Biology subjects

Pedapati, E.

Publications and source records attributed to Pedapati, E..

8 recordsLinked to original sources

bioRxiv2026

Heterogeneity of Brain Dynamics in Genetic and Psychiatric Conditions

Whether the heterogeneity of psychiatric conditions converges on shared neurophysiological alterations or translates into distinct signatures remains unclear. We assembled high-density electroencephalogram (hd-EEG) resting-state recordings from 4,812 individuals aged 5 months to 66 years across 11 psychiatric conditions, a broad spectrum of rare genetic variants, and typically developing (TD) individuals. We established normative developmental trajectories of source-space EEG across spectral organization, connectivity, and signal complexity. Psychiatric conditions showed small deviations, revealing a shared transdiagnostic profile. In contrast, single rare variants showed substantially larger, distinct and sometimes mirror-opposite signatures that collapsed toward the psychiatric profile when pooled. Autism Spectrum Disorder showed some of the smallest group-level effects yet the largest individual deviations, indicating substantial but directionally inconsistent alterations. EEG deviations followed a cortical gradient, with larger effects in sensorimotor regions. We demonstrate that sample sizes in the hundreds are required for robust associations with psychiatric diagnoses. This interactive open resource provides normative scores to benchmark future results.

neuroscience↗

bioRxiv2026

Alpha oscillations are dysrhythmic in Fragile X syndrome

BackgroundAlpha oscillations are dominant rhythms in the human brain, supporting inhibitory control and coordination of neural activity. Altered alpha dynamics are observed across many neuropsychiatric and neurodevelopmental disorders, including Fragile X syndrome (FXS), the most common monogenic cause of autism and intellectual disability. FXS exhibits paradoxical alpha power: elevated absolute but reduced relative power. To resolve this incongruity, we considered that conventional power metrics, relying on averaging, may obscure the underlying critical temporal dynamics of such neural rhythms. MethodsHere, we investigate alpha oscillations in FXS as a model to decompose nonspecific alpha abnormalities into underlying temporal features. We used cycle-by-cycle (bycycle) alpha burst analysis from source-localized resting-state EEG of 70 individuals with FXS (20.5{+/-}10.0 years; 32 females, 38 males) and 71 age- and sex-matched typically developing controls (22.2{+/-}10.7 years; 30 females, 41 males). Statistical modeling examined group, sex, and regional differences in alpha burst features using generalized linear mixed-effects models. ResultsWe reveal that alpha bursts in FXS show reduced count only in males, prolonged periods across sexes, and elevated amplitudes, particularly in males. Spatial mapping identified differential circuit vulnerability: timing-associated dysregulation in cognitive-control regions and amplitude elevations in sensory cortices. Within the FXS group, global alpha burst amplitude correlated with hyperactivity symptoms and inversely with general intelligence scores, and burst count correlated with age. LimitationsThis study is limited by its resting-state design and cross-sectional nature. Future studies should explore task-based modulation of alpha burst features and longitudinal trajectories in FXS. Additionally, fragile X messenger ribonucleoprotein (FMRP) was not quantified for participants, limiting potential stratification by molecular severity. ConclusionsThese findings resolve paradoxical alpha power in FXS into features consistent with interneuron dysfunction, demonstrating the potential for burst-level decomposition in mechanistic hypothesis generation and biomarker development across neurodevelopmental and neuropsychiatric disorders.

neuroscience↗

bioRxiv2025

Aberrant Neural Entrainment to Word-Level Speech Patterns in Fragile X Syndrome: Evidence for a Statistical Learning Deficit

Fragile X syndrome (FXS), the most common inherited cause of intellectual disability and autism spectrum disorder, causes significant language and cognitive impairments. Statistical learning refers to the ability to extract patterns from sensory input through mere exposure and plays a central role in language acquisition. Surprisingly, statistical learning in FXS has not been explored. Given that children with FXS typically follow a delayed developmental trajectory for language, we hypothesized that they would show impaired statistical learning. To test this hypothesis, we used an EEG measure of neural entrainment to index statistical learning of hidden trisyllabic words within a continuous speech stream in children with FXS (n = 17) and in typically developing controls (n = 31). Children with FXS showed significantly reduced neural entrainment to words compared to controls, particularly in the superior temporal gyrus and transverse temporal gyrus (primary auditory cortex), providing evidence of statistical learning impairment. Notably, syllable-level entrainment was preserved or even enhanced in FXS, indicating that word-level deficits cannot be attributed to general auditory processing impairments. In addition, while typically developing controls showed an increase in word-level entrainment over the course of learning, children with FXS failed to show a similar increase over time. Taken together, this pattern of results demonstrates that children with FXS can process rapid, lower-order acoustic structure but struggle to integrate these syllables into longer, chunk-like word representations. Overall, these findings suggest that statistical learning is impaired in FXS, and also suggest neural entrainment to statistical structure as a potential therapeutic target.

neuroscience↗

bioRxiv2025

Event-Related Spatio-Spectral Perturbation (ERSSP): A Scalp-Wide EEG Analysis Framework for Capturing Extralemniscal Thalamocortical Activity, Validated Using a Fragile X Syndrome Model

The extralemniscal thalamocortical pathway regulates large-scale modulation of cortical states but remains inaccessible to traditional EEG analysis due to its diffuse, variable, and asynchronous nature. To address this, we introduce the Event-Related Spatio-Spectral Perturbation (ERSSP) framework, which quantifies spatially distributed time-frequency responses. ERSSP summarizes the number of channels exhibiting significant spectral perturbations, capturing diffuse cortical dynamics from sensor-space EEG. We validated this approach using a passive auditory habituation task in individuals with Fragile X Syndrome (FXS), a condition marked by disrupted thalamocortical modulation. ERSSP revealed enhanced spatial extent of power increases (but not phase-locking) in FXS compared to controls. Results also showed expected gender differences, further supporting biological sensitivity of ERSSP. ERSSP provides a conceptually simple and computationally efficient method for quantifying broadly distributed sensory modulation and may enable new insights into thalamocortical function in both basic and clinical neuroscience.

neuroscience↗

bioRxiv2024

m6A-mediated epi-transcriptomic dysregulation underlies synaptic dysfunction in fragile X syndrome

Fragile X syndrome (FXS), the leading genetic cause of intellectual disability, arises from FMR1 gene silencing and loss of the FMRP protein. N6-methyladenosine (m6A) is a prevalent mRNA modification essential for post-transcriptional regulation. FMRP is known to bind to and regulate the stability of m6A-containing transcripts. However, how loss of FMRP impacts on transcriptome-wide m6A modifications in FXS patients remains unknown. To answer this question, we generated cortical neurons differentiated from induced pluripotent stem cells (iPSC) derived from healthy subjects and FXS patients. In electrophysiology recordings, we validated that synaptic and neuronal network defects in iPSC-derived FXS neurons corresponded to the clinical EEG data of the patients from which the corresponding iPSC line was derived. In analysis of transcriptome-wide methylation, we show that FMRP deficiency led to increased translation of m6A writers, resulting in hypermethylation that primarily affecting synapse-associated transcripts and increased mRNA decay. Conversely, in the presence of an m6A writer inhibitor, synaptic defects in FXS neurons were rescued. Taken together, our findings uncover that an FMRP-dependent epi-transcriptomic mechanism contributes to FXS pathogenesis by disrupting m6A modifications in FXS, suggesting a promising avenue for m6A- targeted therapies.

neuroscience↗

bioRxiv2024

Frontal Cortex Hyperactivation and Gamma Desynchrony in Fragile X Syndrome: Correlates of Auditory Hypersensitivity

Fragile X syndrome (FXS) is an X-linked disorder that often leads to intellectual disability, anxiety, and sensory hypersensitivity. While sound sensitivity (hyperacusis) is a distressing symptom in FXS, its neural basis is not well understood. It is postulated that hyperacusis may stem from temporal lobe hyperexcitability or dysregulation in top-down modulation. Studying the neural mechanisms underlying sound sensitivity in FXS using scalp electroencephalography (EEG) is challenging because the temporal and frontal regions have overlapping neural projections that are difficult to differentiate. To overcome this challenge, we conducted EEG source analysis on a group of 36 individuals with FXS and 39 matched healthy controls. Our goal was to characterize the spatial and temporal properties of the response to an auditory chirp stimulus. Our results showed that males with FXS exhibit excessive activation in the frontal cortex in response to the stimulus onset, which may reflect changes in top-down modulation of auditory processing. Additionally, during the chirp stimulus, individuals with FXS demonstrated a reduction in typical gamma phase synchrony, along with an increase in asynchronous gamma power, across multiple regions, most strongly in temporal cortex. Consistent with these findings, we observed a decrease in the signal-to-noise ratio, estimated by the ratio of synchronous to asynchronous gamma activity, in individuals with FXS. Furthermore, this ratio was highly correlated with performance in an auditory attention task. Compared to controls, males with FXS demonstrated elevated bidirectional frontotemporal information flow at chirp onset. The evidence indicates that both temporal lobe hyperexcitability and disruptions in top-down regulation play a role in auditory sensitivity disturbances in FXS. These findings have the potential to guide the development of therapeutic targets and back-translation strategies.

neuroscience↗

bioRxiv2023

Hypersensitivity to distractors in Fragile X syndrome from loss of modulation of cortical VIP interneurons.

Attention deficit is one of the most prominent and disabling symptoms in Fragile X Syndrome (FXS). Hypersensitivity to sensory stimuli contributes to attention difficulties by overwhelming and/or distracting affected individuals, which disrupts activities of daily living at home and learning at school. We find that auditory or visual distractors selectively impair visual discrimination performance in both humans and mice with FXS, but not their typically developing controls. Vasoactive intestinal polypeptide (VIP) neurons were significantly modulated by incorrect responses in the post-stimulus period during early distractor trials in WT mice, consistent with their known role as error signals. Strikingly, however, VIP cells from Fmr1-/- mice showed little modulation in error trials, and this correlated with their poor performance on the distractor task. Thus, VIP interneurons and their reduced modulatory influence on pyramidal cells, could be a potential therapeutic target for attentional difficulties in FXS.

neuroscience↗

bioRxiv2017

Impaired perceptual learning in Fragile X syndrome is mediated by parvalbumin neuron dysfunction in V1 and is reversible.

Atypical sensory processing is a core characteristic in autism spectrum disorders1 that negatively impacts virtually all activities of daily living. Sensory symptoms are predictive of the subsequent appearance of impaired social behavior and other autistic traits2, 3. Thus, a better understanding of the changes in neural circuitry that disrupt perceptual learning in autism could shed light into the mechanistic basis and potential therapeutic avenues for a range of autistic symptoms2. Likewise, the lack of directly comparable behavioral paradigms in both humans and animal models currently limits the translational potential of discoveries in the latter. We adopted a symptom-to-circuit approach to uncover the circuit-level alterations in the Fmr1-/- mouse model of Fragile X syndrome (FXS) that underlie atypical visual discrimination in this disorder4, 5. Using a go/no-go task and in vivo 2-photon calcium imaging in primary visual cortex (V1), we find that impaired discrimination in Fmr1-/- mice correlates with marked deficits in orientation tuning of principal neurons, and a decrease in the activity of parvalbumin (PV) interneurons in V1. Restoring visually evoked activity in PV cells in Fmr1-/- mice with a chemogenetic (DREADD) strategy was sufficient to rescue their behavioral performance. Finally, we found that human subjects with FXS exhibit strikingly similar impairments in visual discrimination as Fmr1-/- mice. We conclude that manipulating orientation tuning in autism could improve visually guided behaviors that are critical for playing sports, driving or judging emotions.

neuroscience↗