title: Group delay measurement from spiral ganglion cells in the basal turn of the guinea pig cochlea.
abstract: Measurements of group delay were made extracellularly from spiral ganglion cells in the 3.7 to 5.0-mm region of the guinea pig cochlea, using sinusoidally amplitude modulated tones with constant modulating frequency (100 Hz) and depth of modulation (0.19). Threshold cochlear tuning was accompanied by frequency-dependent group delays. The group delay on the low-frequency tail was independent of carrier frequency; the interunit variation was 0.28-1.28 ms. The difference in group delay between CF and the low-frequency tail decreased as the CF threshold increased (-0.09 +/- 0.02 ms per 10 dB, beginning at 0.62 +/- 0.07 ms at 0 dB SPL). The group delay decreased above CF; at the units' maximum frequency it was less than the low-frequency tail value, and was sometimes negative. Following arterial injections of furosemide the CF threshold increased and the group delay peak decreased; the low-frequency tail was unaffected. The group delay decreased with increasing intensity; the reduction near and above CF was not only larger than that on the low-frequency tail, but also the change at 5-10 dB above threshold was far greater than expected from the Q10dB of the suprathreshold iso-rate tuning curves. A minimum-phase analysis suggested that the group delay response above CF, together with its nonlinear behavior, can be accounted for by a high-frequency, level-independent, amplitude plateau, in combination with the single unit, amplitude nonlinearity which is known to exist above CF.
mesh_terms: D000818:Animals; D001309:Auditory Threshold / Q000502:physiology; D003051:Cochlea / Q000502:physiology*; D005072:Evoked Potentials, Auditory; D005665:Furosemide / Q000494:pharmacology; D006168:Guinea Pigs; D010898:Pitch Perception / Q000502:physiology*; D013136:Spiral Ganglion / Q000187:drug effects / Q000502:physiology*; D009435:Synaptic Transmission / Q000187:drug effects
chemical_list: D005665:Furosemide