Biology subjects

Peltier, S. J.

Publications and source records attributed to Peltier, S. J..

5 recordsLinked to original sources

bioRxiv2026

The Intrinsic Manifold of Spontaneous Activity Constrains Cortical Responses to Naturalistic Stimuli

The cerebral cortex constrains its spontaneous activity to a low-dimensional manifold learnable from resting state functional magnetic resonance imaging (fMRI) data. However, it remains unclear whether this intrinsic manifold also captures cortical responses to complex, naturalistic stimuli. To test this, we pretrained a deep variational autoencoder model on 3-Tesla resting-state fMRI data to learn the latent structure of spontaneous activity, and then applied this model without finetuning to 7-Tesla fMRI data acquired during movie-watching. Despite the different field strengths, the model generalized robustly from resting to movie-watching states. The latent representation of stimulus-evoked responses was confined to a subspace that occupied about 13% of the latent space spanned by spontaneous activity, demonstrating that task-related neural responses do not require a distinct representational space. By representing cortical dynamics as an evolving latent trajectory, we found striking differences across individuals or between brain states. During movie watching, the velocity of the latent trajectory provided a reliable marker of cortical engagement, and its temporal structure was highly reliable and sensitive to naturalistic events. These findings suggest that the intrinsic manifold of spontaneous activity forms a full reservoir of cortical states that the brain can differentially engage when interacting with the external environment.

neuroscience↗

bioRxiv2024

Image Processing in the Acute to Chronic Pain Signatures (A2CPS) Project

The Acute to Chronic Pain Signatures (A2CPS) project is a large-scale, multi-site initiative aimed at identifying biomarkers and biosignatures that predict the transition from acute to chronic pain. The project is collecting multimodal, longitudinal data from over 2,500 individuals at risk for developing chronic pain after surgery. Here we describe the neuroimaging component of A2CPS, including the acquisition protocols, processing pipelines, and contents of the initial data release. The imaging protocol includes structural, diffusion, resting-state and task-based functional magnetic resonance imaging (MRI) data. Data are collected across multiple clinical sites using different scanner manufacturers, with attention to protocol harmonization and quality control. The processing pipeline integrates several established neuroimaging tools to extract potential biomarkers, including measures of brain structure, connectivity, and pain-related neural signatures. The first data release includes pre-surgical imaging data for 595 participants, with high quality ratings across modalities (98.7% of sMRI, 99.8% of dMRI, and 94.6% of fMRI images were rated as acceptable or better). Initial analyses demonstrate expected relationships between brain-derived measures and clinical variables, such as associations between brain age and psychological factors. This dataset represents a valuable resource for both pain research and neuroimaging methods development, with future releases planned to include additional participants and expanded analysis pipelines and processed data derivatives.

neuroscience↗

bioRxiv2022

Age-related differences in GABA: Impact of analysis technique

Previous research using magnetic resonance spectroscopy (MRS) has indicated that GABA levels decline in multiple brain regions over the course of healthy aging. However, brain atrophy also occurs during healthy aging, and as a result the tissue composition of MRS voxels (i.e., the percentage of grey matter, white matter, and cerebrospinal fluid in the voxel) may also differ between age groups. Many authors therefore argue for applying a correction to GABA estimates in order to control for differences in tissue composition. Here, we use data from a large healthy aging study to investigate the influence of three tissue correction strategies on age-group differences in GABA. We also evaluate the use of different analysis packages and reference metabolites on group differences. A 3T MEGA-PRESS sequence was used to obtain spectra from seven voxels placed in the visual, auditory, and sensorimotor cortex of 58 young adults (aged 18-29 years) and 85 older adults. We obtained several different estimates of GABA concentrations from the spectra using two analysis software packages (Gannet 3.1 and LCModel), three reference metabolites (water, creatine and N-acetylaspartate) and four tissue correction strategies. Young adults consistently demonstrated significantly higher GABA concentrations in the visual, auditory, and sensorimotor cortex when we used an uncorrected GABA estimate referenced either to water or creatine. When uncorrected GABA was referenced to N-acetylaspartate, age-related differences were observed only in the right ventral visual cortex. Similarly, when any of the four tissue corrections were applied to the data, only age-related differences in the left and right ventral visual cortex voxels remained. Correlations between GABA concentration estimates obtained from different software packages were moderate, as were correlations between uncorrected GABA estimates when different baseline metabolites were used. Correlations between all tissue corrections we explored were extremely high. These results confirm that reports of age-related differences in GABA concentrations are driven, at least in part, by changes in tissue composition.

neuroscience↗

bioRxiv2019

Neural Correlates of Working Memory Training: Evidence for Plasticity in Older Adults

Brain activity typically increases with increasing working memory (WM) load, regardless of age, before reaching an apparent ceiling. However, older adults exhibit greater brain activity and reach ceiling at lower loads than younger adults, possibly reflecting compensation at lower loads and dysfunction at higher loads. We hypothesized that WM training would bolster neural efficiency, such that the activation peak would shift towards higher memory loads after training. Pre-training, older adults showed greater recruitment of the WM network than younger adults across all loads, with decline at the highest load. Ten days of adaptive training on a verbal WM task improved performance and led to greater brain responsiveness at higher loads for both groups. For older adults the activation peak shifted rightward towards higher loads. Finally, training increased task-related functional connectivity in older adults, both within the WM network and between this task-positive network and the task-negative/default-mode network. These results provide new evidence for functional plasticity with training in older adults and identify a potential signature of improvement at the neural level.

neuroscience↗

bioRxiv2018

Neural distinctiveness declines with age in auditory cortex and is associated with auditory GABA levels.

Neural activation patterns in the ventral visual cortex in response to different categories of visual stimuli (e.g., faces vs. houses) are less selective, or distinctive, in older adults than in younger adults, a phenomenon known as age-related neural dedifferentiation. Previous work in animals suggests that age-related reductions of the inhibitory neurotransmitter, gamma aminobutyric acid (GABA), may play a role in this age-related decline in neural distinctiveness. In this study, we investigated whether neural dedifferentiation extends to auditory cortex and whether individual differences in GABA are associated with individual differences in neural distinctiveness in humans. 20 healthy young adults (ages 18-29) and 23 healthy older adults (over 65) completed a functional magnetic resonance imaging (fMRI) scan, during which neural activity was estimated while they listened to foreign speech and music. GABA levels in the auditory, ventrovisual and sensorimotor cortex were estimated in the same individuals in a separate magnetic resonance spectroscopy (MRS) scan. Relative to the younger adults, the older adults exhibited both (1) less distinct activation patterns for music vs. speech stimuli and (2) lower GABA levels in the auditory cortex. Also, individual differences in auditory GABA levels (but not ventrovisual or sensorimotor GABA levels) predicted individual differences in neural distinctiveness in the auditory cortex in the older adults. These results demonstrate that age-related neural dedifferentiation extends to the auditory cortex and suggest that declining GABA levels may play a role in neural dedifferentiation in older adults.\n\nSignificance StatementPrior work has revealed age-related neural dedifferentiation in the visual cortex. GABA levels also decline with age in several parts of the human cortex. Here, we report that these two age-related changes are linked; neural dedifferentiation is associated with lower GABA levels in older adults. We also show that age-related neural dedifferentiation extends to auditory cortex, suggesting that it may be a general feature of the aging brain. These findings provide novel insights into the neurochemical basis of age-related neural dedifferentiation in humans and also offer a potential new avenue for investigating age-related declines in central auditory processing.

neuroscience↗