Mechanisms of inhibition and neuronal integration for signal processing in the primary auditory cortex of the Mongolian gerbil (Meriones unguiculatus)
type: CreativeWork
description: A. A fundamental property of hearing is the decomposition of complex sounds into perceptually distinct frequency components. Each receptor cell in the cochlea and most centrally located neurons respond only to a limited range of frequencies. The individual frequency channels are spatially organized on the cortical surface. This consistent topographical pattern provides a framework for the investigation of other functional organization principles, e.g., the functional properties of neurons in the six cortical layers and the responsiveness of neurons to complex sounds. The frequency specific features of inhibition should play an important role in shaping a neuron’s response to complex behaviorally relevant stimuli. Physiological and immunocytochemical evidence indicates a layer-dependent organization of inhibitory circuits in the neocortex. To investigate the contribution of GABAergic inhibition to frequency tuning in the different cortical layers, single and multi units were recorded in near-radial penetrations before and during iontophoretic application of the GABAA-receptor antagonist bicuculline in the auditory cortex of the lightly anaesthetized gerbil (Meriones unguiculatus). Bicuculline generally increased the spontaneous neuronal activity and enhanced and prolonged onset responses to sound. Application of bicuculline often resulted in a shift of the most sensitive frequency of the neurons’ receptive fields and a decrease of threshold (5.5 dB). A broadening of the frequency tuning evident by lower Q40dB values was observed in 63% of the units. In units with several peaks in their tuning curve or clearly separated response areas, bicuculline application removed inhibitory gaps in the receptive fields and created single-peaked tuning curves. The influence of bicuculline on the receptive field size was not significantly layer-specific but tended to be most pronounced in layers V and VI. In layer VI, "silent" neurons were frequently found that responded to sound on…
abstract: A. A fundamental property of hearing is the decomposition of complex sounds into perceptually distinct frequency components. Each receptor cell in the cochlea and most centrally located neurons respond only to a limited range of frequencies. The individual frequency channels are spatially organized on the cortical surface. This consistent topographical pattern provides a framework for the investigation of other functional organization principles, e.g., the functional properties of neurons in the six cortical layers and the responsiveness of neurons to complex sounds. The frequency specific features of inhibition should play an important role in shaping a neuron’s response to complex behaviorally relevant stimuli. Physiological and immunocytochemical evidence indicates a layer-dependent organization of inhibitory circuits in the neocortex. To investigate the contribution of GABAergic inhibition to frequency tuning in the different cortical layers, single and multi units were recorded in near-radial penetrations before and during iontophoretic application of the GABAA-receptor antagonist bicuculline in the auditory cortex of the lightly anaesthetized gerbil (Meriones unguiculatus). Bicuculline generally increased the spontaneous neuronal activity and enhanced and prolonged onset responses to sound. Application of bicuculline often resulted in a shift of the most sensitive frequency of the neurons’ receptive fields and a decrease of threshold (5.5 dB). A broadening of the frequency tuning evident by lower Q40dB values was observed in 63% of the units. In units with several peaks in their tuning curve or clearly separated response areas, bicuculline application removed inhibitory gaps in the receptive fields and created single-peaked tuning curves. The influence of bicuculline on the receptive field size was not significantly layer-specific but tended to be most pronounced in layers V and VI. In layer VI, "silent" neurons were frequently found that responded to sound on…
author: Foeller, Elisabeth
date published: 2001-11-27
date modified: 2026-07-24T02:51:21Z
provider: Ludwig Maxmilians Universität München
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: Ludwig-Maximilians-Universität