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ISIB CNR

ISIB CNR. COCHLEAR MATURATION AND OTOACOUSTIC EMISSIONS: A TIME-FREQUENCY APPROACH IN PRETERM INFANTS Gabriella Tognola Paolo Ravazzani Marta Parazzini Ferdinando Grandori CNR, Institute of Biomedical Engineering, Milan, Italy. ISIB CNR. BACKGROUND.

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ISIB CNR

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  1. ISIB CNR COCHLEAR MATURATION AND OTOACOUSTIC EMISSIONS: A TIME-FREQUENCY APPROACH IN PRETERM INFANTS Gabriella Tognola Paolo Ravazzani Marta Parazzini Ferdinando Grandori CNR, Institute of Biomedical Engineering, Milan, Italy

  2. ISIB CNR BACKGROUND • Cochlear functionality initiates at the age of about 20 wks (Pujol et al., 1973); • Cochlear morphological changes are terminated at 30-32 wks post-conceptional age (Pujol, 1985); • As to the maturation of cochlear active mechanisms (due to the activity of the outer hair cells), no agreement has been reached yet. • OAEs can be measured in newborns older than 28-30 wks post-conceptional age.

  3. ISIB CNR CLICK EVOKED OTOACOUSTIC EMISSIONS (CEOAE) • Acoustic stimulus: CLICK • CLICK  WIDEBAND stimulus • ALL cochlear receptors are stimulated • Each receptor is tuned to a specific CHARACTERISTIC FREQUENCY and its response has a CHARACTERISTIC LATENCY

  4. ISIB CNR OBJECTIVES • Extraction of elementary CEOAE frequency components; • Quantify the developmental changes in time-frequency distributions of CEOAE; • Comparison with time-frequency distributions of CEOAEs from full-term babies and with latency data from ABR.

  5. ISIB CNR SUBJECTS • 33 pre-term babies (tested by Patrick Brienesse and Pauline de Jager); • Mean gestational age at birth: 30.3 wks (± 1.4 wks); • Each baby had a minimum of three and a maximum of 11 subsequent CEOAE measurements in a period ranging from 1 to 8 wks after birth; • Total CEOAE examined: 307.

  6. wavelets ISIB CNR EXTRACTION OF CEOAE COMPONENTS: THE WAVELET TRANSFORM mother wavelet (t)

  7. ISIB CNR CEOAE AMPLITUDE VS. PCA [from Tognola G. et al., Hearing Research, vol. 199(1-2), 2005, pp. 71-80]

  8. ISIB CNR CEOAE ELEMENTARY FREQUENCY COMPONENTS ORIGINAL CEOAE FREQUENCY COMPONENTS

  9. ISIB CNR AMPLITUDE OF CEOAE COMPONENTS FULL-TERM [from Tognola G. et al., Hearing Research, vol. 199(1-2), 2005, pp. 71-80] PRETERM

  10. LATENCY [ms] LATENCY [ms] LATENCY [ms] FREQUENCY [kHz] FREQUENCY [kHz] FREQUENCY [kHz] ISIB CNR LATENCY OF CEOAE COMPONENTS [from Tognola G. et al., Hearing Research, vol. 199(1-2), 2005, pp. 71-80]

  11. ABR LATENCIES (wave I) CEOAE LATENCIES CEOAE decomposition by means of the Wavelet Transform derived response technique with high-pass noise masking [from Tognola G. et al., Hearing Research, vol. 199(1-2), 2005, pp. 71-80] Eggermont et al., 1991 LATENCY [ms] FREQUENCY [kHz] ISIB CNR LATENCY OF ABR VS. CEOAE

  12. ISIB CNR CONCLUSIONS • Amplitude and latencies of CEOAE components change until the age of about 38 wks • The amplitude increases • Latency decreases • Different increase rates at different frequencies: • Mid-to-high frequencies  FAST increase • Low frequencies  SLOW increase • CEOAE developmental changes very similar to those observed with ABR; • cochlear maturation proceeds from base (high freqs.) to apex (low freqs.)

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