Gamma-aminobutyric acidergic and glycinergic inputs shape coding of amplitude modulation in the chinchilla cochlear nucleus
Related Experiment Video
Updated: Oct 19, 2026

Manufacturing and Using Piggy-back Multibarrel Electrodes for In vivo Pharmacological Manipulations of Neural Responses
Published on: January 18, 2013
P M Backoff1, P Shadduck Palombi, D M Caspary
1Department of Pharmacology, Southern Illinois University School of Medicine, Springfield 62794-9629, USA.
Abstract:
Amplitude modulation is a prominent acoustic feature of biologically relevant sounds, such as speech and animal vocalizations. Enhanced temporal coding of amplitude modulation signals is found in certain dorsal and posteroventral cochlear nucleus neurons when they are compared to auditory nerve. Although mechanisms underlying this improved temporal selectivity are not known, involvement of inhibition has been suggested. gamma-Aminobutyric acid- and glycine-mediated inhibition have been shown to shape the dorsal cochlear nucleus and posteroventral cochlear nucleus response properties to other acoustic stimuli. In the present study, responses to amplitude modulation tones were obtained from chinchilla dorsal cochlear nucleus and posteroventral cochlear nucleus neurons. The amplitude modulation carrier was set to the neuron's characteristic frequency and the modulating frequency varied from 10 Hz. Rate and temporal modulation transfer functions were compared across neurons. Bandpass temporal modulation transfer functions were observed in 74% of the neurons studied. Most cochlear nucleus neurons (90%) displayed flat or lowpass rate modulation transfer functions to amplitude modulation signals presented at 2540 dB (re: characteristic frequency threshold). The role of inhibition in shaping responses to amplitude modulation stimuli was examined using iontophoretic application of glycine or gamma-aminobutyric acidA receptor agonists and antagonists. Blockade of gamma-aminobutyric acidA or glycine receptors increased stimulus-evoked discharge rates for a majority of neurons tested. Synchronization to the envelope was reduced, particularly at low and middle modulating frequencies, with temporal modulation transfer functions becoming flattened and less bandpass in appearance. Application of glycine, gamma-aminobutyric acid or muscimol increased the modulation gain over the low- and mid-modulation frequencies and reduced the discharge rate across envelope frequencies for most neurons tested. These findings support the hypothesis that glycinergic and gamma-aminobutyric acidergic inputs onto certain dorsal cochlear nucleus and posteroventral cochlear nucleus neurons play a role in shaping responses to amplitude modulation stimuli and may be responsible for the reported preservation of amplitude modulation temporal coding in dorsal cochlear nucleus and posteroventral cochlear nucleus neurons at high stimulus intensities or in background noise.
Related Concept Videos
The Cochlea
Hair Cells
Cholinergic Receptors: Muscarinic
The subtypes M1, M3, and M5 couple with the Gq subunit and activate the phospholipase C (PLC) activity, mobilizing intracellular Ca2+. Activation...
G-Protein Gated Ion Channels
Sensory organs,...
Auditory Pathway
When viewed cross-sectionally, the cochlea reveals the scala vestibuli and scala tympani flanking the...
Cholinergic Neurons: Neurotransmission

