Spatial summation in macaque parietal area 7a follows a winner-take-all rule

2011 ◽  
Vol 105 (3) ◽  
pp. 1150-1158 ◽  
Author(s):  
Anna Oleksiak ◽  
P. Christiaan Klink ◽  
Albert Postma ◽  
Ineke J. M. van der Ham ◽  
Martin J. Lankheet ◽  
...  
Keyword(s):  
Receptive Field ◽  
Spatial Attention ◽  
Posterior Parietal Cortex ◽  
Temporal Dynamics ◽  
Spatial Summation ◽  
Parietal Area ◽  
Area 7A ◽  
Summation Rule ◽  
Winner Take All ◽  
Take All

While neurons in posterior parietal cortex have been found to signal the presence of a salient stimulus among multiple items in a display, spatial summation within their receptive field in the absence of an attentional bias has never been investigated. This information, however, is indispensable when one investigates the mechanisms of spatial attention and competition between multiple visual objects. To examine the spatial summation rule in parietal area 7a neurons, we trained rhesus monkeys to fixate on a central cross while two identical stimuli were briefly displayed in a neuron's receptive field. The response to a pair of dots was compared with the responses to the same dots when they were presented individually. The scaling and power parameters of a generalized summation algorithm varied greatly, both across neurons and across combinations of stimulus locations. However, the averaged response of the recorded population of 7a neurons was consistent with a winner-take-all rule for spatial summation. A control experiment where a monkey covertly attended to both stimuli simultaneously suggests that attention introduces additional competition by facilitating the less optimal stimulus. Thus an averaging stage is introduced between ∼200 and 300 ms of the response to a pair of stimuli. In short, the summation algorithm over the population of area 7a neurons carries the signature of a winner-take-all operation, with spatial attention possibly influencing the temporal dynamics of stimulus competition, that is the moment that the “winner” takes “victory” over the “loser” stimulus.

scholarly journals Gravitational models explain shifts on human visual attention

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Dario Zanca ◽  
Marco Gori ◽  
Stefano Melacci ◽  
Alessandra Rufa
Keyword(s):  
Visual Attention ◽  
Temporal Dynamics ◽  
Sensory Information ◽  
Saliency Map ◽  
Feature Maps ◽  
Single Feature ◽  
Single Location ◽  
Two Phases ◽  
Winner Take All ◽  
Take All

Abstract Visual attention refers to the human brain’s ability to select relevant sensory information for preferential processing, improving performance in visual and cognitive tasks. It proceeds in two phases. One in which visual feature maps are acquired and processed in parallel. Another where the information from these maps is merged in order to select a single location to be attended for further and more complex computations and reasoning. Its computational description is challenging, especially if the temporal dynamics of the process are taken into account. Numerous methods to estimate saliency have been proposed in the last 3 decades. They achieve almost perfect performance in estimating saliency at the pixel level, but the way they generate shifts in visual attention fully depends on winner-take-all (WTA) circuitry. WTA is implemented by the biological hardware in order to select a location with maximum saliency, towards which to direct overt attention. In this paper we propose a gravitational model to describe the attentional shifts. Every single feature acts as an attractor and the shifts are the result of the joint effects of the attractors. In the current framework, the assumption of a single, centralized saliency map is no longer necessary, though still plausible. Quantitative results on two large image datasets show that this model predicts shifts more accurately than winner-take-all.

scholarly journals Cue Competition Affects Temporal Dynamics of Edge-assignment in Human Visual Cortex

2011 ◽  
Vol 23 (3) ◽  
pp. 631-644 ◽  
Author(s):  
Joseph L. Brooks ◽  
Stephen E. Palmer
Keyword(s):  
Temporal Dynamics ◽  
Neural Mechanisms ◽  
Cue Competition ◽  
Relative Depth ◽  
Competition And Cooperation ◽  
Neural Representations ◽  
Winner Take All ◽  
Take All ◽  
Figural Assignment ◽  
Ground Organization

Edge-assignment determines the perception of relative depth across an edge and the shape of the closer side. Many cues determine edge-assignment, but relatively little is known about the neural mechanisms involved in combining these cues. Here, we manipulated extremal edge and attention cues to bias edge-assignment such that these two cues either cooperated or competed. To index their neural representations, we flickered figure and ground regions at different frequencies and measured the corresponding steady-state visual-evoked potentials (SSVEPs). Figural regions had stronger SSVEP responses than ground regions, independent of whether they were attended or unattended. In addition, competition and cooperation between the two edge-assignment cues significantly affected the temporal dynamics of edge-assignment processes. The figural SSVEP response peaked earlier when the cues causing it cooperated than when they competed, but sustained edge-assignment effects were equivalent for cooperating and competing cues, consistent with a winner-take-all outcome. These results provide physiological evidence that figure–ground organization involves competitive processes that can affect the latency of figural assignment.

Simulation of motion on the skin. II. Cutaneous mechanoreceptor coding of the width and texture of bar patterns displaced across the OPTACON

1989 ◽  
Vol 62 (6) ◽  
pp. 1437-1460 ◽  
Author(s):  
E. P. Gardner ◽  
C. I. Palmer
Keyword(s):  
Receptive Field ◽  
Receptive Fields ◽  
Leading Edge ◽  
Variable Density ◽  
Pacinian Corpuscles ◽  
Single Row ◽  
Simultaneous Activation ◽  
Computer Controlled ◽  
Winner Take All ◽  
Take All

1. These experiments assay the functional significance of receptive-field architecture for information processing. Rapidly adapting (RA) afferents have been previously shown to converge information from clusters of 14-25 Meissner's corpuscles, whereas afferents innervating Pacinian corpuscles (PCs) have only a single, large receptor terminal. We tested two opposing hypotheses of functional architecture: 1) summation models, in which an afferent integrates signals from all of its terminals, showing monotonic increases in activity as a function of contact area, and 2) winner-take-all models, in which the most strongly activated receptor in the cluster dominates axonal output by cancellation of signals from other branches. 2. Bar and stripe patterns have been swept across the finger or palm of the monkey's hand at speeds of 30-120 mm/s with the use of a computer-controlled grid of sequentially activated miniature probes (OPTACON stimulator). The dense packing of OPTACON probes permits placement of up to five groups of stimulators within an individual receptive field, allowing us to activate one or more clusters of Meissner's corpuscles simultaneously and to stimulate the bulbar corpuscle of PC afferents at different orientations through the skin. Integration of information from moving bar patterns has been tested with two protocols. In the variable width protocol, the total number of activated rows in the pattern is varied from one to five, with a constant spacing of 1.2 mm between pulsed rows. In the variable density protocol, the length of skin stimulated is held constant at 5 mm and the spacing of stimuli varied. 3. RA afferents show no evidence of summation of inputs within their receptive fields. Motion of wide bars across the field increases the duration of firing but not the total spikes evoked by each pulse. Responses to the leading edge of wide bars were found to be identical to those evoked by a single-row bar. Simultaneous activation of two to five rows evokes the same or fewer spikes per pulse than the most effective individual row tested alone. When broad-bar patterns are centered over the field, contacting the maximum number of receptors, RAs follow activity in the dominant branch or terminus, suppressing additional inputs. Lack of summation is observed at all pulse frequencies tested (25-100 Hz). 4. Moving bar patterns evoke responses as long as at least one row stimulates the receptive field; broader patterns evoke longer spike trains whose total number of impulses is proportional to bar width.(ABSTRACT TRUNCATED AT 400 WORDS)

scholarly journals Visual and Vestibular Selectivity for Self-Motion in Macaque Posterior Parietal Area 7a

2018 ◽  
Vol 29 (9) ◽  
pp. 3932-3947 ◽  
Author(s):  
Eric Avila ◽  
Kaushik J Lakshminarasimhan ◽  
Gregory C DeAngelis ◽  
Dora E Angelaki
Keyword(s):  
Temporal Dynamics ◽  
Hippocampal Formation ◽  
Neuronal Population ◽  
Motion Processing ◽  
Response Patterns ◽  
General Belief ◽  
Parietal Area ◽  
Area 7A ◽  
Posterior Parietal ◽  
Self Motion

Abstract We examined the responses of neurons in posterior parietal area 7a to passive rotational and translational self-motion stimuli, while systematically varying the speed of visually simulated (optic flow cues) or actual (vestibular cues) self-motion. Contrary to a general belief that responses in area 7a are predominantly visual, we found evidence for a vestibular dominance in self-motion processing. Only a small fraction of neurons showed multisensory convergence of visual/vestibular and linear/angular self-motion cues. These findings suggest possibly independent neuronal population codes for visual versus vestibular and linear versus angular self-motion. Neural responses scaled with self-motion magnitude (i.e., speed) but temporal dynamics were diverse across the population. Analyses of laminar recordings showed a strong distance-dependent decrease for correlations in stimulus-induced (signal correlation) and stimulus-independent (noise correlation) components of spike-count variability, supporting the notion that neurons are spatially clustered with respect to their sensory representation of motion. Single-unit and multiunit response patterns were also correlated, but no other systematic dependencies on cortical layers or columns were observed. These findings describe a likely independent multimodal neural code for linear and angular self-motion in a posterior parietal area of the macaque brain that is connected to the hippocampal formation.

Interest Groups and Elections

2019 ◽  
pp. 339-357
Author(s):  
Jeffrey M. Berry
Keyword(s):  
Political Parties ◽  
Interest Groups ◽  
Campaign Finance ◽  
Organizational Forms ◽  
Super Pacs ◽  
New Organizational Forms ◽  
Winner Take All ◽  
The Impact ◽  
Take All

The relationships between interest groups, political parties, and elections have always been dynamic, but in recent years change has accelerated in ways that have favored some interests over others. This chapter considers these developments as the result of a variety of factors, the most critical of which are the growth of polarization, a new legal landscape for campaign finance, and new organizational forms. The chapter goes on to suggest, that as bipartisanship has ebbed, elections have become winner-take-all affairs and interest groups are pushed to choose sides. The chapter further suggests that the rise of super PACs is especially notable as wealthy individuals have become increasingly important, single sources of campaign money, supplanting in part traditional interest groups, especially conventional PACs. It concludes that even as sums spent by super PACs and other interest groups have skyrocketed, the impact of their direct spending on persuading voters remains uncertain.

The role of the teacher in learning-based models of parietal area 7a

1988 ◽  
Vol 21 (3) ◽  
pp. 505-512 ◽  
Author(s):  
David Zipser ◽  
Richard A. Andersen
Keyword(s):  
Parietal Area ◽  
Area 7A
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