Epidemiology of Work-Related Traumatic Brain Injury and COVID-19 Pandemic Lockdown Consequences: Experience in a Reference Center in Chile.

INTRODUCTION: Work-related traumatic brain injury is a frequent cause of chronic morbidity, mortality, and high treatment costs. Its causes are highly environmentally determined and were affected by COVID-19 pandemic lockdowns. OBJECTIVE: We aimed to describe traumatic brain injury (TBI) epidemiology in working population and evaluate its modifications during the COVID-19 pandemic. METHODS: We performed a 2-year retrospective epidemiological analysis of TBI patients hospitalized in a tertiary work-related hospital before and during the COVID-19 pandemic. RESULTS: In the prepandemic period, TBI patients were predominantly men, with a bimodal age distribution. Crash accidents were the leading work-related traumatic brain injury cause. During COVID-19 pandemic lockdowns, there was a positive correlation between street traffic and TBI rate, presenting increased motor crash accidents as a cause of TBI. CONCLUSIONS: These results are relevant for planning and focalization of resources for TBI prevention.

The Bangor Gambling Task: Computerized replication and reappraisal of an emotion-based decision task.

Emotion-based decision making (EBDM) is the capacity to make decisions based on prior emotional consequences of actions. Several neuropsychological tasks, using different gambling paradigms and with different levels of complexity, have been designed to assess EBDM. The Bangor Gambling Task (BGT) was created as a brief and simple card gambling-task to assess EBDM. BGT contains a single-card deck and requires participants to decide whether to gamble or not, which can result in wins or losses. Unknown to the participant, the winning probabilities decrease throughout the task (from 0.75 in the first block to 0.25 in the fifth block), requiring participants to reduce their gambling probability to avoid long-term losses. A few studies have offered evidence regarding the BGT convergent validity. However, there are no computerized versions of BGT available, thus slowing the process of gathering information to explore the EBDM mechanisms behind the task, its validity, and clinical usefulness. In this article, we present a computerized version of the BGT using the Matlab environment and make all our code available. We explore BGT's replicability and analyze its probabilistic structure, providing trial-level and block-level analyses. Eighty-one participants performed the computerized version, which followed the same structure as the original version. It took participants 8.5 ± 3.3 minutes to complete the task, which is faster than the paper version. Replicating previous studies, participants diminished their gambling probability throughout the task, learning to inhibit the initially rewarded gambling behavior. This change in gambling probability could be considered a proxy for EBDM. Our analyses suggest that the last blocks are especially sensitive to capturing deficits in EBDM, and we propose some modifications to BGT's original version to enhance the initial exploratory and learning phase. Our results show that the BGT constitutes a quick and simple task to evaluate EBDM capacities.

Social isolation after acquired brain injury: Exploring the relationship between network size, functional support, loneliness and mental health.

Social isolation can be a consequence of acquired brain injury (ABI). Few studies have examined the relationship between social isolation and mental health after ABI. In this cross-sectional and case-control study, we compared 51 ABI survivors and 51 matched healthy controls on measures of social isolation (network size, social support and loneliness) mental health and mental health problems. We explored the relationship between structural, functional and subjective components of social isolation and examined whether they were associated with mental health outcomes. No group differences were found on size of the network and perceived social support. The ABI group exhibited marginally higher levels of loneliness. The ABI group presented higher levels of depression, lower levels of quality of life and emotional wellbeing. In both groups, perception of social support was inversely related to subjective experience of loneliness. The relationship between network size and loneliness was only significant in the ABI group. Only loneliness significantly predicted quality of life, emotional wellbeing, depression and anxiety in people with brain injury. The relationship between social isolation variables in ABI is discussed, as well as the theoretical and clinical implications of focusing on loneliness to improve mental health after brain injury.

The ascending arousal system promotes optimal performance through mesoscale network integration in a visuospatial attentional task.

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-scale network dynamics by combining pupillometry, functional MRI, and graph theoretical analysis to analyze data from a visual motion-tracking task with a parametric load manipulation. We found that attentional load effects were observable in measures of pupil diameter and in a set of brain regions that parametrically modulated their BOLD activity and mesoscale network-level integration. In addition, the regional patterns of network reconfiguration were correlated with the spatial distribution of the α2a adrenergic receptor. Our results further solidify the relationship between ascending noradrenergic activity, large-scale network integration, and cognitive task performance.

Nasal respiration entrains neocortical long-range gamma coherence during wakefulness.

Recent studies have shown that slow cortical potentials in archi-, paleo- and neocortex can phase-lock with nasal respiration. In some of these areas, gamma activity (γ: 30-100 Hz) is also coupled to the animal's respiration. It has been hypothesized that these functional relationships play a role in coordinating distributed neural activity. In a similar way, inter-cortical interactions at γ frequency have also been associated as a binding mechanism by which the brain generates temporary opportunities necessary for implementing cognitive functions. The aim of the present study is to explore whether nasal respiration entrains inter-cortical functional interactions at γ frequency during both wakefulness and sleep. Six adult cats chronically prepared for electrographic recordings were employed in this study. Our results show that during wakefulness, slow cortical respiratory potentials are present in the olfactory bulb and several areas of the neocortex. We also found that these areas exhibit cross-frequency coupling between respiratory phase and γ oscillation amplitude. We demonstrate that respiratory phase modulates the inter-cortical gamma coherence between neocortical electrode pairs. On the contrary, slow respiratory oscillation and γ cortical oscillatory entrainments disappear during non-rapid eye movement and rapid eye movement sleep. These results suggest that a single unified phenomenon involves cross-frequency coupling and long-range γ coherence across the neocortex. This fact could be related to the temporal binding process necessary for cognitive functions during wakefulness.

A pupil size, eye-tracking and neuropsychological dataset from ADHD children during a cognitive task.

Attention Deficit/Hyperactive Disorder (ADHD) is diagnosed based on observed behavioral outcomes alone. Given that some brain attentional networks involve circuits that control the eye pupil, we monitored pupil size in ADHD- diagnosed children and also in control children during a visuospatial working memory task. We present here the full dataset, consisting of pupil size time series for each trial and subject. There are data from, 22 control, and 28 ADHD-diagnosed children. There are also data from a subset of 17 ADHD children that performed the task twice, on- and off-medication. In addition, our dataset also includes gaze position data from each trial and subject, and also scores from the Weschler Intelligence Scale for Children. In this context, the dataset can serve as a resource to analyze dynamic eye movement and pupil changes as a function of known behavioral changes and scores in neuropsychological tests, which reflect neurocognitive processing.

Reduced delta-band modulation underlies the loss of P300 responses in disorders of consciousness.

OBJECTIVE: The P300 component of a sensory event-related potential is one of the major electrophysiological markers used to explore remnants of cognitive function in patients with disorders of consciousness (DoC). However, measuring the P300 in patients is complicated by significant inter-trial variability commonly observed in levels of arousal and awareness. To overcome this limitation, we analyzed single-trial modulation of power in the delta and theta frequency bands, which underlie the P300. METHODS: In a preliminary cross-sectional study using a 24-channel EEG and a passive own-name oddball paradigm, we analyzed event-related synchronization (ERS) across trials in the delta and theta bands in a sample of 10 control and 12 DoC subjects. RESULTS: In comparison to controls, DoC subjects presented a low percentage of trials where delta ERS was observed. In particular, coordinated modulation between delta and theta in response to the stimulus was absent, with a high percentage of trials where only theta ERS was observed. Further, we found a positive correlation between the percentage of epochs with delta ERS and the strength of the P300. CONCLUSIONS: Reduced modulation of spectral activity in the delta band in response to stimuli indicates a dissociation in the activity of the neural networks that oscillate in delta and theta ranges and contribute to the generation of the P300. SIGNIFICANCE: The reduction in spectral modulation observed in DoC provides a deeper understanding of neurophysiological dysfunction and the means to develop a more fine-grained marker of residual cognitive function in individual patients.

Local cortical activity of distant brain areas can phase-lock to the olfactory bulb's respiratory rhythm in the freely behaving rat.

An important unresolved question about neural processing is the mechanism by which distant brain areas coordinate their activities and relate their local processing to global neural events. A potential candidate for the local-global integration are slow rhythms such as respiration. In this study, we asked if there are modulations of local cortical processing that are phase-locked to (peripheral) sensory-motor exploratory rhythms. We studied rats on an elevated platform where they would spontaneously display exploratory and rest behaviors. Concurrent with behavior, we monitored whisking through electromyography and the respiratory rhythm from the olfactory bulb (OB) local field potential (LFP). We also recorded LFPs from dorsal hippocampus, primary motor cortex, primary somatosensory cortex, and primary visual cortex. We defined exploration as simultaneous whisking and sniffing above 5 Hz and found that this activity peaked at ~8 Hz. We considered rest as the absence of whisking and sniffing, and in this case, respiration occurred at ~3 Hz. We found a consistent shift across all areas toward these rhythm peaks accompanying behavioral changes. We also found, across areas, that LFP gamma (70-100 Hz) amplitude could phase-lock to the animal's OB respiratory rhythm, a finding indicative of respiration-locked changes in local processing. In a subset of animals, we also recorded the hippocampal theta activity and found that occurred at frequencies overlapped with respiration but was not spectrally coherent with it, suggesting a different oscillator. Our results are consistent with the notion of respiration as a binder or integrator of activity between brain regions.

Power and coherence of cortical high-frequency oscillations during wakefulness and sleep.

Recently, a novel type of fast cortical oscillatory activity that occurs between 110 and 160 Hz (high-frequency oscillations (HFO)) was described. HFO are modulated by the theta rhythm in hippocampus and neocortex during active wakefulness and REM sleep. As theta-HFO coupling increases during REM, a role for HFO in memory consolidation has been proposed. However, global properties such as the cortex-wide topographic distribution and the cortico-cortical coherence remain unknown. In this study, we recorded the electroencephalogram during sleep and wakefulness in the rat and analyzed the spatial extent of the HFO band power and coherence. We confirmed that the HFO amplitude is phase-locked to theta oscillations and is modified by behavioral states. During active wakefulness, HFO power was relatively higher in the neocortex and olfactory bulb compared to sleep. HFO power decreased during non-REM and had an intermediate level during REM sleep. Furthermore, coherence was larger during active wakefulness than non-REM, while REM showed a complex pattern in which coherence increased only in intra and decreased in inter-hemispheric combination of electrodes. This coherence pattern is different from gamma (30-100 Hz) coherence, which is reduced during REM sleep. This data show an important HFO cortico-cortical dialog during active wakefulness even when the level of theta comodulation is lower than in REM. In contrast, during REM, this dialog is highly modulated by theta and restricted to intra-hemispheric medial-posterior cortical regions. Further studies combining behavior, electrophysiology and new analytical tools are needed to plunge deeper into the functional significance of the HFO.

Actividad oscilatoria en banda gamma, un promisorio nuevo marcador electroencefalográfico de dolor con potencial utilidad en la monitorización intraoperatoria / Gamma band oscillatory activity, a promising new marker electroencephalographic of pain potential utility in monitoring intraoperative

Chronic pain is a highly prevalent condition in modern medicine. Is the main cause of consultation, the principal cause of disability worldwide and represent enormous costs for all health systems. In most cases, chronic pain is a consequence of long exposures to untreated or subtreated acute pain. Efforts should be done in situation where acute pain is expected in order to prevent its transformation into chronic pain. Surgery is one of those situations. Electroencephalography (EEG) is a powerful tool that has proved its utility for monitoring the brain under general anesthesia. Unfortunately most of the achievements have been developed in the study of unconsciousness and amnesia with little progress in the pain/nociception field. Today the electroencephalographic feature more commonly associated with pain perception is the variation in the amplitude of evoked-related potentials (ERPs). However, new date shows that the ERPs do not always reflect the stimulus intensity nor the amount of perceived pain. New data has shown strong and clear evidence that transient Gamma (30-100 Hz) oscillations are a constant electroencephalographic feature associated with pain perception. Gamma oscillations appear, then, as a promising EEG marker than has the potential to be used for monitoring pain/nociception in anesthesia...

The olfactory bulb theta rhythm follows all frequencies of diaphragmatic respiration in the freely behaving rat.

Sensory-motor relationships are part of the normal operation of sensory systems. Sensing occurs in the context of active sensor movement, which in turn influences sensory processing. We address such a process in the rat olfactory system. Through recordings of the diaphragm electromyogram (EMG), we monitored the motor output of the respiratory circuit involved in sniffing behavior, simultaneously with the local field potential (LFP) of the olfactory bulb (OB) in rats moving freely in a familiar environment, where they display a wide range of respiratory frequencies. We show that the OB LFP represents the sniff cycle with high reliability at every sniff frequency and can therefore be used to study the neural representation of motor drive in a sensory cortex.

Coordinated endothelial nitric oxide synthase activation by translocation and phosphorylation determines flow-induced nitric oxide production in resistance vessels.

BACKGROUND/AIMS: Endothelial nitric oxide synthase (eNOS) is associated with caveolin-1 (Cav-1) in plasma membrane. We tested the hypothesis that eNOS activation by shear stress in resistance vessels depends on synchronized phosphorylation, dissociation from Cav-1 and translocation of the membrane-bound enzyme to Golgi and cytosol. METHODS: In isolated, perfused rat arterial mesenteric beds, we evaluated the effect of changes in flow rate (2-10 ml/min) on nitric oxide (NO) production, eNOS phosphorylation at serine 1177, eNOS subcellular distribution and co-immunoprecipitation with Cav-1, in the presence or absence of extracellular Ca(2+). RESULTS: Increases in flow induced a biphasic rise in NO production: a rapid transient phase (3-5-min) that peaked during the first 15 s, followed by a sustained phase, which lasted until the end of stimulation. Concomitantly, flow caused a rapid translocation of eNOS from the microsomal compartment to the cytosol and Golgi, paralleled by an increase in eNOS phosphorylation and a reduction in eNOS-Cav-1 association. Transient NO production, eNOS translocation and dissociation from Cav-1 depended on extracellular Ca(2+), while sustained NO production was abolished by the PI3K-Akt blocker wortmannin. CONCLUSIONS: In intact resistance vessels, changes in flow induce NO production by transient Ca(2+)-dependent eNOS translocation from membrane to intracellular compartments and sustained Ca(2+)-independent PI3K-Akt-mediated phosphorylation.

Interplay between sniffing and odorant sorptive properties in the rat.

For decades it has been known that the olfactory sensory epithelium can act like a chromatograph, separating odorants based on their air-mucus sorptive properties (Mozell and Jagodowicz, 1973). It has been hypothesized that animals could take advantage of this property, modulating sniffing behavior to manipulate airflow and thereby directing odorant molecules to the portions of the olfactory epithelium where they are best detected (Schoenfeld and Cleland, 2005). We report here a test of this hypothesis in behaving rats, monitoring respiratory activity through diaphragm electromyogram, which allowed us to estimate nasal airflow. In our test rats had to detect either low-sorption (LS) or high-sorption (HS) monomolecular odorant targets from the same stimulus set of six binary odor mixtures. We found that it is more difficult for rats to detect LS than HS targets. Although sniffing bouts are the same duration for each group (∼500 ms), sniffing longer and using more inhalations results in better performance for rats assigned to detect LS targets. LS-detecting rats also increase the duration of individual inhalations (81 ms for LS- vs 69 ms for HS-detecting rats) and sniff at lower frequencies (7.8 Hz for LS- vs 8.6 Hz for HS-detecting rats) when learning to sense the target. When LS-detecting rats do discriminate well, they do so with lower airflow, more sniffs, and lower frequency of sniffing than HS-detecting counterparts. These data show that rats adjust sniff strategies as a function of odorant sorptiveness and provide support for the chromatographic and zonation hypotheses.

Rat behavior in go/no-go and two-alternative choice odor discrimination: differences and similarities.

To elucidate the cognitive structures of animals, neuroscientists use several behavioral tasks. Therefore, it is imperative to have a firm understanding of each task's behavioral parameters in order to parse out possible task effects. We compare two operant discrimination tasks (Go/No-Go: GNG; Two-Alternative Choice: TAC) that are commonly used in olfactory research. Past research has suggested that solving the two tasks requires divergent cognitive strategies. One hypothesis is that the two tasks differ in how an animal optimizes reward rate by means of a speed-accuracy trade-off (SAT). If this is true, then changing tasks could give researchers an additional tool to understand animal cognition. However, no study has systematically analyzed the two tasks in parallel using odor stimuli. Using standardized training protocols, we test GNG and TAC in parallel. Our protocols allow us to isolate the stimulus sampling period from a general reaction time period. We find that the two tasks do not differ with regard to the stimulus sampling period and conclude that the two tasks do not differ in the amount of time it takes an animal to perform a discrimination. Instead, tasks differ in the time it takes to make an overt behavioral response, with GNG showing shorter periods than TAC. We also find no evidence of rats using either task-specific or intertrial interval-dependent SAT schema in order to optimize reward rate. We show that similarities between dependent variables, with the possible exception of response delay, appear to be under experimenter control.

Olfactory oscillations: the what, how and what for.

Olfactory system oscillations play out with beautiful temporal and behavioral regularity on the oscilloscope and seem to scream 'meaning'. Always there is the fear that, although attractive, these symbols of dynamic regularity might be just seductive epiphenomena. There are now many studies that have isolated some of the neural mechanisms involved in these oscillations, and recent work argues that they are functional and even necessary at the physiological and cognitive levels. However, much remains to be done for a full understanding of their functions.

Olfactory system gamma oscillations: the physiological dissection of a cognitive neural system.

Oscillatory phenomena have been a focus of dynamical systems research since the time of the classical studies on the pendulum by Galileo. Fast cortical oscillations also have a long and storied history in neurophysiology, and olfactory oscillations have led the way with a depth of explanation not present in the literature of most other cortical systems. From the earliest studies of odor-evoked oscillations by Adrian, many reports have focused on mechanisms and functional associations of these oscillations, in particular for the so-called gamma oscillations. As a result, much information is now available regarding the biophysical mechanisms that underlie the oscillations in the mammalian olfactory system. Recent studies have expanded on these and addressed functionality directly in mammals and in the analogous insect system. Sub-bands within the rodent gamma oscillatory band associated with specific behavioral and cognitive states have also been identified. All this makes oscillatory neuronal networks a unique interdisciplinary platform from which to study neurocognitive and dynamical phenomena in intact, freely behaving animals. We present here a summary of what has been learned about the functional role and mechanisms of gamma oscillations in the olfactory system as a guide for similar studies in other cortical systems.