scholarly journals Functional ultrasound imaging of the spreading activity following optogenetic stimulation of the rat visual cortex

2021 ◽  
Author(s):  
M. Provansal ◽  
G. Labernede ◽  
C. Joffrois ◽  
A. Rizkallah ◽  
R. Goulet ◽  
...  
Keyword(s):  
Visual Cortex ◽  
Ultrasound Imaging ◽  
Visual Information ◽  
Brain Response ◽  
Information Process ◽  
Optogenetic Stimulation ◽  
Deep Layers ◽  
Sight Restoration ◽  
The Brain ◽  
Stimulation Of

Optogenetic stimulation of the primary visual cortex (V1) is a promising therapy for sight restoration, but it remains unclear what total cerebral volume is activated after surface stimulation. In this study, we expressed the red-shifted opsin ChrimsonR in excitatory neurons within V1 in rats, and used the fine spatial resolution provided by functional ultrasound imaging (fUS) over the whole depth of the brain to investigate the brain response to focal surface stimulation. We observed optogenetic activation of a high proportion of the volume of V1. Extracellular recordings confirmed the neuronal origin of this activation. Moreover, neuronal responses were even located in deep layers under conditions of low irradiance, spreading to the LGN and V2, consistent with a normal visual information process. This study paves the way for the use of optogenetics for cortical therapies, and highlights the value of coupling fUS with optogenetics.

Striatal dopamine mediates hallucination-like perception in mice

Science ◽  
2021 ◽  
Vol 372 (6537) ◽  
pp. eabf4740
Author(s):  
K. Schmack ◽  
M. Bosc ◽  
T. Ott ◽  
J. F. Sturgill ◽  
A. Kepecs
Keyword(s):  
Psychotic Disorders ◽  
Neural Circuit ◽  
Dopamine Neurons ◽  
Striatal Dopamine ◽  
Model Organisms ◽  
High Confidence ◽  
Optogenetic Stimulation ◽  
The Brain ◽  
Central Symptom ◽  
Stimulation Of

Hallucinations, a central symptom of psychotic disorders, are attributed to excessive dopamine in the brain. However, the neural circuit mechanisms by which dopamine produces hallucinations remain elusive, largely because hallucinations have been challenging to study in model organisms. We developed a task to quantify hallucination-like perception in mice. Hallucination-like percepts, defined as high-confidence false detections, increased after hallucination-related manipulations in mice and correlated with self-reported hallucinations in humans. Hallucination-like percepts were preceded by elevated striatal dopamine levels, could be induced by optogenetic stimulation of mesostriatal dopamine neurons, and could be reversed by the antipsychotic drug haloperidol. These findings reveal a causal role for dopamine-dependent striatal circuits in hallucination-like perception and open new avenues to develop circuit-based treatments for psychotic disorders.

scholarly journals Parylene photonics: a flexible, broadband optical waveguide platform with integrated micromirrors for biointerfaces

2020 ◽  
Vol 6 (1) ◽  
Author(s):  
Jay W. Reddy ◽  
Maya Lassiter ◽  
Maysamreza Chamanzar
Keyword(s):  
Optical Waveguides ◽  
Brain Activity ◽  
Low Loss ◽  
Parylene C ◽  
Optogenetic Stimulation ◽  
Patterned Illumination ◽  
The Brain ◽  
532 Nm ◽  
Stimulation Of

Abstract Targeted light delivery into biological tissue is needed in applications such as optogenetic stimulation of the brain and in vivo functional or structural imaging of tissue. These applications require very compact, soft, and flexible implants that minimize damage to the tissue. Here, we demonstrate a novel implantable photonic platform based on a high-density, flexible array of ultracompact (30 μm × 5 μm), low-loss (3.2 dB/cm at λ = 680 nm, 4.1 dB/cm at λ = 633 nm, 4.9 dB/cm at λ = 532 nm, 6.1 dB/cm at λ = 450 nm) optical waveguides composed of biocompatible polymers Parylene C and polydimethylsiloxane (PDMS). This photonic platform features unique embedded input/output micromirrors that redirect light from the waveguides perpendicularly to the surface of the array for localized, patterned illumination in tissue. This architecture enables the design of a fully flexible, compact integrated photonic system for applications such as in vivo chronic optogenetic stimulation of brain activity.

scholarly journals Blindsight and Unconscious Vision: What They Teach Us about the Human Visual System

2016 ◽  
Vol 23 (5) ◽  
pp. 529-541 ◽  
Author(s):  
Sara Ajina ◽  
Holly Bridge
Keyword(s):  
Visual Cortex ◽  
Visual System ◽  
Primary Visual Cortex ◽  
Neural Activity ◽  
Human Visual System ◽  
Visual Information ◽  
Visual Loss ◽  
Physiological Conditions ◽  
The World ◽  
The Brain

Damage to the primary visual cortex removes the major input from the eyes to the brain, causing significant visual loss as patients are unable to perceive the side of the world contralateral to the damage. Some patients, however, retain the ability to detect visual information within this blind region; this is known as blindsight. By studying the visual pathways that underlie this residual vision in patients, we can uncover additional aspects of the human visual system that likely contribute to normal visual function but cannot be revealed under physiological conditions. In this review, we discuss the residual abilities and neural activity that have been described in blindsight and the implications of these findings for understanding the intact system.

Surface stimulation of the brain with a prototype array for a visual cortex prosthesis

2004 ◽  
Vol 11 (7) ◽  
pp. 750-755 ◽  
Author(s):  
Vivek Chowdhury ◽  
John W. Morley ◽  
Minas T. Coroneo
Keyword(s):  
Visual Cortex ◽  
The Brain ◽  
Stimulation Of

scholarly journals Novel neural circuit mechanism for visual edge detection

2015 ◽  
Vol 112 (3) ◽  
pp. 875-880 ◽  
Author(s):  
Charles F. Stevens
Keyword(s):  
Visual Cortex ◽  
Edge Detection ◽  
Visual Information ◽  
Neural Circuit ◽  
Frequency Tuning ◽  
Orientation Tuning ◽  
Image Patch ◽  
Small Parts ◽  
The Brain ◽  
Slope Orientation

The primary visual cortex is organized in a way that assigns a specific collection of neurons the job of providing the rest of the brain with all of the information it needs about each small part of the image present on the retina: Neighboring patches of the visual cortex provide the information about neighboring patches of the visual world. Each one of these cortical patches—often identified as a “pinwheel”—contains thousands of neurons, and its corresponding image patch is centered on a particular location in the retina. For stimuli within their image patch, neurons respond selectively to lines or edges with a particular slope (orientation tuning) and to regions of the patch of different sizes (known as spatial frequency tuning). The same number of neurons is devoted to reporting each possible slope (orientation). For the cells that cover different-sized regions of their image patch, however, the number of neurons assigned depends strongly on their preferred region size. Only a few neurons report on large and small parts of the image patch, but many neurons report visual information from medium-sized areas. I show here that having different numbers of neurons responsible for image regions of different sizes actually carries out a computation: Edges in the image patch are extracted. I also explain how this edge-detection computation is done.

scholarly journals Sonogenetic stimulation of the brain at a spatiotemporal resolution suitable for vision restoration

2021 ◽  
Author(s):  
Sara Cadoni ◽  
Charlie Demene ◽  
Matthieu Provansal ◽  
Diep Nguyen ◽  
Dasha Nelidova ◽  
...  
Keyword(s):  
Visual Cortex ◽  
Neurological Disorders ◽  
Real Life ◽  
Spatiotemporal Resolution ◽  
Brain Machine Interfaces ◽  
Ultrasound Stimulation ◽  
Wide Range ◽  
The Brain ◽  
Stimulation Of

Remote, precisely controlled activation of the brain is a fundamental challenge in the development of brain machine interfaces providing feasible rehabilitation strategies for neurological disorders. Low-frequency ultrasound stimulation can be used to modulate neuronal activity deep in the brain, but this approach lacks spatial resolution and cellular selectivity and loads the brain with high levels of acoustic energy. The combination of the expression of ultrasound-sensitive proteins with ultrasound stimulation (sonogenetic stimulation) can provide cellular selectivity and higher sensitivity, but such strategies have been subject to severe limitations in terms of spatiotemporal resolution in vivo, precluding their use for real-life applications. We used the expression of large-conductance mechanosensitive ion channels (MscL) with high-frequency ultrasonic stimulation for a duration of milliseconds to activate neurons selectively at a relatively high spatiotemporal resolution in the rat retina ex vivo and the primary visual cortex of rodents in vivo. This spatiotemporal resolution was achieved at low energy levels associated with negligible tissue heating and far below those leading to complications in ultrasound neuromodulation. We showed, in an associative learning test, that sonogenetic stimulation of the visual cortex generated light perception. Our findings demonstrate that sonogenetic stimulation is compatible with millisecond pattern presentation for visual restoration at the cortical level. They represent a step towards the precise transfer of information over large distances to the cortical and subcortical regions of the brain via an approach less invasive than that associated with current brain machine interfaces and with a wide range of applications in neurological disorders.

scholarly journals Prior expectations evoke stimulus-specific activity in the deep layers of the primary visual cortex

PLoS Biology ◽  
2020 ◽  
Vol 18 (12) ◽  
pp. e3001023
Author(s):  
Fraser Aitken ◽  
Georgios Menelaou ◽  
Oliver Warrington ◽  
Renée S. Koolschijn ◽  
Nadège Corbin ◽  
...  
Keyword(s):  
Visual Cortex ◽  
Primary Visual Cortex ◽  
Specific Activity ◽  
Predictive Processing ◽  
Cortical Layers ◽  
Computational Architecture ◽  
Deep Layers ◽  
Flow Through ◽  
The Brain ◽  
The Way

The way we perceive the world is strongly influenced by our expectations. In line with this, much recent research has revealed that prior expectations strongly modulate sensory processing. However, the neural circuitry through which the brain integrates external sensory inputs with internal expectation signals remains unknown. In order to understand the computational architecture of the cortex, we need to investigate the way these signals flow through the cortical layers. This is crucial because the different cortical layers have distinct intra- and interregional connectivity patterns, and therefore determining which layers are involved in a cortical computation can inform us on the sources and targets of these signals. Here, we used ultra-high field (7T) functional magnetic resonance imaging (fMRI) to reveal that prior expectations evoke stimulus-specific activity selectively in the deep layers of the primary visual cortex (V1). These findings are in line with predictive processing theories proposing that neurons in the deep cortical layers represent perceptual hypotheses and thereby shed light on the computational architecture of cortex.

Brain Basis of Blindsight

2020 ◽  
Author(s):  
Holly Bridge
Keyword(s):  
Visual Cortex ◽  
Primary Visual Cortex ◽  
Visual Information ◽  
Diffusion Imaging ◽  
Visual Stimuli ◽  
Cortical Blindness ◽  
Functional Brain Imaging ◽  
Rehabilitation Programs ◽  
The World ◽  
The Brain

The sensation of vision arises from the detection of photons of light at the eye, but in order to produce the percept of the world, extensive regions of the brain are required to process the visual information. The majority of information entering the brain via the optic nerve from the eye projects via the lateral geniculate nucleus (LGN) of the thalamus to the primary visual cortex, the largest visual area, having been reorganized such that one side of the brain represents one side of the world. Damage to the primary visual cortex in one hemisphere therefore leads to a loss of conscious vision on the opposite side of the world, known as hemianopia. Despite this cortical blindness, many patients are still able to detect visual stimuli that are presented in the blind region if forced to guess whether a stimulus is present or absent. This is known as “blindsight.” For patients to gain any information (conscious or unconscious) about the visual world, the input from the eye must be processed by the brain. Indeed, there is considerable evidence from functional brain imaging that several visual areas continue to respond to visual stimuli presented within the blind region, even when the patient is unaware of the stimulus. Furthermore, the use of diffusion imaging allows the microstructure of white matter pathways within the visual system to be examined to see whether they are damaged or intact. By comparing patients who have hemianopia with and without blindsight it is possible to determine the pathways that are linked to blindsight function. Through understanding the brain areas and pathways that underlie blindsight in humans and non-human primates, the aim is to use modern neuroscience to guide rehabilitation programs for use after stroke.

Mammalian Visual System Organization

2017 ◽  
Author(s):  
Farran Briggs
Keyword(s):  
Visual Cortex ◽  
Visual System ◽  
Visual Information ◽  
Contextual Information ◽  
Sensory Information ◽  
Visual Image ◽  
Brain Structures ◽  
Object Representations ◽  
System A ◽  
The Brain

Many mammals, including humans, rely primarily on vision to sense the environment. While a large proportion of the brain is devoted to vision in highly visual animals, there are not enough neurons in the visual system to support a neuron-per-object look-up table. Instead, visual animals evolved ways to rapidly and dynamically encode an enormous diversity of visual information using minimal numbers of neurons (merely hundreds of millions of neurons and billions of connections!). In the mammalian visual system, a visual image is essentially broken down into simple elements that are reconstructed through a series of processing stages, most of which occur beneath consciousness. Importantly, visual information processing is not simply a serial progression along the hierarchy of visual brain structures (e.g., retina to visual thalamus to primary visual cortex to secondary visual cortex, etc.). Instead, connections within and between visual brain structures exist in all possible directions: feedforward, feedback, and lateral. Additionally, many mammalian visual systems are organized into parallel channels, presumably to enable efficient processing of information about different and important features in the visual environment (e.g., color, motion). The overall operations of the mammalian visual system are to: (1) combine unique groups of feature detectors in order to generate object representations and (2) integrate visual sensory information with cognitive and contextual information from the rest of the brain. Together, these operations enable individuals to perceive, plan, and act within their environment.

Neural Plasticity in Amblyopia

2021 ◽  
Author(s):  
Benjamin Thompson
Keyword(s):  
Visual Cortex ◽  
Neural Plasticity ◽  
Visual Information ◽  
Randomized Clinical Trials ◽  
Adult Brain ◽  
Abnormal Development ◽  
Sensitive Period ◽  
Early 21St Century ◽  
Functional Changes ◽  
The Brain

Early in life, the brain has a substantial capacity for change, often referred to as neuroplasticity. Disrupted visual input to the brain during an early “critical” or “sensitive period” of heightened neuroplasticity induces structural and functional changes within neural systems and causes amblyopia, a sensory disorder associated with abnormal development of the brain areas involved in perception. Amblyopia impairs a broad range of visual, multisensory, and motor functions, and recovery from amblyopia requires a substantial change in visual information processing within the brain. Therefore, not only is amblyopia caused by an interaction between visual experience and heightened neuroplasticity, recovery from amblyopia also requires significant neuroplastic change within the brain. A number of evidence-based treatments are available for young children with amblyopia whose brains are still rapidly developing and have a correspondingly high level of neuroplasticity. However, adults with amblyopia are often left untreated because of the idea that the adult brain no longer has sufficient neuroplasticity to relearn how to process visual information. In the early 21st century, it became clear that this idea was not correct. A number of interventions that can enhance neuroplasticity in the mature visual cortex have been identified using animal models of amblyopia and are now being translated into human studies. Other promising techniques for enhancing visual cortex neuroplasticity have emerged from studies of adult humans with amblyopia. Examples of interventions that may improve vision in adult amblyopia include refractive correction, patching of the amblyopic eye (reverse patching), monocular and binocular perceptual learning, noninvasive brain stimulation, systemic drugs, and exercise. The next important stage of research within this field will be to conduct fully controlled randomized clinical trials to assess which, if any, of these interventions can be translated into a mainstream treatment for amblyopia in adulthood.

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