Subcortical Neural Synchrony and Absolute Thresholds Predict Frequency Discrimination Independently

Abstract

The neural mechanisms of pitch coding have been debated for more than a century. The two main mechanisms are coding based on the profiles of neural firing rates across auditory nerve fibers with different characteristic frequencies (place-rate coding), and coding based on the phase-locked temporal pattern of neural firing (temporal coding). Phase locking precision can be partly assessed by recording the frequency-following response (FFR), a scalp-recorded electrophysiological response that reflects synchronous activity in subcortical neurons. Although features of the FFR have been widely used as indices of pitch coding acuity, only a handful of studies have directly investigated the relation between the FFR and behavioral pitch judgments. Furthermore, the contribution of degraded neural synchrony (as indexed by the FFR) to the pitch perception impairments of older listeners and those with hearing loss is not well known. Here, the relation between the FFR and pure-tone frequency discrimination was investigated in listeners with a wide range of ages and absolute thresholds, to assess the respective contributions of subcortical neural synchrony and other age-related and hearing loss-related mechanisms to frequency discrimination performance. FFR measures of neural synchrony and absolute thresholds independently contributed to frequency discrimination performance. Age alone, i.e., once the effect of subcortical neural synchrony measures or absolute thresholds had been partialed out, did not contribute to frequency discrimination. Overall, the results suggest that frequency discrimination of pure tones may depend both on phase locking precision and on separate mechanisms affected in hearing loss.

Using frequency-following responses (FFRs) to evaluate the auditory function of frequency-modulation (FM) discrimination

“…Pearson's correlation analysis indicated that PS was significantly correlated with JNDs (r = − 0.587, p = 0.045). This negative correlation between neural index and behavioral threshold of tonal sweeps is as expected and consistent with that of FDL (Marmel et al 2013;Zhang and Gong 2017). The similar correlation analysis was conducted for the other four deviation conditions separately, and it was found that correlation was not significant for the fewer degrees (r = − 0.233, p = 0.465 for 20% and r = − 0.431, p = 0.161 Table 1.…”

“…Frequency discrimination limen (FDL), measured with pure tones, was found to be negatively correlated with pitch strength reflected in FFRs (Marmel et al 2013). However, it was suggested that the neural processing of repetitive FM sweeps in the human auditory cortex differs from that of pure tones (Okamoto and Kakigi 2017).…”

“…The spectral peaks of FFRs locate at each harmonic of stimulus f 0 , with energy mainly concentrating at f 0 . The fidelity of FFRs has been shown to be correlated to pitch perception (Marmel et al 2013) and sensitive to hearing situation (Plyler and Ananthanarayan 2001).…”

The effects of age and hearing loss on interaural phase difference discrimination

“…(3) Reduced synchrony in the transmission of phase-locked signals, which could weaken the strength of the phase locking (Clinard et al, 2010;Marmel et al, 2013).…”

Subcortical representation of musical dyads: Individual differences and neural generators

“…The sustained phase locked response of populations of neurons at this stage of the auditory pathway can be measured as the frequency-following response (FFR; for a review of anatomical generators see Krishnan, 2007), a scalp recorded auditory evoked potential which takes its name from the characteristic peaks in the waveform at periods corresponding to frequency components of the stimulus. Recent work suggests a relation between the integrity of the temporal coding represented by the FFR and pitch discrimination (Carcagno and Plack, 2011;Clinard et al, 2010;Krishnan et al, 2012;Marmel et al, 2013), musical experience (Bidelman et al, 2011a(Bidelman et al, , 2011bWong et al, 2007), tone language experience (Krishnan et al, 2005), and the perception of musical consonance (Bidelman and Krishnan, 2009;Bones et al, 2014). Bones et al (2014) demonstrated that individual differences in consonance perception for dyads could be predicted by the representation of harmonicity in the spectrum of the FFR.…”