MASARYK NEUROSCIENCE HUB

17 Apr

Striato-cortical functional connectivity changes in mild cognitive impairment with Lewy bodies

Background: Functional connectivity changes in clinically overt neurodegenerative diseases such as dementia with Lewy bodies have been described, but studies on connectivity changes in the pre-dementia phase are scarce.

Objectives: We concentrated on evaluating striato-cortical functional connectivity differences between patients with Mild Cognitive Impairment with Lewy bodies and healthy controls and on assessing the relation to cognition.

Methods: Altogether, we enrolled 77 participants (47 patients, of which 35 met all the inclusion criteria for the final analysis, and 30 age- and gender-matched healthy controls, of which 28 met all the inclusion criteria for the final analysis) to study the seed-based connectivity of the dorsal, middle, and ventral striatum. We assessed correlations between functional connectivity in the regions of between-group differences and neuropsychological scores of interest (visuospatial and executive domains z-scores).

Results: Subjects with Mild Cognitive Impairment with Lewy Bodies, as compared to healthy controls, showed increased connectivity from the dorsal part of the striatum particularly to the bilateral anterior part of the temporal cortex with an association with executive functions.

17 Apr

Blind deconvolution decreases requirements on temporal resolution of DCE-MRI: Application to 2nd generation pharmacokinetic modeling

Purpose: Dynamic Contrast-Enhanced (DCE) MRI with 2nd generation pharmacokinetic models provides estimates of plasma flow and permeability surface-area product in contrast to the broadly used 1st generation models (e.g. the Tofts models). However, the use of 2nd generation models requires higher frequency with which the dynamic images are acquired (around 1.5 s per image). Blind deconvolution can decrease the demands on temporal resolution as shown previously for one of the 1st generation models. Here, the temporal-resolution requirements achievable for blind deconvolution with a 2nd generation model are studied.

Methods: The 2nd generation model is formulated as the distributed-capillary adiabatic-tissue-homogeneity (DCATH) model. Blind deconvolution is based on Parker's model of the arterial input function. The accuracy and precision of the estimated arterial input functions and the perfusion parameters is evaluated on synthetic and real clinical datasets with different levels of the temporal resolution.

Results: The estimated arterial input functions remained unchanged from their reference high-temporal-resolution estimates (obtained with the sampling interval around 1 s) when increasing the sampling interval up to about 5 s for synthetic data and up to 3.6-4.8 s for real data. 

17 Apr

Weak coupling of neurons enables very high-frequency and ultra-fast oscillations through the interplay of synchronized phase shifts

Recently, in the past decade, high-frequency oscillations (HFOs), very high-frequency oscillations (VHFOs), and ultra-fast oscillations (UFOs) were reported in epileptic patients with drug-resistant epilepsy. However, to this day, the physiological origin of these events has yet to be understood. Our study establishes a mathematical framework based on bifurcation theory for investigating the occurrence of VHFOs and UFOs in depth EEG signals of patients with focal epilepsy, focusing on the potential role of reduced connection strength between neurons in an epileptic focus. We demonstrate that synchronization of a weakly coupled network can generate very and ultra high-frequency signals detectable by nearby microelectrodes. In particular, we show that a bistability region enables the persistence of phase-shift synchronized clusters of neurons. This phenomenon is observed for different hippocampal neuron models, including Morris-Lecar, Destexhe-Paré, and an interneuron model. The mechanism seems to be robust for small coupling, and it also persists with random noise affecting the external current. Our findings suggest that weakened neuronal connections could contribute to the production of oscillations with frequencies above 1000 Hz, which could advance our understanding of epilepsy pathology and potentially improve treatment strategies. 

17 Apr

Short-term effects of transcranial direct current stimulation on motor speech in Parkinson's disease: a pilot study

Introduction: Hypokinetic dysarthria (HD) is a common motor speech symptom of Parkinson's disease (PD) which does not respond well to PD treatments. We investigated short-term effects of transcranial direct current stimulation (tDCS) on HD in PD using acoustic analysis of speech. Based on our previous studies we focused on stimulation of the right superior temporal gyrus (STG) - an auditory feedback area.

Methods: In 14 PD patients with HD, we applied anodal, cathodal and sham tDCS to the right STG using a cross-over design. A protocol consisting of speech tasks was performed prior to and immediately after each stimulation session. Linear mixed models were used for the evaluation of the effects of each stimulation condition on the relative change of acoustic parameters. We also performed a simulation of the mean electric field induced by tDCS.

Results: Linear mixed model showed a statistically significant effect of the stimulation condition on the relative change of median duration of silences longer than 50 ms (p = 0.015). The relative change after the anodal stimulation (mean = -5.9) was significantly lower as compared to the relative change after the sham stimulation (mean = 12.8), p = 0.014.

11 Apr

Grading system for assessing the confidence in the epileptogenic zone reported in published studies: A Delphi consensus study

Objective: This study was undertaken to develop a standardized grading system based on expert consensus for evaluating the level of confidence in the localization of the epileptogenic zone (EZ) as reported in published studies, to harmonize and facilitate systematic reviews in the field of epilepsy surgery.

Methods: We conducted a Delphi study involving 22 experts from 18 countries, who were asked to rate their level of confidence in the localization of the EZ for various theoretical clinical scenarios, using different scales. Information provided in these scenarios included one or several of the following data: magnetic resonance imaging (MRI) findings, invasive electroencephalography summary, and postoperative seizure outcome.

Results: The first explorative phase showed an overall interrater agreement of .347, pointing to large heterogeneity among experts' assessments, with only 17% of the 42 proposed scenarios associated with a substantial level of agreement. A majority showed preferences for the simpler scale and single-item scenarios. The successive Delphi voting phases resulted in a majority consensus across experts, with more than two thirds of respondents agreeing on the rating of each of the tested single-item scenarios.

11 Apr

Reply to: Questioning the cycad theory of Kii ALS-PDC causation

We read with great interest the Correspondence to our recent Review (Menšíková, K. et al. Endemic parkinsonism: clusters, biology and clinical features. Nat. Rev. Neurol. 19, 599–616 (2023)¹) by Kokubo and colleagues (Kokubo, Y., Morimoto, S. & Yoshida, M. Questioning the cycad theory of Kii ALS–PDC causation. Nat. Rev. Neurol. https://doi.org/10.1038/s41582-024-00936-0 (2024)²). We are aware that Kokubo — together with the late S. Kuzuhara — systematically studied amyotrophic lateral sclerosis–parkinsonism–dementia complex (ALS–PDC) on the Kii Peninsula for more than 30 years. They authored and co-authored numerous papers about this endemic disease, some of them with one of us (R.S.). We therefore considered the comments raised by Kokubo et al. carefully, and here we respond to the questions that they have raised.

Kokubo et al. state that the use of cycad seed in herbal and folk medicine, and as a tonic in children, is very rare. However, in the northeastern Kii (Hohara) focus of ALS–PDC, the seed of Cycas revoluta was prescribed throughout the 1980s by kitoshi (folk medicine practitioners) and dispensed by local pharmacies for the oral treatment of various ailments, including diarrhoea, dysmenorrhoea, gonorrhoea, tuberculosis and neuralgia, in accordance with published guidance³. 

11 Apr

Screening and differential diagnosis of delirium in neurointensive stroke patients

Diagnosing delirium in neurointensive care is difficult because symptoms of delirium, such as inappropriate speech, may be related to aphasia due to primary brain injury. Therefore, validated screening tools are needed. The aim of this study was to compare two Czech versions of already validated screening tools - the Confusion Assessment Method for the Intensive Care Unit (CAM-ICU) and the Intensive Care Delirium Screening Checklist (ICDSC) - in a cohort of acute stroke patients. We also aimed to assess the pitfalls of delirium detection in the context of non-convulsive status epilepticus (NCSE). We analysed 138 stroke patients admitted to the neurological intensive care unit (ICU) or stroke unit. According to expert judgement, which was used as the gold standard, 38 patients (27.54%) developed delirium. The sensitivity and specificity of the ICDSC were 91.60% and 95.33%, respectively, and the positive and negative predictive values were 76.76% and 98.54%, respectively. Similarly, the sensitivity and specificity of CAM-ICU were 75.63% and 96.74%, respectively, and the positive and negative predictive values were 79.65% and 95.93%, respectively. We did not detect an episode of NCSE mimicking delirium in any of our stroke patients who were judged to be delirious by expert assessment.

7 Mar

EEG-Meta-Microstates: Towards a More Objective Use of Resting-State EEG Microstate Findings Across Studies

Over the last decade, EEG resting-state microstate analysis has evolved from a niche existence to a widely used and well-accepted methodology. The rapidly increasing body of empirical findings started to yield overarching patterns of associations of biological and psychological states and traits with specific microstate classes. However, currently, this cross-referencing among apparently similar microstate classes of different studies is typically done by "eyeballing" of printed template maps by the individual authors, lacking a systematic procedure. To improve the reliability and validity of future findings, we present a tool to systematically collect the actual data of template maps from as many published studies as possible and present them in their entirety as a matrix of spatial similarity. The tool also allows importing novel template maps and systematically extracting the findings associated with specific microstate maps from ongoing or published studies. The tool also allows importing novel template maps and systematically extracting the findings associated with specific microstate maps in the literature. The analysis of 40 included sets of template maps indicated that: (i) there is a high degree of similarity of template maps across studies, (ii) similar template maps were associated with converging empirical findings, and (iii) representative meta-microstates can be extracted from the individual studies.