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: [EMAIL PROTECTED]) 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: [EMAIL PROTECTED]) Kind regards Sonja Amoser ************************** Dr. Sonja Amoser Daringergasse 3 1190 Wien [EMAIL PROTECTED]
