Perhaps the most amazing feature of weakly electric fishes are the 'massless'
electrosensory behaviors that they exhibit. These include complex behaviors
such as the jamming avoidance response and social signaling. Because these behaviors
do not require movement, intracellular recordings from the CNS neurons that control
these behaviors can be achieved in awake, behaving animals. These sorts of experiments
have been at the core of our experimental analysis for many years now.
These social electrosensory behaviors also have broader consequences for the
organism, potentially having profound impacts on locomotion control, electrosensory
perception of moving objects, and the spatial
distribution of conspecifics. Due to its pervasive role in behavioral control,
and because these social signals are experimentally tractable, we use these signals as
both experimental tools and experimental measures in almost every experiment we conduct.
|| Madhav M.S., Stamper, S.A., Fortune, E.S., and N.J. Cowan
(2013) Closed-loop stabilization of the Jamming Avoidance Response reveals its locally
unstable and globally nonlinear dynamics., J. Exp. Biol., 216:4272-4284,
|| Linear and non-linear analyses
of the Jamming Avoidance Behavior in which a robotic control system closed the behavioral
loop around this escape behavior in Eigenmannia virescens.
|| Stamper, S.A., Fortune, E.S., and M.J. Chacron (2013) Perception
and coding of envelopes in weakly electric fishes. J. Exp. Biol., 216:2393-2402,
|| This is a review
that covers the rapid progress that has been made in understanding how weakly electric
fishes generate envelope signals through social interactions and movements, and how these
envelope signals are encoded in CNS circuits.
|| Stamper S.A., Madhav M.S., Cowan N.J., and Fortune E.S.
(2012) Beyond the Jamming Avoidance Response: weakly electric fish respond to
the envelope of social electrosensory signals, J. Exp. Biol., 215:4196-4207,
|| Behavioral experiments
show how Eigenmannia virescens regulate the frequencies of low-frequency
envelopes in groups of three individuals by changing their electric organ discharge
|| McGilligray, P., Vonderschen, K., Fortune, E.S., and M.J.
Chacron (2012) Parallel coding of first- and second-order stimulus
attributes by midbrain electrosensory neurons.
J. Neurosci., 32:5510-5524,
|| This work shows how different
combinations of response properties at one level of brain processing, the ELL, are
combined at the next level to extract different features of the stimulus.
| ||Hitschfeld, É.M., Stamper, S.A., Vonderschen, K., Fortune,
E.S., and M.J. Chacron (2009) Effects of restraint and immobilization on
electrosensory behavior of weakly electric fish. ILAR J., 50:361-372,
|| Here we quantitatively
assesed electrosensory behaviors in three experimental conditions - freely
moving, restrained, and immobilized using paralytic drugs. We find no
consistent differences in these three conditions. This suggests 1) that the
fish are likely to not experience pain and distress under each of these
experimental conditions and 2) that this category of experiments involving
electrosensory behaviors when conducted in immobilized fishes match the natural
behavior of the fish under normal conditions.
|| Ramcharitar, J.U., Tan, E.W., E.S. Fortune (2006) Global
electrosensory oscillations enhance directional responses of midbrain neurons
in Eigenmannia. J. Neurophys.,
|| Characterizes the
responses of midbrain neurons to moving objects in the presence and absence of
post-Jamming-Avoidance-Response global stimuli. Remarkably, gamma band
interference seems to enhance direction selectivity in these neurons. This
phenomenon is strongly correlated with a measure of short-term synaptic
depression in these neurons.
|| Ramcharitar, J.U., Tan, E.W., and E.S. Fortune (2005)
Effects of global electrosensory signals on motion processing in the midbrain
of Eigenmannia. J. Comp. Physiol. A, 191:865-872,
|| Characterizes the
magnitudes of the responses of midbrain neurons to moving objects in the
presence and absence of global electrosensory stimuli.
|| Fortune, E.S. and G.J. Rose (2001) Short-term
synaptic plasticity as a temporal filter. Trends in Neurosciences,
|| This Opinion
article argues that synaptic plasticity in sensory systems of many
vertebrate species, including mammals, should be considered a mechanism
for dynamic temporal filtering. A sub-theme is that natural patterns
of afferent activity are necessary to assess the functional roles of
the interplay between synaptic depression and facilitation.
|| Rose, G.J. and E.S. Fortune (1999)
Frequency-dependent PSP depression contributes to low-pass temporal
filtering in Eigenmannia. J. Neurosci., 19:7629-7639,
|| Behavioral and
neuropysiological data demonstrate that short-term depression can act
to enhance low-pass temporal filtering.
|| Fortune, E.S. and G.J. Rose (1997) Passive and
active membrane properties contribute to the temporal filtering
properties of midbrain neurons, in vivo. J. Neurosci.,
measurements of membrane properties were made in vivo to assess
and quantify how passive and active electrical characteristics of
neurons affect their functional properties. Because all neurons in
all animals have such electrical properties, these data are widely