Dr. Eric S. Fortune, PhD
  Department of Biological Sciences
  New Jersey Institute of Technology
  Newark, NJ 07102-1982 USA
  Tel: +1 443 312 9610, FAX: +1 973 596 5689
  e-mail: eric.fortune@njit.edu


Research program: electric fish
Research program: songbirds


Locomotion Control

When an animal moves through its environment, this movement almost always generates massive stimulation of the animal's own sensory receptors. This self-generated sensory information is used in the ongoing control of its locomotor systems.

Weakly electric fish are interesting in this regard due to a special behavior: these animals vigorously and robustly maintain their position within refugia via back and forth swimming: they will work hard to maintain their position in a tube:

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We use this refuge tracking behavior as a tool to understand the sensory and motor mechanisms that these animals use to control their locomotion. On the sensory side, fish must determine the direction of movement of the refuge in order to track its movement. They primarily rely on visual and electrosensory feedback. Here the fish is tracking a moving tube in the dark, but dramatically changes its behavior when the lights are turned on.

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More recently we have begun to look closely at the motor side, with an effort to make EMG recordings while the animal performs the tracking behavior. Further, my colleagues in Noah Cowan's laboratory are studying the mechanics of the anal fin that these fish use for swimming.

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Relevant publications

Sefati, S., Neveln I.D., Roth E., Mitchell T.R., Snyder J.B., Maciver M.A., Fortune E.S., and N.J. Cowan (2013) Mutually opposing forces during locomotion can eliminate the tradeoff between maneuverability and stability. PNAS, 110:19798-18803, PMID:24191034.
Eigenmannia virescens escapes the tradeoff between manueverability and stability by generating forces that directly oppose each other and do not contribute to the translation of the fish.
Stamper, S.A., Roth, E., Cowan, N.J., and E.S. Fortune (2012) Active sensing via movement shapes spatiotemporal patterns of sensory feedback. J. Exp. Biol., 215:1567-1574, PMID:22496294.
Eigenmannia and other species of weakly electric fishes will swim to maintain their position within a moving refuge. We compared the performance of fish in refuge tracking when the fish were in the light and dark. We found that when there were no visual cues, the fish made oscillatory movements that, although dramatically increasing the distance that the fish swam, resulted in the same tracking performance as when the animals were given visual cues.
Roth, E., Zhuang, K., Stamper, S.A., Fortune, E.S., and N.J. Cowan (2011) Stimulus predictability mediates a switch in locomotor smooth pursuit performance for Eigenmannia virescens. PMID:21389203.

Eigenmannia virescens improve their tracking performance depending on the predictability of a refuge trajectory. This nonlinear switch results in reduced tracking error to simpler sinusoidal stimuli despite an often dramatic reduction in motor effort.
Cowan, N.J. and E.S. Fortune (2007) The critical role of locomotion mechanics in decoding sensory systems. J. Neurosci, 27:1123-1128, PMID:17267567.

Simple measurements - the position of the fish - were made during an image-stabilization task where fish swim back and forth to maintain position within a moving refuge. Using basic laws of swimming mechanics, we built a model for sensory computations necessary for the control of the motor system during the task. The model matched neurophysiological properties of the electrosensory system in these fish. These physiological properties, particularly high-pass filtering of sensory signals, are found in a wide array of sensory systems and may reflect a common role in motor control.
@ericfortunephd 11-Dec-2015