Biology subjects

Rodenkirch, C.

Publications and source records attributed to Rodenkirch, C..

3 recordsLinked to original sources

bioRxiv2024

Cervical transcutaneous vagus nerve stimulation enhances speech recognition in noise: A crossover, placebo-controlled study

Speech comprehension in noisy environments remains a significant challenge, even among individuals with clinically normal hearing and users of hearing aids and cochlear implants. While conventional assistive hearing devices address limitations in the auditory periphery, they do not directly enhance the brains capacity to segregate speech from background noise. Because tonic vagus nerve stimulation (VNS) has demonstrated potential for rapidly improving central sensory processing, this study investigated whether tonic transcutaneous cervical VNS (tcVNS) can augment speech-in-noise intelligibility. Two cohorts of older human adults (60-84 years) participated in a placebo-controlled, crossover study. Participants completed speech-in-noise assessments using either QuickSIN or AzBio sentences, while receiving tonic tcVNS to the neck, or placebo stimulation to the neck-shoulder junction. Speech-in-noise performance was assessed by measuring participants accuracy in repeating sentences presented at varying signal-to-noise ratios (SNR) within background babble. Tonic tcVNS improved speech-in-noise intelligibility compared to placebo. At the group-level, the SNR threshold for 50% speech intelligibility (SNR-50) improved by 0.76 dB in QuickSIN (p=0.016) and by 0.38 dB in AzBio (p=0.045). For individual participants, 50% demonstrated improvements that met a minimum clinically important difference (MCID) of 1 dB. Tonic tcVNS evoked progressively greater improvements as SNR increased in QuickSIN (p=0.021) and AzBio (p=0.00023), with the largest gains above 0 dB SNR. In 55% of participants, tcVNS improved intelligibility beyond an MCID benchmark of 4.9% at 5 dB SNR. While the magnitude of tcVNS-evoked improvements was inversely related to baseline speech-in-noise impairment (p=0.028), with the most impaired individuals demonstrating the largest gains, it did not correlate with hearing loss severity (p=0.97) or age (p=0.88). Our findings indicate that tonic tcVNS can evoke immediate and clinically meaningful enhancements in speech-in-noise comprehension. This suggests tcVNS may complement conventional assistive hearing technologies and inform novel therapies for sensory processing disorders.

neuroscience↗

bioRxiv2024

Diversity of ancestral brainstem noradrenergic neurons across species and multiple biological factors

The brainstem cell group, locus coeruleus (LC), is present across vertebrates and influences cardiorespiratory, metabolic, immune, and cognitive functions by activating in two putatively distinct firing patterns. Yet, the degree to which the LC firing rates and patterns are homogenous across species has never been assessed due to inherently limited sample sizes. To remedy this, we pooled cross-species data from 20 laboratories to show that firing rates differ across species and are modulated by sex, age, and type of in vitro or in vivo preparation. Contrary to the prevailing dual-mode firing pattern schema, we observed patterns spread across a low-dimensional manifold, with subregions enriched for specific biological factors and neurodegenerative disease models. Our findings show considerable diversity in an ancestral vertebrate neuromodulatory system.

neuroscience↗

bioRxiv2023

Non-invasive vagus nerve stimulation improves sensory performance in humans

Accurate senses depend on high-fidelity encoding by sensory receptors and error-free processing in the brain. Progress has been made towards restoring damaged sensory receptors. However, methods for on-demand treatment of impaired central sensory processing are scarce. Prior invasive studies demonstrated that continuous vagus nerve stimulation (VNS) in rodents can activate the locus coeruleus-norepinephrine system to rapidly improve central sensory processing. Here, we investigated whether transcutaneous VNS improves sensory performance in humans. We conducted three sham-controlled experiments, each with 12 neurotypical adults, that measured the effects of transcutaneous VNS on metrics of auditory and visual performance, and heart rate variability (HRV). Continuous stimulation was delivered to cervical (tcVNS) or auricular (taVNS) branches of the vagus nerve while participants performed psychophysics tasks or passively viewed a display. Relative to sham stimulation, tcVNS improved auditory performance by 37% (p=0.00052) and visual performance by 23% (p=0.038). Participants with lower performance during sham conditions experienced larger tcVNS-evoked improvements (p=0.0040). Lastly, tcVNS increased HRV during passive viewing, corroborating vagal engagement. No evidence for an effect of taVNS was observed. These findings validate the effectiveness of tcVNS in humans and position it as a method for on-demand interventions of impairments associated with central sensory processing dysfunction.

neuroscience↗