Instabilities in Newtonian and non-Newtonian fluids

[spa] Durante la tesis se realizó un estudio experimental de inestabilidades hidrodinámicas en dos sistemas muy diferentes. Estudiamos inestabilidades laterales en dedos de Saffaman-Taylor sujetos a dos tipos de perturbación (desorden estático y perturbación periódica). Observamos una inestabilidad con una longitud de onda seleccionada del orden del ancho del canal. También estudiamos el flujo oscilatorio de un fluido de Maxwell en un tubo, comparándolo con uno Newtoniano. Observados grandes diferencias entre ambos casos. El flujo Maxweliano se hace inestable a números de Reynolds mayor 1

Long-Range a-Synchronization as Control Signal for BCI: A Feasibility Study

First published February 7, 2023Shifts in spatial attention are associated with variations in α band (α, 8–14 Hz) activity, specifically in interhemispheric imbalance. The underlying mechanism is attributed to local α-synchronization, which regulates local inhibition of neural excitability, and frontoparietal synchronization reflecting long-range communication. The direction-specific nature of this neural correlate brings forward its potential as a control signal in brain-computer interfaces (BCIs). In the present study, we explored whether long-range α-synchronization presents lateralized patterns dependent on voluntary attention orienting and whether these neural patterns can be picked up at a single-trial level to provide a control signal for active BCI. We collected electroencephalography (EEG) data from a cohort of healthy adults (n = 10) while performing a covert visuospatial attention (CVSA) task. The data show a lateralized pattern of α-band phase coupling between frontal and parieto-occipital regions after target presentation, replicating previous findings. This pattern, however, was not evident during the cue-to-target orienting interval, the ideal time window for BCI. Furthermore, decoding the direction of attention trial-by-trial from cue-locked synchronization with support vector machines (SVMs) was at chance level. The present findings suggest EEG may not be capable of detecting long-range α-synchronization in attentional orienting on a single-trial basis and, thus, highlight the limitations of this metric as a reliable signal for BCI control.This research was supported by the Agència de Gestió d’Ajuts Universitaris i de Recerca Generalitat de Catalunya Grant 2017 SGR 1545. This project has been co-funded with 50% by the European Regional Development Fund under the framework of the FEDER Operative Programme for Catalunya 2014-2020 Ministerio de Ciencia e Innovación (Ref: PID2019-108531GB-I00 AEI/FEDER)

Exploring sensory sensitivity, cortical excitability, and habituation in episodic migraine, as a function of age and disease severity, using the pattern-reversal task

Cortical excitability; Migraine; Visual sensitivityExcitabilitat cortical; Migranya; Sensibilitat visualExcitabilidad cortical; Migraña; Sensibilidad visualBackground Migraine is a cyclic, neurosensory disorder characterized by recurrent headaches and altered sensory processing. The latter is manifested in hypersensitivity to visual stimuli, measured with questionnaires and sensory thresholds, as well as in abnormal cortical excitability and a lack of habituation, assessed with visual evoked potentials elicited by pattern-reversal stimulation. Here, the goal was to determine whether factors such as age and/or disease severity may exert a modulatory influence on sensory sensitivity, cortical excitability, and habituation. Methods Two similar experiments were carried out, the first comparing 24 young, episodic migraine patients and 28 healthy age- and gender-matched controls and the second 36 middle-aged, episodic migraine patients and 30 healthy age- and gender-matched controls. A neurologist confirmed the diagnoses. Migraine phases were obtained using eDiaries. Sensory sensitivity was assessed with the Sensory Perception Quotient and group comparisons were carried out. We obtained pattern-reversal visual evoked potentials and calculated the N1-P1 Peak-to-Peak amplitude. Two linear mixed-effects models were fitted to these data. The first model had Block (first block, last block) and Group (patients, controls) as fixed factors, whereas the second model had Trial (all trials) and Group as fixed factors. Participant was included as a random factor in both. N1-P1 first block amplitude was used to assess cortical excitability and habituation was defined as a decrease of N1-P1 amplitude across Blocks/Trials. Both experiments were performed interictally. Results The final samples consisted of 18 patients with episodic migraine and 27 headache-free controls (first experiment) and 19 patients and 29 controls (second experiment). In both experiments, patients reported increased visual hypersensitivity on the Sensory Perception Quotient as compared to controls. Regarding N1-P1 peak-to-peak data, there was no main effect of Group, indicating no differences in cortical excitability between groups. Finally, significant main effects of both Block and Trial were found indicating habituation in both groups, regardless of age and headache frequency. Conclusions The results of this study yielded evidence for significant hypersensitivity in patients but no significant differences in either habituation or cortical excitability, as compared to headache-free controls. Although the alterations in patients may be less pronounced than originally anticipated they demonstrate the need for the definition and standardization of optimal methodological parameters.The authors disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: AMM salary has been partially financed by a predoctoral grant from the “Fundacio Institut de Recerca Hospital Universitari Vall d’Hebron” (VHIR/BEQUESPREDOC/2020/MARTI). AVB salary has been partially financed by a Juan de la Cierva-Formacion grant (FJC2018-036804-I) and a Juan de la Cierva-Incorporación grant (IJC2020-043139-I) from the Spanish Ministry of Science and Innovation. XCC salary has been co-funded by the European Regional Development Fund (001-P-001682) under the framework of the FEDER Operative Programme for Catalunya 2014–2020, with 1,527,637.88 euros. EC salary has been funded by Rıo Hortega grant Accion Estrategica en Salud 2017–2020, Instituto de Salud Carlos III (CM20/00217). SSF has been supported by grants from the Ministerio de Ciencia e Innovación (PID2019-108531 GB-I00 AEI/FEDER) and AGAUR Generalitat de Catalunya (2021 SGR 00911). The project leading to these results has received funding from “la Caixa” Foundation under the project code “LCF/PR/PR16/51110005”