Unit Responses in the Rat Cochlear Nucleus to Tones of Rapidly Varying Frequency and Amplitude

Abstract

Abstract M øller , A. R. Unit responses in the rat cochlear nucleus to tones of rapidly varying frequency and amplitude . Acta physiol. scand. 1971. 81 . 540–556. The response of single units in the cochlear nucleus of the rat to sweep tones (FM sounds) and short tone‐bunts (AM sounds) has been investigated. It was found that the response pattern to Fhl sounds became more restricted with regard to tone frequency at a certain rate of tone‐frequency change. The probability of firing within a narrow frequency range surrounding the unit's CF became frequently more than ten times greater than that at low sweep‐speeds. For a certain range of higher sweep‐rate, cycle histograms become narrower and higher than at low sweep‐rates. The range of frequency change where the peaks had maximal height was found to lie in the region between 1 and 15 MHz/sec for units with CF from 5 to 30 kHz. This effect was found to persist over a sound‐intensity range of more than 60 dB, but was less marked at very low intensity levels. The threshold of the units investigated did not become lowered at any rate of frequency change. The cycle histograms of the response to sounds of constant frequency and variable duration (AM sounds) differed significantly from that to FM sounds. Only occasionally was an increase in height of the cycle histograms seen when the duration of the sounds was narrowed and the repetition rate increased.