Guyonnet-Hencke, T. | bioRxiv Science

bioRxiv2024

Fast and robust objective EEG audiometry

The current gold standard of audiometry relies on subjective behavioral responses, which is impractical and unreliable for certain groups such as children, individuals with severe disabilities, or the disabled elderly. This study presents a novel electroencephalography (EEG) system that is easy to setup and estimates audiometric thresholds quickly. Air-conduction audiometric thresholds at 250, 500, 1000, 2000, 4000, and 8000 Hz and 5 dB resolution were estimated from ten elderly patients with asymmetric sensorineural hearing loss and five normal hearing young adults using three different systems: the novel EEG system, conventional pure-tone audiometry (PTA), and an automated behavioral test with the same stimulus properties as in the EEG test. EEG data was collected for 15 minutes from 32 semi-dry EEG electrodes. Later, the EEG system was trimmed to 8 electrodes and 7.5 minutes of data with satisfactory results. Correlation and regression analysis validated the hearing thresholds derived from both EEG configurations relative to the behavioral hearing thresholds-Pearsons correlation of 0.82 between PTA and 8-electrode 7.5-minute EEG data. The results of this study open the door to fast and objective hearing threshold estimation with EEG.

neuroscience↗

bioRxiv2022

A Parcellation Scheme of Mouse Isocortex Based on Reversals in Connectivity Gradients

The brain is composed of several anatomically clearly separated structures. This parcellation is often extended into the isocortex, based on anatomical, physiological or functional differences. Here, we derive a parcellation scheme based purely on the spatial structure of long-range synaptic connections within the cortex. To that end, we analyzed a publicly available dataset of average mouse brain connectivity, and split the isocortex into disjunct regions. Instead of clustering connectivity based on modularity, our scheme is inspired by methods that split sensory cortices into subregions where gradients of neuronal response properties, such as the location of the receptive field, reverse. We calculated comparable gradients from voxelized brain connectivity data and automatically detected reversals in them. This approach better respects the known presence of functional gradients within brain regions than clustering-based approaches. Placing borders at the reversals resulted in a parcellation into 41 subregions that differs significantly from an established scheme in nonrandom ways, but is comparable in terms of the modularity of connectivity between regions. It reveals unexpected trends of connectivity, such as a tripartite split of somatomotor regions along an anterior to posterior gradient. The method can be readily adapted to other organisms and data sources, such as human functional connectivity.

neuroscience↗