Examining localization error in MEG for the complex auditory brainstem response (cABR) across early development

Abstract

The complex auditory brainstem response (cABR) has gained wide research interest over the last decade as it is argued to reflect early sensory encoding of complex sounds, such as speech, along the auditory pathway. Recent adoption of cABR recording in MEG, instead of 3 EEG electrodes, allows further examination of the underlying sources. In adults, while the onset component of cABR to transient events (e.g., consonants) can be reliably localized to the auditory brainstem, the frequency-following component to longer periodic events (e.g., vowels, lexical tones) may contain contribution from auditory cortex. This study thus expands to evaluate the localization accuracy of both onset response and FFR through simulation, both of which are crucial for speech. Simulated source activities are placed in the auditory brainstem versus superior temporal gyrus. Using the forward model, the activities are projected to MEG sensor space with realistic room noise and head movement. The simulated sensor space signal then undergoes inverse modeling to calculate source activation. Differences between the simulated source activity versus calculated source activity are calculated to reflect localization accuracy. This process is repeated using infant head models at 3, 6, 9, and 12 months and adult head model to examine changes across ages.