Sense Research Articles

Attention rhythmically shapes sensory tuning.

Attention is key to perception and human behavior, and evidence shows that it periodically samples sensory information (<20Hz). However, this view has been recently challenged due to methodological concerns and gaps in our understanding of the function and mechanism of rhythmic attention. Here we used an intensive ∼22-hour psychophysical protocol combined with reverse correlation analyses to infer the neural representation underlying these rhythms. Participants (male/female) performed a task in which covert spatial (sustained and exploratory) attention was manipulated, and then probed at various delays. Our results show that sustained and exploratory attention periodically modulate perception via different neural computations. While sustained attention suppresses distracting stimulus features at the alpha (∼12Hz) frequency, exploratory attention increases the gain around task-relevant stimulus feature at the theta (∼6Hz) frequency. These findings reveal that both modes of rhythmic attention differentially shape sensory tuning, expanding the current understanding of the rhythmic sampling theory of attention.Significance statement For the past decade, low-frequency rhythms have been observed in attentional performance. Here, we go beyond description and assess the underlying neural computations in the sensory system. We used an intensive psychophysical protocol combined with reverse correlation analysis to infer the system's sensitivity to and selectivity for stimulus feature (orientation) across time, and for two attention modes, i.e., sustained and exploratory attention. Our results reveal that sustained and exploratory attention modes differentially shape the sensory tuning to stimulus features: respectively altering either noise suppression or signal enhancement rhythmically, leading to alternating periods of performance enhancement and decrement.

Complementary Organization of Mouse Driver and Modulator Cortico-Thalamo-Cortical Circuits.

Corticocortical (CC) projections in the visual system facilitate hierarchical processing of sensory information. In addition to direct CC connections, indirect cortico-thalamo-cortical (CTC) pathways through the pulvinar nucleus of the thalamus can relay sensory signals and mediate cortical interactions according to behavioral demands. While the pulvinar connects extensively to the entire visual cortex, it is unknown whether transthalamic pathways link all cortical areas or whether they follow systematic organizational rules. Because mouse pulvinar neurons projecting to different areas are spatially intermingled, their input/output relationships have been difficult to characterize using traditional anatomical methods. To determine the organization of CTC circuits, we mapped the higher visual areas (HVAs) of male and female mice with intrinsic signal imaging and targeted five pulvinar→HVA pathways for projection-specific rabies tracing. We aligned post-mortem cortical tissue to in vivo maps for precise quantification of the areas and cell types projecting to each pulvinar→HVA population. Layer 5 corticothalamic (L5CT) "driver" inputs to the pulvinar originate predominantly from primary visual cortex (V1), consistent with the CC hierarchy. L5CT inputs from lateral HVAs specifically avoid driving reciprocal connections, consistent with the "no-strong-loops" hypothesis. Conversely, layer 6 corticothalamic (L6CT) "modulator" inputs are distributed across areas and are biased toward reciprocal connections. Unlike previous studies in primates, we find that every HVA receives disynaptic input from the superior colliculus. CTC circuits in the pulvinar thus depend on both target HVA and input cell type, such that driving and modulating higher-order pathways follow complementary connection rules similar to those governing first-order CT circuits.Significance statement Understanding the function of the pulvinar will require knowledge of its anatomical connections. Using state-of-the-art rabies tracing, we establish a map of brain-wide and CTC pulvinar connections. While the primate tectopulvinar pathway selectively targets dorsal visual areas, we find ubiquitous SC input in the mouse. This extrageniculate projection supports unconscious visually-guided behavior, suggesting that all visual cortical areas contribute to such functions in mice. Our results also unify longstanding anatomical hypotheses. Namely, "driver" CTC inputs are feedforward relays and adhere to the "no-strong-loops" hypothesis. "Modulator" L6CT inputs are overrepresented in the target HVA, reflecting the reciprocal connectivity described in previous bulk tracing studies. Together, these findings constitute a comprehensive map to guide future experimental and theoretical studies of pulvinar function.

Superior colliculus controls the activity of the substantia nigra pars compacta and ventral tegmental area in an asymmetrical manner.

Dopaminergic (DA) neurons of the substantia nigra pars compacta (SNc) and ventral tegmental area (VTA) play a crucial role in controlling animals' orienting and approach behaviors toward relevant environmental stimuli. The ventral midbrain receives sensory input from the superior colliculus (SC), a tectal region processing information from contralateral receptive fields of various modalities. Given the significant influence of dopamine release imbalance in the left and right striatum on animals' movement direction, our study aimed to investigate the lateralization of the connection between the lateral SC and the midbrain DA system in male rats. We explored the circuit's anatomy using transsynaptic viral tract-tracing, and its physiology using in vivo single unit and ex vivo multielectrode array recordings of SNc and VTA neuronal activity combined with optogenetic stimulation of either ipsilateral or contralateral SC or its terminals. During the experiments, DA neurons were identified optogenetically (in vivo recordings) or pharmacologically (ex vivo recordings). Anatomical findings revealed a bilateral innervation pattern of the lateral SC to the ventral midbrain, with a significantly stronger ipsilateral connection, particularly evident in the SNc, involving both DA and non-DA neurons. This anatomical asymmetry was also expressed during in vivo and ex vivo recordings, which showed a predominance of ipsilateral connection, especially within the SNc. Ex vivo recordings also confirmed that this lateralized pathway is direct. The described features of the SC to VTA/SNc neuronal circuit, particularly its anatomical and physiological asymmetry, suggest its involvement in orienting and approach behaviors guided by the direction of incoming sensory stimuli.Significance statement The direction of animals' behavior is a manifestation of asymmetry in dopamine (DA) release between the left and right striatum - unilateral activation of DA neurons biases movement towards the contralateral side. Our study demonstrates that such activation is induced by the ipsilateral superior colliculus (SC), which processes sensory information from the contralateral body side. Notably, our previous findings indicate that the SC innervates and activates the rostromedial tegmental nucleus, a primary inhibitory input to the DA system, albeit in the contralateral hemisphere. Thus, our research describes a SC-originating neuronal circuit that directly enhances the activity of ipsilateral DA neurons while simultaneously diminishing the activity of contralateral DA neurons, thereby amplifying the imbalance in DA release between the hemispheres.

Specification of claustro-amygdalar and palaeocortical neurons and circuits.

The ventrolateral pallial (VLp) excitatory neurons in the claustro-amygdalar complex and piriform cortex (PIR; which forms part of the palaeocortex) form reciprocal connections with the prefrontal cortex (PFC), integrating cognitive and sensory information that results in adaptive behaviours1-5. Early-life disruptions in these circuits are linked to neuropsychiatric disorders4-8, highlighting the importance of understanding their development. Here we reveal that the transcription factors SOX4, SOX11 and TFAP2D have a pivotal role in the development, identity and PFC connectivity of these excitatory neurons. The absence of SOX4 and SOX11 in post-mitotic excitatory neurons results in a marked reduction in the size of the basolateral amygdala complex (BLC), claustrum (CLA) and PIR. These transcription factors control BLC formation through direct regulation of Tfap2d expression. Cross-species analyses, including in humans, identified conserved Tfap2d expression in developing excitatory neurons of BLC, CLA, PIR and the associated transitional areas of the frontal, insular and temporal cortex. Although the loss and haploinsufficiency of Tfap2d yield similar alterations in learned threat-response behaviours, differences emerge in the phenotypes at different Tfap2d dosages, particularly in terms of changes observed in BLC size and BLC-PFC connectivity. This underscores the importance of Tfap2d dosage in orchestrating developmental shifts in BLC-PFC connectivity and behavioural modifications that resemble symptoms of neuropsychiatric disorders. Together, these findings reveal key elements of a conserved gene regulatory network that shapes the development and function of crucial VLp excitatory neurons and their PFC connectivity and offer insights into their evolution and alterations in neuropsychiatric disorders.

Structural changes of muscle spindles in the multifidus muscle after intervertebral disk injury are resolved by targeted muscle activation.

Fibrosis of muscle spindles (sensory organs) in back muscles induced by intervertebral disc (IVD) degeneration could limit transmission of muscle stretch to the sensory receptor and explain the proprioceptive deficits common in back pain. Exercise reduces back muscles fibrosis. This study investigated whether targeted muscle activation via neurostimulation reverses or resolves muscle spindle fibrosis in a model of IVD injury. In eighteen sheep, lumbar (L)1-2 and L3-4 IVD degeneration was induced by partial thickness anulus fibrosis incision and a neurostimulator was implanted. After IVD-degeneration developed for 3 months, neurostimulation of the L2 nerve root activated multifidus in nine randomly selected animals. Multifidus muscle adjacent to the spinous process of L2 (non-stimulated) and L4 (stimulated) was harvested 3 months after activation. Muscle spindles were identified in Van Giessen's-stained sections. Connective tissue spindle capsule thickness, and cross-sectional area (CSA) of the spindle, its periaxial fluid and sensory elements were measured. Immunofluorescence assays evaluated Collagen-I and -III. Multifidus muscle spindle capsule thickness and Collagen-1 were significantly less in the neurostimulation animals than IVD-injury animals at L4 (stimulated muscle) (P < 0.05), but not L2 (non-stimulated muscle). Spindle capsule thickness was less in lateral than medial regions. CSA of the muscle spindle and sensory elements was less in neurostimulated animals at L4. Targeted multifidus activation reverses or prevents accumulation of connective tissue of the multifidus muscle spindle capsule caused by IVD injury. Reduced fibrosis should maintain sensory function of this important muscle mechanoreceptor and might provide an effective solution to resolve the commonly identified proprioceptive deficits in back pain and maintain healthy spine function.

Developing a brain inspired multilobar neural networks architecture for rapidly and accurately estimating concrete compressive strength

Concrete compressive strength is a critical parameter in construction and structural engineering. Destructive experimental methods that offer a reliable approach to obtaining this property involve time-consuming procedures. Recent advancements in artificial neural networks (ANNs) have shown promise in simplifying this task by estimating it with high accuracy. Nevertheless, conventional ANNs often require deep networks to achieve acceptable results in cases with large datasets and where generalization is required for a variety of mixtures. This leads to increased training durations and susceptibility to noise, causing reduced accuracy and potential information loss in deep networks. In order to address these limitations, this study introduces a novel multi-lobar artificial neural network (MLANN) architecture inspired by the brain’s lobar processing of sensory information, aiming to improve the accuracy and efficiency of estimating concrete compressive strength. The MLANN framework employs various architectures of hidden layers, referred to as “lobes,” each with a unique arrangement of neurons to optimize data processing, reduce training noise, and expedite training time. Within the study context, an MLANN is developed, and its performance is evaluated to predict the compressive strength of concrete. Moreover, it is compared against two traditional cases, ANN and ensemble learning neural networks (ELNN). The study results indicated that the MLANN architecture significantly improves the estimation performance, reducing the root mean square error by up to 32.9% and mean absolute error by up to 25.9% while also enhancing the A20 index by up to 17.9%, ensuring a more robust and generalizable model. This advancement in model refinement can ultimately enhance the design and analysis processes in civil engineering, leading to more reliable and cost-effective construction practices.

Elongator is a microtubule polymerase selective for polyglutamylated tubulin.

Elongator is a tRNA-modifying complex that regulates protein translation. Recently, a moonlighting function of Elongator has been identified in regulating the polarization of the microtubule cytoskeleton during asymmetric cell division. Elongator induces symmetry breaking of the anaphase midzone by selectively stabilizing microtubules on one side of the spindle, contributing to the downstream polarized segregation of cell-fate determinants, and therefore to cell fate determination. Here, we investigate how Elongator controls microtubule dynamics. Elongator binds both to the tip of microtubules and to free GTP-tubulin heterodimers using two different subcomplexes, Elp123 and Elp456, respectively. We show that these activities must be coupled for Elongator to decrease the tubulin critical concentration for microtubule elongation. As a consequence, Elongator increases the growth speed and decreases the catastrophe rate of microtubules. Surprisingly, the Elp456 subcomplex binds to tubulin tails and has strong selectivity towards polyglutamylated tubulin. Hence, microtubules assembled by Elongator become selectively enriched with polyglutamylated tubulin, as observed in vitro, in mouse and Drosophila cell lines, as well as in vivo in Drosophila Sensory Organ Precursor cells. Therefore, Elongator rewrites the tubulin code of growing microtubules, placing it at the core of cytoskeletal dynamics and polarization during asymmetric cell division.

Robustly Flexible Wearable Electronic Textiles Enabled by Polymer Brush-Assisted Metal Deposition for Human Motion Sensing

Robustly Flexible Wearable Electronic Textiles Enabled by Polymer Brush-Assisted Metal Deposition for Human Motion Sensing

Suboptimal but intact integration of Bayesian components during perceptual decision-making in autism

BackgroundAlterations in sensory perception, a core phenotype of autism, are attributed to imbalanced integration of sensory information and prior knowledge during perceptual statistical (Bayesian) inference. This hypothesis has gained momentum in recent years, partly because it can be implemented both at the computational level, as in Bayesian perception, and at the level of canonical neural microcircuitry, as in predictive coding. However, empirical investigations have yielded conflicting results with evidence remaining limited. Critically, previous studies did not assess the independent contributions of priors and sensory uncertainty to the inference.MethodWe addressed this gap by quantitatively assessing both the independent and interdependent contributions of priors and sensory uncertainty to perceptual decision-making in autistic and non-autistic individuals (N = 126) during an orientation categorization task.ResultsContrary to common views, autistic individuals integrated the two Bayesian components into their decision behavior, and did so indistinguishably from non-autistic individuals. Both groups adjusted their decision criteria in a suboptimal manner.LimitationsThis study focuses on explicit priors in a perceptual categorization task and high-functioning adults. Thus, although the findings provide strong evidence against a general and basic alteration in prior integration in autism, they cannot rule out more specific cases of reduced prior effect – such as due to implicit prior learning, particular level of decision making (e.g., social), and level of functioning of the autistic person.ConclusionsThese results reveal intact inference for autistic individuals during perceptual decision-making, challenging the notion that Bayesian computations are fundamentally altered in autism.

Image-Driven Hybrid Structural Analysis Based on Continuum Point Cloud Method with Boundary Capturing Technique

Conventional approaches for the structural health monitoring of infrastructures often rely on physical sensors or targets attached to structural members, which require considerable preparation, maintenance, and operational effort, including continuous on-site adjustments. This paper presents an image-driven hybrid structural analysis technique that combines digital image processing (DIP) and regression analysis with a continuum point cloud method (CPCM) built on a particle-based strong formulation. Polynomial regressions capture the boundary shape change due to the structural loading and precisely identify the edge and corner coordinates of the deformed structure. The captured edge profiles are transformed into essential boundary conditions. This allows the construction of a strongly formulated boundary value problem (BVP), classified as the Dirichlet problem. Capturing boundary conditions from the digital image is novel, although a similar approach was applied to the point cloud data. It was shown that the CPCM is more efficient in this hybrid simulation framework than the weak-form-based numerical schemes. Unlike the finite element method (FEM), it can avoid aligning boundary nodes with regression points. A three-point bending test of a rubber beam was simulated to validate the developed technique. The simulation results were benchmarked against numerical results by ANSYS and various relevant numerical schemes. The technique can effectively solve the Dirichlet-type BVP, yielding accurate deformation, stress, and strain values across the entire problem domain when employing a linear strain model and increasing the number of CPCM nodes. In addition, comparative analysis with conventional displacement tracking techniques verifies the developed technique’s robustness. The proposed technique effectively circumvents the inherent limitations of traditional monitoring methods resulting from the reliance on physical gauges or target markers so that a robust and non-contact solution for remote structural health monitoring in real-scale infrastructures can be provided, even in unfavorable experimental environments.

A REVIEW ARTICLE ON PHYSIOLOGY OF VISION

The visual pathway predominantly travels beneath the cortex for most of its length. Visual signals in the optic nerves may intersect at the chiasma and then proceed through the optic tracts. The term Ayurveda derives from two words: "Ayu," meaning life, and "Ved," signifying knowledge or science. Therefore, "AYURVEDA" as a whole translates to "the science of life." According to Ayurvedic principles, the universe consists of five funda-mental elements. The body maintains an ideal equilibrium of these elements, and any disruption to this balance results in a state of unhealthiness we refer to as illness. The classical texts of Ayurveda provide detailed insights into the physiology of the sense organs, sensation, perception, and the mind's role in the perception process in an exceptional manner. Indriya (sense faculty) serves as the specialized tool that helps the soul in recognizing even the slightest changes in both the external and internal environments. Indriya acts as the essential element that differentiates living entities from non-living ones. The concept of Indriya pancha panchak, introduced by Achar-ya Charaka, delves into both the anatomical and physiological features of the sense organs. The five sensory faculties include sight (chakshurendriya), hearing (shrotrendriya), smell (ghranendriya), taste (rasanendriya), and touch (sparshnendriya). Each sensory faculty is associated with a specific object: sound (shabda) pertains to hearing, touch (sparsha) relates to the tactile sense, color (rupa) corresponds to sight, taste (rasa) is associated with the gustatory sense, and smell (gandha) links with the olfactory sense organ. Every sensory faculty pos-sesses an excess of one material element. Developed from particular material constituents, each specific sense faculty perceives the properties of its corresponding element. The mechanics of how the external world is per-ceived is referred to as the visual process or the physiology of vision. Ayurveda introduces a special concept known as the Tridosha theory. The three fundamental elements of the human body are collectively termed Tridosha (Vata, Pitta, Kapha). The Tridosha governs the physiological and voluntary activities of the body. Ayur-veda elaborates on the physiology of vision by considering the roles of vata and pitta. Pitta encompasses five different types: Ranjak, Pachak, Alochak, Sadhak, and Bhrajak. The "Alochak Pitta" is recognized as the seat of "Drishti." The retinal pigments Rhodopsin, Iodopsin, and Melanin symbolize Alochak Pitta. Alochak pitta is fur-ther categorized into two types: chakshu vaisheshik located in the eye and buddhi vaisheshik found in the brain. There are three stages in this visual process: the light refraction phase, the phase in which light energy is trans-formed into an electrical impulse, and lastly, the peripheral and central neurophysiology involving the geniculate bodies and optic radiations prior to synapsing in the occipital cortex.

Mapping patterns of thought onto brain activity during movie-watching.

Movie-watching is a central aspect of our lives and an important paradigm for understanding the brain mechanisms behind cognition as it occurs in daily life. Contemporary views of ongoing thought argue that the ability to make sense of events in the 'here and now' depend on the neural processing of incoming sensory information by auditory and visual cortex, which are kept in check by systems in association cortex. However, we currently lack an understanding of how patterns of ongoing thoughts map onto the different brain systems when we watch a film, partly because methods of sampling experience disrupt the dynamics of brain activity and the experience of movie-watching. Our study established a novel method for mapping thought patterns onto the brain activity that occurs at different moments of a film, which does not disrupt the time course of brain activity or the movie-watching experience. We found moments when experience sampling highlighted engagement with multi-sensory features of the film or highlighted thoughts with episodic features, regions of sensory cortex were more active and subsequent memory for events in the movie was better-on the other hand, periods of intrusive distraction emerged when activity in regions of association cortex within the frontoparietal system was reduced. These results highlight the critical role sensory systems play in the multi-modal experience of movie-watching and provide evidence for the role of association cortex in reducing distraction when we watch films.

Notch1 is required to maintain supporting cell identity and vestibular function during maturation of the mammalian balance organs.

The inner ear houses both hearing and balance sensory modalities. The hearing and balance organs consist of similar cell types, including sensory hair cells and associated supporting cells. Previously we showed that Notch1 is required for maintaining supporting cell survival during cochlear maturation. To understand the role of Notch during vestibular maturation, we deleted Notch1 from the vestibular organs of both male and female mice at birth. Histological analyses showed a reduction of supporting cells accompanied by an increase in type II hair cells, indicating a conversion of supporting cells to hair cells. Analysis of mature sensory organs indicate the converted hair cells survive, despite a severe reduction of supporting cells. Vestibular sensory evoked potentials (VsEPs), thought to be generated within the striola regions of the maculae, were absent, indicating that NOTCH1 is critical for striolar function. Specialized type I hair cells in the striola failed to develop the complex calyces typical of these cells. Notch1 mutants did not exhibit vestibular behaviors such as circling and head shaking, but showed difficulties with tests of balance and swimming. These results indicate that, unlike the cochlea, supporting cells in balance organs retain the plasticity to convert to hair cells which can survive into adulthood. Despite hair cell survival, vestibular function is compromised likely due to the loss of supporting cells and altered innervation.Significance Statement While the role of Notch has been investigated thoroughly during cochlear development and maturation, less is known about how Notch regulates vestibular maturation. Here, we show that deletion of Notch1 results in vestibular physiological and behavioral dysfunction by 3 months of age. In contrast to the cochlea, vestibular supporting cells retained the ability to convert to hair cells, and survived into adulthood. However, some specialized hair cells in the central region of the vestibular organs were reduced and not innervated properly. These results show that vestibular supporting cells retain the ability to convert to hair cells during maturation and can be manipulated by altering Notch signaling.

Prior Information Shapes Perceptual Confidence.

Decisional confidence refers to the subjective evaluation of the accuracy of a decision based on sensory information. While these judgments are typically grounded in the strength of evidence leading to a decision, they are also subjected to influence from top-down factors such as prior expectations. Previous research has highlighted the impact of prior information on decision parameters such as reaction times and decision criteria placement. However, a comprehensive understanding of how prior information shapes confidence ratings is still lacking. In this study, we manipulate prior knowledge by inducing varying levels of target probability expectation (low: 33%, random: 50%, high: 67%) in a perceptual detection task. In each trial both type-1 (detection) and type-2 (confidence) responses were recorded. First, we replicate previous findings, demonstrating that decisional priors impact decision criteria but not task sensitivity. Secondly, we reveal the strong effect that prior expectations exert on type-2 decisions, with this influence being moderated by a congruency effect between the given prior, the actual stimulus presented, and the provided response. Moreover, we find that confidence is higher in correct compared to incorrect responses, with low-probability trials leading to higher confidence judgments in correct choices compared to random and liberal trials. Finally, we unveil that prior-dependent modulation rates in criterion and confidence were positively associated. These results underscore the intricate interplay between prior expectations, decision-making, and confidence levels, demonstrating that what we perceive is not solely a data-driven phenomenon but can be already shaped by the available information about the state of the world.

Capillary connections between sensory circumventricular organs and adjacent parenchyma enable local volume transmission.

Among contributors to diffusible signaling are portal systems which join two capillary beds through connecting veins. Portal systems allow diffusible signals to be transported in high concentrations directly from one capillary bed to the other without dilution in the systemic circulation. Two portal systems have been identified in the brain. The first was discovered almost a century ago and connects the median eminence to the anterior pituitary gland. The second was discovered a few years ago and links the suprachiasmatic nucleus to the organum vasculosum of the lamina terminalis, a sensory circumventricular organ (CVO). Sensory CVOs bear neuronal receptors for sensing signals in the fluid milieu. They line the surface of brain ventricles and bear fenestrated capillaries thereby lacking blood-brain barriers. It is not known whether the other sensory CVOs, namely the subfornical organ (SFO), and area postrema (AP) form portal neurovascular connections with nearby parenchymal tissue. To preserve the integrity of the vasculature of CVOs and their adjacent neuropil, we combined iDISCO clearing and light-sheet microscopy to acquire volumetric images of blood vessels and traced the vasculature in two experiments. In the first, the whole brain vasculature was registered to the Allen Brain Atlas in order to identify the nuclei to which the SFO and AP are attached. In the second study, regionally specified immunolabeling was used to identify the attachment sites and vascular connections between the AP, and the SFO to their respective parenchymal attachment sites. There are venous portal pathways linking the capillary vessels of the SFO and the posterior septal nuclei, namely the septofimbrial nucleus and the triangular nucleus of the septum. Unlike the arrangement of portal vessels, the AP and the nucleus of the solitary tract share a common capillary bed. Taken together, the results reveal that all three sensory CVOs bear direct capillary connections to adjacent neuropil, providing a direct route for diffusible signals to travel from their source to their targets.

Imageless imagery in aphantasia revealed by early visual cortex decoding.

Activity in the early visual cortex is thought to tightly couple with conscious experience, including feedback-driven mental imagery. However, in aphantasia (a complete lack of visual imagery), the state of mental imagery, what takes its place, or how any activity relates to qualia remains unknown. This study analyzed univariate (amplitude) and multivariate (decoding) blood-oxygen-level-dependent (BOLD) signals in primary visual cortex during imagery attempts. "Imagery" content could be decoded equally well in both groups; however, unlike in those with imagery, neural signatures in those with validated aphantasia were ipsilateral and could not be cross-decoded with perceptual representations. Further, the perception-induced BOLD response was lower in those with aphantasia compared with controls. Together, these data suggest that an imagery-related representation, but with less or transformed sensory information, exists in the primary visual cortex of those with aphantasia. Our data challenge the classic view that activity in primary visual cortex should result in sensory qualia.

Sublethal Urea Exposure in Nile Tilapia: Morphological, Behavioural, and Histological Alteration.

The pace of research efforts has been extraordinarily accelerated across the globe to address the contamination issues caused by pesticides, and fertilizers, especially in the aquatic ecosystem. The sole aim of this study was to assess the effect of urea on Nile Tilapia (Oreochromis niloticus). For this purpose, the fish fingerlings were exposed to increasing concentrations of urea such as 0, 1, 2.5, 5, 10, 20, and 40 g/l for 72 hr. Survival analysis suggested a strong correlation between the increasing doses of urea and the mortality rate among tested fingerlings. This study reported remarkable morphological, and behavioural alternation such as increased operculum movement, bottom-dwelling, lethargy, secretion of mucus, reduction in food intake, and bleeding in the fin and around the mouth in the treated group. Haematological analysis revealed that a significant reduction in RBC count and Hb along with an increase in WBC number is associated with urea toxicity. Our study showed a significant rise in glucose concentration upon urea toxicity in Nile tilapia fingerlings for the first time, emphasizing the adverse effect of fertilizers on carbohydrate metabolism. Significant rises in the enzymatic activity such as alanine aminotransferase (ALT), alkaline phosphatase (ALP), and aspartate aminotransferase (AST) upon urea treatment emphasize the possibilities of liver damage, biliary obstruction, and abnormal glucose metabolism. Histological analysis of urea-treated fish compared to normal fish revealed that urea toxicity drastically altered the tissue architecture of fish's gills, eyes, intestine, and stomach. As the visual systems of mammals and fish resemble in more aspects, our findings may be useful in understanding the impact of pollutants on sensory organs concerning humans. We conclude that our findings highlight the importance of urea toxicity on Nile tilapia fingerlings and invite multidisciplinary research to uncover molecular mechanisms underlying urea toxicity.

Sustained EEG responses to rapidly unfolding stochastic sounds reflect Bayesian inferred reliability tracking.

How does the brain track and process rapidly changing sensory information? Current computational accounts suggest that our sensations and decisions arise from the intricate interplay between bottom-up sensory signals and constantly changing expectations regarding the statistics of the surrounding world. A significant focus of recent research is determining which statistical properties are tracked by the brain as it monitors the rapid progression of sensory information. Here, by combining EEG (three experiments N ≥ 22 each) and computational modelling, we examined how the brain processes rapid and stochastic sound sequences that simulate key aspects of dynamic sensory environments. Passively listening participants were exposed to structured tone-pip arrangements that contained transitions between a range of stochastic patterns. Predictions were guided by a Bayesian predictive inference model. We demonstrate that listeners automatically track the statistics of unfolding sounds, even when these are irrelevant to behaviour. Transitions between sequence patterns drove a shift in the sustained EEG response. This was observed to a range of distributional statistics, and even in situations where behavioural detection of these transitions was at floor. These observations suggest that the modulation of the EEG sustained response reflects a process of belief updating within the brain. By establishing a connection between the outputs of the computational model and the observed brain responses, we demonstrate that the dynamics of these transition-related responses align with the tracking of "precision" - the confidence or reliability assigned to a predicted sensory signal - shedding light on the intricate interplay between the brain's statistical tracking mechanisms and its response dynamics.

“Decoding Ambiguity”: Asian Elephants’ (Elephas maximus) use previous experiences and sensory information to make decisions regarding ambiguity

“Decoding Ambiguity”: Asian Elephants’ (Elephas maximus) use previous experiences and sensory information to make decisions regarding ambiguity

Anesthesia alters complexity of spontaneous and stimulus-related neuronal firing patterns in rat visual cortex

Complexity of neuronal firing patterns may serve as an indicator of sensory information processing across different states of consciousness. Recent studies have shown that spontaneous changes in brain states can occur during general anesthesia, which may influence neuronal complexity and the state of consciousness. In this study, we investigated how the firing patterns of cortical neurons, both at rest and during visual stimulation, are affected by spontaneously changing brain states under varying levels of anesthesia. Extracellular unit activity was measured in the primary visual cortex of unrestrained rats as the inhaled concentration of desflurane was incrementally reduced to 6%, 4%, 2%, and 0%. Using dimensionality reduction and density-based clustering on individual unit activities, we identified five distinct population states, which underwent dynamic transitions independent of the anesthetic level during both resting and stimulus conditions. One population state that occurred mainly in deep anesthesia exhibited a paradoxically increased number of active neurons and asynchronous spiking, suggesting a spontaneous reversal towards an awake-like condition. However, this was contradicted by the observation of low neuronal complexity in both spontaneous and stimulus-related spike activity, which more closely aligns with unconsciousness. Our findings reveal that transient neuronal states with distinct spiking patterns can emerge in visual cortex at constant anesthetic concentrations. The reduced complexity in states associated with deep anesthesia likely indicates a disruption of conscious sensory information processing.