scholarly journals Behavioral origin of sound-evoked activity in visual cortex

2021 ◽  
Author(s):  
Célian Bimbard ◽  
Timothy PH Sit ◽  
Anna Lebedeva ◽  
Kenneth D Harris ◽  
Matteo Carandini
Keyword(s):  
Visual Cortex ◽  
Primary Visual Cortex ◽  
Neural Activity ◽  
Evoked Responses ◽  
Sensory Cortices ◽  
Evoked Activity ◽  
Low Dimensional ◽  
Multisensory Information

Sensory cortices are increasingly thought to encode multisensory information. For instance, primary visual cortex (V1) appears to be influenced by sounds. Here we show that sound-evoked responses in mouse V1 are low-dimensional, similar across neurons and across brains, and can be explained by highly stereotyped uninstructed movements of eyes and body. Thus, neural activity previously interpreted as being sensory or multisensory may have a behavioral origin.

scholarly journals Visual exposure optimizes stimulus encoding in primary visual cortex

2018 ◽  
Author(s):  
Andreea Lazar ◽  
Chris Lewis ◽  
Pascal Fries ◽  
Wolf Singer ◽  
Danko Nikolić
Keyword(s):  
Visual Cortex ◽  
Primary Visual Cortex ◽  
Visual Processing ◽  
Neuronal Response ◽  
Extended Period ◽  
Sensory Cells ◽  
Neuronal Populations ◽  
Visual Exposure ◽  
Early Visual Cortex ◽  
Sensory Cortices

SummarySensory exposure alters the response properties of individual neurons in primary sensory cortices. However, it remains unclear how these changes affect stimulus encoding by populations of sensory cells. Here, recording from populations of neurons in cat primary visual cortex, we demonstrate that visual exposure enhances stimulus encoding and discrimination. We find that repeated presentation of brief, high-contrast shapes results in a stereotyped, biphasic population response consisting of a short-latency transient, followed by a late and extended period of reverberatory activity. Visual exposure selectively improves the stimulus specificity of the reverberatory activity, by increasing the magnitude and decreasing the trial-to-trial variability of the neuronal response. Critically, this improved stimulus encoding is distributed across the population and depends on precise temporal coordination. Our findings provide evidence for the existence of an exposure-driven optimization process that enhances the encoding power of neuronal populations in early visual cortex, thus potentially benefiting simple readouts at higher stages of visual processing.

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.

Neural Representation of the Luminance and Brightness of a Uniform Surface in the Macaque Primary Visual Cortex

2001 ◽  
Vol 86 (5) ◽  
pp. 2559-2570 ◽  
Author(s):  
Masaharu Kinoshita ◽  
Hidehiko Komatsu
Keyword(s):  
Visual Cortex ◽  
Receptive Field ◽  
Primary Visual Cortex ◽  
Neural Activity ◽  
Dynamic Range ◽  
Neural Representation ◽  
Homogeneous Surface ◽  
V1 Neurons ◽  
Classical Receptive Field ◽  
Multiple Unit

The perceived brightness of a surface is determined not only by the luminance of the surface (local information), but also by the luminance of its surround (global information). To better understand the neural representation of surface brightness, we investigated the effects of local and global luminance on the activity of neurons in the primary visual cortex (V1) of awake macaque monkeys. Single- and multiple-unit recordings were made from V1 while the monkeys were performing a visual fixation task. The classical receptive field of each neuron was identified as a region responding to a spot stimulus. Neural responses were assessed using homogeneous surfaces at least three times as large as the receptive field as stimuli. We first examined the sensitivity of neurons to variation in local surface luminance, while the luminance of the surround was held constant. The activity of a large majority of surface-responsive neurons (106/115) varied monotonically with changes in surface luminance; in some the dynamic range was over 3 log units. This monotonic relation between surface luminance and neural activity was more evident later in the stimulus period than early on. The effect of the global luminance on neural activity was then assessed in 81 of the surface-responsive neurons by varying the luminance of the surround while holding the luminance of the surface constant. The activity of one group of neurons (25/81) was unaffected by the luminance of the surround; these neurons appear to encode the physical luminance of a surface covering the receptive field. The responses of the other neurons were affected by the luminance of the surround. The effects of the luminances of the surface and the surround on the activities of 26 of these neurons were in the same direction (either increased or decreased), while the effects on the remaining 25 neurons were in opposite directions. The activities of the latter group of neurons seemed to parallel the perceived brightness of the surface, whereas the former seemed to encode the level of illumination. There were differences across different types of neurons with regard to the layer distribution. These findings indicate that global luminance information significantly modulates the activity of surface-responsive V1 neurons and that not only physical luminance, but also perceived brightness, of a homogeneous surface is represented in V1.

scholarly journals Blockade of retinal or cortical activity does not prevent the development of callosal patches normally associated with ocular dominance columns in primary visual cortex

2021 ◽  
Vol 38 ◽  
Author(s):  
Hsueh Chung Lu ◽  
Robyn J. Laing ◽  
Jaime F. Olavarria
Keyword(s):  
Visual Cortex ◽  
Primary Visual Cortex ◽  
Neural Activity ◽  
Single Injection ◽  
Ocular Dominance ◽  
Cell Activity ◽  
Ocular Dominance Columns ◽  
Callosal Connections ◽  
Monocular Enucleation ◽  
Physiological Evaluation

Abstract Callosal patches in primary visual cortex of Long Evans rats, normally associated with ocular dominance columns, emerge by postnatal day 10 (P10), but they do not form in rats monocularly enucleated a few days before P10. We investigated whether we could replicate the results of monocular enucleation by using tetrodotoxin (TTX) to block neural activity in one eye, or in primary visual cortex. Animals received daily intravitreal (P6–P9) or intracortical (P7–P9) injections of TTX, and our physiological evaluation of the efficacy of these injections indicated that the blockade induced by a single injection lasted at least 24 h. Four weeks later, the patterns of callosal connections in one hemisphere were revealed after multiple injections of horseradish peroxidase in the other hemisphere. We found that in rats receiving either intravitreal or cortical injections of TTX, the patterns of callosal patches analyzed in tangential sections from the flattened cortex were not significantly different from the pattern in normal rats. Our findings, therefore, suggest that the effects of monocular enucleation on the distribution of callosal connections are not due to the resulting imbalance of afferent ganglion cell activity, and that factors other than neural activity are likely involved.

scholarly journals Microstimulation in the primary visual cortex: activity patterns and their relation to visual responses and evoked saccades

2020 ◽  
Author(s):  
R. Oz ◽  
H. Edelman-Klapper ◽  
S. Nivinsky-Margalit ◽  
H. Slovin
Keyword(s):  
Visual Cortex ◽  
Primary Visual Cortex ◽  
Neural Activity ◽  
Visual Processing ◽  
Visual Stimuli ◽  
Temporal Patterns ◽  
Visual Responses ◽  
Population Activity ◽  
Spatio Temporal ◽  
Saccade Generation

AbstractIntra cortical microstimulation (ICMS) in the primary visual cortex (V1) can generate the visual perception of phosphenes and evoke saccades directed to the stimulated location in the retinotopic map. Although ICMS is widely used, little is known about the evoked spatio-temporal patterns of neural activity and their relation to neural responses evoked by visual stimuli or saccade generation. To investigate this, we combined ICMS with Voltage Sensitive Dye Imaging in V1 of behaving monkeys and measured neural activity at high spatial (meso-scale) and temporal resolution. Small visual stimuli and ICMS evoked population activity spreading over few mm that propagated to extrastriate areas. The population responses evoked by ICMS showed faster dynamics and different spatial propagation patterns. Neural activity was higher in trials w/saccades compared with trials w/o saccades. In conclusion, our results uncover the spatio-temporal patterns evoked by ICMS and their relation to visual processing and saccade generation.

scholarly journals Anticipatory Changes in Regional Cerebral Hemodynamics: A New Role for Dopamine?

2009 ◽  
Vol 101 (6) ◽  
pp. 2738-2740 ◽  
Author(s):  
Can Ozan Tan
Keyword(s):  
Visual Cortex ◽  
Primary Visual Cortex ◽  
Neural Activity ◽  
Cerebral Hemodynamics ◽  
Physiological Data ◽  
Cerebral Microcirculation ◽  
Hemodynamic Responses ◽  
On Demand ◽  
Demand Allocation

Recently, adaptively timed, anticipatory changes in hemodynamic responses, independent of neural activity, were described in primate primary visual cortex. Task-related properties of these responses point to a possible link between regional cerebral microcirculation and dopaminergic signaling. In this report, this link is elaborated on the basis of known physiological data and further experiments are proposed to test the possible role of dopamine in task-dependent, “on-demand” allocation of metabolic resources.

scholarly journals Retinotopic-like maps of spatial sound in primary ‘visual’ cortex of blind human echolocators

2019 ◽  
Vol 286 (1912) ◽  
pp. 20191910 ◽  
Author(s):  
Liam J. Norman ◽  
Lore Thaler
Keyword(s):  
Visual Cortex ◽  
Primary Visual Cortex ◽  
Functional Organization ◽  
Brain Activity ◽  
Sensory Modality ◽  
Spatial Sound ◽  
Sensory Cortices ◽  
Spatial Locations ◽  
The Brain ◽  
Rule Out

The functional specializations of cortical sensory areas were traditionally viewed as being tied to specific modalities. A radically different emerging view is that the brain is organized by task rather than sensory modality, but it has not yet been shown that this applies to primary sensory cortices. Here, we report such evidence by showing that primary ‘visual’ cortex can be adapted to map spatial locations of sound in blind humans who regularly perceive space through sound echoes. Specifically, we objectively quantify the similarity between measured stimulus maps for sound eccentricity and predicted stimulus maps for visual eccentricity in primary ‘visual’ cortex (using a probabilistic atlas based on cortical anatomy) to find that stimulus maps for sound in expert echolocators are directly comparable to those for vision in sighted people. Furthermore, the degree of this similarity is positively related with echolocation ability. We also rule out explanations based on top-down modulation of brain activity—e.g. through imagery. This result is clear evidence that task-specific organization can extend even to primary sensory cortices, and in this way is pivotal in our reinterpretation of the functional organization of the human brain.

scholarly journals Erasing motion: Scrambling direction selectivity in visual cortex during saccades

2021 ◽  
Author(s):  
Satoru K Miura ◽  
Massimo Scanziani
Keyword(s):  
Visual Cortex ◽  
External World ◽  
Direction Selectivity ◽  
Efference Copy ◽  
Visual Input ◽  
Visual Scene ◽  
General Mechanism ◽  
Motion Direction ◽  
Sensory Cortices ◽  
Evoked Activity

A prominent feature of sensory processing is the ability to distinguish whether the activation of the sensory periphery is caused by changes in the external world or by the animal's own actions. Saccades, rapid eye movements executed by animals across phyla, cause the visual scene to momentarily shift on the retina. The mechanisms by which visual systems differentiate between motion of the visual scene induced by saccades from motion due to changes in the external world are not fully understood. Here, we discovered that in mouse primary visual cortex (V1), the two types of motion evoke distinct patterns of activity across the population of neurons. As a result, a decoder of motion direction trained on the response to motion in the external world fails to generalize when tested on the response to saccades that induce similar motion on the retina. This is because during saccades, V1 combines the visual input with a strong non-visual input arriving from the pulvinar nucleus of the thalamus. This non-visual input is an efference copy - a copy of the oculomotor command that differs depending on the direction of the saccades. Silencing the pulvinar prevented the non-visual input from reaching V1, such that the pattern of activity in V1 was now similar no matter whether the motion was generated in the external world or by saccades. Thus, the pulvinar input to V1 ensures differential responses to the external and self-generated motion and may prevent downstream areas from extracting motion information about visual stimulus shifts generated by saccades. Changing the pattern of evoked activity through an efference copy may be a general mechanism that enables sensory cortices in mammals to distinguish between external and self-generated stimuli.

scholarly journals Model-based decoupling of evoked and spontaneous neural activity in calcium imaging data

2020 ◽  
Vol 16 (11) ◽  
pp. e1008330
Author(s):  
Marcus A. Triplett ◽  
Zac Pujic ◽  
Biao Sun ◽  
Lilach Avitan ◽  
Geoffrey J. Goodhill
Keyword(s):  
Spontaneous Activity ◽  
Neural Activity ◽  
Calcium Imaging ◽  
Temporal Dynamics ◽  
Population Level ◽  
Imaging Data ◽  
Evoked Activity ◽  
Zebrafish Optic Tectum ◽  
Low Dimensional ◽  
Mouse Visual Cortex

The pattern of neural activity evoked by a stimulus can be substantially affected by ongoing spontaneous activity. Separating these two types of activity is particularly important for calcium imaging data given the slow temporal dynamics of calcium indicators. Here we present a statistical model that decouples stimulus-driven activity from low dimensional spontaneous activity in this case. The model identifies hidden factors giving rise to spontaneous activity while jointly estimating stimulus tuning properties that account for the confounding effects that these factors introduce. By applying our model to data from zebrafish optic tectum and mouse visual cortex, we obtain quantitative measurements of the extent that neurons in each case are driven by evoked activity, spontaneous activity, and their interaction. By not averaging away potentially important information encoded in spontaneous activity, this broadly applicable model brings new insight into population-level neural activity within single trials.

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