Postnatal maturation of contralateral DPOAE suppression in a precocious animal model (chinchilla) of the human neonate.
CONCLUSIONS
In the neonatal chinchilla, the degree of contralateral distortion product otoacoustic emission (DPOAE) suppression and the latency and time constants of suppression are immature for 40-60 days. This suggests that olivocochlear efferent innervation of outer hair cells is not fully mature at birth in this animal model, and this may also be the case for human neonates.


OBJECTIVE
To track postnatal changes in the dynamics of the olivocochlear efferent system in an animal model with cochlear development at birth similar to that in humans.


METHODS
Real-time measurements of contralateral DPOAE suppression were made in 79 ears of anaesthetized chinchillas, ranging in age from 1 day to 70 days. An adult control group (13 ears) was also tested. DPOAE (2f1-f2; f2 = 4.4 kHz; f2/f1 = 1.22) input/output functions were measured. Dynamics of contralateral broadband noise suppression were measured, including latency and suppression time constants.


RESULTS
DPOAE amplitude input/output functions are immature until 20-30 days postnatally. The maturation period for contralateral suppression amplitude is about 30 days. Latency of onset suppression was 40 ms at birth reducing to adult values (23 ms) at 40 days. The DPOAE suppression time constant was about 350 ms at birth and mature (230 ms) at 60 days.
Auditory Science Laboratory, Hospital for Sick Children, Toronto, Canada. rvh@sickkids.ca
Robert V
RV
Harrison
Ujimoto
U
Konomi
Sohit
S
Kanotra
Adrian L
AL
James
D000161:Acoustic Stimulation / Q000379:methods*; D000367:Age Factors; D000818:Animals; D000831:Animals, Newborn / Q000502:physiology*; D001309:Auditory Threshold / Q000502:physiology; D002682:Chinchilla / Q000502:physiology*; D003051:Cochlea / Q000196:embryology / Q000502:physiology; D018072:Hair Cells, Auditory, Outer / Q000502:physiology*; D006311:Hearing Disorders / Q000175:diagnosis; D023421:Models, Animal; D017084:Otoacoustic Emissions, Spontaneous / Q000502:physiology*; D012680:Sensitivity and Specificity