes. Larval
zebrafish,
in addition to being an excellent genetic system, are transparent which
makes optical imaging of neuron morphology (Figure 2) and activity as
well
as targeted neuron ablations possible in whole, in vivo preparations.
With
these techniques, we are able to combine functional imaging studies of
neurons with behavior. In order to look simultaneously at neuron
activity
and fish movement, we label cells with calcium sensitive dyes and
simultaneously
image neurons firing with confocal microscopy and axial movements with
high-speed video. With a complementary set of techniques, we kill
neurons
with cell targeted laser ablations and can compare behavior before and
after the cells are removed (Figure 3). Because with such ablations we
are able to very specifically remove cells without collateral damage,
these
techniques allow fine manipulation of the system.
| References |
Hale, M. E., J. H. Long, M. J.
McHenry, and M. W.
Westneat Evolution of
behavior and neural control of the
Fast-Start Escape Response. Evolution. In press.
Hale, M. E., D.A. Ritter and J. R. Fetcho (2001)
A confocal study
of spinal interneurons in living larval zebrafish. J. Comp.
Neurol.437:1-16.
Bhatt, D. H., M. E. Hale, and J. R. Fetcho (2001)
Activation of
zebrafish
spinal interneurons in different forms of the escape behavior. Society
for Neuroscience Abstracts. 27:830.1
Hale, M. E. 2000. Startle responses of fish without
Mauthner neurons:
Escape
behavior of the lumpfish (Cyclopterus lumpus). Bio. Bull.199:180-182.
Hale, M.E. and J. R. Fetcho 2000. Alternative
neuromotor mechnisms of
the
startle response in fishes. Society for Neuroscience Abstracts.
26:746.2.
Hale, M. E. 2000. Fast start behaviors of fish lacking
Mauthner
neurons. Am.
Zool. 41:1040-1041A
Hale, M. E. 1999. Effects of size and ontogeny on the
fast-start
performance
of several salmonid species. J. Exp. Biol. 202:1465-1479
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Last updated 8/3/06
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