Jayne E. Yack, Elisabeth K. V. Kalko and Annemarie Surlykke (2007):
Neuroethology of ultrasonic hearing in nocturnal butterflies (Hedyloidea). J.
Comp. Physiol. A, 193(6), 577-590.
Abstract: Nocturnal Hedyloidea butterflies possess ultrasound-sensitive ears
that mediate evasive flight maneuvers. Tympanal ear morphology, auditory
physiology and behavioural responses to ultrasound are described for Macrosoma
heliconiaria, and evidence for hearing is described for eight other hedylid
species. The ear is formed by modifications of the cubital and subcostal veins
at the forewing base, where the thin (1–3 μm), ovoid (520 × 220 μm) tympanal
membrane occurs in a cavity. The ear is innervated by nerve IIN1c, with three
chordotonal organs attaching to separate regions of the tympanal membrane.
Extracellular recordings from IIN1c reveal sensory responses to ultrasonic (>20
kHz), but not low frequency (<10 kHz) sounds. Hearing is broadly tuned to
frequencies between 40 and 80 kHz, with best thresholds around 60 dB SPL. Free
flying butterflies exposed to ultrasound exhibit a variety of evasive
maneuvers, characterized by sudden and unpredictable changes in direction,
increased velocity, and durations of ∼500 ms. Hedylid hearing is compared to
that of several other insects that have independently evolved ears for the same
purpose-bat detection. Hedylid hearing may also represent an interesting
example of evolutionary divergence, since we demonstrate that the ears are
homologous to low frequency ears in some diurnal Nymphalidae butterflies.
For reprints please contact: Jayne E. Yack (email:
URL: http://www.springerlink.com/content/w284103466q082k4/
Christine Köppl and Otto Gleich (2007): Evoked cochlear potentials in the barn
owl. J. Comp. Physiol. A, 193(6), 601-612
Abstract: Gross electrical responses to tone bursts were measured in adult barn
owls, using a single-ended wire electrode placed onto the round window.
Cochlear microphonic (CM) and compound action potential (CAP) responses were
evaluated separately. Both potentials were physiologically vulnerable.
Selective abolishment of neural responses at high frequencies confirmed that
the CAP was of neural origin, while the CM remained unaffected. CAP latencies
decreased with increasing stimulus frequency and CAP amplitudes were correlated
with known variations in afferent fibre numbers from the different papillar
regions. This suggests a local origin of the CAP along the tonotopic gradient
within the basilar papilla. The audiograms derived from CAP and CM threshold
responses both showed a broad frequency region of optimal sensitivity, very
similar to behavioural and single-unit data, but shifted upward in absolute
sensitivity. CAP thresholds rose above 8 kHz, while CM responses showed
unchanged sensitivity up to 10 kHz.
For reprints please contact: Christine Köppl (Email:
URL: http://www.springerlink.com/content/8tq7575588k0v117/
G. Marsat and G. S. Pollack (2007): Efficient inhibition of bursts by bursts in
the auditory system of crickets. J. Comp. Physiol. A, 193(6), 625-633
Abstract: In crickets, auditory information about ultrasound is carried
bilaterally to the brain by the AN2 neurons. The ON1 neuron provides
contralateral inhibitory input to AN2, thereby enhancing bilateral contrast
between the left and right AN2s, an important cue for sound localization. We
examine how the structures of the spike trains of these neurons affect this
inhibitory interaction. As previously shown for AN2, ON1 responds to salient
peaks in stimulus amplitude with bursts of spikes. Spike bursts, but not
isolated spikes, reliably signal the occurrence of specific features of the
stimulus. ON1 and AN2 burst at similar times relative to the amplitude envelope
of the stimulus, and bursts are more tightly time-locked to stimulus feature
than the isolated spikes. As a consequence, spikes that, in the absence of
contralateral inhibition, would occur within AN2 bursts are more likely to be
preceded by spikes in ON1 (mainly also in bursts) than are isolated AN2 spikes.
This leads to a large decrease in the burst rate of the inhibited AN2. We
conclude that the match in coding properties of ON1 and AN2 allows
contralateral inhibition to be most efficient for those portions of the
response that carry the behaviourally relevant information, i.e. for bursts.
For reprints please contact: G. S. Pollack (Email: )
URL: http://www.springerlink.com/content/952347k3520w8928/
Ying Zhang and Masashi Kawasaki (2007): Interruption of pacemaker signals is
mediated by GABAergic inhibition of the pacemaker nucleus in the African
electric fish Gymnarchus niloticus. J. Comp. Physiol. A, 193(6), 665-675.
Abstract: The wave-type African weakly electric fish Gymnarchus niloticus
produces electric organ discharges (EODs) from an electric organ in the tail
that is driven by a pacemaker complex in the medulla, which consists of a
pacemaker nucleus, two lateral relay nuclei and a medial relay nucleus. The
prepacemaker nucleus (PPn) in the area of the dorsal posterior nucleus of the
thalamus projects exclusively to the pacemaker nucleus and is responsible for
EOD interruption behavior. The goal of the present study is to test the
existence of inhibition of the pacemaker nucleus by the PPn.
Immunohistochemical results showed clear anti-GABA immunoreactive labeling of
fibers and terminals in the pacemaker nucleus, but no apparent anti-glycine
immunoreactivity anywhere in the pacemaker complex. GABA injection into the
pacemaker nucleus could induce EOD interruptions that are comparable to the
interruptions induced by glutamate injection into the PPn. Application of the
GABAA receptor blocker bicuculline methiodide reversibly eliminated the effects
of stimulation of the PPn. Thus the EOD interruption behavior in Gymnarchus is
mediated through GABAergic inhibition of the pacemaker nucleus by the PPn.
For reprints please contact: Masashi Kawasaki (Email:
URL: http://www.springerlink.com/content/u6x35u59618rw171/
John Meitzen, David J. Perkel and Eliot A. Brenowitz (2007): Seasonal changes
in intrinsic electrophysiological activity of song control neurons in wild song
sparrows. J. Comp. Physiol. A, 193(6),677-683.
Abstract: Song behavior and its underlying neural substrate can change
seasonally in adult songbirds. To test whether environmental cues induce
seasonal changes in electrophysiological characteristics of song control
neurons, we measured in vitro intrinsic neuronal activity in the song control
nucleus RA of adult male song sparrows (Melospiza melodia) in both the fall
non-breeding and spring breeding seasons. We found that RA neurons in
spring-captured birds show a more than threefold increase in spontaneous firing
rate compared to those from fall-captured birds. We conclude that environmental
cues are sufficient to induce seasonal changes in electrophysiological
properties of song control neurons, and that changes in these properties may
underlie seasonal changes in song behavior.
For reprints please contact: John Meitzen (Email:
URL: http://www.springerlink.com/content/wn12215535753t6p/
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University of Vienna, Dept. of Behavioural Biology
Sonja Amoser, PhD
Althanstrasse 14
1090 Vienna
Austria
tel: +43 (1) 4277 54467
fax: +43 (1) 4277 54506
mobile: +43 (664) 500 61 06
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