Biology subjects

Railo, H.

Publications and source records attributed to Railo, H..

13 recordsLinked to original sources

bioRxiv2025

Structural Brain Correlates of Speech Disfluency in Early Childhood: A Dimensional Analysis in a Non-Clinical Cohort

Most neuroimaging studies of speech disfluency have compared individuals who stutter with fluent controls. However, treating speech disfluency as a continuous, dimensional trait offers new insights into the neural basis of fluency during early childhood. This study aimed to investigate whether naturally occurring variation in speech disfluency is associated with grey matter structure in a non-clinical, population-based sample of 5-year-old children. The study included 120 participants (65M, 55F) from the FinnBrain Birth Cohort study. Speech disfluency was evaluated as a continuous measure from audiovisual speech samples, with transcription and analysis conducted using the SALT software. Ambrose & Yairi (1999) classification system was used to categorize speech disfluencies into stuttering-like (SLD) and other disfluency types. T1-weighted images obtained through magnetic resonance imaging were analyzed using voxel-based morphometry (VBM) with the CAT12 toolbox and complemented by surface-based morphometry with FreeSurfer. Whole-brain statistical analysis was employed to examine the association between grey matter metrics and speech disfluency. We found that VBM-derived proportional grey matter volume in the left middle frontal gyrus, left posterior cerebellum, and right superior frontal gyrus was positively associated with speech disfluency, specifically SLD, in children (p <.001; p=.002; p <.001, FDR corrected). No significant associations were found for cortical thickness or surface area. Additionally, no notable sex differences were observed. Our findings suggest that speech disfluency in early childhood is linked to localized structural differences in regions supporting motor planning and cognitive control, without broader changes in cortical thickness or surface area. Importantly, similar brain regions have been implicated in studies comparing children who stutter to those who do not, suggesting that normal variation in disfluency captures meaningful neurobiological differences even in non-clinical populations. This supports the value of treating speech disfluency as a spectrum and underscores the importance of longitudinal, multimodal research to clarify how these structural features evolve and influence later fluency outcomes.

neuroscience↗

bioRxiv2023

Conscious and unconscious contributions to auditory feedback control of speech - Neural correlates and behavioral consequences

During vocalization, mismatches between expected and perceived auditory feedback are processed rapidly and automatically, suggesting that feedback control of vocalization operates unconsciously. However, whether consciousness modulates speech feedback control remains little studied. To address this question, we concurrently measured behavioral vocal responses and electroencephalography (EEG) in 30 participants while they vocalized and their auditory feedback was perturbed with individually calibrated perceptual threshold level pitch shifts. Following each vocalization trial, participants rated if they consciously detected a pitch shift in their auditory feedback. We analyzed the data on a trial-by-trial basis to test if vocal responses to pitch perturbations were modulated by conscious perception. Our results revealed that even on trials where the participants reported not noticing the pitch shift at all, a compensatory vocal response to the altered auditory feedback was generated. Conscious detection of a pitch shift was associated with an increased magnitude of vocal responses roughly 500-700 ms after the pitch shift compared to the unconscious trials. Conscious detection of the pitch shift correlated with early (Auditory awareness negativity, AAN) and late (Late positivity, LP) neural responses as indexed by the modulation of event-related potentials (ERPs). Source localization of the ERPs suggested that conscious pitch shift detection was associated with increased neural activity within the temporal, frontal and parietal cortical networks known to be involved in speech motor control. These findings emphasize the importance of investigating the role of consciousness in regulating speech feedback control, and their effect on the underlying neural and behavioral functions.

neuroscience↗

bioRxiv2023

Rapid withdrawal from threatening animals is movement-specific and mediated by reflex-like neural processing

Responses to potentially dangerous stimuli are among the most basic animal behaviors. While research has shown that threats automatically capture the attention of human participants, research has failed to demonstrate automatic behavioral responses to threats in humans. Using a novel naturalistic paradigm, we show that two species of animals humans often report fearing trigger rapid withdrawal responses: participants withdrew their arm from photos of snakes and spiders faster, and with higher acceleration when compared to bird and butterfly stimuli. The behavior was specific to withdrawal as approach movements or button-press/release tasks failed to detect a similar difference. Moreover, between-participant differences in how aversive they found the stimuli predicted the participants withdrawal speed, indicating that the paradigm was also sensitive to trait-level differences between individuals. Using electroencephalography (EEG), we show that the fast withdrawal was mediated by two attentional processes. First, fast withdrawal responses were associated with early amplification of sensory signals (40-110 ms after stimulus). Second, a later correlate of feature-based attention (early posterior negativity, EPN, 200-240 ms after stimulus) revealed the opposite pattern: Stronger EPN was associated with slower behavioral responses, suggesting that the deployment of attention towards the threatening stimulus features, or failure to "disengage" attention from the stimulus, was detrimental for withdrawal speed. Altogether, the results suggest that rapid behavioral withdrawal from a threatening animal is mediated by reflex-like attentional processing, and later, conscious attention to stimulus features may hinder escaping the treat.

neuroscience↗

bioRxiv2023

Multiple independent components contribute to event-related potential correlates of conscious vision

Research has revealed two major event-related potential (ERP) markers of visual awareness: the earlier Visual Awareness Negativity (VAN, around 150-250 ms after stimulus onset), and the following Late Positivity (LP, around 300-500 ms after stimulus onset). Understanding the neural sources that give rise to VAN and LP is important in order to understand what kind of neural processes enable conscious visual perception. Although the ERPs afford high temporal resolution, their spatial resolution is limited because multiple separate sources sum up at the scalp level. In the present study, we sought to characterize the locations and time-courses of independent neural sources underlying the ERP correlates of visual awareness by means of Independent Component Analysis (ICA). ICA allows identifying and localizing the temporal dynamics of different neural sources that contribute to the ERP correlates of conscious perception. The present results show that while LP reflects a combination of multiple sources distributed among frontal, parietal and occipito-temporal cortex, the sources of VAN are localized to posterior areas including occipital and temporal cortex. In addition, our analysis reveals that activity in very early sources (roughly -100-100 ms after stimulus onset) in temporal and fronto-parietal cortices correlates with conscious vision.

neuroscience↗

bioRxiv2022

Human ability to initiate reflexive eye movements towards unseen targets without the primary visual cortex

Some patients with a visual field loss due to a lesion in the primary visual cortex (V1) can shift their gaze to stimuli presented in their blind visual field. The extent to which a similar "blindsight" capacity is present in neurologically healthy individuals remains unknown. Using retinotopically navigated transcranial magnetic stimulation (TMS) of V1 (Experiment 1) and metacontrast masking (Experiment 2) to suppress conscious vision, we examined neurologically healthy humans ability to make saccadic eye movements toward visual targets that they reported not seeing. In the TMS experiment, the participants were more likely to initiate a saccade when a stimulus was presented, and they reported not seeing it, than in trials which no stimulus was presented. However, this happened only in a very small proportion (~8%) of unseen trials, suggesting that saccadic reactions were largely based on conscious perception. In both experiments, saccade landing location was influenced by unconscious information: When the participants denied seeing the target but made a saccade, the saccade was made toward the correct location (TMS: 68%, metacontrast: 63%) more often than predicted by chance. Signal detection theoretic measures suggested that in the TMS experiment, saccades toward unseen targets may have been based on weak conscious experiences. In both experiments, reduced visibility of the target stimulus was associated with slower and less precise gaze shifts. These results suggest that saccades made by neurologically healthy humans may be influenced by unconscious information, although the initiation of saccades is largely based on conscious vision.

neuroscience↗

bioRxiv2022

Changes in late frontal event-related potentials to self-produced foreign phonemes correlate with improvements in pronunciation

Learning to pronounce a foreign phoneme requires an individual to acquire a motor program that enables the reproduction of the new acoustic target sound. This process is largely based on the use of auditory feedback to detect pronunciation errors to adjust vocalization. While early auditory evoked neural activity underlies automatic detection and adaptation to vocalization errors, little is known about the neural correlates of acquiring novel speech targets. To investigate the neural processes that mediate the learning of foreign phoneme pronunciation, we recorded event-related potentials (ERP) when participants (N=19) pronounced native or foreign phonemes. Behavioral results indicated that the participants pronunciation of the foreign phoneme improved during the experiment. Early auditory responses (N1 and P2 waves, approx. 85-290 ms after the sound onset) revealed no differences between foreign and native phonemes. In contrast, the amplitude of the fronto-centrally distributed late slow wave (LSW, 320-440 ms) was modulated by the pronunciation of the foreign phonemes, and the effect changed during the experiment, paralleling the improvement in pronunciation. These results suggest that the LSW may reflect higher-order monitoring processes that signal successful pronunciation and help learn novel phonemes.

neuroscience↗

bioRxiv2020

Resting state EEG as a biomarker of Parkinson's disease: Influence of measurement conditions

Resting state electroencephalographic (EEG) recording could provide cost-effective means to aid in the detection of neurological disorders such as Parkinsons disease (PD). We examined how many electrodes are needed for classification of PD based on EEG, which electrode locations provide most value for classification, and whether data recorded eyes open or closed yield comparable results. We used a nested cross-validated classifier which included a budget-based search algorithm for selecting the optimal electrodes for classification. By iterating over variable budgets, we show that with eyes open recording, only 10 electrodes, localized over motor and occipital areas enable relatively accurate classification (AUC = .82) between PD patients (N=20) and age-matched healthy control participants (N=20). Classification accuracy only slightly increased when all 64 electrodes were included (AUC = .85). With the data recorded eyes closed, classification was not statistically significantly above chance even with full set of 64 electrodes (AUC = .55). These results show that classification based on small number of EEG electrodes is a promising tool for classifying PD, but measurement conditions and electrode locations can have a significant effect on classifier performance.

neuroscience↗

bioRxiv2020

Subliminal perception can be predicted from prestimulus activity

Individuals are able to discriminate visual stimuli they report not consciously seeing. This phenomenon is known as "subliminal perception." Such capacity is often assumed to be relatively automatic in nature, and rely on stimulus-driven activity in low-level cortical areas. Instead, here we asked to what extent neural activity before stimulus presentation influences subliminal perception. We asked participants to discriminate the location of a briefly presented low-contrast visual stimulus, and then rate how well they saw the stimulus. Consistent with previous studies, participants correctly discriminated with slightly above chance-level accuracy the location of a stimulus they reported not seeing. Signal detection analyses indicated that while subjects categorized their percepts as "unconscious", their capacity to discriminate these stimuli lay on the same continuum as conscious vision. We show that the accuracy of discriminating the location of a subliminal stimulus could be predicted with relatively high accuracy (AUC = .70) based on lateralized electroencephalographic (EEG) activity before the stimulus, the hemifield where the stimulus was presented, and accuracy of previous trials discrimination response. Altogether, our results suggest that rather than being a separate unconscious capacity, subliminal perception is based on similar processes as conscious vison.

neuroscience↗

bioRxiv2019

Reduced speaking-induced suppression of auditory evoked-potentials in early Parkinson’s disease suggests deficits in monitoring self-produced speech

ObjectiveSpeech deficits are common in Parkinsons disease, and behavioural findings suggest that the deficits may be due to impaired monitoring of self-produced speech. The neural mechanisms of speech deficits are not well understood. We examined a well-documented electrophysiological correlate of speech self-monitoring in patients with Parkinsons disease and control participants. MethodsWe measured evoked electroencephalographic responses to self-produced and passively heard sounds (/a/ phonemes) in age-matched controls (N=18), and Parkinsons disease patients who had minor speech impairment, but reported subjectively experiencing no speech deficits (N=17). ResultsDuring speaking, auditory evoked activity 100 ms after phonation (N1 wave) was less suppressed in Parkinsons disease than controls when compared to the activity evoked by passively heard phonemes. This difference between the groups was driven by increased amplitudes to self-produced phonemes, and reduced amplitudes passively heard phonemes in Parkinsons disease. ConclusionsThe finding indicates that auditory evoked activity is abnormally modulated during speech in Parkinsons patients who do not subjectively notice speech impairment. This mechanism could play a role in producing speech deficits in as the disease progresses.

neuroscience↗

bioRxiv2019

TMS of V1 eliminates unconscious processing of chromatic stimuli

Some of the neurological patients with primary visual cortex (V1) lesions can guide their behavior based on stimuli presented to their blind visual field. One example of this phenomenon is the ability to discriminate colors in the absence of awareness. These so-called patients with blindsight must have a neural pathway that bypasses the V1, explaining their ability to unconsciously process stimuli. To test if similar pathways function in neurologically healthy individuals or if unconscious processing depends on the V1, we disturbed the visibility of a chromatic stimulus with metacontrast masking (Experiment 1) or transcranial magnetic stimulation (TMS) of the V1 (Experiment 2). We measured unconscious processing using the redundant target effect (RTE), which is the speeding up of reaction times in response to dual stimuli compared with one stimulus, when the task is to respond to any number of stimuli. An unconscious chromatic RTE was found when the visibility of the redundant chromatic stimulus was suppressed with a visual mask. When TMS was applied to the V1 to disturb the perception of the redundant chromatic stimulus, the RTE was eliminated. Based on our results and converging evidence from previous studies, we conclude that the unconscious processing of chromatic information depends on the V1 in neurologically healthy participants.

neuroscience↗

bioRxiv2019

Consciousness as a Concrete Physical Phenomenon

Why any type of neural activation is associated with subjective, conscious experience is a fundamental unsolved question in neuroscience. To bridge the gap between neural activity and conscious experience, one seemingly must tie together two very different entities. The paradigmatic view in consciousness science is that subjective experiences are private and cannot be scientifically observed or described: science can only discover correlations between subjective experiences and their neural realizers, but never observe or describe the experiences themselves. We present a metatheory of consciousness that explains how subjective experiences are related to empirical observations and models, and why the two appear so different from each other. We argue that consciousness is a concrete physical process that causally interacts with other physical phenomena. This entails that consciousness can be empirically observed and characterized. The reason why subjective experiences and empirical observations and models of them appear so different is explained by what we call the observer-observed distinction. Empirical observations are always distinct from the observer, but a subject and her experiences constitute a single physical-biological system. We argue that once science has completely described 1) the constitutive neural mechanisms that are isomorphic with experiences, 2) the etiological mechanisms that experiences are based on, and 3) their causal power, then science has provided an exhaustive description of phenomenology. Our conclusion is that, if we accept this framework we call Naturalistic Monism, consciousness collapses into a standard problem of science.

neuroscience↗

bioRxiv2018

Impairment in updating spatial representations in Parkinson’s disease correlates with dopaminergic deficiency

Movement in Parkinsons disease (PD) is fragmented, and the patients depend on visual information in their behavior. This suggests that the patients may have deficits in internally monitoring their own movements. Internal monitoring of movements is assumed to rely on corollary discharge signals that enable the brain to predict the sensory consequences of actions. We studied early-stage PD patients (N=14), and age-matched healthy control participants (N=14) to examine whether PD patients reveal deficits in updating their sensory representations after eye movements. The participants performed a double-saccade task where, in order to accurately fixate a second target, the participant must correct for the displacement caused by the first saccade. In line with previous reports, the patients had difficulties in fixating the second target when the eye movement was performed without visual guidance. Furthermore, the patients had difficulties in taking into account the error in the first saccade when making a saccade towards the second target, especially when eye movements were made towards the side with dominant motor symptoms. Across PD patients, the impairments in saccadic eye movements correlated with the integrity of the dopaminergic system as measured with [123I]FP-CIT SPECT: Patients with lower striatal (caudate, anterior putamen and posterior putamen) dopamine transporter binding made larger errors in saccades. This effect was strongest when patients made memory-guided saccades towards the second target. Our results provide tentative evidence that the motor deficits in PD may be partly accounted by deficits in internal monitoring of movements.

neuroscience↗

bioRxiv2017

Adaptive significance of frontal eyes: Binocular disparity improves the capacity of vision

Binocular disparity results in a tangible subjective experience of three-dimensional world, but whether disparity also augments objective perceptual performance remains debated. We hypothesized that the improved coding of depth enabled by binocular disparity allows participants to individuate more object at a glance as the objects can be more efficiently differentiated from each other and the background. We asked participants to enumerate objects in briefly presented naturalistic (Experiment 1) and artificial (Experiment 2) scenes in immersive virtual reality. This type of enumeration task yields well-documented capacity limits where up to 3-4 items can be enumerated rapidly and accurately, known as subitizing. Our results show that although binocular disparity did not yield a large general improvement in enumeration accuracy or reaction times, it improved participants ability to process the items right after the limit of perceptual capacity. Binocular disparity also sped-up response times by 27 ms on average when artificial stimuli (cubes) were used. Interestingly, the influence of disparity on subjectively experienced depth revealed a clearly different pattern than the influence of disparity on objective performance. This suggests that the functional and subjective sides of stereopsis can be dissociated. Altogether our results suggest that binocular disparity may increase the number of items the visual system can simultaneously process. This may help animals to better resolve and track objects in complex, cluttered visual environments.

evolutionary biology↗