scholarly journals A distinct population of heterogeneously color-tuned neurons in macaque visual cortex

2021 ◽  
Vol 7 (8) ◽  
pp. eabc5837
Author(s):  
Sunny Nigam ◽  
Sorin Pojoga ◽  
Valentin Dragoi
Keyword(s):  
Visual Cortex ◽  
Natural Scenes ◽  
Natural Environments ◽  
Social Signals ◽  
Distinct Population ◽  
Area V4 ◽  
Cortex Area ◽  
Close Proximity ◽  
Color Signals ◽  
High Degree

Color is a key feature of natural environments that higher mammals routinely use to detect food, avoid predators, and interpret social signals. The distribution of color signals in natural scenes is widely variable, ranging from uniform patches to highly nonuniform regions in which different colors lie in close proximity. Whether individual neurons are tuned to this high degree of variability of color signals is unknown. Here, we identified a distinct population of cells in macaque visual cortex (area V4) that have a heterogeneous receptive field (RF) structure in which individual subfields are tuned to different colors even though the full RF is only weakly tuned. This spatial heterogeneity in color tuning indicates a higher degree of complexity of color-encoding mechanisms in visual cortex than previously believed to efficiently extract chromatic information from the environment.

scholarly journals Coherent natural scene structure facilitates the extraction of task-relevant object information in visual cortex

2020 ◽  
Author(s):  
Daniel Kaiser ◽  
Greta Häberle ◽  
Radoslaw M. Cichy
Keyword(s):  
Visual Cortex ◽  
Rural Environment ◽  
Natural Scenes ◽  
Natural Environments ◽  
Response Patterns ◽  
Scene Structure ◽  
Processing Pathways ◽  
Typical Composition ◽  
High Level ◽  
The Brain

AbstractLooking for objects within complex natural environments is a task everybody performs multiple times each day. In this study, we explore how the brain uses the typical composition of real-world environments to efficiently solve this task. We recorded fMRI activity while participants performed two different categorization tasks on natural scenes. In the object task, they indicated whether the scene contained a person or a car, while in the scene task, they indicated whether the scene depicted an urban or a rural environment. Critically, each scene was presented in an “intact” way, preserving its coherent structure, or in a “jumbled” way, with information swapped across quadrants. In both tasks, participants’ categorization was more accurate and faster for intact scenes. These behavioral benefits were accompanied by stronger responses to intact than to jumbled scenes across high-level visual cortex. To track the amount of object information in visual cortex, we correlated multivoxel response patterns during the two categorization tasks with response patterns evoked by people and cars in isolation. We found that object information in object- and body-selective cortex was enhanced when the object was embedded in an intact, rather than a jumbled scene. However, this enhancement was only found in the object task: When participants instead categorized the scenes, object information did not differ between intact and jumbled scenes. Together, these results indicate that coherent scene structure facilitates the extraction of object information in a task-dependent way, suggesting that interactions between the object and scene processing pathways adaptively support behavioral goals.

STIMULUS COMPETITION IN ATTENTION: A NEURAL MODEL OF VISUAL CORTEX AREA V4

2008 ◽  
Vol 17 (05) ◽  
pp. 915-923 ◽  
Author(s):  
ETIENNE HUGUES ◽  
JORGE V. JOSÉ
Keyword(s):  
Visual Cortex ◽  
Receptive Field ◽  
Firing Rate ◽  
Neural Model ◽  
Neural Mechanisms ◽  
Neuron Firing ◽  
Area V4 ◽  
Neuron Response ◽  
Cortex Area ◽  
Network Properties

When a monkey is presented simultaneously two stimuli in the receptive field of a neuron in the visual cortex area V4, the neuron firing rate response is intermediate between the neuron response when both stimuli are presented alone. This phenomenon is called stimulus competition. To study its basic underlying neural mechanisms, we calculate the neuron firing rate response to different stimulus configurations. We find that stimulus competition can arise from the neuron's response properties alone, but only for a limited set of stimulus pair parameters. Furthermore, network properties may be important in modifying the inputs so that competition may occur for much wider sets of stimulus pairs.

scholarly journals Generalist camouflage can be more successful than microhabitat specialisation in natural environments

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Emmanuelle Sophie Briolat ◽  
Lina María Arenas ◽  
Anna E. Hughes ◽  
Eric Liggins ◽  
Martin Stevens
Keyword(s):  
Survival Benefit ◽  
Search Task ◽  
Natural Scenes ◽  
Science Methods ◽  
Natural Environments ◽  
Background Matching ◽  
Computer Based ◽  
Visual Scenes ◽  
Small Targets ◽  
Predator Defence

Abstract Background Crypsis by background-matching is a critical form of anti-predator defence for animals exposed to visual predators, but achieving effective camouflage in patchy and variable natural environments is not straightforward. To cope with heterogeneous backgrounds, animals could either specialise on particular microhabitat patches, appearing cryptic in some areas but mismatching others, or adopt a compromise strategy, providing partial matching across different patch types. Existing studies have tested the effectiveness of compromise strategies in only a limited set of circumstances, primarily with small targets varying in pattern, and usually in screen-based tasks. Here, we measured the detection risk associated with different background-matching strategies for relatively large targets, with human observers searching for them in natural scenes, and focusing on colour. Model prey were designed to either ‘specialise’ on the colour of common microhabitat patches, or ‘generalise’ by matching the average colour of the whole visual scenes. Results In both the field and an equivalent online computer-based search task, targets adopting the generalist strategy were more successful in evading detection than those matching microhabitat patches. This advantage occurred because, across all possible locations in these experiments, targets were typically viewed against a patchwork of different microhabitat areas; the putatively generalist targets were thus more similar on average to their various immediate surroundings than were the specialists. Conclusions Demonstrating close agreement between the results of field and online search experiments provides useful validation of online citizen science methods commonly used to test principles of camouflage, at least for human observers. In finding a survival benefit to matching the average colour of the visual scenes in our chosen environment, our results highlight the importance of relative scales in determining optimal camouflage strategies, and suggest how compromise coloration can succeed in nature.

scholarly journals Transformation from independent to integrative coding of multi-object arrangements in human visual cortex

2017 ◽  
Author(s):  
Daniel Kaiser ◽  
Marius V. Peelen
Keyword(s):  
Visual Cortex ◽  
Visual System ◽  
Activity Patterns ◽  
Spatial Arrangement ◽  
Living Room ◽  
Natural Scenes ◽  
Response Patterns ◽  
Object Representations ◽  
Individual Object ◽  
Object Coding

AbstractTo optimize processing, the human visual system utilizes regularities present in naturalistic visual input. One of these regularities is the relative position of objects in a scene (e.g., a sofa in front of a television), with behavioral research showing that regularly positioned objects are easier to perceive and to remember. Here we use fMRI to test how positional regularities are encoded in the visual system. Participants viewed pairs of objects that formed minimalistic two-object scenes (e.g., a “living room” consisting of a sofa and television) presented in their regularly experienced spatial arrangement or in an irregular arrangement (with interchanged positions). Additionally, single objects were presented centrally and in isolation. Multi-voxel activity patterns evoked by the object pairs were modeled as the average of the response patterns evoked by the two single objects forming the pair. In two experiments, this approximation in object-selective cortex was significantly less accurate for the regularly than the irregularly positioned pairs, indicating integration of individual object representations. More detailed analysis revealed a transition from independent to integrative coding along the posterior-anterior axis of the visual cortex, with the independent component (but not the integrative component) being almost perfectly predicted by object selectivity across the visual hierarchy. These results reveal a transitional stage between individual object and multi-object coding in visual cortex, providing a possible neural correlate of efficient processing of regularly positioned objects in natural scenes.

scholarly journals Visual cortex represents the statistical distributions of objects in natural scenes

2010 ◽  
Vol 10 (7) ◽  
pp. 1260-1260
Author(s):  
D. Stansbury ◽  
T. Naselaris ◽  
A. Vu ◽  
J. Gallant
Keyword(s):  
Visual Cortex ◽  
Natural Scenes ◽  
Statistical Distributions

scholarly journals Predictors of proximity to others in colony housed shelter cats (Felis silvestris catus)

2016 ◽  
pp. 24 ◽  
Author(s):  
Malini Suchak ◽  
Michael Piombino ◽  
Kalina Bracco
Keyword(s):  
Past History ◽  
Individual Variability ◽  
Felis Silvestris Catus ◽  
Future Studies ◽  
The Past ◽  
Close Proximity ◽  
History Of ◽  
Adult Cats ◽  
Stress Behaviors ◽  
High Degree

Colony housing of cats allows shelters to maximize the number of cats housed in limited space. Most research on colony-housed cats examines stress in relation to group size or enclosure size.  While this is important for evaluating welfare, it is equally important to understand how cats are interacting socially in these colonies. We observed 259 adult cats housed in groups of two to eight individuals. Scan samples were used to assess how frequently individual cats were in close proximity to other cats. These data were used to measure individual differences in sociability and patterns of proximity to certain partners. We used information about the past history of the cat, which was collected upon admission to the shelter to identify predictors of time spent in proximity. There was a high degree of inter-individual variability in sociability. Strays tended to spend less time in proximity to other cats, and this effect was most pronounced in females.However, none of the information collected upon admission predicted patterns of proximity to certain partners, or which cats spent time in association witheach other. Future studies should explore the implications of differences in sociability by associating observations of social behavior and stress behaviors.

scholarly journals Figure-Ground Organization in Visual Cortex for Natural Scenes

eNeuro ◽  
2016 ◽  
Vol 3 (6) ◽  
pp. ENEURO.0127-16.2016 ◽  
Author(s):  
Jonathan R. Williford ◽  
Rüdiger von der Heydt
Keyword(s):  
Visual Cortex ◽  
Natural Scenes ◽  
Ground Organization
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