Wadghiri, Y. Z. | Search bioRxiv

bioRxiv2022

Towards reliable reconstruction of the mouse brain thalamocortical connectivity using diffusion MRI

Diffusion magnetic resonance imaging (dMRI) tractography has yielded intriguing insights into brain circuits and their relationship to behavior in response to gene mutations or neurological diseases across a number of species. Still, existing tractography approaches suffer from limited sensitivity and specificity, leading to uncertain interpretation of the reconstructed connections. Hence, in this study, we aimed to optimize the imaging and computational pipeline for reliable reconstruction of the mouse brain thalamocortical network. We developed a dMRI-based atlas of the mouse forebrain with structural labels imported from the Allen Mouse Brain Atlas (AMBA). Using the atlas and tracer data from the Allen Mouse Brain Connectivity Atlas (AMBCA) as ground truth, we investigated the accuracy of reconstructed node-to-node thalamocortical structural connectivity and effects of imaging and tractography parameters. Our results suggest that these parameters significantly affect tractography outcomes and our atlas can be used to investigate macroscopic structural connectivity in the mouse brain. Furthermore, tractography in mouse brain gray matter still face challenges and need improved imaging and tractography methods.

bioengineering↗

bioRxiv2021

Locus coeruleus activity improves cochlear implant performance

Cochlear implants are neuroprosthetic devices that can provide hearing to deaf patients1. Despite significant benefits offered by cochlear implants, there are highly variable outcomes in how quickly hearing is restored and perceptual accuracy after months or years of use2,3. Cochlear implant use is believed to require neuroplasticity within the central auditory system, and differential engagement of neuroplastic mechanisms might contribute to outcome variability4-7. Despite extensive studies on how cochlear implants activate the auditory system4,8-12, our understanding of cochlear implant-related neuroplasticity remains limited. One potent factor enabling plasticity is the neuromodulator norepinephrine from the brainstem locus coeruleus. Here we examined behavioral responses and neural activity in locus coeruleus and auditory cortex of deafened rats fitted with multi-channel cochlear implants. Animals were trained on a reward-based auditory task, with considerable individual differences of learning rates and maximum performance. Photometry from locus coeruleus predicted when implanted subjects would begin responding to sounds and longer-term perceptual accuracy, which were augmented by optogenetic locus coeruleus stimulation. Auditory cortical responses to cochlear implant stimulation reflected behavioral performance, with enhanced responses to rewarded stimuli and decreased distinction between unrewarded stimuli. Adequate engagement of central neuromodulatory systems is thus a potential clinically-relevant target for optimizing neuroprosthetic device use.

neuroscience↗