scholarly journals Attentional amplification of neural codes for number independent of other quantities along the dorsal visual stream

eLife ◽  
2019 ◽  
Vol 8 ◽  
Author(s):  
Elisa Castaldi ◽  
Manuela Piazza ◽  
Stanislas Dehaene ◽  
Alexandre Vignaud ◽  
Evelyn Eger
Keyword(s):  
Dorsal Stream ◽  
7 Tesla ◽  
Visual Stream ◽  
Activation Patterns ◽  
Extraction Mechanism ◽  
Human Volunteers ◽  
Neuronal Processing ◽  
Item Size ◽  
Orthogonal Dimension ◽  
Dorsal Visual Stream

Humans and other animals base important decisions on estimates of number, and intraparietal cortex is thought to provide a crucial substrate of this ability. However, it remains debated whether an independent neuronal processing mechanism underlies this ‘number sense’, or whether number is instead judged indirectly on the basis of other quantitative features. We performed high-resolution 7 Tesla fMRI while adult human volunteers attended either to the numerosity or an orthogonal dimension (average item size) of visual dot arrays. Along the dorsal visual stream, numerosity explained a significant amount of variance in activation patterns, above and beyond non-numerical dimensions. Its representation was selectively amplified and progressively enhanced across the hierarchy when task relevant. Our results reveal a sensory extraction mechanism yielding information on numerosity separable from other dimensions already at early visual stages and suggest that later regions along the dorsal stream are most important for explicit manipulation of numerical quantity.

scholarly journals Attentional amplification of neural codes for number independent of other quantities along the dorsal visual stream

2019 ◽  
Author(s):  
Elisa Castaldi ◽  
Manuela Piazza ◽  
Stanislas Dehaene ◽  
Alexandre Vignaud ◽  
Evelyn Eger
Keyword(s):  
Dorsal Stream ◽  
7 Tesla ◽  
Visual Stream ◽  
Activation Patterns ◽  
Extraction Mechanism ◽  
Human Volunteers ◽  
Neuronal Processing ◽  
Item Size ◽  
Orthogonal Dimension ◽  
Dorsal Visual Stream

Humans and other animals base important decisions on estimates of number, and intraparietal cortex is thought to provide a crucial substrate of this ability. However, it remains debated whether an independent neuronal processing mechanism underlies this 'number sense', or whether number is instead judged indirectly on the basis of other quantitative features. We performed high-resolution 7 Tesla fMRI while adult human volunteers attended either to the numerosity or to an orthogonal dimension (average item size) of visual dot arrays. Numerosity explained a significant amount of variance in activation patterns, above and beyond non-numerical dimensions. Its representation was progressively enhanced along the dorsal visual pathway and was selectively amplified by attention when task relevant. These results reveal a dedicated extraction mechanism for numerosity that operates independently of other quantitative dimensions of the stimuli, and suggest that later stages along the dorsal stream are most important for the explicit manipulation of numerical quantity.

Decoding conjunctions of direction-of-motion and binocular disparity from human visual cortex

2012 ◽  
Vol 107 (9) ◽  
pp. 2335-2341 ◽  
Author(s):  
Kiley J. Seymour ◽  
Colin W. G. Clifford
Keyword(s):  
Visual Processing ◽  
Binocular Disparity ◽  
Dorsal Stream ◽  
Visual Stream ◽  
Activation Patterns ◽  
Independent Information ◽  
Uncrossed Disparity ◽  
Multivariate Pattern ◽  
Joint Encoding ◽  
Dorsal Visual Stream

Motion and binocular disparity are two features in our environment that share a common correspondence problem. Decades of psychophysical research dedicated to understanding stereopsis suggest that these features interact early in human visual processing to disambiguate depth. Single-unit recordings in the monkey also provide evidence for the joint encoding of motion and disparity across much of the dorsal visual stream. Here, we used functional MRI and multivariate pattern analysis to examine where in the human brain conjunctions of motion and disparity are encoded. Subjects sequentially viewed two stimuli that could be distinguished only by their conjunctions of motion and disparity. Specifically, each stimulus contained the same feature information (leftward and rightward motion and crossed and uncrossed disparity) but differed exclusively in the way these features were paired. Our results revealed that a linear classifier could accurately decode which stimulus a subject was viewing based on voxel activation patterns throughout the dorsal visual areas and as early as V2. This decoding success was conditional on some voxels being individually sensitive to the unique conjunctions comprising each stimulus, thus a classifier could not rely on independent information about motion and binocular disparity to distinguish these conjunctions. This study expands on evidence that disparity and motion interact at many levels of human visual processing, particularly within the dorsal stream. It also lends support to the idea that stereopsis is subserved by early mechanisms also tuned to direction of motion.

scholarly journals Neural Modulation by Binocular Disparity Greatest in Human Dorsal Visual Stream

2010 ◽  
Vol 104 (1) ◽  
pp. 169-178 ◽  
Author(s):  
Loredana Minini ◽  
Andrew J. Parker ◽  
Holly Bridge
Keyword(s):  
Binocular Disparity ◽  
Large Range ◽  
Dorsal Stream ◽  
Cortical Activation ◽  
Bold Signal ◽  
Visual Stream ◽  
Neural Modulation ◽  
Visual Areas ◽  
Parietal Cortices ◽  
Dorsal Visual Stream

Although cortical activation to binocular disparity can be demonstrated throughout occipital and parietal cortices, the relative contributions to depth perception made by different human cortical areas have not been established. To investigate whether different regions are optimized for specific disparity ranges, we have measured the responses of occipital and parietal areas to different magnitudes of binocular disparity. Using stimuli consisting of sinusoidal depth modulations, we measured cortical activation when the stimuli were located at pedestal disparities of 0, 0.1, 0.35, and 0.7° from fixation. Across all areas, occipital and parietal, there was an increase in BOLD signal with increasing pedestal disparity, compared with a plane at zero disparity. However, the greatest modulation of response by the different pedestals was found in the dorsal visual areas and the parietal areas. These differences contrast with the response to the zero disparity plane, compared with fixation, which is greatest in the early visual areas, smaller in the ventral and dorsal visual areas, and absent in parietal areas. Using the simultaneously acquired psychophysical data we also measured a greater response to correct than to incorrect trials, an effect that increased with rising pedestal disparity and was greatest in dorsal visual and parietal areas. These results illustrate that the dorsal stream, along both its occipital and parietal branches, can reliably discriminate a large range of disparities.

scholarly journals Your head is there to move you around: Goal-driven models of the primate dorsal pathway

2021 ◽  
Author(s):  
Patrick J Mineault ◽  
Shahab Bakhtiari ◽  
Blake A Richards ◽  
Christopher C Pack
Keyword(s):  
Moving Objects ◽  
Explanatory Power ◽  
Dorsal Stream ◽  
Visual Pathway ◽  
Mammalian Brain ◽  
Visual Stream ◽  
Dorsal Pathway ◽  
Simulated Environment ◽  
Self Motion ◽  
Dorsal Visual Stream

Neurons in the dorsal visual pathway of the mammalian brain are selective for motion stimuli, with the complexity of stimulus representations increasing along the hierarchy. This progression is similar to that of the ventral visual pathway, which is well characterized by artificial neural networks (ANNs) optimized for object recognition. In contrast, there are no image-computable models of the dorsal stream with comparable explanatory power. We hypothesized that the properties of dorsal stream neurons could be explained by a simple learning objective: the need for an organism to orient itself during self-motion. To test this hypothesis, we trained a 3D ResNet in a self-supervised manner to predict an agent's self-motion parameters from visual stimuli in a simulated environment. We found that the responses in this network accounted well for the selectivity of neurons in a large database of single-neuron recordings from the dorsal visual stream of non-human primates. In contrast, ANNs trained for action recognition or with a contrastive objective could not explain responses in the dorsal stream, despite also being trained on naturalistic videos with moving objects. These results demonstrate that an ecologically relevant, self-supervised cost function can account for dorsal stream properties in the primate brain.

scholarly journals “Real-time” obstacle avoidance in the absence of primary visual cortex

2009 ◽  
Vol 106 (37) ◽  
pp. 15996-16001 ◽  
Author(s):  
Christopher L. Striemer ◽  
Craig S. Chapman ◽  
Melvyn A. Goodale
Keyword(s):  
Visual Cortex ◽  
Real Time ◽  
Obstacle Avoidance ◽  
Primary Visual Cortex ◽  
Posterior Parietal Cortex ◽  
Dorsal Stream ◽  
Visual Pathways ◽  
Visual Stream ◽  
Reaching Task ◽  
Visual Inputs

When we reach toward objects, we easily avoid potential obstacles located in the workspace. Previous studies suggest that obstacle avoidance relies on mechanisms in the dorsal visual stream in the posterior parietal cortex. One fundamental question that remains unanswered is where the visual inputs to these dorsal-stream mechanisms are coming from. Here, we provide compelling evidence that these mechanisms can operate in “real-time” without direct input from primary visual cortex (V1). In our first experiment, we used a reaching task to demonstrate that an individual with a dense left visual field hemianopia after damage to V1 remained strikingly sensitive to the position of unseen static obstacles placed in his blind field. Importantly, in a second experiment, we showed that his sensitivity to the same obstacles in his blind field was abolished when a short 2-s delay (without vision) was introduced before reach onset. These findings have far-reaching implications, not only for our understanding of the time constraints under which different visual pathways operate, but also in relation to how these seemingly “primitive” subcortical visual pathways can control complex everyday behavior without recourse to conscious vision.

scholarly journals Visuopathy of prematurity: is retinopathy just the tip of the iceberg?

2021 ◽  
Author(s):  
Sigrid Hegna Ingvaldsen ◽  
Tora Sund Morken ◽  
Dordi Austeng ◽  
Olaf Dammann
Keyword(s):  
Visual Processing ◽  
Structural Changes ◽  
Developmental Trajectories ◽  
Visual Pathway ◽  
Visual Stream ◽  
Visual Deficits ◽  
Cortical Areas ◽  
Cellular Architecture ◽  
Increased Risk ◽  
Dorsal Visual Stream

AbstractResearch on retinopathy of prematurity (ROP) focuses mainly on the abnormal vascularization patterns that are directly visible for ophthalmologists. However, recent findings indicate that children born prematurely also exhibit changes in the retinal cellular architecture and along the dorsal visual stream, such as structural changes between and within cortical areas. Moreover, perinatal sustained systemic inflammation (SSI) is associated with an increased risk for ROP and the visual deficits that follow. In this paper, we propose that ROP might just be the tip of an iceberg we call visuopathy of prematurity (VOP). The VOP paradigm comprises abnormal vascularization of the retina, alterations in retinal cellular architecture, choroidal degeneration, and abnormalities in the visual pathway, including cortical areas. Furthermore, VOP itself might influence the developmental trajectories of cerebral structures and functions deemed responsible for visual processing, thereby explaining visual deficits among children born preterm.

scholarly journals fMRI reveals a lower visual field preference in dorsal visual stream regions during hand actions

2011 ◽  
Vol 11 (11) ◽  
pp. 952-952 ◽  
Author(s):  
S. Rossit ◽  
T. McAdam ◽  
A. Mclean ◽  
M. Goodale ◽  
J. Culham
Keyword(s):  
Visual Field ◽  
Lower Visual Field ◽  
Visual Stream ◽  
Dorsal Visual Stream

scholarly journals Conscious awareness of visual space: A tripartite encoding model.

2020 ◽  
Author(s):  
Dhanraj Vishwanath
Keyword(s):  
Visual Space ◽  
Spatial Separation ◽  
Ideal Observer ◽  
Conscious Awareness ◽  
Relative Depth ◽  
Visual Stream ◽  
3D Vision ◽  
Fine Grained ◽  
Near Space ◽  
Dorsal Visual Stream

The prevailing model of 3D vision proposes that the visual system recovers a single objective and internally consistent representation of physical 3D space based on a process of ideal-observer probabilistic inference. A significant challenge for this model has been in explaining the contents of our subjective awareness of visual space. Here I argue that integrating phenomenological observations, empirical data, evolutionary logic and neurophysiological evidence leads to the conjecture that the human conscious awareness of visual space is underwritten by multiple, sometimes mutually inconsistent, spatial encodings. By assessing four primary competencies in the conscious awareness of space, three major types of spatial encodings are conjectured. Among the most primitive of these is proposed to support the competency of the conscious awareness of distance at an ambulatory scale (operationally defined as egocentric distance) and is hypothesised to involve temporal archicortex regions. The second is proposed to support the competency of awareness of object layout and 3D shape without scale (operationally, relative depth), likely instantiated in the ventral visual stream of the neocortex. This encoding is hypothesised to have evolved from more primitive encodings that provide a depth-ordered segmentation of the visual field. The third encoding is proposed to support the competency of fine-grained awareness of intra- and inter-object spatial separation in near space (operationally, scaled or absolute depth) and instantiated in the dorsal visual stream. This encoding is conjectured to underlie the phenomenology of object solidity, spatial separation, tangibility and object realness that is often referred to as stereopsis. The combined effect of the first and third competencies (ambulatory distance and near-space scaled spatial separation) is conjectured to contribute to the feeling of spatial immersion and presence.

Age-Related Changes in the Allocation of Vertical Attention

2018 ◽  
Vol 24 (10) ◽  
pp. 1121-1124 ◽  
Author(s):  
Aleksandra Mańkowska ◽  
Kenneth M. Heilman ◽  
John B. Williamson ◽  
Michał Harciarek
Keyword(s):  
Spatial Attention ◽  
Right Hemisphere ◽  
Ventral Stream ◽  
Midsagittal Plane ◽  
Visual Stream ◽  
Leftward Bias ◽  
Healthy Elderly ◽  
Age Related ◽  
The Right ◽  
Dorsal Visual Stream

AbstractObjectives: Healthy individuals often have a leftward and upward attentional spatial bias; however, there is a reduction of this leftward bias with aging. The right hemisphere mediates leftward spatial attention and age-related reduction of right hemispheric activity may account for this reduced leftward bias. The right hemisphere also appears to be responsible for upward bias, and this upward bias might reduce with aging. Alternatively, whereas the dorsal visual stream allocates attention downward, the ventral stream allocates attention upward. Since with aging there is a greater atrophy of the dorsal than ventral stream, older participants may reveal a greater upward bias. The main purpose of this study was to learn if aging influences the vertical allocation of spatial attention. Methods: Twenty-six young (17 males; mean age 44.62±2.57 years) and 25 healthy elderly (13 males; mean age 72.04±.98 years), right-handed adults performed line bisections using 24 vertical lines (24 cm long and 2 mm thick) aligned with their midsagittal plane. Results: Older adults had a significantly greater upward bias than did younger adults. Conclusions: Normal upward attentional bias increases with aging, possibly due to an age-related reduction of the dorsal attentional stream that is responsible for the allocation of downward attention. (JINS, 2018, 24, 1121–1124)

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