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New article in J. Comp. Physiol. A 193(6)

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Subject: New article in J. Comp. Physiol. A 193(6)
From: "Sonja Amoser" <>
Date: Fri, 1 Jun 2007 10:43:11 +0200
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: 

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: 


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:  )

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: 

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: 

University of Vienna, Dept. of Behavioural Biology
Sonja Amoser, PhD

Althanstrasse 14
1090 Vienna
tel: +43 (1) 4277 54467
fax: +43 (1) 4277 54506
mobile: +43 (664) 500 61 06

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