Can central neurons reproduce sound waveforms? An analysis of the neurophonic potential in the laminar nucleus of the chicken.
Extracellular field potentials in response to pure tones, clicks and noise were recorded with microelectrodes from the laminar nucleus (NL) of the anesthetized chicken. Slow "on" and "off" potentials reversed polarity with recording depth, indicating that synaptically activated dendrites of fusiform cells were dorsal for ipsilateral and ventral for contralateral stimuli. Oscillations at sound frequency were found to be maintained for the duration of the stimulus (neurophonic potential, or NP). In contrast to slow "on" and "off" potentials, NPs were gradually shifted in phase as the electrodes penetrated the NL from dorsal to ventral. Neurophonic oscillation frequencies obtained with clicks and noise were equal to best pure tone frequencies yielding maximal NP amplitudes. Autocorrelation functions calculated from steady state NPs in response to pure tone stimuli indicated a presence of sine waves in noise, and power spectra typically consisted of single frequency components. NPs, slow "on" and slow "off" potentials were sharply tuned over similar frequency ranges and tuning tended to be sharper for higher frequencies. The NP represents an electrical replica of the sound waveform which may be present across the fusiform cell membrane.
Schwarz
D W
DW
Rotary Hearing Center, University of British Columbia, Vancouver, Canada.
D000161:Acoustic Stimulation; D000818:Animals; D001301:Audiometry, Pure-Tone; D001306:Auditory Pathways / Q000502:physiology; D002645:Chickens; D003051:Cochlea / Q000502:physiology; D016057:Evoked Potentials, Auditory, Brain Stem / Q000502:physiology*; D005260:Female; D008839:Microelectrodes; D009474:Neurons / Q000502:physiology*; D009991:Oscillometry; D011149:Pons / Q000502:physiology*; D011930:Reaction Time / Q000502:physiology