Visual Brain Research Articles

Mouse visual cortex as a limited resource system that self-learns an ecologically-general representation.

Studies of the mouse visual system have revealed a variety of visual brain areas that are thought to support a multitude of behavioral capacities, ranging from stimulus-reward associations, to goal-directed navigation, and object-centric discriminations. However, an overall understanding of the mouse's visual cortex, and how it supports a range of behaviors, remains unknown. Here, we take a computational approach to help address these questions, providing a high-fidelity quantitative model of mouse visual cortex and identifying key structural and functional principles underlying that model's success. Structurally, we find that a comparatively shallow network structure with a low-resolution input is optimal for modeling mouse visual cortex. Our main finding is functional-that models trained with task-agnostic, self-supervised objective functions based on the concept of contrastive embeddings are much better matches to mouse cortex, than models trained on supervised objectives or alternative self-supervised methods. This result is very much unlike in primates where prior work showed that the two were roughly equivalent, naturally leading us to ask the question of why these self-supervised objectives are better matches than supervised ones in mouse. To this end, we show that the self-supervised, contrastive objective builds a general-purpose visual representation that enables the system to achieve better transfer on out-of-distribution visual scene understanding and reward-based navigation tasks. Our results suggest that mouse visual cortex is a low-resolution, shallow network that makes best use of the mouse's limited resources to create a light-weight, general-purpose visual system-in contrast to the deep, high-resolution, and more categorization-dominated visual system of primates.

P18 Bullous leukocytoclastic vasculitis in a patient with known undifferentiated autoimmune rheumatic disease

P18 Bullous leukocytoclastic vasculitis in a patient with known undifferentiated autoimmune rheumatic disease

Retina-derived signals control pace of neurogenesis in visual brain areas but not circuit assembly

Brain development is orchestrated by both innate and experience-dependent mechanisms, but their relative contributions are difficult to disentangle. Here we asked if and how central visual areas are altered in a vertebrate brain depleted of any and all signals from retinal ganglion cells throughout development. We transcriptionally profiled neurons in pretectum, thalamus and other retinorecipient areas of larval zebrafish and searched for changes in lakritz mutants that lack all retinal connections. Although individual genes are dysregulated, the complete set of 77 neuronal types develops in apparently normal proportions, at normal locations, and along normal differentiation trajectories. Strikingly, the cell-cycle exits of proliferating progenitors in these areas are delayed, and a greater fraction of early postmitotic precursors remain uncommitted or are diverted to a pre-glial fate. Optogenetic stimulation targeting groups of neurons normally involved in processing visual information evokes behaviors indistinguishable from wildtype. In conclusion, we show that signals emitted by retinal axons influence the pace of neurogenesis in visual brain areas, but do not detectably affect the specification or wiring of downstream neurons.

A representation of abstract linguistic categories in the visual system underlies successful lipreading

There is considerable debate over how visual speech is processed in the absence of sound and whether neural activity supporting lipreading occurs in visual brain areas. Much of the ambiguity stems from a lack of behavioral grounding and neurophysiological analyses that cannot disentangle high-level linguistic and phonetic/energetic contributions from visual speech. To address this, we recorded EEG from human observers as they watched silent videos, half of which were novel and half of which were previously rehearsed with the accompanying audio. We modeled how the EEG responses to novel and rehearsed silent speech reflected the processing of low-level visual features (motion, lip movements) and a higher-level categorical representation of linguistic units, known as visemes. The ability of these visemes to account for the EEG – beyond the motion and lip movements – was significantly enhanced for rehearsed videos in a way that correlated with participants’ trial-by-trial ability to lipread that speech. Source localization of viseme processing showed clear contributions from visual cortex, with no strong evidence for the involvement of auditory areas. We interpret this as support for the idea that the visual system produces its own specialized representation of speech that is (1) well-described by categorical linguistic features, (2) dissociable from lip movements, and (3) predictive of lipreading ability. We also suggest a reinterpretation of previous findings of auditory cortical activation during silent speech that is consistent with hierarchical accounts of visual and audiovisual speech perception.

Pulvinar quantitative susceptibility mapping predicts visual hallucinations post-deep brain stimulation in Parkinson's disease.

We have reported the relationship between low pulvinar nuclei (PN) intensity in susceptibility-weighted imaging and the appearance of visual hallucinations and cognitive function. The aim of the study was to examine the changes in the quantitative susceptibility mapping (QSM) in patients with Parkinson's disease (PD) who underwent deep brain stimulation (DBS) and verify whether the PN susceptibility value (SV) on QSM can predict visual hallucination and cognitive changes after DBS. This study examined 24 patients with PD who underwent DBS along with QSM imaging on magnetic resonance imaging (MRI). All MRIs were performed within 3 months before surgery. The PN SV was further assessed based on the QSM. Then, associations were examined among cognitive changes, hallucination, and PN SV. The cognitive function of the patient was compared immediately before surgery and at 1 year postoperatively. Visual hallucinations were observed in seven patients during the follow-up period. The PN SV was ≥0.045ppm in nine patients with PD, and six of them had visual hallucinations, whereas only one of 15 patients with PD with SV of<0.045ppm had visual hallucinations (Fisher's exact test, p = .0037). The SV of>0.045ppm at the PN in QSM in patients with PD may provide useful information suggesting visual hallucination and cognitive deterioration after DBS treatment.

Contributions of the Basal Ganglia to Visual Perceptual Decisions.

The basal ganglia (BG) make up a prominent nexus between visual and motor-related brain regions. In contrast to the BG's well-established roles in movement control and value-based decision making, their contributions to the transformation of visual input into an action remain unclear, especially in the context of perceptual decisions based on uncertain visual evidence. This article reviews recent progress in our understanding of the BG's contributions to the formation, evaluation, and adjustment of such decisions. From theoretical and experimental perspectives, the review focuses on four key stations in the BG network, namely, the striatum, pallidum, subthalamic nucleus, and midbrain dopamine neurons, which can have different roles and together support the decision process.

Invited Session IV: Studies of the visual cortex with sub-millimeter resolution: Imaging the visual brain at high spatiotemporal resolution.

Since the discovery of orientation-selective neurons in the cat primary visual cortex (V1), how the mammalian nervous system computes the orientation of visual stimuli has been a flagship question in neuroscience. With the recent advances in in vivo imaging of neural activity using genetically encoded indicators and two-photon fluorescence microscopy, we can now achieve synapse-resolving functional imaging and kilohertz imaging of membrane voltage in the mouse V1. I will describe our recent advancements in imaging visual processing at high spatiotemporal resolution, as well as two studies on the orientation selectivity of neurons in the mouse visual pathway.

Fixation-related fMRI analysis reveals the neural basis of natural reading of unspaced and spaced Chinese sentences.

Although there are many eye-movement studies focusing on natural sentence reading and functional magnetic resonance imaging research on reading with serial visual presentation paradigms, there is a scarcity of investigations into the neural mechanism of natural sentence reading. The present study recruited 33 adults to read unspaced and spaced Chinese sentences with the eye tracking and functional magnetic resonance imaging data recorded simultaneously. By using fixation-related functional magnetic resonance imaging analysis, this study showed that natural reading of Chinese sentences produced activations in ventral visual, dorsal attention, and semantic brain regions, which were modulated by the properties of words such as word length and word frequency. The multivoxel pattern analysis showed that the activity pattern in the left middle temporal gyrus could significantly predict the visual layout categories (i.e. unspaced vs. spaced conditions). Dynamic causal modeling analysis showed that there were bidirectional brain connections between the left middle temporal gyrus and the left inferior occipital cortex in the unspaced Chinese sentence reading but not in the spaced reading. These results provide a neural mechanism for the natural reading of Chinese sentences from the perspective of word segmentation.

Attentional tracking within and across visual hemifields and brain hemispheres.

Attentional tracking within and across visual hemifields and brain hemispheres.

Plasticity and genetic effects contribute to different axes of neural divergence in a community of mimetic Heliconius butterflies.

Changes in ecological preference, often driven by spatial and temporal variation in resource distribution, can expose populations to environments with divergent information content. This can lead to adaptive changes in the degree to which individuals invest in sensory systems and downstream processes, to optimize behavioural performance in different contexts. At the same time, environmental conditions can produce plastic responses in nervous system development and maturation, providing an alternative route to integrating neural and ecological variation. Here, we explore how these two processes play out across a community of Heliconius butterflies. Heliconius communities exhibit multiple Mullerian mimicry rings, associated with habitat partitioning across environmental gradients. These environmental differences have previously been linked to heritable divergence in brain morphology in parapatric species pairs. They also exhibit a unique dietary adaptation, known as pollen feeding, that relies heavily on learning foraging routes, or trap-lines, between resources, which implies an important environmental influence on behavioural development. By comparing brain morphology across 133 wild-caught and insectary-reared individuals from seven Heliconius species, we find strong evidence for interspecific variation in patterns of neural investment. These largely fall into two distinct patterns of variation; first, we find consistent patterns of divergence in the size of visual brain components across both wild and insectary-reared individuals, suggesting genetically encoded divergence in the visual pathway. Second, we find interspecific differences in mushroom body size, a central component of learning and memory systems, but only among wild caught individuals. The lack of this effect in common-garden individuals suggests an extensive role for developmental plasticity in interspecific variation in the wild. Finally, we illustrate the impact of relatively small-scale spatial effects on mushroom body plasticity by performing experiments altering the cage size and structure experienced by individual H. hecale. Our data provide a comprehensive survey of community level variation in brain structure, and demonstrate that genetic effects and developmental plasticity contribute to different axes of interspecific neural variation.

Panoramic Motion Perception Inspired Fly Visual Brain Joint Neural Network on Omnidirectional Collision Detection

Biological systems have a great number of visual motion detection neurons, some of which can preferentially react to specific visual regions. Nevertheless, little work has been performed about how they can be used to develop neural network models for omnidirectional collision detection. Hereby, an artificial fly visual brain neural network with presynaptic and postsynaptic subnetworks, for the first time, is developed to detect the changes of visual motion in panoramic scenes. Herein, the presynaptic subnetwork, which originates from the preferential response characteristics of five fly visual neurons, responds to all the moving objects in the panoramic field; the postsynaptic network, which is based on the properties of the angle and height detection neurons in the fly’s brain system, collects the excitatory intensities of the visual neurons, and outputs the real-time activities of the main object closest to the panoramic camera. Hereafter, a computational model is constructed to implement omnidirectional collision detection, relying upon the artificial visual brain neural network and three functional neurons. The theoretical analysis has verified that the collision detection model’s computational complexity depends mainly on the image input resolution. Three experimental conclusions can be clearly drawn: (i) the motion characteristics of the main object in the panoramic environment can be clearly exhibited in the neural network; (ii) the collision detection model can not only outperform the compared models but also successfully perform omnidirectional collision detection; and (iii) it spends 0.24 s or so to execute visual information processing per frame with the resolution of 120 × 80.

Presence of Embolic Source and Outcome in Central Retinal Artery Occlusion.

The etiology of central retinal artery occlusion (CRAO) is unclear in approximately 50% of patients, suggesting pathomechanical heterogeneity; moreover, little is known about outcomes according to etiology. This study investigated whether the presence of an embolic source affects outcome in CRAO. CRAO patients within 7 days of symptom onset were retrospectively enrolled. Clinical parameters, including initial and 1-month visual acuity, CRAO subtype, and brain images, were reviewed. CRAO etiology was categorized as CRAO with or without an embolic source (CRAO-E+ and CRAO-E-). Visual improvement was defined as a decrease in logarithm of the minimum angle of resolution ≥0.3 at 1 month. A total of 114 patients with CRAO were included. Visual improvement was noted in 40.4% of patients. Embolic sources were identified in 55.3% of patients, and visual improvement group rather than no improvement group was more commonly associated with the presence of an embolic source. In multivariable logistic regression analysis, CRAO-E+ independently predicted visual improvement (odds ratio 3.00, 95% CI 1.15-7.81, p = 0.025). CRAO-E+ was found to be associated with a better outcome. CRAO-E+ may be more prone to recanalization than that CRAO-E-.

Stubborn Predictions in Primary Visual Cortex.

Perceivers can use past experiences to make sense of ambiguous sensory signals. However, this may be inappropriate when the world changes and past experiences no longer predict what the future holds. Optimal learning models propose that observers decide whether to stick with or update their predictions by tracking the uncertainty or "precision" of their expectations. However, contrasting theories of prediction have argued that we are prone to misestimate uncertainty-leading to stubborn predictions that are difficult to dislodge. To compare these possibilities, we had participants learn novel perceptual predictions before using fMRI to record visual brain activity when predictive contingencies were disrupted-meaning that previously "expected" events became objectively improbable. Multivariate pattern analyses revealed that expected events continued to be decoded with greater fidelity from primary visual cortex, despite marked changes in the statistical structure of the environment, which rendered these expectations no longer valid. These results suggest that our perceptual systems do indeed form stubborn predictions even from short periods of learning-and more generally suggest that top-down expectations have the potential to help or hinder perceptual inference in bounded minds like ours.

A novel approach to CSF pressure measurement via lumbar puncture that shortens the measurement time with a high level of accuracy

Intracranial pressure (ICP) is an important parameter in clinical management and diagnosis of several neurological diseases which is indirectly measured via lumbar puncture (LP). In routine measurements of cerebrospinal fluid pressure (PCSF) from lumbar region, a spinal needle and a spinal manometer are used. PCSF measurement via LP with the use of a spinal manometer may not yield correct PCSF results due to prolonged times required to obtain an accurate pressure value. Equilibrium pressure may be underestimated in circumstances where spinal manometry procedure is terminated prematurely, with the wrong assumption that equilibrium pressure is reached. Elevated PCSF levels can lead to visual loss and brain damage when go undiagnosed. In this study, the spinal needle-spinal manometer combination was modelled with a first-order differential equation and a time constant (τ) was defined as the product of the resistance to flow of the needle with the bore area of the manometer divided by the dynamic viscosity of CSF, i.e. τ= RA/ρCSF. Each needle/manometer combination had a unique constant as a predictor of the equilibrium pressure. The fluid pressure in the manometer rose in an exponential manner which was tested in a simulated environment using 22G spinal needles namely Braun-Spinocan, Pajunk-Sprotte and M.Schilling. Curve fitting of the manometer readings were obtained with regression coefficients of R2 ≥ 0.99 to determine measurement time constants. The residual differences between predicted and true values were less than 1.18 cmH2O. For a given needle/manometer combination, time required to reach equilibrium pressure was identical for all pressure levels. PCSF measured at reduced times can easily be interpolated to their equilibrium level allowing clinicians to obtain PCSF values with high accuracy within seconds. This method can be used as an indirect estimation of ICP in routine clinical practice.

Visual brain: The role of EEG alpha rhythm in perception, attention and vigilance

Visual brain: The role of EEG alpha rhythm in perception, attention and vigilance

Neural effects of visual typicality and predictability in the visual brain and beyond

Neural effects of visual typicality and predictability in the visual brain and beyond

Visual alertness and brain diffusion tensor imaging at term age predict neurocognitive development at preschool age in extremely preterm-born children.

Cognitive development is characterized by the structural and functional maturation of the brain. Diffusion-weighted magnetic resonance imaging (dMRI) provides methods of investigating the brain structure and connectivity and their correlations with the neurocognitive outcome. Our aim was to examine the relationship between early visual abilities, brain white matter structures, and the later neurocognitive outcome. This study included 20 infants who were born before 28 gestational weeks and followed until the age of 6.5 years. At term age, visual alertness was evaluated and dMRI was used to investigate the brain white matter structure using fractional anisotropy (FA) in tract-based spatial statistics analysis. The JHU DTI white matter atlas was used to locate the findings. The neuropsychological assessment was used to assess neurocognitive performance at 6.5 years. Optimal visual alertness at term age was significantly associated with better visuospatial processing (p<.05), sensorimotor functioning (p<.05), and social perception (p<.05) at 6.5 years of age. Optimal visual alertness related to higher FA values, and further, the FA values positively correlated with the neurocognitive outcome. The tract-based spatial differences in FA values were detected between children with optimal and nonoptimal visual alertness according to performance at 6.5 years. We provide neurobiological evidence for the global and tract-based spatial differences in the white matter maturation between extremely preterm children with optimal and nonoptimal visual alertness at term age and a link between white matter maturation, visual alertness and the neurocognitive outcome at 6.5 years proposing that early visual function is a building block for the later neurocognitive development.

Surreal space in René Magritte's Le Blanc-Seing (1965).

"The function of painting is to make poetry visible… to render thought visible." René Magritte Pictorial art reveals some of the visual brain's "neural rules" and processing hierarchy. This article examines one salient exemplar drawn from the vast oeuvre of the great Belgian surrealist, René Magritte (1898-1967). The painting Le Blanc-Seing (1965) is a virtual course in perception, with many elements illustrating figure-ground segregation, object identification, cues for depth perception, Gestalt Laws of occlusion-continuation, and visual scene organization. Le Blanc-Seing is visually stunning, beautifully rendered, and, at first glance, otherwise unremarkable. However, Magritte has embedded several jarring surreal effects in the painting that provide clues about the visual brain's visual processing hierarchy in scene construction. This includes elements whose alternation between two incompatible percepts cannot be explained in terms of local spatiochromatic statistics (Ritchie & van Buren, 2020). Finally, I provide a plausible pictorial inspiration (never before demonstrated) for the painting in a brief scene from a 1924 German silent film.

The relationship between musical training and the processing of audiovisual correspondences: Evidence from a reaction time task.

Numerous studies have reported both cortical and functional changes for visual, tactile, and auditory brain areas in musicians, which have been attributed to long-term training induced neuroplasticity. Previous investigations have reported advantages for musicians in multisensory processing at the behavioural level, however, multisensory integration with tasks requiring higher level cognitive processing has not yet been extensively studied. Here, we investigated the association between musical expertise and the processing of audiovisual crossmodal correspondences in a decision reaction-time task. The visual display varied in three dimensions (elevation, symbolic and non-symbolic magnitude), while the auditory stimulus varied in pitch. Congruency was based on a set of newly learned abstract rules: "The higher the spatial elevation, the higher the tone", "the more dots presented, the higher the tone", and "the higher the number presented, the higher the tone", and accuracy and reaction times were recorded. Musicians were significantly more accurate in their responses than non-musicians, suggesting an association between long-term musical training and audiovisual integration. Contrary to what was hypothesized, no differences in reaction times were found. The musicians' advantage on accuracy was also observed for rule-based congruency in seemingly unrelated stimuli (pitch-magnitude). These results suggest an interaction between implicit and explicit processing-as reflected on reaction times and accuracy, respectively. This advantage was generalised on congruency in otherwise unrelated stimuli (pitch-magnitude pairs), suggesting an advantage on processes requiring higher order cognitive functions. The results support the notion that accuracy and latency measures may reflect different processes.

The psychosis human connectome project: Design and rationale for studies of visual neurophysiology

Visual perception is abnormal in psychotic disorders such as schizophrenia. In addition to hallucinations, laboratory tests show differences in fundamental visual processes including contrast sensitivity, center-surround interactions, and perceptual organization. A number of hypotheses have been proposed to explain visual dysfunction in psychotic disorders, including an imbalance between excitation and inhibition. However, the precise neural basis of abnormal visual perception in people with psychotic psychopathology (PwPP) remains unknown. Here, we describe the behavioral and 7 tesla MRI methods we used to interrogate visual neurophysiology in PwPP as part of the Psychosis Human Connectome Project (HCP). In addition to PwPP (n = 66) and healthy controls (n = 43), we also recruited first-degree biological relatives (n = 44) in order to examine the role of genetic liability for psychosis in visual perception. Our visual tasks were designed to assess fundamental visual processes in PwPP, whereas MR spectroscopy enabled us to examine neurochemistry, including excitatory and inhibitory markers. We show that it is feasible to collect high-quality data across multiple psychophysical, functional MRI, and MR spectroscopy experiments with a sizable number of participants at a single research site. These data, in addition to those from our previously described 3 tesla experiments, will be made publicly available in order to facilitate further investigations by other research groups. By combining visual neuroscience techniques and HCP brain imaging methods, our experiments offer new opportunities to investigate the neural basis of abnormal visual perception in PwPP.