Vicente Medel

Adolfo Ibáñez University · Latin American Brain Health Institute (BrainLat)

Background The human brain integrity relies on the synergistic interplay between neural activity and supporting vascular and metabolic processes throughout life. This relationship, ruled by allostatic mechanisms, regulates brain architecture and activity. White matter hyperintensities (WMH) serve as indicators of the vascular impact on brain struct...

Background During the pandemic, Social Isolation (SI) and the perception of loneliness emerged as critical factors associated with significant psychological and physical impacts (Tyrrell, C. & Williams, N., 2020; González, D., 2021). This study examines gender differences and explores the impact of social isolation and the perception of loneliness...

Background The human brain integrity relies on the synergistic interplay between neural activity and supporting vascular and metabolic processes throughout life. This relationship, ruled by allostatic mechanisms, regulates brain architecture and activity. White matter hyperintensities (WMH) serve as indicators of the vascular impact on brain struct...

Structural inequality, the uneven distribution of resources and opportunities, influences health outcomes. However, the biological embedding of structural inequality in aging and dementia, especially among underrepresented populations, is unclear. We examined the association between structural inequality (country-level and state-level Gini indices)...

The aperiodic component of brain field potentials, like EEG, LFP and intracortical recordings, has shown to be a valuable tool in basic neuroscience and in clinical applications. Aperiodic activity is modeled as a power law of the power spectral density, with the aperiodic exponent as the key parameter. Part of the interest in this parameter lies i...

Neuromodulators regulate large-scale brain network topology to support adaptive behaviour. Disease models offer a unique window into how neuromodulatory systems impact large-scale brain network organisation. Here, we take advantage of Parkinson’s disease – with its profound dopaminergic loss and pro-dopaminergic treatment strategies – to inform how...

Background Structural income inequality – the uneven income distribution across regions or countries – could affect brain structure and function, beyond individual differences. However, the impact of structural income inequality on the brain dynamics and the roles of demographics and cognition in these associations remains unexplored. Methods Here...

Background Previous studies have shown that major surgical and medical hospital admissions are associated with cognitive decline in older people (aged 40-69 years at recruitment), which is concerning for patients and caregivers. We aimed to validate these findings in a large cohort and investigate associations with neurodegeneration using MRI.

Brain clocks, which quantify discrepancies between brain age and chronological age, hold promise for understanding brain health and disease. However, the impact of diversity (including geographical, socioeconomic, sociodemographic, sex and neurodegeneration) on the brain-age gap is unknown. We analyzed datasets from 5,306 participants across 15 cou...

BACKGROUND Education influences brain health and dementia. However, its impact across regions, specifically Latin America (LA) and the United States (US), is unknown. METHODS A total of 1412 participants comprising controls, patients with Alzheimer's disease (AD), and frontotemporal lobar degeneration (FTLD) from LA and the US were included. We st...

The human brain must support both stable and flexible neural dynamics in order to adapt to changing contexts. This paper investigates the role of the thalamus, a crucial subcortical structure, in orchestrating these opposing dynamics in the cerebral cortex. Through two distinct classes of cortical projections, the thalamus is able to support distin...

Aging affects brain structure and function alongside metabolic and vascular processes leading to energetic impairments. While local neurometabolic dysfunction in aging is well-documented, the influence of systemic cardiometabolic and vascular markers on brain structure and function remains less understood. We examine the link between cardiometaboli...

Background The hypothesis of decreased neural inhibition in dementia has been sparsely studied in functional magnetic resonance imaging (fMRI) data across patients with different dementia subtypes, and the role of social and demographic heterogeneities on this hypothesis remains to be addressed. Methods We inferred regional inhibition by fitting a...

High-altitude hypoxia triggers brain function changes reminiscent of those in healthy aging and Alzheimer’s disease, compromising cognition and executive functions. Our study sought to validate high-altitude hypoxia as a model for assessing brain activity disruptions akin to aging. We collected EEG data from 16 healthy volunteers during acute high-...

Brain clocks, which quantify discrepancies between brain age and chronological age, hold promise for understanding brain health and disease. However, the impact of multimodal diversity (geographical, socioeconomic, sociodemographic, sex, neurodegeneration) on the brain age gap (BAG) is unknown. Here, we analyzed datasets from 5,306 participants acr...

INTRODUCTION Alzheimer's disease (AD) and behavioral variant frontotemporal dementia (bvFTD) lack mechanistic biophysical modeling in diverse, underrepresented populations. Electroencephalography (EEG) is a high temporal resolution, cost‐effective technique for studying dementia globally, but lacks mechanistic models and produces non‐replicable res...

Introduction The functional evaluation of auditory-nerve activity in spontaneous conditions has remained elusive in humans. In animals, the frequency analysis of the round-window electrical noise recorded by means of electrocochleography yields a frequency peak at around 900 to 1000 Hz, which has been proposed to reflect auditory-nerve spontaneous...

INTRODUCTION Age‐related hearing loss is an important risk factor for cognitive decline. However, audiogram thresholds are not good estimators of dementia risk in subjects with normal hearing or mild hearing loss. Here we propose to use distortion product otoacoustic emissions (DPOAEs) as an objective and sensitive tool to estimate the risk of cogn...

Perceptual updating has been proposed to rely upon evolving activity within a recurrent, distributed thalamocortical network whose interconnections are modulated by bursts of ascending neuromodulatory neurotransmitters, such as noradrenaline. To test this hypothesis mechanistically, we leveraged a combination of pupillometry, fMRI and recurrent neu...

Perceptual updating has been proposed to rely upon evolving activity within a recurrent, distributed thalamocortical network whose interconnections are modulated by bursts of ascending neuromodulatory neurotransmitters, such as noradrenaline. To test this hypothesis mechanistically, we leveraged a combination of pupillometry, fMRI and recurrent neu...

Introduction The mechanisms underlying tinnitus perception are still under research. One of the proposed hypotheses involves an alteration in top-down processing of auditory activity. Low-frequency oscillations in the delta and theta bands have been recently described in brain and cochlear infrasonic signals during selective attention paradigms in...

Background Abnormal gamma oscillations (γ) have been systematically reported in preclinical animal models of Alzheimer’s disease (AD) and human AD patients. However, little is known about the underlying mechanisms, non‐linear dynamics, and high‐order interactions of γ in dementia. Method To bridge this gap, we combined EEG and fMRI with three nove...

Background White matter hyperintensities (WMHs) are frequently seen on FLAIR MRI images in aging and Dementia. It has been hypothesized that an imbalance in norepinephrine (NE) signaling could lead to a “hypometabolism” by decreasing astrocyte metabolism which has been proposed as an important cause leading to local demyelination.We hypothesize tha...

Background Neuroimaging biomarkers are intensively investigated in Alzheimer disease (AD) and the behavioral variant frontotemporal dementia (bvFTD). However, advanced ND biomarkers (i.e., PET and plasma) are expensive or not widely available/validated in underrepresented regions. EEG emerges as a promising alternative, due to its low‐cost, non‐inv...

The Latin American Brain Health Institute (BrainLat) has released a unique multimodal neuroimaging dataset of 780 participants from Latin American. The dataset includes 530 patients with neurodegenerative diseases such as Alzheimer’s disease (AD), behavioral variant frontotemporal dementia (bvFTD), multiple sclerosis (MS), Parkinson’s disease (PD),...

Characterization of brain states is essential for understanding its functioning in the absence of external stimuli. Brain states differ on their balance between excitation and inhibition, and on the diversity of their activity patterns. These can be respectively indexed by 1/f slope and Lempel–Ziv complexity (LZc). However, whether and how these tw...

While consciousness never fades during wakefulness, there is a paradoxical coexistence of consciousness during dreaming states. It’s also possible for sensory awareness to be either present or absent when awakened from seemingly-identical states of sedation and anaesthesia. Traditionally, these states have been characterised in terms of their elect...

The human brain displays a rich repertoire of states that emerge from the microscopic interactions of cortical and subcortical neurons. Difficulties inherent within large-scale simultaneous neuronal recording limit our ability to link biophysical processes at the microscale to emergent macroscopic brain states. Here we introduce a microscale biophy...

While consciousness never fades during wakefulness, there is a paradoxical coexistence of consciousness during dreaming states. It is also possible for sensory awareness to be either present or absent when awakened from seemingly-identical states of sedation and anaesthesia. Traditionally, these states have been characterised by their electroenceph...

The mechanisms underlying tinnitus perception are still under research. One of the proposed hypotheses involves an alteration in top-down processing of auditory activity. Low-frequency oscillations in the delta and theta bands have been recently described in brain and cochlear infrasonic signals during selective attention paradigms in normal hearin...

Introduction The functional evaluation of auditory-nerve activity in spontaneous conditions has remained elusive in humans. In animals, the frequency analysis of the round-window electrical noise recorded by means of electrocochleography yields a frequency peak at around 900 to 1000 Hz, which has been proposed to reflect auditory-nerve spontaneous...

Introduction Frailty is a geriatric syndrome frequently associated with executive dysfunction and white matter hyperintensities (WMH). But the relation between executive dysfunction and brain changes is poorly understood in frail subjects. Our hypothesis is that frontal-WMH mediates the association between frailty and executive dysfunction. Method...

Video games are a valuable tool for studying the effects of training and neural plasticity on the brain. However, the underlaying mechanisms related to plasticity-induced brain structural changes and their impact in brain dynamics are unknown. Here, we used a semi-empirical whole-brain model to study structural neural plasticity mechanisms linked t...

Gender inequality across the world has been associated with a higher risk to mental health problems and lower academic achievement in women compared to men. We also know that the brain is shaped by nurturing and adverse socio-environmental experiences. Therefore, unequal exposure to harsher conditions for women compared to men in gender-unequal cou...

Age-related hearing loss (presbycusis) at moderate levels (>40 dB HL) has been recognized as an important risk factor for cognitive decline. However, whether individuals with mild hearing loss (audiogram thresholds between 25 and 40 dB HL) or even those with normal audiograms (<25 dB HL) have a higher risk of dementia is still debated. Importantly,...

We are delighted to present you the Proceedings of the 2022 CNS meeting. The CNS meeting encourages approaches that combine theoretical, computational, and experimental work in the neurosciences, and provides an opportunity for participants to share their views. The abstracts corresponding to speakers' talks and posters are what you find collected...

Perception is thought to rely upon evolving activity within a recurrent, distributed thalamocortical network whose interconnections are modulated by bursts of noradrenaline. To test this hypothesis, we leveraged a combination of pupillometry, fMRI and recurrent neural network modelling of an ambiguous figures task. Shifts in the perceptual interpre...

Perception is thought to rely upon evolving activity within a recurrent, distributed thalamocortical network whose interconnections are modulated by bursts of ascending neuromodulatory neurotransmitters, such as noradrenaline. To test this hypothesis, we leveraged a combination of pupillometry, fMRI and recurrent neural network modelling of an ambi...

Perceptual updating has been proposed to rely upon evolving activity within a recurrent, distributed thalamocortical network whose interconnections are modulated by bursts of ascending neuromodulatory neurotransmitters, such as noradrenaline. To test this hypothesis mechanistically, we leveraged a combination of pupillometry, fMRI and recurrent neu...

Perceptual updating has been proposed to rely upon evolving activity within a recurrent, distributed thalamocortical network whose interconnections are modulated by bursts of ascending neuromodulatory neurotransmitters, such as noradrenaline. To test this hypothesis mechanistically, we leveraged a combination of pupillometry, fMRI and recurrent neu...

Integration and segregation are two fundamental principles of brain organization. The brain manages the transitions and balance between different functional segregated or integrated states through neuromodulatory systems. Recently, computational and experimental studies suggest a pro-segregation effect of cholinergic neuromodulation. Here, we studi...

Brain activity is constrained by local availability of chemical energy, which is generated through compartmentalized metabolic processes. By analyzing data of whole human brain gene expression, we characterize the spatial distribution of seven glucose and monocarboxylate membrane transporters that mediate astrocyte–neuron lactate shuttle transfer o...

Human brain structure changes throughout the lifespan. Altered brain growth or rates of decline are implicated in a vast range of psychiatric, developmental and neurodegenerative diseases. In this study, we identified common genetic variants that affect rates of brain growth or atrophy in what is, to our knowledge, the first genome-wide association...

Integration and segregation are accepted as two fundamental principles of brain organization. The brain manages the transitions between different functional states, more segregated or integrated, through neuromodulatory systems. Recently computational and experimental works suggest a pro-segregation effect of cholinergic neuromodulation. Here, we s...

Spontaneous fluctuations occur at different spatial and temporal scales in the brain. Depending on its scale, these activities can show characteristic hallmarks. From a mesoscale perspective, in spontaneous conditions, cortical neurons fire action potentials in a seemingly stochastic manner, which extrapolated to an entire population shows a dynami...

Previous research has shown that the autonomic nervous system provides essential constraints over ongoing cognitive function. However, there is currently a relative lack of direct empirical evidence for how this interaction manifests in the brain at the macroscale level. Here, we examine the role of ascending arousal and attentional load on large-s...

Background Brain activity complexity is a promising correlate of states of consciousness. Previous studies have shown higher complexity for awake compared with deep anaesthesia states. However, little attention has been paid to complexity in intermediate states of sedation. Methods We analysed the Lempel–Ziv complexity of EEG signals from subjects...

Characterization of cortical states is essential for understanding brain functioning in the absence of external stimuli. The balance between excitation and inhibition and the number of non-redundant activity patterns, indexed by the 1/f slope and LZc respectively, distinguish cortical states. However, the relation between these two measures has not...

Resting-state functional MRI activity is organized as a complex network. However, this coordinated brain activity changes with time, raising questions about its evolving temporal arrangement. Does the brain visit different configurations through time in a random or ordered way? Advances in this area depend on developing novel paradigms that would a...

Human brain structure changes throughout our lives. Altered brain growth or rates of decline are implicated in a vast range of psychiatric, developmental, and neurodegenerative diseases. While heritable, specific loci in the genome that influence these rates are largely unknown. Here, we sought to find common genetic variants that affect rates of b...

Los fragmentos aquí presentados no constituyen la forma más desarrollada del pensamiento de Nishida, sino se sitúan más bien en la gestación de la segunda etapa de su filosofía, etapa que, cabe mencionar, es la menos estudiada en occidente. En el texto, Nishida tiende a desarrollar un lenguaje místico al abordar los nudos más problemáticos de su ex...

Esta tesis es una investigación del concepto de fenomenología en Ludwig Wittgenstein (1889 –1951) buscando una comprensión fidedigna del autor, de su contexto, de sus problemas y de su filosofía. El concepto de fenomenología aquí tiene una dimensión más o menos distinta, como se verá, al de la fenomenología tradicional. Es evidente que cuando habla...