Decoding Neural Mechanisms Of Surround Suppression In Feature Based Attention
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Decoding Neural Mechanisms Of Surround Suppression In Feature Based Attention
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Author : Wanghaoming Fang
language : en
Publisher:
Release Date : 2021
Decoding Neural Mechanisms Of Surround Suppression In Feature Based Attention written by Wanghaoming Fang and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2021 with Electronic dissertations categories.
Feature-based attention (FBA) selectively enhances processing of an attended feature at the expense of unattended or task-irrelevant features. Recent studies showed that FBA modulates the perceptual space with both a monotonic profile (i.e., feature-similarity gain) and a non-monotonic profile (i.e., surround suppression). A significant question arises regarding the neural mechanism of the non-monotonic surround suppression effect. Previous studies have suggested that two candidate neuronal mechanisms could underlie these attentional modulations: a shift of neuronal tuning preference toward the attended feature, or a multiplicative gain modulation that scales the overall responses without changing their tuning property. Yet the empirical evidence for these mechanisms is still lacking. In the current work, we explored how these neuronal mechanism manifest at the level of fMRI BOLD measurement using a simulation approach. Specifically, we employed an encoding/decoding approach by first simulating voxel responses from neuronal population assuming either mechanism and then applying a regression-based inverted encoding model (IEM) and a Bayesian method to decode population representations. We found that both methods captured the signature patterns associated with these different neuronal mechanisms. In our second aim, we systematically varied the correlation structure of voxel noise to further compare these different multivariate methods in a stimulus classification task. Our results showed a clear advantage of the Bayesian method over IEM, suggesting that the Bayesian method was superior for deciphering neural representation given the prevalent noise correlation and variable tuning width in the brain. In sum, our current simulation work may provide a proof of concept for future empirical studies investigating cortical mechanism of FBA using non-invasive methods, as well as guidance for choosing suitable methods in these investigations.
Feature Based Attention In Primate Visual Cortex
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Author : Philipp Schwedhelm
language : de
Publisher:
Release Date : 2015
Feature Based Attention In Primate Visual Cortex written by Philipp Schwedhelm and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2015 with categories.
The scope of this thesis, after a brief summary of the core ideas of top-down attentional control is given (Chapter 2.1), is to shed some light on the cortical control circuit underlying the deployment of feature-based attention. A first study (Chapter 2.2) deduces from human psychophysical performance how an attentional signal acts on a local sensory population of motion-selective neurons. A second empirical study (Chapter 2.3) attempts to identify and characterize resource limitations for the deployment of feature-based attention in macaque monkeys. In particular, the aim of the study was ...
Neural Mechanisms Of Attention And Speech Perception In Complex Spatial Acoustic Environment
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Author : Prachi Patel
language : en
Publisher:
Release Date : 2023
Neural Mechanisms Of Attention And Speech Perception In Complex Spatial Acoustic Environment written by Prachi Patel and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2023 with categories.
Furthermore, I show that these features are orthogonal to each other and do not interact. This representation enables successful decoding of both spatial and phonetic information. These findings contribute to defining the functional organization of responses in the human auditory cortex, with implications for more accurate neurophysiological models of spatial speech processing. I take a step further to investigate the role of attention in encoding the direction and phonetic features of speech. I play a mixture of male and female spatialized talkers eg. male at left side to the listener and female at right side (talker's locations switch randomly after each sentence). I ask the listener to follow a given talker e.g. follow male talker as they switch their location after each uttered sentence. While the listener performs this experiment, I collect intracranial EEG data from their auditory cortex. I investigate the bottom-up stimulus dependent and attention independent encoding of such a cocktail party speech and the top-down attention driven role in the encoding of location and speech features.
Neural Mechanisms Of Selective Attention To Visual Features
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Author : Sean Patrick Fannon
language : en
Publisher:
Release Date : 2006
Neural Mechanisms Of Selective Attention To Visual Features written by Sean Patrick Fannon and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2006 with Attention categories.
Perceptual Consequences Of Surround Suppression And Plasticity In Visual Motion Processing
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Author : Liu Liu
language : en
Publisher:
Release Date : 2017
Perceptual Consequences Of Surround Suppression And Plasticity In Visual Motion Processing written by Liu Liu and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2017 with categories.
"The visual nervous system transforms the input from the visual scene into electrical signals. The electrical signals are in turn read out by other areas of the brain to form perceptual decisions. The relationship between neuronal responses evoked by sensory stimuli and their perceptual correlates is an important research question in modern computational and systems neuroscience. Previous studies of this relationship focused on correlating the response of single neurons to stimuli in their receptive field (RF), defined as a region of the visual space where selective stimuli can evoke a response. However, single neurons are part of a local circuitry that controls their selectivity and modulates their response. The local circuitry is composed of many neurons that encode surrounding regions of the visual space. The neurons in the circuit can interact via excitatory or inhibitory connections. The interactions are crucial for contextual modulation of single neuron response, since any stimulus on the RF of a neuron is part of a larger visual context. Aside from the contextual modulation of neuronal responses, another part of the sensory-to-decision transformation is how the responses of neurons are read out from a population. Correlations in the responses of neurons can have a large impact in the amount of information in a population, and this correlation should be quantified when considering a population readout.Another level of complexity is that downstream areas must use this sensory code flexibly in perceptual decision making. Many neurons and areas can contain the information about the sensory stimulus, and the readout should correspond to the experience of the animal. This thesis investigates these issues in order. In chapter 2, I determine the neural basis for a type of contextual modulation in our motion perception, the worsening of motion perception at large stimulus size. Large stimuli suppress the firing rate of neurons in a form of contextual modulation known as surround suppression. I simultaneously record from multiple neurons in the middle temporal visual area (MT), and I perform a simulation of the recorded responses and the correlation structure. I find surround suppression improves the population sensitivity for small stimuli at the expense of weaker sensitivity for large stimuli. In chapter 3, I examine the underlying circuitry mechanisms for surround suppression. Recent work suggests that the cortex operates in a theoretical network where excitation alone is strong enough to induce instability but inhibition maintains the stability. I pharmacologically manipulate the efficacy of inhibitory processes and find that the neuronal dynamics are consistent with the predictions. I then perform additional experiments to confirm that this network mechanism can be generalized to different stimulus dimensions in MT. In chapter 4, I examine the flexibility of the readout of sensory information. The readout of sensory evidence for visual perception is plastic and depends on recent training experience. I use reversible inactivation and microstimulation to probe the causal relationship between MT neuronal response and perception. I find the causal contribution of MT to visual motion perception depends on training the animals on a specific task of motion integration. This thesis has implications in the broader context of neural coding in health and diseases. Previous work shows that natural aging or disease processes can lead to deficits in our sensory perception, and the reduction of inhibition efficacy has been implicated. Therefore, an understanding of the inhibitory interactions in local cortical circuitry may lead to future treatments and interventions." --
Neural Mechanisms Of Selective Attention To Visual Features
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Author :
language : en
Publisher:
Release Date : 2003
Neural Mechanisms Of Selective Attention To Visual Features written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2003 with categories.
Neural mechanisms of selective attention to visual features.
Experimental Evidence For Top Down Attentional Selection In The Selective Tuning Model Of Visual Attention
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Author : Sang-Ah Yoo
language : en
Publisher:
Release Date : 2019
Experimental Evidence For Top Down Attentional Selection In The Selective Tuning Model Of Visual Attention written by Sang-Ah Yoo and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2019 with categories.
To overcome limited processing capacity, our visual system facilitates information that relates to the task at hand while inhibiting irrelevant information via selective attention. Among various attention models and theories, the Selective Tuning model of visual attention (ST) is a computation model of visual processing that is based on biological mechanisms. This model emphasizes the role of top-down feedback processing in visual perception and has predicted its unique consequences, such as an attentional surround suppression in which the attentional focus is accompanied by an inhibitory surround. The previous studies have experimentally validated STs predictions, indicating that the components in ST do reflect actual visual processing in the brain. Nevertheless, many aspects of ST still need to be elaborated and several predictions and assumptions remain untested. The series of works in this dissertation investigate different aspects of top-down feedback processing in visual perception that ST has proposed to corroborate this model and to broaden our understanding of visual attention. The first study examined whether top-down feedback processing is necessary for an attention-demanding, fine-grained visual localization (Chapter 2). The subsequent two studies focused on the properties of different types of the attentional surround suppression, the end-result of top-down feedback processing. The second study suggested the interplay between the location-based and feature-based surround suppression and tested the potential factors that could manipulate the spatial extent of the location-based suppressive surround (Chapter 3). The last study demonstrated feature-based surround suppression in motion processing and its neurophysiological mechanism (Chapter 4). Collectively, this work reinforces functional significance of top-down, attention-mediated feedback for visual processing and supports the validity of ST as well.
Capabilities And Consequences Of Feature Based Attention
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Author : Angus Chapman
language : en
Publisher:
Release Date : 2022
Capabilities And Consequences Of Feature Based Attention written by Angus Chapman and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2022 with categories.
Attention--the process of selecting and prioritizing relevant stimuli in our environment--has long been considered a highly important cognitive process that enables us to deal with the large volume of information that we encounter at any moment. While we still do not have a complete understanding of the mechanisms that guide selection, different theories have carved out how attention might function with respect to distinct stimulus domains, namely spatial locations, bound objects, or basic visual features. A large body of research has emerged that investigates the behavioral implications of attentional selection within these domains, as well as the neural processes that underlie this selection. To extend upon this work, in this dissertation I present a series of studies exploring fundamental aspects of feature-based attention: how attention spreads between different features within a single object, as well as globally across locations in the visual field; how broader and narrower ranges of relevant colors can be attended simultaneously and efficiently; how attention warps the perception of colors in service of efficient processing, and; how information about target and distractor colors are carried within a neural marker of visual processing, and how representations of those colors are affected by attention. In each of these studies, I tie the main findings back to broader theories connecting feature-based attention with object-based and spatial theories of attention. By considering how these theories interact and make claims about the nature of attentional selection, I argue for a framework in which attention is thought of as a process by which the representational content of information is shaped in support of adaptive behavior, as opposed to a mechanism which highlights particular types of stimuli.
Feature Based Attention And Temporal Selection
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Author : Sarah Christine Tyler
language : en
Publisher:
Release Date : 2014
Feature Based Attention And Temporal Selection written by Sarah Christine Tyler and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2014 with categories.
Attention mechanisms serve to unify our experience of the world, from the earliest stages of selecting parts of the scene for further analysis, to maintaining and manipulating information about objects and how they change over time. Those aspects of the environment we attend to depend strongly on the availability of rich sensory cues and our ability to actively search and identify critical features. Critically, our ability to understand complex actions depends on integrating the flow of information over time into a coherent, continuous event; however, we must selectively attend within that temporal flow to relevant features for further perceptual analysis. This dissertation explores the neural processes involved in attention towards relevant features imbedded in temporal sequences, as well as the properties of the features themselves that promote awareness. Necessary to the selective attentive process is the ability to filter out unimportant information, as well as efficiently utilize the perceptual information available. Using psychophysical and imaging methods, I will examine how the attentive demands involved in analyzing visual features within temporal events can be altered depending on the saliency of the features, task demands, and the interaction of both with top-down volitional control. The first study explores how feature-based attention successfully promotes discrimination of first- and third-order feature defined biological motion targets, and the impact of feature saliency on discrimination performance. We found that saliency of token features impacts perception of biological motion when subjects must integrate either within vs. across multiple feature dimensions. The second study explores the neural mechanisms involved in attending to features imbedded in a dynamic sequence. Our results find that parts of the attentional system involved in filtering out unnecessary perceptual information plays a particular role in attending to temporal features. Finally, the third study focuses on the ability of observers to extract meaningful features from complex temporal patterns and the interference of distracters on attentional engagement. Our results suggest that while persistent features are robust against attentional interference, subjects cannot isolate low-salient transient timing information from temporal sequences. Together, these studies uncover aspects of feature-attention that are modulated by adding temporal structure to visual stimuli.
Visual Cortical Representations Of Bottom Up Salience And Perceptual Continuity
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Author : Brittany Edna Burrows
language : en
Publisher:
Release Date : 2011
Visual Cortical Representations Of Bottom Up Salience And Perceptual Continuity written by Brittany Edna Burrows and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2011 with categories.
The amount of information available to the retina far exceeds the processing capacity of the visual system. Visual attention provides a means by which we can make use of the information available with optimal efficiency, allowing us to selectively process objects that are most likely to help us achieve our behavioral goals while filtering out others. Decades of research have revealed that visual representations of objects aligned with the locus of attention are enhanced, resulting in perceptual benefits. The attentional modulation of visual cortical responses, however, has been almost exclusively characterized within the context of volitionally deployed, top-down attention. Although the behavioral correlates of involuntarily deployed, bottom-up attention are well known, the underlying neural mechanism and its relationship to top-down attention are not. In Chapters 2 and 3 of this thesis, I describe experiments that investigate the neural correlates and mechanisms of bottom-up attention. In order to examine the neural correlates of bottom-up attention, we measured responses of single neurons in area V4 to "popout" stimuli, which differ uniformly from surrounding items and draw attention in a bottom-up manner, and compared them to responses to "conjunction" stimuli, which are composed of a combination of surrounding features and require top-down selection. We found that V4 responses are modulated by popout stimuli. This selectivity was more robust when larger numbers of surrounding items and multiple features were included in the display, and it was absent when only a few items were presented immediately outside the receptive field (RF). We next examined the relationship between bottom-up and top-down attention by measuring responses to these same stimuli while top-down attention was directed to locations distant from the RF. We found that popout selectivity was eliminated, indicating that the salience of popout stimuli is not sufficient to drive selection by V4 neurons under these conditions. These results demonstrate that neurons in feature-selective cortex are influenced by bottom-up attention, but that this influence is limited by top-down attention. Whether the source of the signal initiating attentional deployment is top-down or bottom-up, our gaze is typically aligned with the locus of our attention, making use of the high density of photoreceptors at the fovea of the retina. As we move our eyes around a visual scene to briefly fixate objects for further processing, we do not perceive the explosive onset of motion between each fixation that is created by these eye movements, nor do we perceive a series of individual snapshots from each fixation. Instead, we have a seamless visual experience of our surroundings. This perception of continuity across eye movements is crucial to efficient behavior, and yet the neural mechanisms that support a continuous visual experience are not well understood. In Chapter 4 of this thesis, I describe an experiment that investigates the neural representations of perceptual continuity during saccadic eye movements. In order to examine whether V4 neurons are involved in creating a continuous perceptual experience, we measured the responses of V4 neurons to probe stimuli presented during the preparation of saccadic eye movements to targets distant from the RF. We observed that the responses of area V4 neurons to probe stimuli depended on the similarity between the neuronal preference and the target of a saccade. Specifically, the suppression of V4 responses normally present during the preparation of saccades to targets outside of a neuron's RF was absent when the features of the target were congruent with the preference of the recorded neuron. This target-dependent modulation resulted in a substantial effect of the target match/non-match manipulation on neuronal selectivity. The results are consistent with a computational model in which saccade preparation automatically results in a global target-dependent modulation of visual cortical signals. We suggest that this modulation may contribute to the continuity of perception across saccadic eye movements. The results of this thesis demonstrate that V4 neurons are selective for stimuli that draw bottom-up attention. Surprisingly, this selectivity depends on the availability of top-down attentional resources, suggesting that these two distinct varieties of visual attention rely, at least in part, on a common mechanism. Additionally, this thesis provides evidence that V4 neurons contribute to a seamless perceptual experience by maintaining important visual information transaccadically.