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Activity Of Primary Auditory Neurons In The Cochlear Ganglion
Of The Emu (Dromaius Novaehollandiae): Spontaneous Discharge, Frequency Tuning, And Phase Locking
Manley GA; Koppl
C; Yates GK ,
Institut fur Zoologie,
Technische Universit at Munchen,
Garching, Germany.
1997 Mar
The spontaneous and pure-tone
sound-driven activity of primary auditory units was recorded in the
cochlear ganglion of emu chicks aged between post-hatching days 1 and 14.
Spontaneous activity tended to increase both with the chick's age and as a
function of the unit's characteristic frequency (CF). The CF of 887 units
ranged from 0.04 to 4 kHz, the thresholds down to 0 dB SPL. Although the CF
range did not change, the thresholds improved with age during the first two
weeks after hatching, by up to 18 dB at the highest frequencies. The
threshold spread between units of similar CF in single animals was up to 60
dB. Rate-threshold tuning- curve symmetry varied with CF. In low-frequency
units, the slope of the low-frequency tuning-curve flank was on average
steeper than the high-frequency flank, whereas for high-frequency units,
the reverse was true. Units of CF > 0.5 kHz generally showed
low-frequency "tails" similar to those seen in mammalian primary
auditory fibers. The mean tuning-curve frequency selectivity increased with
CF. For units of CF > 0.2 kHz, thresholds were moderately correlated
with tuning-curve frequency selectivity. Significant phase locking was
observed up to about 4 kHz, the corner frequency of phase locking being at
1.15 kHz.
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