Cortical BOLD responses track perceived loudness linearly but show steepening at high levels

Evidence

In all regions, linear loudness models yielded at least slightly better goodness-of-fits as compared to linear sound intensity models, although still being outmatched by quadratic fits with sound intensity in the majority of cortical ROIs. The example plots of the different model fits in the left and right posterior medial HG (Fig. 2b ) reveal that the significant quadratic component is attributable to a steeper increase of BOLD responses at the highest sound levels (in this regard, the examples are representative for all ROIs). Across ROIs, only 4 (out of the total 24) quadratic loudness models reached significance, indicating that the relationship between the responses and categorical loudness is sufficiently described by a linear model. — Dijk, Pim van, Physiology, Psychoacoustics and…, 2632

Categorization

• XREF: The nonlinear steepening at high sound levels echoes the compressive cochlear nonlinearity and basilar-membrane gain findings from earlier hearing physiology chapters.