Biology subjects

Prokofyev, A. O.

Publications and source records attributed to Prokofyev, A. O..

12 recordsLinked to original sources

bioRxiv2025

Vowel-like patterns modulate auditory P100m response but not its association with language abilities in children with ASD

BackgroundThe P100/P100m component of auditory event-related potentials/fields is considered a potential biomarker of atypical arousal and language abnormalities in children with ASD. When elicited by complex speech-like sounds with regular temporal or frequency structure, P100/P100m may be influenced by sustained negativity (SN), which can reduce its amplitude due to opposing current polarity. MethodsUsing MEG, we investigated how acoustic regularities affect P100m latency and amplitude differences between TD children and those with ASD. MEG was recorded in 35 ASD and 39 TD boys (7-12 years) in response to control sounds (non-periodic, non-vowels) and stimuli with temporal regularity (periodic non-vowels), frequency regularity (non-periodic vowels), or both (periodic vowels). P100m was estimated using distributed source localization. ResultsIn both groups, P100m amplitude and latency decreased in response to acoustic regularities, accompanied by a proportional increase in SN. No group differences were observed in P100m latency, amplitude, or their modulation by stimulus characteristics. In ASD, P100m latency variability was increased, and higher P100m amplitudes in the left auditory cortex were negatively associated with cumulative language and intellectual abilities. ConclusionsIn children, changes in P100m in response to acoustic regularities are most parsimoniously explained by an enhancement of SN with opposite polarity. No consistent relationship was found between P100m parameters or their modulation by acoustic regularities and ASD diagnosis. However, variations in cortical maturation and/or habituation processes, which affect the left-hemispheric P100m, may be relevant to cognitive and language functioning in children with ASD.

neuroscience↗

bioRxiv2025

Enhanced Neural Plasticity of the Primary Visual Cortex in Visual Snow Syndrome: Evidence from MEG Gamma Oscillations

Visual Snow Syndrome (VSS) is a neurological disorder characterized by persistent visual disturbances and associated symptoms. Although the neural basis of VSS remains poorly understood, it may involve increased neuronal excitability and/or altered neuroplasticity in the visual cortex, which could, in turn, affect visual gamma oscillations. An altered excitation-inhibition (E-I) balance is hypothesized to alter the modulation of gamma power and frequency by stimulation intensity, while maladaptive neuroplasticity may impact time-dependent changes in gamma power during repeated stimulation. To investigate potential alterations in E-I balance and neuroplasticity in VSS, we magnetoencephalography to record visual gamma oscillations in 26 VSS patients and 27 healthy controls. Participants were exposed to repeatedly presented high-contrast annular gratings, which were either static or drifting at varying speeds to systematically manipulate stimulation intensity. We also measured heart rate variability (HRV) during rest and repetitive visual stimulation to explore the relationship between time-dependent gamma changes and parasympathetic activation, which is known to promote activity-dependent plasticity. Our results showed no significant group differences in gamma power or frequency, nor in their modulation by drift rate, suggesting that the excitation-inhibition (E-I) balance in the primary visual cortex remains largely intact in VSS. Both groups exhibited an initial brief decrease in gamma power followed by a sustained linear increase with stimulus repetition, likely reflecting activity-dependent plasticity. HRV parameters were comparable across groups, with the parasympathetic-sympathetic balance index correlating with repetition-related increase in gamma power, further supporting the link between time-dependent gamma changes and neuroplasticity. Notably, VSS patients exhibited a steeper repetition-related increase in gamma power, indicating atypically heightened activity-dependent plasticity in this group. These findings provide the first experimental evidence suggesting that altered activity-dependent neuroplasticity plays a role in the pathophysiology of VSS. Furthermore, they identify repetition-related increases in gamma power as a potential biomarker of aberrant neuroplasticity, offering novel insights into VSS pathophysiology and potential avenues for targeted therapeutic interventions.

neuroscience↗

bioRxiv2024

Attenuated processing of vowels in the left hemisphere predicts speech-in-noise perception deficit in children with autism

BackgroundDifficulties with speech-in-noise perception in autism spectrum disorders (ASD) may be associated with impaired analysis of speech sounds, such as vowels, which represent the fundamental phoneme constituents of human speech. Vowels elicit early (< 100 ms) sustained processing negativity (SPN) in the auditory cortex that reflects the detection of an acoustic pattern based on the presence of formant structure and/or periodic envelope information (f0) and its transformation into an auditory "object". MethodsWe used magnetoencephalography (MEG) and individual brain models to investigate whether SPN is altered in children with ASD and whether this deficit is associated with impairment in their ability to perceive speech in the background of noise. MEG was recorded while boys with ASD and typically developing boys passively listened to sounds that differed in the presence/absence of f0 periodicity and formant structure. Word-in-noise perception was assessed in the separate psychoacoustic experiment using stationary and amplitude modulated noise with varying signal-to-noise ratio. ResultsSPN was present in both groups with similarly early onset. In children with ASD, SPN associated with processing formant structure was reduced predominantly in the cortical areas lateral to and medial to the primary auditory cortex, starting at [~] 150 - 200 ms after the stimulus onset. In the left hemisphere, this deficit correlated with impaired ability of children with ASD to recognize words in amplitude-modulated noise, but not in stationary noise ConclusionsThese results suggest that perceptual grouping of vowel formants into phonemes is impaired in children with ASD and that, in the left hemisphere, this deficit contributes to their difficulties with speech perception in fluctuating background noise.

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bioRxiv2023

Changes in high-frequency aperiodic 1/f slope and periodic activity reflect post-stimulus functional inhibition in the visual cortex.

It has been shown that cessation of intensive sensory stimulation is associated with a transient increase in functional inhibition in the sensory cortical areas. However, the electrophysiological correlates of this post-stimulus inhibition in the human brain have not been properly investigated. To investigate post-stimulus inhibition, we recorded magnetoencephalogram (MEG) at rest and after cessation of visual stimulation of varying intensity (high-contrast gratings drifting at a slow, medium, or high rate) in 25 healthy women aged 18-40 years. We analyzed condition- and intensity-related changes in MEG parameters sensitive to functional inhibition: periodic alpha-beta power, peak alpha frequency (PAF), and 1/f aperiodic slope. We also investigated the association of these parameters with sensory sensitivity and avoidance assessed by a questionnaire. To evaluate the influence of hormonal status on the studied parameters, participants were examined twice, during the follicular and luteal phases of the menstrual cycle (MC). Regardless of MC phase, increasing intensity of the preceding visual stimulation resulted in increased posterior post-stimulus alpha-beta power, PAF, and a more negative/steeper aperiodic (1/f) slope of the power spectrum in the 35-45 Hz range. Compared to rest, the post-stimulus period was characterized by higher PAF, a steeper 35-45 Hz 1/f slope in posterior cortical areas, and a widespread increase in beta power. While condition- and intensity-dependent changes in alpha-beta power and 1/f slope were correlated, changes in PAF did not correlate with either of them. Greater intensity-dependent increase in visual alpha-beta power predicted higher subjective sensory sensitivity/avoidance, suggesting stronger regulatory top-down modulation of visual cortex in individuals with heightened sensitivity. Our results show that several MEG parameters concordantly indicate a post-stimulus enhancement of inhibition that is proportional to the intensity of the preceding visual stimulation. While post-stimulus changes in alpha-beta power and 1/f slope may share some common mechanisms, changes in PAF reflect a distinct aspect of inhibitory regulation. Our results inform potential inhibition-based biomarkers for clinical and translational research. Key pointsO_LIThe cessation of visual stimulation leads to a transient increase in functional inhibition. C_LIO_LIChanges in MEG parameters reflect post-stimulus enhancement of inhibition. C_LIO_LIThese changes scale with the intensity of the preceding stimulation. C_LI

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bioRxiv2022

Different hemispheric lateralization for periodicity and formant structure of vowels in the auditory cortex and its changes between childhood and adulthood

The spectral formant structure and periodicity pitch are the major features that determine the identity of vowels and the characteristics of the speaker. However, very little is known about how the processing of these features in the auditory cortex changes during development. To address this question, we independently manipulated the periodicity and formant structure of vowels while measuring auditory cortex responses using MEG in children aged 7-12 years and adults. We analyzed the sustained negative shift of source current associated with these vowel properties, which was present in the auditory cortex in both age groups despite differences in the transient components of the auditory response. In adults, the sustained activation associated with formant structure was lateralized to the left hemisphere early in the auditory processing stream requiring neither attention nor semantic mapping. This lateralization was not yet established in children, in whom the right hemisphere contribution to formant processing was strong and decreased during or after puberty. In contrast to the formant structure, periodicity was associated with a greater response in the right hemisphere in both children and adults. These findings suggest that left-lateralization for the automatic processing of vowel formant structure emerges relatively late in ontogenesis and pose a serious challenge to current theories of hemispheric specialization for speech processing.

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bioRxiv2022

Losses resulting from deliberate exploration trigger beta oscillations in frontal cortex

We examined the neural signature of directed exploration by contrasting MEG beta (16-30 Hz) power changes between disadvantageous and advantageous choices in the two-choice probabilistic reward task. We analyzed the choices made after the participants have learned the probabilistic contingency between choices and their outcomes, i.e., acquired the inner model of choice values. Therefore, rare disadvantageous choices might serve explorative, environment-probing purposes. The study brought two main findings. Firstly, decision making leading to disadvantageous choices took more time and evidenced greater large-scale suppression of beta oscillations than its advantageous alternative. Additional neural resources recruited during disadvantageous decisions strongly suggest their deliberately explorative nature. Secondly, an outcome of disadvantageous and advantageous choices had qualitatively different impact on feedback-related beta oscillations. After the disadvantageous choices, only losses - but not gains - were followed by late beta synchronization in frontal cortex. Our results are consistent with the role of frontal beta oscillations in the stabilization of neural representations for selected behavioral rule when explorative strategy conflicts with value-based behavior. Punishment for explorative choice being congruent with its low value in the reward history is more likely to strengthen, through punishment-related beta oscillations, the representation of exploitative choices consistent with the inner utility model.

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bioRxiv2022

Altered visual cortex excitability in premenstrual dysphoric disorder: evidence from magnetoencephalographic gamma oscillations and perceptual suppression

Premenstrual dysphoric disorder (PMDD) is a psychiatric condition characterized by extreme mood shifts, anxiety, and irritability during the premenstrual period. Abnormal sensitivity to allopregnanolone, a neurosteroid that normally potentiates inhibition, and an increased ratio of neural excitation-to-inhibition (E/I) have been linked to the pathophysiology of PMDD. We hypothesized that in subjects with PMDD these factors will lead to an altered frequency of magnetoencephalographic (MEG) visual gamma oscillations, altered modulation of their power by the strength of excitatory drive and to an altered perceptual spatial suppression. We examined women with PMDD and age-matched control women twice: during the asymptomatic follicular and symptomatic luteal phases of the menstrual cycle (MC). MEG gamma oscillations were recorded while modulating excitatory drive to the visual cortex by increasing drift rate of high-contrast visual grating. Visual perceptual suppression was assessed as the degree of deterioration of motion direction discrimination with increasing stimulus size. In women with PMDD, the peak frequency of the gamma response (GR) and its modulation by the drift rate were normal, whereas modulation of the GR power was significantly altered. A moderate increase in drift rate had an unusually strong facilitating effect on the GR power in PMDD, regardless of the MC phase. In contrast, the normally suppressive effect of a strong increase in drift rate was attenuated in PMDD during the luteal phase and predicted symptom severity assessed on the same day. Perceptual spatial suppression did not differ between the groups, but decreased from the follicular to the luteal phase only in PMDD subjects. The atypical GR power modulation suggests that neuronal excitability in the visual cortex is constitutively elevated in women with PMDD, and that this E/I imbalance is further exacerbated during the luteal phase, possibly due to an abnormal sensitivity to neurosteroids. However, the unchanged frequency of GR and normal spatial suppression in women with PMDD speak against the dysfunction of their inhibitory neurons, at least those involved in generation of visual gamma oscillations. Three key pointsO_LIAtypical modulation of visual gamma power by excitatory drive in women with PMDD suggests the presence of neuronal hyperexcitability, which is exacerbated during the symptomatic luteal phase, possibly due to altered sensitivity to neurosteroids. C_LIO_LIThe peak frequency of gamma oscillations does not differ between women with PMDD and control women and demonstrates the luteal phase-specific effect of the 1st scan in both groups, which suggest normal functioning of inhibitory neurons in the visual cortex in PMDD. C_LIO_LIThe presence of normal perceptual spatial suppression also speaks against inhibitory deficit in the visual cortex in PMDD. C_LI

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bioRxiv2020

Left hemispheric deficit in the sustained neuromagnetic response to periodic click trains in children with ASD.

Deficits in perception and production of vocal pitch are often observed in people with autism spectrum disorders (ASD), but the neural basis of these abnormalities is unknown. In magnetoencephalogram (MEG), spectrally complex periodic sounds trigger two continuous neural responses - the Auditory Steady State Response (ASSR) and the Sustained Field (SF). It has been shown that the SF in neuro-typical individuals is associated with low-level analysis of pitch in the pitch processing center of the Heschls gyrus. Therefore, this auditory response may reflect vocal pitch processing abnormalities in ASD. The SF, however, has never been studied in people with these disorders. We used MEG and individual brain models to investigate the ASSR and SF evoked by monaural 40 Hz click trains in 7-13-year-old boys with ASD (N=35) and neuro-typical (NT) boys (N=35). In agreement with the previous research in adults, the cortical sources of the SF in children were located in the left and the right Heschls gyri, anterolateral to those of the ASSR. In both groups, the SF and ASSR dominated in the right hemisphere and were higher contralaterally to the stimulated ear. The ASSR increased with age in both NT and ASD children and did not differ between the groups. The SF was moderately decreased in both hemispheres and was markedly delayed and displaced in the left hemisphere in boys with ASD. The SF delay in participants with ASD was present irrespective of their intelligence level and severity of autism symptoms. We suggest that the selective left-hemispheric SF abnormalities in children with ASD reflect a low-level deficiency in pitch processing that may contribute to their difficulties with perception and production of linguistic prosody.

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bioRxiv2019

Rapid cortical plasticity induced by active learning of novel words in human adults

Human speech requires that new words are routinely memorized, yet neurocognitive mechanisms of such acquisition of memory remain highly debatable. Major controversy concerns the question whether cortical plasticity related to word learning occurs in neocortical speech-related areas immediately after learning, or neocortical plasticity emerges only on the second day after a prolonged time required for consolidation after learning. The functional spatiotemporal pattern of cortical activity related to such learning also remains largely unknown. In order to address these questions, we examined magnetoencephalographic responses elicited in the cerebral cortex by passive presentations of eight novel pseudowords before and immediately after an operant conditioning task. This associative procedure forced participants to perform an active search for unique meaning of four pseudowords that referred to movements of left and right hands and feet. The other four pseudowords did not require any movement and thus were not associated with any meaning. Familiarization with novel pseudowords led to a bilateral repetition suppression of cortical responses to them; the effect started before or around the uniqueness point and lasted for more than 500 ms. After learning, response amplitude to pseudowords that acquired meaning was greater compared with response amplitude to pseudowords that were not assigned meaning; the effect was significant within 144-362 ms after the uniqueness point, and it was found only in the left hemisphere. Within this time interval, a learning-related selective response initially emerged in cortical areas surrounding the Sylvian fissure: anterior superior temporal sulcus, ventral premotor cortex, the anterior part of intraparietal sulcus and insula. Later within this interval, activation additionally spread to more anterior higher-tier brain regions, and reached the left temporal pole and the triangular part of the left inferior frontal gyrus extending to its orbital part. Altogether, current findings evidence rapid plastic changes in cortical representations of meaningful auditory word-forms occurring almost immediately after learning. Additionally, our results suggest that familiarization resulting from stimulus repetition and semantic acquisition resulting from an active learning procedure have separable effects on cortical activity.

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bioRxiv2018

Additive effect of contrast and velocity proves the role of strong excitatory drive in suppression of visual gamma response.

Visual gamma oscillations are generated through interactions of excitatory and inhibitory neurons and are strongly modulated by sensory input. A moderate increase in excitatory drive to the visual cortex via increasing contrast or motion velocity of drifting gratings results in strengthening of the gamma response (GR). However, increasing the velocity beyond some transition point leads to the suppression of the GR. There are two theoretical models that can explain such suppression. The excitatory drive model infers that, at high drifting rates, GR suppression is caused by excessive excitation of inhibitory neurons. Since contrast and velocity have an additive effect on excitatory drive, this model predicts that the GR transition point for low-contrast gratings would be reached at a higher velocity, as compared to high-contrast gratings. The alternative velocity tuning model implies that the GR is maximal when the drifting rate of the grating corresponds to the preferable velocity of the motion-sensitive V1 neurons. This model predicts that lowering contrast either will not affect the transition point or will shift it to a lower drifting rate. We tested these models with magnetoencephalography-based recordings of the GR during presentation of low (50%) and high (100%) contrast gratings drifting at four velocities. We found that lowering contrast led to a highly reliable shift of the GR suppression transition point to higher velocities, thus supporting the excitatory drive model. No effects of contrast or velocity were found for the alpha-beta response power. The results have important implications for the understanding of the neural mechanisms underlying gamma oscillations and the development of gamma-based biomarkers of brain disorders.

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bioRxiv2018

Efforful verb recollection drives beta suppression in mesial frontal regions involved in action initiation.

Whether the motor cortex activation accompanying concrete verbs comprehension is necessary for verbs conceptual processing is still a hotly debated topic in the literature. Answering this question, we examined to what extent the more difficult access to verb semantics requires an additional engagement of cortical motor system in verb generation task. Using power suppression of MEG beta oscillations (15-30 Hz) as an index of sensorimotor activation, we presented to our participants the noun cues which either were strongly associated with a single verb and prompted the fast and effortless verb retrieval, or were weakly associated with multiple verbs and were more difficult to respond to. A whole-brain analysis of beta suppression revealed that the only cortical regions sensitive to the difficulty of semantic access were the higher order motor areas on the medial and lateral surfaces of the frontal lobe. This differential activation of cortical motor system accompanied effortful verb retrieval and preceded the preparation of vocal response for more than 500 milliseconds. Since the mid-frontal frontal brain areas are involved in maintaining abstract representations of actions during their initiating and planning, we argue that our finding supports the view that motor associations contribute to retrieval of verb semantics.

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bioRxiv2017

Modulation of visual gamma oscillation by excitatory drive and the excitation/inhibition balance in the visual cortex

Gamma-band oscillations arise from the interplay between neural excitation (E) and inhibition (I) and may provide a non-invasive window into the state of cortical circuitry. A bell-shaped modulation of gamma response power by increasing the intensity of sensory input was observed in animals and is thought to reflect neural gain control. Here we sought to find a similar input-output relationship in humans with MEG via modulating the intensity of a visual stimulation by changing the velocity/temporal-frequency of visual motion.\n\nIn the first experiment, adult participants observed static and moving gratings. The frequency of the MEG gamma response monotonically increased with motion velocity whereas power followed a bell-shape. In the second experiment, on a large group of children and adults, we found that despite drastic developmental changes in frequency and power of gamma oscillations, the relative suppression at high motion velocities was scaled to the same range of values across the life-span.\n\nIn light of animal and modeling studies, the modulation of gamma power and frequency at high stimulation intensities characterizes the capacity of inhibitory neurons to counterbalance increasing excitation in visual networks. Gamma suppression may thus provide a non-invasive measure of inhibitory-based gain control in the healthy and diseased brain.

neuroscience↗