Tonotopic representation of loudness in the human cortex

Abstract

A prominent feature of the auditory system is that neurons show tuning to audio frequency; each neuron has a characteristic frequency (CF) to which it is most sensitive. Furthermore, there is an orderly mapping of CF to position, which is called tonotopic organization and which is observed at many levels of the auditory system. In a previous study (Thwaites et al., 2016) we examined cortical entrainment to two auditory transforms predicted by a model of loudness, instantaneous loudness and short-term loudness, using speech as the input signal. The model is based on the assumption that neural activity is combined across CFs (i.e. across frequency channels) before the transform to short-term loudness. However, it is also possible that short-term loudness is determined on a channel-specific basis. Here we tested these possibilities by assessing neural entrainment to the overall and channel-specific instantaneous loudness and the overall and channel-specific short-term loudness. The results showed entrainment to channel-specific instantaneous loudness at latencies of 45 and 100 ms (bilaterally, in and around Heschl's gyrus). There was entrainment to overall instantaneous loudness at 165 ms in dorso-lateral sulcus (DLS). Entrainment to overall short-term loudness occurred primarily at 275 ms, bilaterally in DLS and superior temporal sulcus. There was only weak evidence for entrainment to channel-specific short-term loudness.

Temporal Loudness Weights Are Frequency Specific

“…The assumption that temporal processing precedes spectral integration is compatible with the present finding of frequency-specific temporal loudness weights. It is also compatible with neurophysiological data showing entrainment to channel-specific instantaneous loudness in cortical MEG components up to about 100 ms ( Thwaites et al, 2017 ). One should keep in mind, however, that the attack-decay type of temporal integration assumed by the TVL-model does not predict a primacy effect, as demonstrated by simulation results in Fischenich et al (2019) .…”

Editorial: Loudness: From Neuroscience to Perception

“…This result suggests that temporal integration precedes spectral integration. This is consistent with the most recent version of the TVL model of loudness (Moore et al, 2016(Moore et al, , 2018 and with recent neurophysiological data (Thwaites et al, 2017).…”

Auditory features modelling reveals sound envelope representation in striate cortex

“…While primary auditory cortex was not sensitive to quilt durations, possibly due to the narrow frequency tuning which characterizes its response (Moerel et al, 2015;Thwaites et al, 2017), only bilateral portion of STS displayed an activity which parametrically varied with quilt lengths. These regions have been recognized as a major hub to encode the temporal structure of speech.…”

“…While the primary auditory cortex was not sensitive to quilt durations, possibly due to the narrow frequency tuning which characterizes its response (Moerel et al, 2015;Thwaites et al, 2017), activity of the bilateral portion of STS varied as function of quilt lengths (Overath et al, 2015). Moreover, it was shown that portions of STG encode amplitude variations of speech and amplitude-modulated tone stimuli independent from other spectro-temporal features (Oganian and Chang, 2019).…”