Paul H. Delano, Elizabeth Pavez, Luis Robles and Pedro E. Maldonado (2008):
Stimulus-dependent oscillations and evoked potentials in chinchilla auditory
cortex. J. Comp. Physiol. A 194(8), 693-700.
Abstract: Besides the intensity and frequency of an auditory stimulus, the
length of time that precedes the stimulation is an important factor that
determines the magnitude of early evoked neural responses in the auditory
cortex. Here we used chinchillas to demonstrate that the length of the
silent period before the presentation of an auditory stimulus is a critical
factor that modifies late oscillatory responses in the auditory cortex. We
used tetrodes to record local-field potential (LFP) signals from the left
auditory cortex of ten animals while they were stimulated with clicks, tones
or noise bursts delivered at different rates and intensity levels. We found
that the incidence of oscillatory activity in the auditory cortex of
anesthetized chinchillas is dependent on the period of silence before
stimulation and on the intensity of the auditory stimulus. In 62.5% of the
recordings sites we found stimulus-related oscillations at around 8-20 Hz.
Stimulus-induced oscillations were largest and consistent when stimuli were
preceded by 5 s of silence and they were absent when preceded by less than
500 ms of silence. These results demonstrate that the period of silence
preceding the stimulus presentation and the stimulus intensity are critical
factors for the presence of these oscillations.
URL: http://www.springerlink.com/content/b441717r470237t5/
For reprints please contact Paul H. Delano (Email:
Anja Weinrich, Michael Kunst, Andrea Wirmer, Gay R. Holstein and Ralf
Heinrich (2008): Suppression of grasshopper sound production by nitric
oxide-releasing neurons of the central complex. J. Comp. Physiol. A 194(8),
763-776.
Abstract: The central complex of acridid grasshoppers integrates sensory
information pertinent to reproduction-related acoustic communication.
Activation of nitric oxide (NO)/cyclic GMP-signaling by injection of NO
donors into the central complex of restrained Chorthippus biguttulus females
suppresses muscarine-stimulated sound production. In contrast, sound
production is released by aminoguanidine (AG)-mediated inhibition of nitric
oxide synthase (NOS) in the central body, suggesting a basal release of NO
that suppresses singing in this situation. Using anti-citrulline
immunocytochemistry to detect recent NO production, subtypes of columnar
neurons with somata located in the pars intercerebralis and tangential
neurons with somata in the ventro-median protocerebrum were distinctly
labeled. Their arborizations in the central body upper division overlap with
expression patterns for NOS and with the site of injection where NO donors
suppress sound production. Systemic application of AG increases the
responsiveness of unrestrained females to male calling songs. Identical
treatment with the NOS inhibitor that increased male song-stimulated sound
production in females induced a marked reduction of citrulline accumulation
in central complex columnar and tangential neurons. We conclude that
behavioral situations that are unfavorable for sound production (like being
restrained) activate NOS-expressing central body neurons to release NO and
elevate the behavioral threshold for sound production in female
grasshoppers.
URL: http://www.springerlink.com/content/up6342740m086q1l/
For reprints please contact Ralf Heinrich (Email:
Kind regards
Sonja Amoser
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Dr. Sonja Amoser
Daringergasse 3
1190 Wien
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