Contribution
Neural correlates of binaural loudness summation obtained by functional MR imaging
* Presenting author
Abstract:
Neural correlates of level and loudness have been analysed for stimuli presented either to the left ear only, to the right ear only, or simultaneously to both ears. The question is, to what extent activation maps for binaural stimulation are directly predictable from the results for monaural stimulation, and which regions in cortex might exhibit a specific binaural interaction component. The study is continuing previous work investigating the physiological correlate of loudness functions for monaural stimulus presentation over a wide dynamic range (Behler and Uppenkamp, Neuroimage 139, 176-188, 2016). The current paradigm is specifically targeting binaural loudness summation. All listeners participated in a psychoacoustic experiment to gather individual loudness functions for monaural and binaural stimulation. Functional MRI was used to collect responses from auditory regions for individually adjusted levels leading to the same loudness in all three conditions, monaural left, monaural right and binaural. An additional binaural interaction component could be detected, indicating that the brain activation in response to binaural stimuli is not just a linear superposition of monaural responses. This opens a way to investigate the physiological processes underlying the observation that individuals with similar audiometric thresholds may show large differences with respect to their binaural loudness summation.