scholarly journals Figure-ground organization in visual cortex for natural scenes

2016 ◽  
Author(s):  
Jonathan R. Williford ◽  
Rüdiger von der Heydt
Keyword(s):  
Visual Cortex ◽  
Temporal Cortex ◽  
Stimulus Onset ◽  
Natural Scenes ◽  
Area V2 ◽  
Response Onset ◽  
Static Images ◽  
Simple Figure ◽  
Image Context ◽  
Ground Organization

AbstractFigure-ground organization and border-ownership assignment are essential for understanding natural scenes. It has been shown that many neurons in the macaque visual cortex signal border-ownership in displays of simple geometric shapes such as squares, but how well these neurons resolve border-ownership in natural scenes is not known. We studied area V2 neurons in behaving macaques with static images of complex natural scenes. We found that about half of the neurons were border-ownership selective for contours in natural scenes and this selectivity originated from the image context. The border-ownership signals emerged within 70 ms after stimulus onset, only ~30 ms after response onset. A substantial fraction of neurons were highly consistent across scenes. Thus, the cortical mechanisms of figure-ground organization are fast and efficient even in images of complex natural scenes. Understanding how the brain performs this task so fast remains a challenge.Significance StatementHere we show, for the first time, that neurons in primate visual area V2 signal border-ownership for objects in complex natural scenes. Surprisingly, these signals appear as early as the border-ownership signals for simple figure displays. In fact, they emerge well before object selective activity appears in infero-temporal cortex, which rules out feedback from that region as an explanation. Thus, “objectness” is detected by extremely fast mechanisms that do not depend on feedback from the known object-recognition centers.

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

scholarly journals Early Visual Cortex Assigns Border Ownership in Natural Scenes According to Image Context

2014 ◽  
Vol 14 (10) ◽  
pp. 588-588 ◽  
Author(s):  
J. R. Williford ◽  
R. von der Heydt
Keyword(s):  
Visual Cortex ◽  
Natural Scenes ◽  
Early Visual Cortex ◽  
Image Context

scholarly journals Incongruent Abstract Stimulus–Response Bindings Result in Response Interference: fMRI and EEG Evidence from Visual Object Classification Priming

2012 ◽  
Vol 24 (3) ◽  
pp. 760-773 ◽  
Author(s):  
Aidan J. Horner ◽  
Richard N. Henson
Keyword(s):  
Temporal Cortex ◽  
Repetition Effect ◽  
Stimulus Onset ◽  
Visual Object ◽  
Stimulus Response ◽  
Repetition Suppression ◽  
Priming Paradigm ◽  
Response Onset ◽  
Abstract Stimulus ◽  
The Brain

Stimulus repetition often leads to facilitated processing, resulting in neural decreases (repetition suppression) and faster RTs (repetition priming). Such repetition-related effects have been attributed to the facilitation of repeated cognitive processes and/or the retrieval of previously encoded stimulus–response (S-R) bindings. Although previous research has dissociated these two forms of learning, their interaction in the brain is not fully understood. Utilizing the spatial and temporal resolutions of fMRI and EEG, respectively, we examined a long-lag classification priming paradigm that required response repetitions or reversals at multiple levels of response representation. We found a repetition effect in occipital/temporal cortex (fMRI) that was time-locked to stimulus onset (EEG) and robust to switches in response, together with a repetition effect in inferior pFC (fMRI) that was time-locked to response onset (EEG) and sensitive to switches in response. The response-sensitive effect occurred even when changing from object names (words) to object pictures between repetitions, suggesting that S-R bindings can code abstract representations of stimuli. Most importantly, we found evidence for interference effects when incongruent S-R bindings were retrieved, with increased neural activity in inferior pFC, demonstrating that retrieval of S-R bindings can result in facilitation or interference, depending on the congruency of response between repetitions.

scholarly journals Figure-Ground Organization in Natural Scenes: Performance of a Recurrent Neural Model Compared with Neurons of Area V2

eNeuro ◽  
2019 ◽  
Vol 6 (3) ◽  
pp. ENEURO.0479-18.2019 ◽  
Author(s):  
Brian Hu ◽  
Rüdiger von der Heydt ◽  
Ernst Niebur
Keyword(s):  
Neural Model ◽  
Natural Scenes ◽  
Area V2 ◽  
Ground Organization

scholarly journals Firing Rate Distributions and Efficiency of Information Transmission of Inferior Temporal Cortex Neurons to Natural Visual Stimuli

1999 ◽  
Vol 11 (3) ◽  
pp. 601-631 ◽  
Author(s):  
Alessandro Treves ◽  
Stefano Panzeri ◽  
Edmund T. Rolls ◽  
Michael Booth ◽  
Edward A. Wakeman
Keyword(s):  
Simple Model ◽  
Information Transmission ◽  
Firing Rate ◽  
Visual Stimulation ◽  
Time Window ◽  
Temporal Cortex ◽  
Exponential Model ◽  
Inferior Temporal Cortex ◽  
Natural Scenes ◽  
Static Images

The distribution of responses of sensory neurons to ecological stimulation has been proposed to be designed to maximize information transmission, which according to a simple model would imply an exponential distribution of spike counts in a given time window. We have used recordings from inferior temporal cortex neurons responding to quasi-natural visual stimulation (presented using a video of everyday lab scenes and a large number of static images of faces and natural scenes) to assess the validity of this exponential model and to develop an alternative simple model of spike count distributions. We find that the exponential model has to be rejected in 84% of cases (at the p < 0.01 level). A new model, which accounts for the firing rate distribution found in terms of slow and fast variability in the inputs that produce neuronal activation, is rejected statistically in only 16% of cases. Finally, we show that the neurons are moderately efficient at transmitting information but not optimally efficient.

scholarly journals Figure-ground organization in the visual cortex: does meaning matter?

2018 ◽  
Vol 119 (1) ◽  
pp. 160-176 ◽  
Author(s):  
Hee-kyoung Ko ◽  
Rüdiger von der Heydt
Keyword(s):  
Visual Cortex ◽  
Object Recognition ◽  
Temporal Lobe ◽  
Stimulus Onset ◽  
Top Down ◽  
General Rules ◽  
The Face ◽  
Shape Selective ◽  
Shape Categorization ◽  
Ground Organization

Figure-ground organization in the visual cortex is generally assumed to be based partly on general rules and partly on specific influences of object recognition in higher centers as found in the temporal lobe. To see if shape familiarity influences figure-ground organization, we tested border ownership-selective neurons in monkey V1/V2 with silhouettes of human and monkey face profiles and “nonsense” silhouettes constructed by mirror-reversing the front part of the profile. We found no superiority of face silhouettes compared with nonsense shapes in eliciting border-ownership signals overall. However, in some neurons, border-ownership signals differed strongly between the two categories consistently across many different profile shapes. Surprisingly, this category selectivity appeared as early as 70 ms after stimulus onset, which is earlier than the typical latency of shape-selective responses but compatible with the earliest face-selective responses in the inferior temporal lobe. Although our results provide no evidence for a delayed top-down influence from object recognition centers, they indicate sophisticated shape categorization mechanisms that are much faster than generally assumed. NEW & NOTEWORTHY A long-standing question is whether low-level sensory representations in cortex are influenced by cognitive “top-down” signals. We studied figure-ground organization in the visual cortex by comparing border-ownership signals for face profiles and matched nonsense shapes. We found no sign of “face superiority” in the population border-ownership signal. However, some neurons consistently differentiated between the face and nonsense categories early on, indicating the presence of shape classification mechanisms that are much faster than previously assumed.

scholarly journals Early Numerosity Encoding in Visual Cortex Is Not Sufficient for the Representation of Numerical Magnitude

2018 ◽  
Vol 30 (12) ◽  
pp. 1788-1802 ◽  
Author(s):  
Michele Fornaciai ◽  
Joonkoo Park
Keyword(s):  
Visual Cortex ◽  
Neural Activity ◽  
Stimulus Onset ◽  
Neural Representation ◽  
Numerical Magnitude ◽  
Sensory Representation ◽  
Area V2 ◽  
Early Visual Cortex ◽  
Multivariate Pattern ◽  
Number Perception

Recent studies have demonstrated that the numerosity of visually presented dot arrays is represented in low-level visual cortex extremely early in latency. However, whether or not such an early neural signature reflects the perceptual representation of numerosity remains unknown. Alternatively, such a signature may indicate the raw sensory representation of the dot-array stimulus before becoming the perceived representation of numerosity. Here, we addressed this question by using the connectedness illusion, whereby arrays with pairwise connected dots are perceived to be less numerous compared with arrays containing isolated dots. Using EEG and fMRI in two independent experiments, we measured neural responses to dot-array stimuli comprising 16 or 32 dots, either isolated or pairwise connected. The effect of connectedness, which reflects the segmentation of the visual stimulus into perceptual units, was observed in the neural activity after 150 msec post stimulus onset in the EEG experiment and in area V3 in the fMRI experiment using a multivariate pattern analysis. In contrast, earlier neural activity before 100 msec and in area V2 was strictly modulated by numerosity regardless of connectedness, suggesting that this early activity reflects the sensory representation of a dot array before perceptual segmentation. Our findings thus demonstrate that the neural representation for numerosity in early visual cortex is not sufficient for visual number perception and suggest that the perceptual encoding of numerosity occurs at or after the segmentation process that takes place later in area V3.

scholarly journals The lateral intraparietal sulcus takes viewpoint changes into account during memory-guided attention in natural scenes

2021 ◽  
Vol 226 (4) ◽  
pp. 989-1006
Author(s):  
Ilenia Salsano ◽  
Valerio Santangelo ◽  
Emiliano Macaluso
Keyword(s):  
Spatial Information ◽  
Temporal Cortex ◽  
Independent Effect ◽  
Long Term Memory ◽  
Natural Scenes ◽  
Behavioral Measures ◽  
Attention Network ◽  
Low Contrast ◽  
Dorsal Attention Network

AbstractPrevious studies demonstrated that long-term memory related to object-position in natural scenes guides visuo-spatial attention during subsequent search. Memory-guided attention has been associated with the activation of memory regions (the medial-temporal cortex) and with the fronto-parietal attention network. Notably, these circuits represent external locations with different frames of reference: egocentric (i.e., eyes/head-centered) in the dorsal attention network vs. allocentric (i.e., world/scene-centered) in the medial temporal cortex. Here we used behavioral measures and fMRI to assess the contribution of egocentric and allocentric spatial information during memory-guided attention. At encoding, participants were presented with real-world scenes and asked to search for and memorize the location of a high-contrast target superimposed in half of the scenes. At retrieval, participants viewed again the same scenes, now all including a low-contrast target. In scenes that included the target at encoding, the target was presented at the same scene-location. Critically, scenes were now shown either from the same or different viewpoint compared with encoding. This resulted in a memory-by-view design (target seen/unseen x same/different view), which allowed us teasing apart the role of allocentric vs. egocentric signals during memory-guided attention. Retrieval-related results showed greater search-accuracy for seen than unseen targets, both in the same and different views, indicating that memory contributes to visual search notwithstanding perspective changes. This view-change independent effect was associated with the activation of the left lateral intra-parietal sulcus. Our results demonstrate that this parietal region mediates memory-guided attention by taking into account allocentric/scene-centered information about the objects' position in the external world.

scholarly journals Myelin densities in retinotopically defined dorsal visual areas of the macaque

2021 ◽  
Author(s):  
Xiaolian Li ◽  
Qi Zhu ◽  
Wim Vanduffel
Keyword(s):  
Visual Cortex ◽  
Visual Field ◽  
Cortical Thickness ◽  
New World Monkeys ◽  
Isotropic Resolution ◽  
Density Mapping ◽  
Area V2 ◽  
Visual Areas ◽  
Density Results

AbstractThe visuotopic organization of dorsal visual cortex rostral to area V2 in primates has been a longstanding source of controversy. Using sub-millimeter phase-encoded retinotopic fMRI mapping, we recently provided evidence for a surprisingly similar visuotopic organization in dorsal visual cortex of macaques compared to previously published maps in New world monkeys (Zhu and Vanduffel, Proc Natl Acad Sci USA 116:2306–2311, 2019). Although individual quadrant representations could be robustly delineated in that study, their grouping into hemifield representations remains a major challenge. Here, we combined in-vivo high-resolution myelin density mapping based on MR imaging (400 µm isotropic resolution) with fine-grained retinotopic fMRI to quantitatively compare myelin densities across retinotopically defined visual areas in macaques. Complementing previously documented differences in populational receptive-field (pRF) size and visual field signs, myelin densities of both quadrants of the dorsolateral posterior area (DLP) and area V3A are significantly different compared to dorsal and ventral area V3. Moreover, no differences in myelin density were observed between the two matching quadrants belonging to areas DLP, V3A, V1, V2 and V4, respectively. This was not the case, however, for the dorsal and ventral quadrants of area V3, which showed significant differences in MR-defined myelin densities, corroborating evidence of previous myelin staining studies. Interestingly, the pRF sizes and visual field signs of both quadrant representations in V3 are not different. Although myelin density correlates with curvature and anticorrelates with cortical thickness when measured across the entire cortex, exactly as in humans, the myelin density results in the visual areas cannot be explained by variability in cortical thickness and curvature between these areas. The present myelin density results largely support our previous model to group the two quadrants of DLP and V3A, rather than grouping DLP- with V3v into a single area VLP, or V3d with V3A+ into DM.

Sign in / Sign up

Export Citation Format

Share Document