By: Elizabeth Schnabel Advised By: Fuh-Cherng Jeng Ph.D. Infant mean: .3518 µV Adult mean: .25 µV P= .420 FIGURE 5 Box and whisker plot of Infant and Adult PCFR pitch strength. Infants mean pitch strength is larger then Adults. Results Methods Introduction Reference Research Questions The proposed project investigates a frequency following response (FFR) that is provoked by a tonal stimulus in adults and infants. FFR is a stimulus evoked neural response much like the Auditory Brainstem Response (ABR) which is commonly used in infant hearing screenings in Ohio. The FFR is a series of sinusoidal peaks in response to sustained neural activity elicited from a steady state or time varying stimulus. The intervals between the FFR peaks are phase-locked to the period of the stimulus harmonics, especially the fundamental frequency. When the FFR is found to follow the spectral changes in the stimuli, the response is then referred to as a Pitch Contour Following Response (PCFR). Recent studies have shown the feasibility of recording the PCFR from normal hearing adults by using the stimulus of Mandarin tones and iterated rippled noise (IRN) Krishnan (2004), Krishnan, Xu, Gandour, and Cariani (2005), and Swaminathan, Krishnan, and Gandour (2008) . Due to the need to further define the characteristics of the PCFR and its developmental trajectory, the present study investigates if the PCFR is recordable in infants and the characteristics of this response compared to those obtained in adults. The individuals of each group, infants and adults, were presented with two trials of a rising Mandarin tone “yi” meaning ‘aunt'. The implications of the PCFR will be to use it as a non-invasive way to study infant pitch perception and advance our knowledge in what features in speech or music are most important to achieve better speech perception. Krishnan, A., Xu, Y. (2004). Human frequency-following response: Representation of pitch contours in Chinese tones. Hearing Research,189,1-12. Krishnan, A., Xu, Y., Gandour, J., Cariani, P. (2005). Encoding of pitch in the human brainstem is sensitive to language experience. Cognitive Brain Research, 25(1), 161-168. Swaminathan, J., Krishnan, A., Gandour, J.T. (2008b). Pitch encoding in speech and nonspeech contexts in the human auditory brainstem. NeuroReport, 19(11), 1163-1167. SUBJECTS • 6 Normal hearing infants • 10 Normal hearing adults STIMULUS • Voiced Mandarin Chinese syllable with a rising lexical tone “yi” meaning “aunt” PROCEDURE • Normal hearing was established for participants • Electrodes placed on forehead and on each mastoid • State of restfulness was achieved • Stimulus and recording was started • 2 trials of 1200 tokens • 2 trials of 1200 control – ear tip removed and plugged • Clean up and reimbursement forms completed Infant_003 Adult_010 FIGURE 1 Typical spectrogram and autocorrelation of Infant and Adult PCRF. Preliminary data suggests that PCFR is recordable in infants, the PCFR developmental trajectory is unclear, and that the mean of infant pitch strength is greater then adults. Discussion Pitch Contour Following Response in Infants Stimulus Infant_003 Control Figure 4 F0 configurations of the stimulus, PCFR, and control from Infant_003 One Month Four Month Five Month Seven Month FIGURE 5 Linear Regression from all Infant participants according to age in months One Month Four Month Five Month Seven Month FIGURE 2 Spectrograms and Autocorrelations from all Infant participants according to age in months. (1) Is PCFR able to be recorded from infants? (2) Does the PCFR response get stronger as an infant gets older? (3) How does infant response compare to adult response? r= 0.13571 p= 0.16339 slope= 82.523 FIGURE 3 Independent Samples T-test comparing Infant and Adult PCFR pitch strength. There is not a significant difference between Infant and Adult PCFR pitch strength FIGURE 3 Infant PCFR pitch strength according to age in months. There is not a clear developmental trajectory of infant’s PCFR, according to pitch strength amplitudes.