title: Thresholding of auditory cortical representation by background noise.
abstract: It is generally thought that background noise can mask auditory information. However, how the noise specifically transforms neuronal auditory processing in a level-dependent manner remains to be carefully determined. Here, with in vivo loose-patch cell-attached recordings in layer 4 of the rat primary auditory cortex (A1), we systematically examined how continuous wideband noise of different levels affected receptive field properties of individual neurons. We found that the background noise, when above a certain critical/effective level, resulted in an elevation of intensity threshold for tone-evoked responses. This increase of threshold was linearly dependent on the noise intensity above the critical level. As such, the tonal receptive field (TRF) of individual neurons was translated upward as an entirety toward high intensities along the intensity domain. This resulted in preserved preferred characteristic frequency (CF) and the overall shape of TRF, but reduced frequency responding range and an enhanced frequency selectivity for the same stimulus intensity. Such translational effects on intensity threshold were observed in both excitatory and fast-spiking inhibitory neurons, as well as in both monotonic and nonmonotonic (intensity-tuned) A1 neurons. Our results suggest that in a noise background, fundamental auditory representations are modulated through a background level-dependent linear shifting along intensity domain, which is equivalent to reducing stimulus intensity.
authors.affiliation: Department of Physiology, School of Basic Medicine, Southern Medical University, Guangzhou Guangdong, China ; Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California Los Angeles, CA, USA.
authors.forename: Feixue
authors.initials: F
authors.lastname: Liang
authors.affiliation: Department of Physiology, School of Basic Medicine, Southern Medical University, Guangzhou Guangdong, China ; Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California Los Angeles, CA, USA.
authors.forename: Lin
authors.initials: L
authors.lastname: Bai
authors.affiliation: Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California Los Angeles, CA, USA.
authors.forename: Huizhong W
authors.initials: HW
authors.lastname: Tao
authors.affiliation: Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California Los Angeles, CA, USA.
authors.forename: Li I
authors.initials: LI
authors.lastname: Zhang
authors.affiliation: Department of Physiology, School of Basic Medicine, Southern Medical University, Guangzhou Guangdong, China.
authors.forename: Zhongju
authors.initials: Z
authors.lastname: Xiao
mesh_terms: D000161:Acoustic Stimulation / Q000379:methods; D000818:Animals; D001303:Auditory Cortex / Q000502:physiology*; D001309:Auditory Threshold / Q000502:physiology*; D005072:Evoked Potentials, Auditory / Q000502:physiology; D005260:Female; D016014:Linear Models; D009474:Neurons / Q000502:physiology*; D009622:Noise; D018408:Patch-Clamp Techniques; D017207:Rats, Sprague-Dawley
keywords: auditory cortex; background noise; fast-spike inhibitory neuron; frequency tuning; intensity tuning; loose-patch recording; tonal receptive field