The Salience Detector Hypothesis and Non-Speech Sounds

Introduction: Intracranial electroencephalography (iEEG) has permitted such high temporal resolution of task-related cortical signals as to reveal auditory ‘Onset’ profiles of the posterior superior temporal region (pSTR). Our work contrasting responses to speech and noise has led us to elaborate the salience detector hypothesis of auditory Onset sites (Brown EC, et al. NeuroImage, 2021; 248:118840). It is predicted that Onset sites show more intense recurrent intrastimulus activity upon a state change toward enhanced salience.

Methods: In subjects with iEEG, we detected cortical activity during an auditory task. Stimuli of 2 seconds duration each include 30 questions, 10 signal correlated noise (SCN) stimuli, and 60 paired non-speech stimuli. Paired stimuli involve 20 matched pairs each of instrument and alarm sounds, consonant and dissonant piano chords, and voices and screams. We strictly identified auditory Onset sites as those responding with a transient increase in high gamma activity to both question and SCN stimuli. We then observed relative peak activity response within paired stimuli.

Results: Preliminary analysis has been completed in 14 subjects. A total of 43 electrode contacts of the pSTR were identified as auditory Onset, 25 on the left and 18 on the right. When instrument sounds followed alarm sounds, the median recurrent activation was 67.3% that of the preceding sound while it was 77.5% for the opposite order; p=0.005. When dissonant chords followed consonant chords, the median relative response was 71.9% while it was 70.3% for the opposite order; p=0.540. When a scream followed a voice, the average relative response was 87.9% while it was 58.2% for the opposite order; p< 0.001.

Conclusion : These preliminary findings provide partial support for the Salience Detector Hypothesis of Onset sites of the pSTR. As predicted, for Alarm-Instrument and Scream-Voice pairs the recurrent activity was stronger when the second stimulus was the more salient sound. Responses to Consonant and Dissonant piano chords behaved differently. Further analysis will include comparing responses at different functional and anatomical sites.