Biology subjects

Alain, C.

Publications and source records attributed to Alain, C..

13 recordsLinked to original sources

bioRxiv2025

Theta-mediated conceptual reinstatement in vmPFC precedes perceptual reinstatement in ventral visual cortex during memory recall

When recalling past episodes, different features of an experience, such as conceptual meaning and perceptual detail, are reconstructed and reinstated across distributed cortical regions. However, current models of human memory remain unclear how these feature-specific reinstatements unfold over time, and whether they interact hierarchically during memory retrieval. Using magnetoencephalography (MEG) and time-resolved encoding-retrieval cross-phase classification analysis, we compared the time course of conceptual and perceptual reinstatement during cued visual recall. Conceptual information decoding in the ventromedial prefrontal cortex (vmPFC) preceded perceptual information decoding in the ventral visual cortex (VVC), and the two were expressed in distinct frequency bands: theta (4-8 Hz) for conceptual and gamma (30-40 Hz) for perceptual information. Cross-correlation and spectral Granger causality analyses revealed that during reinstatement conceptual information in vmPFC predicted and directed perceptual information in VVC, with theta-band information flow predominantly from vmPFC to VVC. In addition, bottom-up connectivity from VVC to vmPFC was expressed in the alpha band. These findings suggest that memory retrieval proceeds from abstract conceptual reconstruction to the reinstatement of perceptual details, mediated by theta oscillatory communication between prefrontal and sensory areas. We propose a hierarchical interactive model in which vmPFC initiates conceptual activation through theta-band top-down signals, while VVC provides alpha-band feedback for evaluating reconstructed perceptual details.

neuroscience↗

bioRxiv2025

Differential reliance on sensory reinstatement and internally transformed representation during vivid retrieval of visual and auditory episodes

Auditory memory is considered less detailed yet more durable than visual memory, implying a modality-specific memory retrieval process. We used fMRI and multivoxel pattern analyses to examine how 25 participants encoded and retrieved naturalistic sounds and videos. Both auditory and visual targets reinstated item-specific fine activation patterns in the association cortex during retrieval, and reinstatement strength correlates with subjective memory vividness. However, auditory episodes showed a markedly larger reliance on internally constructed representations than visual episodes, quantified by retrieval-retrieval similarity after removing encoding traces. Sensory reinstatement correlated more to the (detail-related) posterior hippocampus, while internal representations also correlated to the (gist-related) anterior hippocampus. Furthermore, temporal voice areas preserved gist-level (human versus non-human) information from encoding to retrieval, whereas fusiform face representations degraded. These findings reveal that auditory and visual memories share a common sensory reinstatement mechanism, but differ in the neural mechanism that supports retrieval, with participants favouring gist over perceptual details during auditory memory retrieval.

neuroscience↗

bioRxiv2025

When Melodies Cue Memories: Electrophysiological Correlates of Autobiographically Salient Music Listening in Older Adults

Autobiographical memory is essential for older adults, providing a foundation for self-identity. Healthy aging is accompanied by changes in memory retrieval. However, musical memory remains relatively preserved, suggesting it may serve as an effective cue for autobiographical memory recall. Autobiographically salient (ABS) music (i.e., deeply encoded songs associated to important people, places, and events) is posited to engage distinct memory processes than familiar (FAM) music (i.e., songs that are recognized but lack personal significance). We tested this in 36 older adults (70.6 {+/-} 6.6 years, 20 females) who listened to music of varying degrees of personal significance, including ABS, FAM, and unfamiliar (UFAM) music. In Experiment 1, participants pressed a button as quickly as possible when they recognized the excerpt as ABS, FAM, or UFAM. In Experiment 2, we measured event-related potentials and time-frequency responses while participants listened to the same stimuli and rated familiarity and memory at the end of each excerpt. Participants had the fastest reaction times for ABS, followed by FAM, then UFAM music. We observed a sustained evoked response from 2238 to 5000 ms post-stimulus onset that was largest in amplitude for ABS music, compared to FAM and UFAM music, over right frontal-central regions. We also observed less beta power suppression for ABS than FAM music between 1300 and 5000 ms over bilateral frontal-central-parietal areas. Our behavioral and neurophysiological findings show that ABS music is associated with faster and stronger memory-related activity distinct from FAM music.

neuroscience↗

bioRxiv2025

Neural signatures of stream segregation: From childhood to adulthood

When faced with noisy environments, listeners perform auditory scene analysis, which allows them to parse the auditory target from concurrent interferences. Stream segregation involves organizing similar sound waves into a coherent stream, while distinguishing dissimilar acoustic components and attributing them to distinct sources. Two event-related potential components have been identified as "neural signatures" of stream segregation: the Object-Related Negativity (ORN) and the P400. Our study aims to examine (i) the maturation of neural and behavioural correlates of stream segregation and (ii) the development of the relationship between stream segregation and speech perception in noise. ORN/P400 were recorded while 8-23 year-olds performed an active stream segregation task based on temporal coherence. Participants also performed speech identification in noise tasks (behaviourally). Behavioral results indicate an improvement in both stream segregation and speech perception in noise from childhood to adulthood. Amplitude of the ORN (but not P400) decreases, and latency of both ORN and P400 decreases throughout development. Critically, P400 amplitude significantly predicts stream segregation performance. Overall, our results suggest that the neural mechanisms underlying stream segregation follow a prolonged maturation trajectory, and support the progressive maturation of auditory scene analysis and speech perception in noise. RESEARCH HIGHLIGHTS- Neurophysiological indices of stream segregation mature from childhood to adulthood - Neural indices of top-down attentive processing of complex auditory sequences predict stream segregation, irrespective of the listeners age - In adults (but not in children or adolescents), stream segregation predicts speech perception in noise - Stream segregation may thus operate as a bottleneck to speech in noise difficulties in children and adolescents

neuroscience↗

bioRxiv2024

Neural Mechanism Underlying Successful Classification of Amnestic Mild Cognitive Impairment Using Multi-Sensory-Evoked Potentials

Early detection of amnestic mild cognitive impairment (aMCI) is crucial for timely interventions. This study combines scalp recordings of lateralized auditory, visual, and somatosensory stimuli with a flexible and interpretable support vector machine learning pipeline to differentiate individuals diagnosed with aMCI from healthy controls. Event-related potentials (ERPs) and functional connectivity (FC) matrices from each modality successfully predicted aMCI. Reduced ERP amplitude in aMCI contributed to classification. The analysis of FC using phase-locking value revealed higher FC in aMCI than controls in frontal regions, which predicted worse cognitive performance, and lower FC in posterior regions from delta to alpha frequency. We observe optimal classification accuracy (96.1%), sensitivity (97.7%) and specificity (94.3%) when combining information from all sensory conditions than when using information from a single modality. The results highlight the clinical potential of sensory-evoked potentials in detecting aMCI, with optimal classification using both amplitude and oscillatory-based FC measures from multiple modalities.

neuroscience↗

bioRxiv2024

Accumulated reserves hold back age-related neural compensation in speech-in-noise perception

During cognitive tasks, increased frontoparietal neural activity and functional connectivity are commonly observed in older adults. Cognitive reserves accrued from positive life choices can provide additional neural resources to cope with aging. However, how cognitive reserves interact with upregulated neural activity in older adults is poorly understood. We measured brain activity with fMRI during a speech-in-noise task and assessed whether cognitive reserve accumulated from long-term musical training bolsters or holds back age-related upregulated activity. Older musicians exhibited less upregulation of task-induced functional connectivity than older non-musicians in auditory dorsal regions, which predicted better behavioral performance in older musicians. These results suggest that cognitive reserve may hold back neural recruitment. Besides functional connectivity strength, we also found that older musicians showed more youth-like fine spatial patterns of functional connectivity than older non-musicians. Our findings enlightened the intricate interplay between cognitive reserve and age-related upregulated activity during speech in noise perception. Significance StatementUnderstanding the interplay between cognitive reserve and age-related neural changes is vital for developing strategies to mitigate cognitive decline in older adults. This study reveals that long-term musical training, which provides cognitive reserve for speech perception, helps older musicians preserve youth-like levels of functional connectivity and fine-scale activity patterns in the auditory dorsal stream during speech-in-noise perception. Unlike older non-musicians, who exhibit age-related neural upregulation, older musicians maintain youth-like connectivity patterns akin to those of younger adults, resulting in superior speech-in-noise perception. These findings support the "Hold-back upregulation" hypothesis and suggest that musical training counteracts age-related declines by preserving youthful brain function. The results offer valuable insights for designing interventions to enhance aging populations cognitive function and communication abilities.

neuroscience↗

bioRxiv2024

Assessing Cognitive Functions Remotely Using a Music-Game-Like Program

There is a growing need to develop ways of assessing cognitive functions remotely and providing interventions using a web-based approach. The Ipsilon Test is a music-based cognitive assessment and training tablet application. On each trial, it presents simplified musical notation with colours, spatial cues, and gestural references so that users can translate spatial information into motor actions by tapping on the screen. In this study, we examined the correlation between the performance of a group of healthy older adults on the Ipsilon test and standard measures of cognitive function--a total of 30 participants aged 58 and over were recruited for the study. Before and after one week of training using the web-based program Ipsilon, all participants completed an online version of the Montreal Cognitive Assessment (MoCA) and the visual Stroop task. Of the participants recruited, 22 participants completed the Ipsilon training and cognitive testing. In our sample, performance on the Ipsilon test was generally high, with all participants scoring above the chance level. Importantly, we found a correlation between Ipsilon test performance and pre-Ipsilon MoCA scores. In addition, participants who scored higher on the Ipsilon test also showed improvement in the visual Stroop task after Ipsilon training, particularly in the ability to inhibit irrelevant information. These results suggest the Ipsilon test is a practical web-based cognitive assessment and training tool. Future research will explore its relationship with other cognitive tests and its diagnostic power for differentiating individuals with normal cognition from those with cognitive disorders.

neuroscience↗

bioRxiv2022

Age-related hearing loss alters real-time dynamics of auditory cortical-brainstem coding during speech perception

Real-time modulation of brainstem frequency-following responses (FFRs) by online changes in cortical arousal state via the corticofugal (top-down) pathway has been demonstrated previously in young adults and is more prominent in the presence of background noise. FFRs during high cortical arousal states also have a stronger relationship with speech perception. Aging is associated with increased auditory brain responses, which might reflect degraded inhibitory processing within the peripheral and ascending pathways, or changes in attentional control regulation via descending auditory pathways. Here, we tested the hypothesis that online corticofugal interplay is impacted by age-related hearing loss. We measured EEG in older adults with normal-hearing (NH) and mild to moderate hearing-loss (HL) while they performed speech identification tasks in different noise backgrounds. We measured power to index online cortical arousal states during task engagement. Subsequently, we split brainstem speech-FFRs, on a trial-by-trial basis, according to fluctuations in concomitant cortical power into low or high FFRs to index cortical-brainstem modulation. We found cortical power was smaller in the HL than NH group. In NH listeners, -FFRs modulation for clear speech (i.e., without noise) also resembled that previously observed in younger adults for speech in noise. Cortical-brainstem modulation was further diminished in HL older adults in the clear condition and by noise in NH older adults. Machine learning classification showed low FFR frequency spectra yielded higher accuracy for classifying listeners perceptual performance in both NH and HL participants. Moreover, low FFRs decreased with increased hearing thresholds at 0.5-2 kHz for clear speech but noise generally reduced low FFRs in the HL group. Collectively, our study reveals cortical arousal state actively shapes brainstem speech representations and provides a potential new mechanism for older listeners difficulties perceiving speech in cocktail party-like listening situations in the form of a miss-coordination between cortical and subcortical levels of auditory processing.

neuroscience↗

bioRxiv2020

Mismatch Negativity Predicts Pattern Separation

We are so tuned to sensory changes that we can detect novelty within hundreds of milliseconds. To what extent does our capacity to automatically discriminate auditory inputs influence encoding of long-term memories? We recorded mismatch negativity (MMN), an event-related potential (ERP) indexing perceptual discrimination, as participants were presented with sound patterns while watching a muted movie. MMN strength predicted how well naive listeners separated the previously heard from new micropatterns on a subsequent recognition test, providing evidence that the MMN translates into mnemonic pattern separation. Our investigation is the first to show that our capacity to discriminate auditory inputs, as measured by MMN, gives rise to unique memories.

neuroscience↗

bioRxiv2020

Involuntary orienting and conflict resolution during auditory attention: The role of ventral and dorsal streams

Selective attention to sound object features such as pitch and location is associated with enhanced brain activity in ventral and dorsal streams, respectively. We examined the role of these pathways in involuntary orienting and conflict resolution using functional magnetic resonance imaging (fMRI). Participants were presented with two tones that may share, or not, the same non-spatial (frequency) or spatial (location) auditory features. In separate blocks of trials, participants were asked to attend to sound frequency or sound location and ignore the change in the task-irrelevant feature. In both attend-frequency and attend-location tasks, response times were slower when the task-irrelevant feature changed than when it stayed the same (involuntary orienting). This behavioural cost coincided with enhanced activity in the prefrontal cortex and superior temporal gyrus (STG). Conflict resolution was examined by comparing situations where the change in stimulus features was congruent (both features changed) and incongruent (only one feature changed). Participants were slower and less accurate for incongruent than congruent sound features. This congruency effect was associated with enhanced activity in the prefrontal cortex, and was greater in the right STG and medial frontal cortex during the attend-location than during the attend-frequency task. Together, these findings do not support a strict division of labour into ventral and dorsal streams, but rather suggest interactions between these pathways in situations involving changes in task-irrelevant sound feature and conflict resolution. These findings also validate the Test of Attention in Listening task by revealing distinct neural correlates for involuntary orienting and conflict resolution.

neuroscience↗

bioRxiv2019

Decoding age-related changes in the spatiotemporal neural processing of speech using machine learning

Speech comprehension in noisy environments depends on complex interactions between sensory and cognitive systems. In older adults, such interactions may be affected, especially in those individuals who have more severe age-related hearing loss. Using a data-driven approach, we assessed the temporal (when in time) and spatial (where in the brain) characteristics of the cortexs speech-evoked response that distinguish older adults with or without mild hearing loss. We used source montage to model scalp-recorded during a phoneme discrimination task conducted under clear and noise-degraded conditions. We applied machine learning analyses (stability selection and control) to choose features of the speech-evoked response that are consistent over a range of model parameters and support vector machine (SVM) classification to investigate the time course and brain regions that segregate groups and speech clarity. Whole-brain data analysis revealed a classification accuracy of 82.03% [area under the curve (AUC)=81.18%; F1-score 82.00%], distinguishing groups within [~]50 ms after speech onset (i.e., as early as the P1 wave).We observed lower accuracy of 78.39% [AUC=78.74%; F1-score=79.00%] and delayed classification performance when the speech token were embedded in noise, with group segregation at 60 ms. Separate analysis using left (LH) and right hemisphere (RH) regions showed that LH speech activity was better at distinguishing hearing groups than activity measured over the RH. Moreover, stability selection analysis identified 13 brain regions (among 1428 total spatiotemporal features from 68 regions) where source activity segregated groups with >80% accuracy (clear speech); whereas 15 regions were critical for noise-degraded speech to achieve a comparable level of group segregation (76% accuracy). Our results identify two core neural networks associated with complex speech perception in older adults and confirm a larger number of neural regions, particularly in RH and frontal lobe, are active when processing degraded speech information.

bioengineering↗

bioRxiv2019

Disentangling group specific QTL allele effects from genetic background epistasis using admixed individuals in GWAS: an application to maize flowering

When handling a structured population in association mapping, group-specific allele effects may be observed at quantitative trait loci (QTLs) for several reasons: (i) a different linkage disequilibrium (LD) between SNPs and QTLs across groups, (ii) group-specific genetic mutations in QTL regions, and/or (iii) epistatic interactions between QTLs and other loci that have differentiated allele frequencies between groups. We present here a new genome-wide association (GWAS) approach to identify QTLs exhibiting such group-specific allele effects. We developed genetic materials including admixed progeny from different genetic groups with known genome-wide ancestries (local admixture). A dedicated statistical methodology was developed to analyze pure and admixed individuals jointly, allowing one to disentangle the factors causing the heterogeneity of allele effects across groups. This approach was applied to maize by developing an inbred \"Flint-Dent\" panel including admixed individuals that was evaluated for flowering time. Several associations were detected revealing a wide range of configurations of allele effects, both at known flowering QTLs (Vgt1, Vgt2 and Vgt3) and new loci. We found several QTLs whose effect depended on the group ancestry of alleles while others interacted with the genetic background. The existence of directional epistasis was highlighted by comparing admixed with pure individuals and was consistent with epistatic interactions identified at the level of QTLs. Our GWAS approach provides useful information on the stability of QTL effects across genetic groups and can be applied to a wide range of species.\n\nAuthor summaryIdentification of genomic regions involved in genetic architecture of traits has become commonplace in quantitative genetics studies. Genetic structure is a common feature in human, animal and plant species and most current methods target genomic regions whose effects on traits are conserved between genetic groups. However, a heterogeneity of allele effects may be observed due to different factors: a group-specific correlation between the alleles of the tagged marker and those of the causal variant, a group-specific mutation at the causal variant or an epistatic interaction between the causal variant and the genetic background. We propose a new method adapted to structured populations including admixed individuals, which aims to identify these genomic regions and to unravel the previous factors. method was applied to a maize inbred diversity panel including lines from the dent and the flint genetic groups, as well as admixed lines, evaluated for flowering time. Several genomic regions were detected with various configurations of allele effects, with evidence of epistatic interactions between some of the loci and the genetic background.

genetics↗

bioRxiv2019

Afferent-efferent connectivity between auditory brainstem and cortex accounts for poorer speech-in-noise comprehension in older adults

Age-related hearing loss leads to poorer speech comprehension, particularly in noise. Speech-in-noise (SIN) deficits among the elderly could result from weaker neural activity within, or poorer signal transmission between brainstem and auditory cortices. By recording neuroelectric responses from brainstem (BS) and primary auditory cortex (PAC), we show that beyond simply attenuating neural activity, hearing loss in older adults compromises the transmission of speech information between subcortical and cortical hubs of the auditory system. The strength of afferent BS[->]PAC neural signaling (but not the reverse efferent flow; PAC[->]BS) varied with mild declines in hearing acuity and this \"bottom-up\" functional connectivity robustly predicted older adults SIN perception. Our neuroimaging findings underscore the importance of brain connectivity, particularly afferent neural communication, in understanding the biological basis of age-related hearing deficits in real-world listening environments.

neuroscience↗