21 Apr

Global coincident bursts of high frequency oscillations across the human cortex coordinate large-scale memory processing

Oscillations in the high gamma and ripple frequency ranges are known to coordinate local hippocampal and neocortical neuronal assemblies during memory encoding and recall. Here, we explored spatiotemporal dynamics and the role of global coordination of these fast oscillatory discharges across the sensory and associational cortical areas in distinct phases of memory processing. Individual bursts of high frequency oscillations were detected in intracranial recordings from epilepsy patients remembering word lists for immediate free recall. We found constant coincident bursting across visual and higher order processing areas, peaking before recall and elevated during encoding of words. This global co-bursting was modulated by memory processing, engaged approximately half of the recorded electrode contact sites, and clustered into a sequence of multiple consecutive bursting events. Our results suggest a general role of global coincident high frequency oscillations in organizing large-scale information processing across the brain necessary especially, but not exclusively, for memory functions.

21 Apr

Dynamic functional connectivity is related to cognitive performance of prodromal Lewy body dementia

Keywords: Cognitive domains; Dynamic connectivity states; Dynamic functional connectivity; Fast eigenvector centrality; Prodromal Lewy body dementia; Resting state fMRI.

21 Apr

Collaborative Genomics for Dystonia in Central and Eastern Europe: Successes Achieved, New Frontiers Ahead

The application and clinical utility of genomic analyses are well established in the field of movement disorders, where high-throughput molecular tests have revolutionized the rate, speed, and precision of diagnosis.¹ Nevertheless, there is a wide appreciation of inequitable access to genomic programs with maldistribution of enrollment into precision-medicine studies for individuals living with a movement disorder in “underrepresented” geographical regions.^2-4 Although successes in diversifying cohorts and overcoming diagnostic disparities have been shown for some forms of movement disorders, most notably for Parkinson's disease,^5, 6 significant room for improvement of inclusion and investigation remains for other patient groups, such as individuals with dystonia. Lim and colleagues⁷ recently proposed a seminal definition of underrepresented populations in genomic research, highlighting patients from Eastern European countries as an important portion of underserved individuals who face barriers to systematic genetic characterization. The investigation of the impact of state-of-the-art genomic testing approaches in such disadvantaged populations has often started to focus on more common conditions, exacerbating the issue of underrepresentation of patients with rare genetic dystonias from these regions.⁷

16 Mar

Language network disruption in patients with Lewy body diseases

Lewy body diseases, including Parkinson’s disease and dementia with Lewy bodies, are marked by neuronal α‑synuclein aggregation, motor parkinsonism, cognitive impairment and diverse non‑motor symptoms including communication impairments. Compared to other symptoms, non‑motor communication impairments remain under-explored, especially outside English‑speaking cohorts. The aim of this study was to elucidate the neural underpinnings of linguistic deficits as assessed by fMRI in Czech-speaking patients diagnosed with neuronal Lewy body disease and mild cognitive impairment (LBD-MCI). Scores from the Short Neuropsychological Battery and resting‑state functional MRI data were analyzed in 26 Czech‑speaking patients with LBD‑MCI and 24 healthy controls. Analyses targeted regions of interest within the dorsal and ventral language networks. We applied graph theory metrics, within‑network connectivity and seed‑based functional connectivity analysis. Graph analysis revealed dorsal‑stream disruption in LBD‑MCI: reduced clustering coefficient, increased path length, and diminished node strength, each correlating with language functions; ventral‑stream topology remained intact. Within‑network analyses showed impaired connectivity across both pathways, but weaker coupling between the opercular inferior frontal gyrus and posterior superior temporal gyrus predicted behavioral scores in language functioning, further highlighting dorsal vulnerability. Seed‑based analysis identified reduced frontotemporal connectivity in the dorsal stream and decreased fronto‑occipital and temporo-cerebellar connections in the ventral stream. 

16 Mar

Intracranial electroencephalographic connectivity analysis to localize epileptogenic networks: Systematic review and meta-analysis from ILAE Epilepsy Surgery Networks Task Force

Intracranial electroencephalographic (iEEG) connectivity analysis is a promising method to localize epileptic networks and guide surgical planning in focal drug-resistant epilepsy. Despite numerous studies exploring its utility, the added value of iEEG connectivity over standard clinical presurgical evaluation remains unclear. We assess the current evidence on the efficacy of iEEG connectivity analyses to improve seizure outcomes following epilepsy surgery through a systematic review and meta-analysis. Following PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) reporting guidelines, we searched PubMed and Embase for studies (2006-2024) of adult focal drug-resistant epilepsy patients who underwent surgical resection or ablation, reported outcomes at least 1 year postsurgery, and used iEEG connectivity analysis to localize networks. Reviews, nonhuman studies, and studies lacking iEEG connectivity analysis or network localization were excluded. We derived classification metrics (true/false positives/negatives) based on concordance between iEEG findings, clinical localization, and outcome. Subgroup meta-analyses and meta-regressions determined differences by seizure type, lesion status, and analysis approach. Of 2881 studies screened, 25 met criteria (n = 909). The pooled odds ratio comparing seizure outcome prediction using iEEG connectivity versus standard clinical evaluation was 1.36 (95% confidence interval = 1.10-1.69, p = .004), indicating a significant overall benefit. 

16 Mar

PRPF8-associated retinitis pigmentosa variant induces human neural retina-autonomous photoreceptor defects

Retinitis pigmentosa (RP) is an inherited retinal disorder characterized by the progressive loss of photoreceptors that currently lacks effective treatment. Here, we investigated the effects of the PRPF8-Y2334N variant on neural retina cells using human induced pluripotent stem cell (hiPSC)-derived retinal organoids. Expression of PRPF8-Y2334N variant resulted in photoreceptor defects, including thinning of the outer segment layer. This indicates that the neural retina is impacted independently of retinal pigment epithelium (RPE). At the molecular level, we observed relatively minor changes in mRNA expression in multiple retinal cells. We also found splicing alterations in genes associated with neural and retinal diseases, including those involved in intraflagellar transport, suggesting that these genes may represent common targets of splicing factor mutations. Finally, we detected the misexpression of several circular RNAs (circRNAs), which could serve as early biomarkers of splicing defects caused by RP mutations. Together, we present a model of RP that recapitulates photoreceptor degeneration and demonstrates that these defects are independent of RPE degeneration.

16 Mar

Local Field Aperiodic Spectral Power Modulated by Deep Brain Stimulation in Parkinson's Disease

Background: Aperiodic spectral broadband power has been described recently as reflecting Parkinson's disease (PD) severity. It has therefore become an increasing focus of research interest in the context of the new adaptive deep brain stimulation (DBS) approach.

Objective: We aimed to study the influence of DBS on the main parameters of the aperiodic spectral component of local field potentials (LFPs).

Methods: LFPs were recorded from the subthalamic nucleus (STN) in patients with PD (n = 22) during a simple experimental paradigm that included 5 minutes of resting state and a short gait task during DBS OFF and ON conditions (off medication). Classical spectral analysis was performed using fast Fourier transform; the analysis of the aperiodic component was performed by fitting oscillations and a one-over-F approach. In a subset of the patients (n = 14), it was possible to evaluate the symptom progression over time after 1 year by analyzing the control measurement.

Results: The severity of hypokinetic/rigid symptomatology, measured by International Parkinson and Movement Disorders Society Unified Parkinson's Disease Rating Scale, correlated significantly with both of the aperiodic components characteristics of the STN LFPs: the slope and the offset. These parameters were significantly modified by DBS, as evaluated with a Wilcoxon signed-rank test during the resting state and during the gait task. 

13 Feb

Complex multi-echo fMRI dataset: New strategies in processing of multi-echo data

This publication introduces a novel, publicly available dataset designed to support the development and evaluation of advanced algorithms and processing workflows for complex multi-echo functional magnetic resonance imaging (fMRI) data.

The dataset comprises multi-echo fMRI and electrophysiological recordings collected from 83 healthy, right-handed adult participants.

Data was acquired with two 3 T MR scanners and is available on OpenNeuro under the title "Complex multi-echo fMRI dataset: New strategies in processing of multi-echo data".