scholarly journals Gestalts at threshold could reveal Gestalts as predictions

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Thiago Leiros Costa ◽  
Johan Wagemans
Keyword(s):  
Predictive Processing ◽  
Top Down ◽  
Visual Neurons ◽  
Chance Performance ◽  
Response Profile ◽  
Early Visual Cortex ◽  
Feedback Connections ◽  
And Control ◽  
Contrast Response

AbstractWe review and revisit the predictive processing inspired “Gestalts as predictions” hypothesis. The study of Gestalt phenomena at and below threshold can help clarify the role of higher-order object selective areas and feedback connections in mid-level vision. In two psychophysical experiments assessing manipulations of contrast and configurality we showed that: (1) Gestalt phenomena are robust against saliency manipulations across the psychometric function even below threshold (with the accuracy gains and higher saliency associated with Gestalts being present even around chance performance); and (2) peak differences between Gestalt and control conditions happened around the time where responses to Gestalts are starting to saturate (mimicking the differential contrast response profile of striate vs. extra-striate visual neurons). In addition, Gestalts are associated with steeper psychometric functions in all experiments. We propose that these results reflect the differential engagement of object-selective areas in Gestalt phenomena and of information- or percept-based processing, as opposed to energy- or stimulus-based processing, more generally. In addition, the presence of nonlinearities in the psychometric functions suggest differential top-down modulation of the early visual cortex. We treat this as a proof of principle study, illustrating that classic psychophysics can help assess possible involvement of hierarchical predictive processing in Gestalt phenomena.

Conditionality and Homelessness Services; ‘Practice Realities’ in a Drop-in Centre

2011 ◽  
Vol 10 (4) ◽  
pp. 547-557 ◽  
Author(s):  
Rachael Dobson
Keyword(s):  
Study Analysis ◽  
Front Line ◽  
Top Down ◽  
Bottom Up ◽  
Case Study Analysis ◽  
Support Practices ◽  
And Control ◽  
Policies And Practices

This article provides insights into the client−practitioner interaction, as understood through the eyes of those working at the front-line in a Drop-in Centre for homeless clients. Through a case-study analysis of ‘official’ techniques and informal approaches, it is argued that conditional practices are present in contemporary support practices. However, the picture is fragmented, with practitioners arguing for, but also deviating from, conditional strategies that aspire to shape client behaviour. Choices about appropriate responses are occasionally permeated by ‘top−down’ policy messages that aim to responsibilise and generate change in clients. However there is evidence of ‘bottom−up’ drivers informed by experiences of working with clients at the grassroots. These ‘practice realities’ shift an analysis of conditional tactics from just a moralising and disciplining approach, and suggest a more complex set of events at the front-line. Insights add to ongoing commentary about an apparent policy emphasis on rectifying the behaviour of citizens at the sharp end. Conclusions highlight the role of complexity for understanding therapeutic and disciplining elements in policies and practices. Such debates are especially relevant where they connect to the care and control of individuals understood by practitioners as both transgressive and vulnerable.

scholarly journals The Dorsal Attention Network Reflects Both Encoding Load and Top–down Control during Working Memory

2018 ◽  
Vol 30 (2) ◽  
pp. 144-159 ◽  
Author(s):  
Steve Majerus ◽  
Frédéric Péters ◽  
Marion Bouffier ◽  
Nelson Cowan ◽  
Christophe Phillips
Keyword(s):  
Working Memory ◽  
Recognition Task ◽  
Top Down ◽  
Sensory Stimuli ◽  
Attention Network ◽  
Large Sets ◽  
Dorsal Attention Network ◽  
Memory Control ◽  
And Control

The dorsal attention network is consistently involved in verbal and visual working memory (WM) tasks and has been associated with task-related, top–down control of attention. At the same time, WM capacity has been shown to depend on the amount of information that can be encoded in the focus of attention independently of top–down strategic control. We examined the role of the dorsal attention network in encoding load and top–down memory control during WM by manipulating encoding load and memory control requirements during a short-term probe recognition task for sequences of auditory (digits, letters) or visual (lines, unfamiliar faces) stimuli. Encoding load was manipulated by presenting sequences with small or large sets of memoranda while maintaining the amount of sensory stimuli constant. Top–down control was manipulated by instructing participants to passively maintain all stimuli or to selectively maintain stimuli from a predefined category. By using ROI and searchlight multivariate analysis strategies, we observed that the dorsal attention network encoded information for both load and control conditions in verbal and visuospatial modalities. Decoding of load conditions was in addition observed in modality-specific sensory cortices. These results highlight the complexity of the role of the dorsal attention network in WM by showing that this network supports both quantitative and qualitative aspects of attention during WM encoding, and this is in a partially modality-specific manner.

The Synergy Between Neuroscience and Control Theory: The Nervous System as Inspiration for Hard Control Challenges

2020 ◽  
Vol 3 (1) ◽  
pp. 243-267 ◽  
Author(s):  
Manu S. Madhav ◽  
Noah J. Cowan
Keyword(s):  
Nervous System ◽  
Control Theory ◽  
Control Systems ◽  
Neural Control ◽  
Theoretic Model ◽  
Top Down ◽  
Engineering Control ◽  
And Control ◽  
The Brain

Here, we review the role of control theory in modeling neural control systems through a top-down analysis approach. Specifically, we examine the role of the brain and central nervous system as the controller in the organism, connected to but isolated from the rest of the animal through insulated interfaces. Though biological and engineering control systems operate on similar principles, they differ in several critical features, which makes drawing inspiration from biology for engineering controllers challenging but worthwhile. We also outline a procedure that the control theorist can use to draw inspiration from the biological controller: starting from the intact, behaving animal; designing experiments to deconstruct and model hierarchies of feedback; modifying feedback topologies; perturbing inputs and plant dynamics; using the resultant outputs to perform system identification; and tuning and validating the resultant control-theoretic model using specially engineered robophysical models.

scholarly journals Waves to Waveforms: Performing the Thresholds of Sensors and Sense-Making in the Anthropocene

Arts ◽  
2018 ◽  
Vol 7 (4) ◽  
pp. 70
Author(s):  
Richard Carter
Keyword(s):  
Data Driven ◽  
Sense Making ◽  
Present Moment ◽  
Human Intervention ◽  
Free Verse ◽  
Top Down ◽  
Conceptual Background ◽  
And Control ◽  
Coastal Shorelines

This paper details the technical and conceptual background for the developing art project Waveform. This project is a creative-critical meditation on the role of digital sensors in monitoring and representing environmental change. It explores the origins and functioning of the global sensory architectures used to detect and assess these changes, deconstructing the connotations of omniscience, abstraction, and control associated with the ‘top-down’, data-driven mappings they generate. In so doing, Waveform enacts a speculative instance of how digital sensors can highlight the ambiguities and tensions of life in an increasingly damaged ecology. This experimental aspect involves capturing images of coastal shorelines using an airborne camera drone, and then analysing these using software that maps the outlines of incoming waves. The resulting data is then processed by software that generates text resembling free-verse poetry. These steps are not autonomous, and are subject to human intervention at each stage, with the generated poems being curated so as to engage themes concerning coast, a changing climate, and scientific knowledge-making. The outcome is an assemblage of artefacts, processes, and representations that can suggest alternative narratives of sensing and sense-making, so as to better apprehend the complexities of the present moment.

Morphogenesis of a New Human Herpes-Type Virus Isolate (Sasha Virus)

1973 ◽  
Vol 31 ◽  
pp. 592-593
Author(s):  
R. F. Zeigel ◽  
W. Munyon
Keyword(s):  
Virus Isolate ◽  
Calf Serum ◽  
Uranyl Acetate ◽  
Human Herpes ◽  
Human Embryonic Lung ◽  
Human Herpes Virus ◽  
Intracytoplasmic Inclusions ◽  
Hel Cells ◽  
And Control

In continuing studies on the role of viruses in biochemical transformation, Dr. Munyon has succeeded in isolating a highly infectious human herpes virus. Fluids of buccal pustular lesions from Sasha Munyon (10 mo. old) uiere introduced into monolayer sheets of human embryonic lung (HEL) cell cultures propagated in Eagles’ medium containing 5% calf serum. After 18 hours the cells exhibited a dramatic C.P.E. (intranuclear vacuoles, peripheral patching of chromatin, intracytoplasmic inclusions). Control HEL cells failed to reflect similar changes. Infected and control HEL cells were scraped from plastic flasks at 18 hrs. of incubation and centrifuged at 1200 × g for 15 min. Resultant cell packs uiere fixed in Dalton's chrome osmium, and post-fixed in aqueous uranyl acetate. Figure 1 illustrates typical hexagonal herpes-type nucleocapsids within the intranuclear virogenic regions. The nucleocapsids are approximately 100 nm in diameter. Nuclear membrane “translocation” (budding) uias observed.

Top-Down Processing and Visual Reorientation Illusions in a Virtual Reality Environment

2004 ◽  
Vol 63 (3) ◽  
pp. 143-149 ◽  
Author(s):  
Fred W. Mast ◽  
Charles M. Oman
Keyword(s):  
Virtual Reality ◽  
Visual Processing ◽  
Line Length ◽  
Perceptual Cues ◽  
Virtual Reality Environment ◽  
Top Down ◽  
Test Conditions ◽  
The Subject ◽  
Processing Mechanisms

The role of top-down processing on the horizontal-vertical line length illusion was examined by means of an ambiguous room with dual visual verticals. In one of the test conditions, the subjects were cued to one of the two verticals and were instructed to cognitively reassign the apparent vertical to the cued orientation. When they have mentally adjusted their perception, two lines in a plus sign configuration appeared and the subjects had to evaluate which line was longer. The results showed that the line length appeared longer when it was aligned with the direction of the vertical currently perceived by the subject. This study provides a demonstration that top-down processing influences lower level visual processing mechanisms. In another test condition, the subjects had all perceptual cues available and the influence was even stronger.

Sign in / Sign up

Export Citation Format

Share Document