Biology subjects

Dietz, M.

Publications and source records attributed to Dietz, M..

5 recordsLinked to original sources

bioRxiv2025

Towards model-based characterization of individual electrically stimulated nerve fibers

Neuroprosthetics, such as cochlear implants or deep brain stimulators, can restore parts of the function of an impaired system. To improve such prosthetics, a detailed understanding of the electrical stimulation of nerve fibers is required. This knowledge can best be represented by computational models of the process. Currently, most models of individual electrically stimulated nerve fibers are based on many different datasets, which mainly consist of the average analysis values of recordings of many nerve fibers. While this is a valid approach for understanding the basic phenomena, both the combination of many different datasets and the average analysis can confound details in the response of the nerve fiber. To improve computational models of electrically stimulated nerve fibers further, we propose an optimization procedure that can fit the parameters of a neuron model to the response of a single nerve fiber to pulse-train stimulation. We show that in this way, the model can reproduce a wide variety of fiber responses of electrically stimulated auditory nerve fibers of guinea pigs in a remarkably detailed way on a scale of less than 1 ms. We analyze and discuss the certainty and generalizability of the parameter sets thus exposed. The model parameters found by the optimization procedure can then form the basis for a detailed fiber-by-fiber analysis, which we illustrate by a correlation analysis of the predicted phenomena (e.g., spike latency and refractory period) in the fiber response. Author SummaryNeuroprosthetics can partially restore the function of an impaired neural system. Examples of such prosthetics are cochlear implants, which allow deaf people to hear, or deep-brain stimulators, which can reduce the tremor in Parkinsons disease. While the mere existence of such prosthetics is already impressive, there is still room for improvement. Cochlear implant users, for example, have problems understanding speech in background noise, and deep-brain stimulators can have serious side effects, such as speech difficulties or limited fine motor control. To improve such implants, a detailed understanding of the underlying process, the electrical stimulation of nerve fibers, is required. A valuable representation of our understanding of the process is a computational model of electrically stimulated nerve fibers. Here, we optimized the parameters of one model, such that the behavior of 118 individual nerve fibers was represented, resulting in a single parameter set per fiber. In this way, a single model can reproduce a wide variety of response patterns, which allows for a detailed analysis of the individual fiber based on these parameters.

neuroscience↗

bioRxiv2024

Individual differences in the effects of musical familiarity and musical features on brain activity during relaxation

Finding a way to relax is increasingly difficult in our overstimulating modern society and chronic stress can have severe psychological and physiological consequences. Music is a promising tool to promote relaxation by lowering heart rate, modulating mood and thoughts, and providing a sense of safety. Here, we used functional magnetic resonance imaging (fMRI) to investigate how music influence brain activity during relaxation with a particular focus on the participants experience of different types of music. In a 2x2 design, 57 participants were scanned while rating how relaxed they felt after listening to 28-second excerpts of either familiar or unfamiliar relaxation music with calm or energetic features. Behaviourally, calm music was the strongest predictor of relaxation, followed by familiar music. fMRI results revealed activations of auditory, motor, emotion, and memory areas, for listening to familiar compared to unfamiliar music. This suggests increased audio-motor synchronization and participant engagement of known music. Listening to unfamiliar music was correlated with attention-related brain activity, suggesting increased attentional load for this music. Behaviourally, we identified four clusters of participants based on their relaxation response to the different types of music. These groups also displayed distinct auditory and motor activity patterns, suggesting that the behavioural responses are linked to changes in music processing. Interestingly, some individuals found energetic music to be relaxing if it is familiar, whereas others only found calm music to be relaxing. Such individual behavioural and neurological differences in relaxation responses to music emphasise the importance of developing personalised music-based interventions. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=123 SRC="FIGDIR/small/625650v1_ufig1.gif" ALT="Figure 1"> View larger version (42K): org.highwire.dtl.DTLVardef@34ccc0org.highwire.dtl.DTLVardef@6e7f84org.highwire.dtl.DTLVardef@75d428org.highwire.dtl.DTLVardef@1bb999d_HPS_FORMAT_FIGEXP M_FIG C_FIG Highlights- Participants listen to relaxation tracks varying in familiarity and energy levels - Sedative music followed by familiar music increased relaxation ratings the most - Auditory, motor, memory and attention activations depending on the music type - 4 distinct clusters of behavioural responses to familiar or sedative music - These groups are also present in brain activity

neuroscience↗

bioRxiv2023

Longitudinal Observations of the Effects of Ischemic Stroke on Binaural Perception

Acute ischemic stroke, characterized by a localized reduction in blood flow to specific areas of the brain, has been shown to affect binaural auditory perception. In a previous study conducted during the acute phase of ischemic stroke, two tasks of binaural hearing were performed: binaural tone-in-noise detection, and lateralization of stimuli with interaural time- or level differences (Dietze et al., 2022, Front. Neurosci. 16:1022354). Various lesion-specific, as well as individual, differences in binaural performance between patients in the acute phase of stroke and a control group were demonstrated. For the current study, we re-invited the same group of patients, whereupon a subgroup repeated the experiments during the subacute and chronic phases of stroke. Similar to the initial study, this subgroup consisted of patients with lesions in different locations, including cortical and subcortical areas. At the group level, the results from the tone-in-noise detection experiment remained consistent across the three measurement phases, as did the number of deviations from normal performance in the lateralization task. However, the performance in the lateralization task exhibited variations over time among individual patients. Some patients demonstrated improvements in their lateralization abilities, indicating recovery, whereas others lateralization performance deteriorated during the later stages of stroke. Notably, our analyses did not reveal consistent patterns for patients with similar lesion locations. These findings suggest that recovery processes are more individual than the acute effects of stroke on binaural perception. Individual impairments in binaural hearing abilities after the acute phase of ischemic stroke have been demonstrated and should therefore also be targeted in rehabilitation programs.

neuroscience↗

bioRxiv2019

Brainstem mechanisms contributing to accurate source localisation are suited to the reverberant structure of natural acoustic scenes

Listeners perceive sound-energy as originating from the direction of its source, even as direct sound is followed milliseconds later by reflected sound from multiple different directions. Early-arriving sound is emphasised in the ascending auditory pathway, including the medial superior olive (MSO) where binaural neurons encode the interaural time difference (ITD) cue for spatial location. Behaviourally, weighting of ITD conveyed during rising sound-energy is stronger at 600 Hz, a frequency with higher reverberant energy, than at 200 Hz where reverberant energy is lower. Here we computationally explore the combined effectiveness of adaptation before ITD-encoding, and excitatory binaural coincidence detection within MSO neurons, in emphasising ITD conveyed in early-arriving sound. With excitatory inputs from adapting model spherical bushy cells (SBCs) of the bilateral cochlear nuclei, a Hodgkin-Huxley-type model MSO neuron reproduces the frequency-dependent emphasis of rising vs. peak sound-energy in ITD-encoding. Maintaining the adaptation in model SBCs, and adjusting membrane speed in model MSO neurons, hemispheric populations of model SBCs and MSO neurons, with simplified membranes for computational efficiency, also reproduce the stronger weighting of ITD information conveyed during rising sound-energy at 600 Hz compared to 200 Hz. This hemispheric model further demonstrates a link between strong weighting of spatial information during rising sound-energy, and correct unambiguous lateralisation of reverberant speech.

neuroscience↗

bioRxiv2019

Dietary polyunsaturated fatty acid supply improves Daphnia performance during vertical migration

O_LIDiel vertical migration (DVM) is a common predator avoidance strategy of zooplankton. Migration to deeper water layers during the day to escape visually hunting predators most likely requires physiological adaptations to periodically changing temperatures. Polyunsaturated fatty acids (PUFA) are essential nutrients that play crucial roles in membrane temperature acclimation. Exposure to cold temperatures typically results in an increase in the relative abundance of PUFA in cell membranes and PUFA requirements of Daphnia have been shown to increase with decreasing temperatures.\nC_LIO_LITo assess the significance of dietary PUFA for coping with temperature fluctuations experienced during DVM, we reared Daphnia magna at either constantly warm or fluctuating temperatures simulating DVM both with and without dietary PUFA supplementation.\nC_LIO_LIWe show that the well-known positive effect of dietary eicosapentaenoic acid (EPA) supplementation on offspring production and population growth rates of Daphnia is more pronounced at alternating temperatures than at constantly warm temperatures. Exposure to alternating temperatures caused modification in body PUFA concentrations and, consequently, increased lipid peroxidation. However, detrimental effects of lipid peroxidation were not evident.\nC_LIO_LIOur data demonstrate that the capacity to cope with the distinct temperature fluctuations experienced during DVM increases with dietary EPA supplementation, suggesting that an adequate dietary PUFA supply is crucial especially for migrating Daphnia populations. A dietary deficiency in long-chain PUFA may thus severely constrain predator evasion, potentially resulting in increased mortality and cascading effects on lower trophic levels.\nC_LI

physiology↗