scholarly journals Disentangling the Role of Cortico-Basal Ganglia Loops in Top–Down and Bottom–Up Visual Attention: An Investigation of Attention Deficits in Parkinson Disease

2015 ◽  
Vol 27 (6) ◽  
pp. 1215-1237 ◽  
Author(s):  
Giorgio Tommasi ◽  
Mirta Fiorio ◽  
Jérôme Yelnik ◽  
Paul Krack ◽  
Francesca Sala ◽  
...  
Keyword(s):  
Visual Attention ◽  
Parkinson Disease ◽  
Attentional Capture ◽  
Motor Response ◽  
Response Selection ◽  
The Other ◽  
Top Down ◽  
Movement Initiation ◽  
Bottom Up ◽  
Brain Functions

It is solidly established that top–down (goal-driven) and bottom–up (stimulus-driven) attention mechanisms depend on distributed cortical networks, including prefrontal and frontoparietal regions. On the other hand, it is less clear whether the BG also contribute to one or the other of these mechanisms, or to both. The current study was principally undertaken to clarify this issue. Parkinson disease (PD), a neurodegenerative disorder primarily affecting the BG, has proven to be an effective model for investigating the contribution of the BG to different brain functions; therefore, we set out to investigate deficits of top–down and bottom–up attention in a selected cohort of PD patients. With this objective in mind, we compared the performance on three computerized tasks of two groups of 12 parkinsonian patients (assessed without any treatment), one otherwise pharmacologically treated and the other also surgically treated, with that of a group of controls. The main behavioral tool for our study was an attentional capture task, which enabled us to tap the competition between top–down and bottom–up mechanisms of visual attention. This task was suitably combined with a choice RT and a simple RT task to isolate any specific deficit of attention from deficits in motor response selection and initiation. In the two groups of patients, we found an equivalent increase of attentional capture but also comparable delays in target selection in the absence of any salient distractor (reflecting impaired top–down mechanisms) and movement initiation compared with controls. In contrast, motor response selection processes appeared to be prolonged only in the operated patients. Our results confirm that the BG are involved in both motor and cognitive domains. Specifically, damage to the BG, as it occurs in PD, leads to a distinct deficit of top–down control of visual attention, and this can account, albeit indirectly, for the enhancement of attentional capture, reflecting weakened ability of top–down mechanisms to antagonize bottom–up control.

scholarly journals Different Roles of Top-Down and Bottom-Up Processes in the Distribution of Size-Fractionated Phytoplankton in Gwangyang Bay

Water ◽  
2021 ◽  
Vol 13 (12) ◽  
pp. 1682
Author(s):  
Yoonja Kang ◽  
Yeongji Oh
Keyword(s):  
Nutrient Availability ◽  
Fast Response ◽  
Nutrient Addition ◽  
The Other ◽  
Zooplankton Grazing ◽  
Top Down ◽  
Bottom Up ◽  
Phytoplankton Distribution ◽  
Summer Bloom ◽  
Gwangyang Bay

The interactive roles of zooplankton grazing (top-down) and nutrient (bottom-up) processes on phytoplankton distribution in a temperate estuary were investigated via dilution and nutrient addition experiments. The responses of size-fractionated phytoplankton and major phytoplankton groups, as determined by flow cytometry, were examined in association with zooplankton grazing and nutrient availability. The summer bloom was attributed to nanoplankton, and microplankton was largely responsible for the winter bloom, whereas the picoplankton biomass was relatively consistent throughout the sampling periods, except for the fall. The nutrient addition experiments illustrated that nanoplankton responded more quickly to phosphate than the other groups in the summer, whereas microplankton had a faster response to most nutrients in the winter. The dilution experiments ascribed that the grazing mortality rates of eukaryotes were low compared to those of the other groups, whereas autotrophic cyanobacteria were more palatable to zooplankton than cryptophytes and eukaryotes. Our experimental results indicate that efficient escape from zooplankton grazing and fast response to nutrient availability synergistically caused the microplankton to bloom in the winter, whereas the bottom-up process (i.e., the phosphate effect) largely governed the nanoplankton bloom in the summer.

scholarly journals The Research of Bottom-Up and Top-Down Combination Visual Attention Calculative Method

2012 ◽  
Vol 29 ◽  
pp. 3520-3524
Author(s):  
Hui Wang ◽  
Gang Liu ◽  
Yuanyuan Dang
Keyword(s):  
Visual Attention ◽  
Top Down ◽  
Bottom Up

scholarly journals Visual attention strategies for target object detection

2021 ◽  
Author(s):  
◽  
Ibrahim Mohammad Hussain Rahman
Keyword(s):  
Visual Attention ◽  
Object Detection ◽  
Target Object ◽  
Detection Accuracy ◽  
Estimation Model ◽  
Top Down ◽  
Bottom Up ◽  
Feature Map ◽  
Low Level ◽  
Visual Tasks

<p>The human visual attention system (HVA) encompasses a set of interconnected neurological modules that are responsible for analyzing visual stimuli by attending to those regions that are salient. Two contrasting biological mechanisms exist in the HVA systems; bottom-up, data-driven attention and top-down, task-driven attention. The former is mostly responsible for low-level instinctive behaviors, while the latter is responsible for performing complex visual tasks such as target object detection.  Very few computational models have been proposed to model top-down attention, mainly due to three reasons. The first is that the functionality of top-down process involves many influential factors. The second reason is that there is a diversity in top-down responses from task to task. Finally, many biological aspects of the top-down process are not well understood yet.  For the above reasons, it is difficult to come up with a generalized top-down model that could be applied to all high level visual tasks. Instead, this thesis addresses some outstanding issues in modelling top-down attention for one particular task, target object detection. Target object detection is an essential step for analyzing images to further perform complex visual tasks. Target object detection has not been investigated thoroughly when modelling top-down saliency and hence, constitutes the may domain application for this thesis.  The thesis will investigate methods to model top-down attention through various high-level data acquired from images. Furthermore, the thesis will investigate different strategies to dynamically combine bottom-up and top-down processes to improve the detection accuracy, as well as the computational efficiency of the existing and new visual attention models. The following techniques and approaches are proposed to address the outstanding issues in modelling top-down saliency:  1. A top-down saliency model that weights low-level attentional features through contextual knowledge of a scene. The proposed model assigns weights to features of a novel image by extracting a contextual descriptor of the image. The contextual descriptor plays the role of tuning the weighting of low-level features to maximize detection accuracy. By incorporating context into the feature weighting mechanism we improve the quality of the assigned weights to these features.  2. Two modules of target features combined with contextual weighting to improve detection accuracy of the target object. In this proposed model, two sets of attentional feature weights are learned, one through context and the other through target features. When both sources of knowledge are used to model top-down attention, a drastic increase in detection accuracy is achieved in images with complex backgrounds and a variety of target objects.  3. A top-down and bottom-up attention combination model based on feature interaction. This model provides a dynamic way for combining both processes by formulating the problem as feature selection. The feature selection exploits the interaction between these features, yielding a robust set of features that would maximize both the detection accuracy and the overall efficiency of the system.  4. A feature map quality score estimation model that is able to accurately predict the detection accuracy score of any previously novel feature map without the need of groundtruth data. The model extracts various local, global, geometrical and statistical characteristic features from a feature map. These characteristics guide a regression model to estimate the quality of a novel map.  5. A dynamic feature integration framework for combining bottom-up and top-down saliencies at runtime. If the estimation model is able to predict the quality score of any novel feature map accurately, then it is possible to perform dynamic feature map integration based on the estimated value. We propose two frameworks for feature map integration using the estimation model. The proposed integration framework achieves higher human fixation prediction accuracy with minimum number of feature maps than that achieved by combining all feature maps.  The proposed works in this thesis provide new directions in modelling top-down saliency for target object detection. In addition, dynamic approaches for top-down and bottom-up combination show considerable improvements over existing approaches in both efficiency and accuracy.</p>

Wired for Warmth

2012 ◽  
Vol 2 (3) ◽  
pp. 17-28
Author(s):  
Alan E. Singer
Keyword(s):  
Ethical Behavior ◽  
The Other ◽  
Computer Engineering ◽  
Top Down ◽  
Moral Consciousness ◽  
Bottom Up ◽  
The Real ◽  
Moral Agents ◽  
Artificial Moral Agents ◽  
The Relationship

An aspect of the relationship between philosophy and computer engineering is considered, with particular emphasis upon the design of artificial moral agents. Top-down vs. bottom-up approaches to ethical behavior are discussed, followed by an overview of some of the ways in which traditional ethics has informed robotics. Two macro-trends are then identified, one involving the evolution of moral consciousness in man and machine, the other involving the fading away of the boundary between the real and the virtual.

Neural substrates of visual percepts, imagery, and hallucinations

2002 ◽  
Vol 25 (2) ◽  
pp. 194-195
Author(s):  
Stephen Grossberg
Keyword(s):  
Visual Attention ◽  
Normal Control ◽  
Mental Imagery ◽  
Visual Information ◽  
Neural Substrates ◽  
Visual Hallucinations ◽  
Neural Models ◽  
Top Down ◽  
Bottom Up

Recent neural models clarify many properties of mental imagery as part of the process whereby bottom-up visual information is influenced by top-down expectations, and how these expectations control visual attention. Volitional signals can transform modulatory top-down signals into supra-threshold imagery. Visual hallucinations can occur when the normal control of these volitional signals is lost.

Dissection of early bottom-up and top-down deficits during visual attention in schizophrenia

2011 ◽  
Vol 122 (1) ◽  
pp. 90-98 ◽  
Author(s):  
Andres H. Neuhaus ◽  
Christine Karl ◽  
Eric Hahn ◽  
Niklas R. Trempler ◽  
Carolin Opgen-Rhein ◽  
...  
Keyword(s):  
Visual Attention ◽  
Top Down ◽  
Bottom Up

Visual Attention With Cognitive Aging

2019 ◽  
Author(s):  
David J. Madden ◽  
Zachary A. Monge
Keyword(s):  
Visual Attention ◽  
Visual Processing ◽  
Cognitive Aging ◽  
Brain Regions ◽  
Object Identification ◽  
Features Selection ◽  
Top Down ◽  
Bottom Up ◽  
Attentional Functioning ◽  
Age Related

Age-related decline occurs in several aspects of fluid, speed-dependent cognition, particularly those related to attention. Empirical research on visual attention has determined that attention-related effects occur across a range of information processing components, including the sensory registration of features, selection of information from working memory, controlling motor responses, and coordinating multiple perceptual and cognitive tasks. Thus, attention is a multifaceted construct that is relevant at virtually all stages of object identification. A fundamental theme of attentional functioning is the interaction between the bottom-up salience of visual features and top-down allocation of processing based on the observer’s goals. An underlying age-related slowing is prominent throughout visual processing stages, which in turn contributes to age-related decline in some aspects of attention, such as the inhibition of irrelevant information and the coordination of multiple tasks. However, some age-related preservation of attentional functioning is also evident, particularly the top-down allocation of attention. Neuroimaging research has identified networks of frontal and parietal brain regions relevant for top-down and bottom-up attentional processing. Disconnection among these networks contributes to an age-related decline in attention, but preservation and perhaps even increased patterns of functional brain activation and connectivity also contribute to preserved attentional functioning.

scholarly journals The Global Laboratory of Investment Law Reform Alternatives

AJIL Unbound ◽  
2018 ◽  
Vol 112 ◽  
pp. 237-243
Author(s):  
Wolfgang Alschner
Keyword(s):  
Real Life ◽  
Analytical Framework ◽  
The Other ◽  
Law Reform ◽  
Institutional Choice ◽  
Top Down ◽  
Policy Goal ◽  
Bottom Up ◽  
Investment Law ◽  
Institutional Choices

There are two ways of thinking about institutional choice in the context of multilateral investment law reform. One starts from abstract principles, asking what policy goal investment law is supposed to achieve and what institutional choice most effectively advances that goal. The other draws on practical experimentation, asking what institutional choices states are making and how these choices perform in real life. Sergio Puig and Gregory Shaffer present a compelling analytical framework for the former, top-down approach to investment law reform. In this essay, I will scrutinize their analysis and argue that the latter, bottom-up approach is more promising.

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