Applications of Static and Dynamic Iterated Rippled Noise to Evaluate Pitch Encoding in the Human Auditory Brainstem

Abstract

Abstract-This paper presents a new application of the dynamic iterated rippled noise (IRN) algorithm by generating dynamic pitch contours representative of those that occur in natural speech in the context of EEG and the frequency following response (FFR). Besides IRN steady state and linear rising stimuli, curvilinear rising stimuli were modeled after pitch contours of natural productions of Mandarin Tone 2. Electrophysiological data on pitch representation at the level of the brainstem, as reflected in FFR, were evaluated for all stimuli, static or dynamic. Autocorrelation peaks were observed corresponding to the fundamental period ( ) as well as spectral bands at the fundamental and its harmonics for both a low and a high iteration step. At the higher iteration step, both spectral and temporal FFR representations were more robust, indicating that both acoustic properties may be utilized for pitch extraction at the level of the brainstem. By applying curvilinear IRN stimuli to elicit FFRs, we can evaluate the effects of temporal degradation on 1) the neural representation of linguistically-relevant pitch features in a target population (e.g., cochlear implant) and 2) the efficacy of signal processing schemes in conventional hearing aids and cochlear implants to recover these features.Index Terms-Auditory brainstem, cochlear implant, experience dependent plasticity, frequency following response, iterated rippled noise, pitch, signal processing.

Experience-dependent neural plasticity is sensitive to shape of pitch contours

“…T1, Mandarin high level tone; T2, Mandarin high rising tone; T2L, linear rising ramp that does not occur in Mandarin tonal inventory. The three stimuli were created at a high iteration step from broadband noise [8]. Clear bands of energy are evident at the timevarying f 0 and its harmonics, but unlike speech, IRN stimuli show no formant structure.…”

“…IRN was used to create three time-varying nonspeech f 0 contours using procedures similar to those described in [8]. A high iteration step (32) was used for all contrasts with gain set to 1.…”

“…The perceived pitch has been shown to correspond with a reciprocal of delay; pitch salience increases as a function of the number of iterations [5,6]. The IRN algorithm has recently been modified to incorporate multiple time-dependent delays over a range of iteration steps thereby allowing for dynamic changes in pitch [7] and especially curvilinear pitch contours that occur in natural speech [8]. These modifications enable us to investigate the neural processing of linguistically relevant pitch contours in the nonspeech domain.…”

Age-Related Changes in the Relationship Between Auditory Brainstem Responses and Envelope-Following Responses

“…Wave amplitudes measured from ABRs also provide insight into the representation of phasic information to short stimuli, based on clearly defined peaks that have been mapped onto specific generators in the auditory brainstem and midbrain (Lev and Sohmer 1972;Rowe 1981;Chen and Chen 1991). Frequency-following responses (FFRs) to tonal carriers or to the modulation envelope (envelopefollowing responses or EFRs), though still not widely used in the clinic, are rapidly gaining prominence as a means of assessing processing of complex sounds from the auditory pathway (Cunningham et al 2001;Aiken and Picton 2008;Swaminathan et al 2008;Basu et al 2010;Clinard et al 2010;Krishnan et al 2010;Parbery-Clark et al 2011;Anderson et al 2012). FFRs and EFRs are evoked in response to longer, often more spectro-temporally complex stimuli (Krishnan 1999(Krishnan , 2002Krishnan et al 2004;Swaminathan et al 2008), and are strongly influenced by rostral brainstem and midbrain generators (Kiren et al 1994;Kuwada et al 2002;Akhoun et al 2010;Chandrasekaran and Kraus 2010;Parthasarathy and Bartlett 2012).…”

“…Frequency-following responses (FFRs) to tonal carriers or to the modulation envelope (envelopefollowing responses or EFRs), though still not widely used in the clinic, are rapidly gaining prominence as a means of assessing processing of complex sounds from the auditory pathway (Cunningham et al 2001;Aiken and Picton 2008;Swaminathan et al 2008;Basu et al 2010;Clinard et al 2010;Krishnan et al 2010;Parbery-Clark et al 2011;Anderson et al 2012). FFRs and EFRs are evoked in response to longer, often more spectro-temporally complex stimuli (Krishnan 1999(Krishnan , 2002Krishnan et al 2004;Swaminathan et al 2008), and are strongly influenced by rostral brainstem and midbrain generators (Kiren et al 1994;Kuwada et al 2002;Akhoun et al 2010;Chandrasekaran and Kraus 2010;Parthasarathy and Bartlett 2012). They have been used to show differences in processing of complex stimuli under various pathological conditions, such as age-related hearing loss, dyslexia, and autism (McAnally and Stein 1997;Chandrasekaran et al 2009;Russo et al 2009;Anderson et al 2012;Clinard and Tremblay 2013).…”