Ali Nasimi & Adrian Rees (2010): Regularly firing neurons in the inferior
colliculus have a weak interaural intensity difference sensitivity. J. Comp.
Physiol. A 196 (12), 889-897.
Abstract: The spike discharge regularity may be important in the processing
of information in the auditory pathway. It has already been shown that many
cells in the central nucleus of the inferior colliculus fire regularly in
response to monaural stimulation by the best frequency tones. The aim of
this study was to find how the regularity of units was affected by adding
ipsilateral tone, and how interaural intensity difference sensitivity is
related to regularity. Single unit recordings were performed from 66 units
in the inferior colliculus of the anaesthetized guinea pig in response to
the best frequency tone. Regularity of firing was measured by calculating
the coefficient of variation as a function of time of a unit?s response.
There was a positive correlation between coefficient of variation and
interaural intensity difference sensitivity, indicating that highly regular
units had very weak and irregular units had strong interaural intensity
difference sensitivity responses. Three effects of binaural interaction on
the sustained regularity were observed: constant coefficient of variation
despite change in rate (66% of the units), negative (20%) and positive (13%)
rate?CV relationships. A negative rate-coefficient of variation relationship
was the dominant pattern of binaural interaction on the onset regularity.
For reprints please contact A. Nasimi (email:
Erratum to the above article
Manuela Nowotny, Jennifer Hummel, Melanie Weber, Doreen Möckel & Manfred
Kössl (2010): Acoustic-induced motion of the bushcricket (Mecopoda elongata,
Tettigoniidae) tympanum. J. Comp. Physiol. A 196 (12), 939-945.
Abstract: Bushcrickets have a tonotopically organised hearing organ, the
so-called crista acustica, in the tibia of the forelegs. This organ responds
to a frequency range of about 5?80 kHz and lies behind the anterior tympanum
on top of a trachea branch. We analyzed the sound-induced vibration pattern
of the anterior tympanum, using a Laser-Doppler-Vibrometer Scanning
microscope system, in order to identify frequency-dependent amplitude and
phase of displacement. The vibration pattern evoked by a frequency sweep
(4?79 kHz) showed an amplitude maximum which would correspond to the
resonance frequency of an open tube system. At higher frequencies of about
30 kHz a difference in the amplitude and phase response between the distal
and the proximal part of the tympanum was detected. The inner plate of the
tympanum starts to wobble at this frequency. This higher mode in the motion
pattern is not explained by purely acoustic characteristics of the tracheal
space below the tympanum but may depend on the mechanical impedance of the
tympanum plate. In accordance with a previous hypothesis, the tympanum moves
over the whole tested frequency range in the dorso-ventral direction like a
hinged flap with the largest displacement in its ventral part and no higher
modes of vibration.
For reprints please contact M. Nowotny (email:
Dr. Sonja Amoser