Biology subjects

Demarchi, G.

Publications and source records attributed to Demarchi, G..

11 recordsLinked to original sources

bioRxiv2026

Accelerated neural aging as a systems-level vulnerability for tinnitus

Tinnitus, the perception of sound without an external source, affects 10-15% of individuals, yet its neural mechanisms remain poorly understood. Building on evidence that chronological age predicts tinnitus risk beyond hearing loss, we tested the hypothesis that accelerated neural aging increases susceptibility to tinnitus by integrating cross-sectional resting-state MEG with longitudinal structural imaging data. In a large MEG dataset, spectral parametrization revealed that age-neural relationships were amplified in the tinnitus group compared to age-, sex- & hearing-matched controls. Complementing these findings, prospective analyses using data from the UK Biobank showed that among participants without tinnitus at baseline, stronger age-related declines in white-matter density predicted later tinnitus onset. Collectively, these converging functional and structural findings support accelerated brain aging as a key risk factor for tinnitus.

neuroscience↗

bioRxiv2024

Eye Movements in Silent Visual Speech track Unheard Acoustic Signals and Relate to Hearing Experience

Behavioral and neuroscientific studies have shown that watching a speakers lip movements aids speech comprehension. Intriguingly, even when videos of speakers are presented silently, various cortical regions track auditory features, such as the envelope. Recently, we demonstrated that eye movements track low-level acoustic information when attentively listening to speech. In this study we investigated whether ocular speech tracking occurs during visual speech and how it influences cortical silent speech tracking. Furthermore, we compared the data of hearing individuals with congenitally deaf individuals, and those with acquired deafness or hearing loss (DHH; Deaf or hard of hearing) to assess how auditory deprivation (early vs. late onset) affects neural and ocular speech tracking during silent lip-reading. Using magnetoencephalography (MEG), we examined ocular and neural speech tracking of 75 participants observing silent videos of a speaker played forward and backward. Our main finding is a clear ocular unheard speech tracking effect with a dominance <1 Hz, which was not present for the lip movements. Similarly, we observed a <=1.3 Hz effect of neural unheard speech tracking in temporal regions for hearing participants. Importantly, neural tracking was not directly linked to ocular tracking in this study. Strikingly, across different listening groups, deaf participants with auditory listening experience showed higher ocular speech tracking than hearing participants, while no ocular speech tracking effect was revealed for congenitally deaf participants in a very small sample. This study extends our previous work by demonstrating the involvement of eye movements in speech processing, even in the absence of acoustic input.

neuroscience↗

bioRxiv2024

Carrier-frequency specific omission-related neural activity in ordered sound sequences are independent of omissions-predictability

Regularities in our surroundings lead to predictions about upcoming events. Previous research has shown, that omitted sounds during otherwise regular tone sequences elicit frequency-specific neural activity related to the upcoming but omitted tone. We tested whether this neural response is depending on the unpredictability of the omission. Therefore we recorded MEG data while participants listened to ordered or random tone sequences with omissions occurring either ordered or randomly. Using multivariate pattern analysis shows that the frequency-specific neural pattern during omission within ordered tone sequences occurs independent of the regularity of the omissions suggesting that the auditory predictions based on sensory experiences are not immediately updated by violations of those expectations.

neuroscience↗

bioRxiv2022

Network topology in brain tumor patients with and without structural epilepsy- a prospective MEG-study

It has been proposed that functional connectivity (FC) and network topology (NT) are altered in patients with glial brain tumors. So far there is no consensus on the pattern of these changes, furthermore data on FC in patients with brain metastases (BMs) as well as on the presence and absence of tumor-related epilepsy is lacking. We aimed to analyze preoperative NT of newly diagnosed, singular, supratentorial glial brain tumors (GBTs) and BMs with and without structural epilepsy. FC and NT derived from resting state magnetoencephalography (MEG) were compared between patients (PAs) and matched healthy controls (HCs), between GBTs and BMs as well as between patients with and without structural epilepsy. We investigated all patients, who met our inclusion criteria from February 2019 to March 2021. Clinical data was collected from patients electronic medical charts. We analyzed whole brain (wb) connectivity in six frequency bands, calculated three different network topological parameters (node degree (ND), shortest path length (L), clustering coefficient (CC)) and performed a stratification, where differences in the power were to be found. For data analysis we used Fieldtrip, Brain Connectivity Matlab toolboxes and in-house built scripts. We consecutively included 41 patients (21 men), mean age 60.1ys (range 23-82), who were operated on at our institution. Tumor histology included high-grade gliomas (n=18), low-grade gliomas (n=4), dysembryoplastic neuroepithelial tumor (DNET, n=1), BMs (n=14) and others (n=4). Statistical analysis revealed a significant decrease for wb ND in patients compared to healthy controls in every frequency range analyzed at the descriptive and corrected level (p1-30Hz=0.002, p{gamma}=0.002, p{beta}=0.002, p=0.002, p{theta}=0.024, p{delta}=0.002). Furthermore, at the descriptive level, we found a significant augmentation for wb CC (p1-30Hz=0.031, p{delta}=0.013) in PAs compared to HCs, which did not persist the false discovery rate (FDR) correction. There were no differences in the networks of glial brain tumors and metastases identified. However, we found a significant increase in wb CC in patients with structural epilepsy (p{theta}= 0.048), and significantly lower wb ND (p= 0.039) at the uncorrected level. Our data suggests that network topology is altered in brain tumor patients, which is in line with previous studies. Tumor histology per se might not influence the brains functional network, however, tumor-related epilepsy seems to do so. Longitudinal studies and in-depth analysis of possible factors and confounders might be helpful to further substantiate these findings.

neuroscience↗

bioRxiv2022

Age-related changes in 'cortical' 1/f dynamics are explained by cardiac activity

The power of electrophysiologically measured cortical activity decays with an approximately 1/fX function. The slope of this decay (i.e. the spectral exponent, X) is modulated by various factors such as age, cognitive states or psychiatric/neurological disorders. Interestingly, a mostly parallel line of research has also uncovered similar effects for the spectral slope in the electrocardiogram (ECG). This raises the question whether these bodywide changes in spectral slopes are (in-)dependent. Focusing on well-established age-related changes in spectral slopes we analyzed a total of 1282 recordings of magnetoencephalography (MEG) resting state measurements with concurrent ECG in an age-diverse sample (18-88 years). Using a diverse array of analytical approaches, we demonstrate that the aperiodic signal recorded via surface electrodes/sensors originates from multiple physiological sources. Furthermore, our results suggest that common "artifact" rejection approaches (i.e. ICA) may not be sufficient to separate cardiac from neural activity. In particular, significant parts of age-related changes in aperiodic activity normally interpreted to be of neural origin can be explained by cardiac activity. Moreover, our results suggest that changes (flattening/steepening) of the spectral slope with age are dependent on the recording site and investigated frequency range. Our results highlight the complexity of aperiodic activity while raising concerns when interpreting aperiodic activity as "cortical" without considering physiological influences.

neuroscience↗

bioRxiv2019

Phantom auditory perception (tinnitus) is characterised by stronger anticipatory auditory predictions

How phantom perceptions arise and the factors that make individuals prone to such experiences are not well understood. An attractive phenomenon to study these questions is tinnitus, a very common auditory phantom perception which is not explained by hyperactivity in the auditory pathway alone. Our framework posits that a predisposition to developing (chronic) tinnitus is dependent on individual traits relating to the formation and utilization of sensory predictions. Predictions of auditory stimulus frequency (remote from tinnitus frequency) were studied using a paradigm parametrically modulating regularity (i.e. predictability) of tone sequences and applying decoding techniques on magnetoencephalographic (MEG) data. For processes likely linked to short-term memory, individuals with tinnitus showed an enhanced anticipatory prediction pattern associated with increasing sequence regularity. In contrast, individuals without tinnitus engaged the same processes following the onset of the to-be-decoded sound. We posit that this tendency to optimally anticipate static and changing auditory inputs may determine which individuals faced with persistent auditory pathway hyperactivity factor it into auditory predictions, and thus perceive it as tinnitus. While our study constitutes a first step relating vulnerability to tinnitus with predictive processing, longitudinal studies are needed to confirm the predisposition model of tinnitus development.

neuroscience↗

bioRxiv2019

Cochlear activity in silent cue-target intervals shows a theta rhythmic pattern and is correlated to attentional alpha modulations

A long-standing debate concerns where in the processing hierarchy of the central nervous system (CNS) selective attention takes effect. In the auditory system cochlear processes can be influenced via direct and mediated (by the inferior colliculus) projections from the auditory cortex to the superior olivary complex (SOC). Studies illustrating attentional modulations of cochlear responses have so far been limited to sound-evoked responses. The aim of the present study is to investigate intermodal (audiovisual) selective attention in humans simultaneously at the cortical and cochlear level during a stimulus-free cue-target period. We found that cochlear activity in the silent cue-target periods was modulated by a theta-rhythmic pattern ([~]6 Hz). While this pattern was present independently of attentional focus, cochlear theta activity was clearly enhanced when attending to the upcoming auditory input. On a cortical level, classical posterior alpha and beta power enhancements were found during auditory selective attention. Interestingly, participants with a stronger release of inhibition in auditory brain regions show a stronger attentional modulation of cochlear theta activity. These results hint at a putative theta-rhythmic sampling of auditory input at the cochlear level. Furthermore, our results point to an interindividual variable engagement of efferent pathways in an attentional context that are linked to processes within and beyond processes in auditory cortical regions.

neuroscience↗

bioRxiv2019

Auditory cortical alpha desynchronization prioritizes the representation of memory items during a retention period

Maintaining information in working memory normally happens in dynamic environments, with a multitude of distracting events. This is particularly evident in the auditory system, for example, when trying to memorize a telephone number during ongoing background noise. How relevant to-be-memorized information is protected against the adverse influence of a temporally predictable distractor was the main goal of the present study. For this purpose we adapted a Sternberg task variant established in the visual modality, with either a strong or a weak distracting sound presented at a fixed time during the retention period. Our behavioral analysis confirmed a small, albeit significant deterioration of memory performance in the strong distractor condition. We used a time-generalized decoding approach applied to magnetoencephalography (MEG) data to investigate the extent of memory probe-related information prior to the anticipated distractor onset and found a relative decrease for the strong distractor condition. This effect was paralleled by a pre-distractor alpha power decrease in the left superior temporal gyrus (STG), a cortical region putatively holding memory content relevant information. Based on gating frameworks of alpha oscillations, these results could be interpreted as a failed inhibition of an anticipated strong (more salient) distractor. However, in a critical analysis we found that reduced alpha power in the left STG was associated with relatively increased memory probe-related information. Our results therefore support the view of alpha power reductions in relevant sensory (here auditory) cortical areas to be a mechanism by which to-be-remembered information is prioritized during working memory retention periods.

neuroscience↗

bioRxiv2019

A backward encoding approach to recover subcortical auditory activity

1.Several subcortical nuclei along the auditory pathway are involved in the processing of sounds. One of the most commonly used methods of measuring the activity of these nuclei is the auditory brainstem response (ABR). Due to its low signal-to-noise ratio, ABRs have to be derived by averaging over thousands of artificial sounds such as clicks or tone bursts. This approach cannot be easily applied to natural listening situations (e.g. speech, music), which limits auditory cognitive neuroscientific studies to investigate mostly cortical processes. We propose that by training a backward encoding model to reconstruct evoked ABRs from high-density electrophysiological data, spatial filters can be tuned to auditory brainstem activity. Since these filters can be applied (i.e. generalized) to any other data set using the same spatial coverage, this could allow for the estimation of auditory brainstem activity from any continuous sensor level data. In this study, we established a proof-of-concept by using a backward encoding model generated using a click stimulation rate of 30 Hz to predict ABR activity recorded using EEG from an independent measurement using a stimulation rate of 9 Hz. We show that individually predicted and measured ABRs are highly correlated (r [~] 0.7). Importantly these predictions are stable even when applying the trained backward encoding model to a low number of trials, mimicking a situation with an unfavorable signal-to-noise ratio. Overall, this work lays the necessary foundation to use this approach in more interesting listening situations.

neuroscience↗

bioRxiv2019

Head MagnetoMyography (hMMG): a novel approach to monitor face and whole-head muscular activity

Muscular activity recording is of high basic science and clinical relevance and is typically achieved using electromyography (EMG). While providing detailed information about the state of a specific muscle, this technique has limitations such as the need for a-priori assumptions about electrode placement and difficulty with recording muscular activity patterns from extended body areas at once. For head and face muscle activity, the present work aimed to overcome these restrictions by exploiting magnetoencephalography (MEG) as a whole-head myographic recorder (head magnetomyography, hMMG). This is in contrast to common MEG studies, which treat muscular activity as artifact in electromagnetic brain activity. In a first proof-of-concept step, participants imitated emotional facial expressions performed by a model. Exploiting source projection algorithms, we were able to reconstruct muscular activity, showing spatial activation patterns in accord with the hypothesized muscular contractions. Going one step further, participants passively observed affective pictures with negative, neutral, or positive valence. Applying multivariate pattern analysis to the reconstructed hMMG signal, we were able to decode above chance the valence category of the presented pictures. Underlining the potential of hMMG, a searchlight analysis revealed that generally neglected neck muscles exhibit information on stimulus valence. Results confirm the utility of hMMG as a whole-head electromyographic recorder to quantify muscular activation patterns including muscular regions that are typically not recorded with EMG. This key advantage beyond conventional EMG has substantial scientific and clinical potential.

neuroscience↗

bioRxiv2018

Prediction-related neural activity during silent periods is sharply tuned

Prior experience shapes sensory perception by enabling the formation of expectations with regards to the occurrence of upcoming sensory events. Especially in the visual modality, an increasing number of studies show that prediction-related neural signals carry feature-specific information about the stimulus. This is less established in the auditory modality, in particular without bottom-up signals driving neural activity. We studied whether auditory predictions are sharply tuned to even carry tonotopic specific information. For this purpose, we conducted a Magnetoencephalography (MEG) experiment in which participants passively listened to sound sequences that varied in their regularity (i.e. entropy). Sound presentations were temporally predictable (3 Hz rate), but were occasionally omitted. Training classifiers on the random (high entropy) sound sequence and applying them to all conditions in a time-generalized manner, allowed us to assess whether and how carrier frequency specific information in the MEG signal is modulated according to the entropy level. We show that especially in an ordered (most predictable) sensory context neural activity during the anticipatory and omission periods contains carrier-frequency specific information. Overall our results illustrate in the human auditory system that prediction-related neural activity can be tuned in a tonotopically specific manner.

neuroscience↗