scholarly journals Object-based attention to one of two superimposed surfaces alters responses in human early visual cortex

2011 ◽  
Vol 105 (3) ◽  
pp. 1258-1265 ◽  
Author(s):  
Vivian M. Ciaramitaro ◽  
Jude F. Mitchell ◽  
Gene R. Stoner ◽  
John H. Reynolds ◽  
Geoffrey M. Boynton
Keyword(s):  
Object Representation ◽  
Sensory Information ◽  
Blood Oxygen Level Dependent ◽  
Feature Binding ◽  
Blood Oxygen Level ◽  
Definitive Evidence ◽  
Object Based ◽  
Visual Areas ◽  
Early Visual Cortex ◽  
Feature Based

Faced with an overwhelming amount of sensory information, we are able to prioritize the processing of select spatial locations and visual features. The neuronal mechanisms underlying such spatial and feature-based selection have been studied in considerable detail. More recent work shows that attention can also be allocated to objects, even spatially superimposed objects composed of dynamically changing features that must be integrated to create a coherent object representation. Much less is known about the mechanisms underlying such object-based selection. Our goal was to investigate behavioral and neuronal responses when attention was directed to one of two objects, specifically one of two superimposed transparent surfaces, in a task designed to preclude space-based and feature-based selection. We used functional magnetic resonance imaging (fMRI) to measure changes in blood oxygen level-dependent (BOLD) signals when attention was deployed to one or the other surface. We found that visual areas V1, V2, V3, V3A, and MT+ showed enhanced BOLD responses to translations of an attended relative to an unattended surface. These results reveal that visual areas as early as V1 can be modulated by attending to objects, even objects defined by dynamically changing elements. This provides definitive evidence in humans that early visual areas are involved in a seemingly high-order process. Furthermore, our results suggest that these early visual areas may participate in object-specific feature “binding,” a process that seemingly must occur for an object or a surface to be the unit of attentional selection.

Equal Degrees of Object Selectivity for Upper and Lower Visual Field Stimuli

2010 ◽  
Vol 104 (4) ◽  
pp. 2075-2081 ◽  
Author(s):  
Lars Strother ◽  
Adrian Aldcroft ◽  
Cheryl Lavell ◽  
Tutis Vilis
Keyword(s):  
Visual Field ◽  
Occipital Cortex ◽  
Recognition System ◽  
Blood Oxygen Level Dependent ◽  
Lower Visual Field ◽  
Blood Oxygen Level ◽  
Visual Areas ◽  
Bold Responses ◽  
Cortical Regions ◽  
Lateral Occipital Cortex

Functional MRI (fMRI) studies of the human object recognition system commonly identify object-selective cortical regions by comparing blood oxygen level–dependent (BOLD) responses to objects versus those to scrambled objects. Object selectivity distinguishes human lateral occipital cortex (LO) from earlier visual areas. Recent studies suggest that, in addition to being object selective, LO is retinotopically organized; LO represents both object and location information. Although LO responses to objects have been shown to depend on location, it is not known whether responses to scrambled objects vary similarly. This is important because it would suggest that the degree of object selectivity in LO does not vary with retinal stimulus position. We used a conventional functional localizer to identify human visual area LO by comparing BOLD responses to objects versus scrambled objects presented to either the upper (UVF) or lower (LVF) visual field. In agreement with recent findings, we found evidence of position-dependent responses to objects. However, we observed the same degree of position dependence for scrambled objects and thus object selectivity did not differ for UVF and LVF stimuli. We conclude that, in terms of BOLD response, LO discriminates objects from non-objects equally well in either visual field location, despite stronger responses to objects in the LVF.

Retinotopic variations of the negative blood-oxygen-level dependent hemodynamic response function in human primary visual cortex

2021 ◽  
Vol 125 (4) ◽  
pp. 1045-1057 ◽  
Author(s):  
Natasha de la Rosa ◽  
David Ress ◽  
Amanda J. Taylor ◽  
Jung Hwan Kim
Keyword(s):  
Visual Cortex ◽  
Response Function ◽  
Complex Dynamics ◽  
Hemodynamic Response ◽  
Blood Oxygen Level Dependent ◽  
Blood Oxygen ◽  
Oxygen Level ◽  
Hemodynamic Response Function ◽  
Blood Oxygen Level ◽  
Early Visual Cortex

We investigate dynamics of the negative hemodynamic response function (nHRF), the negative blood-oxygen-level-dependent (BOLD) response (NBR) evoked by a brief stimulus, in human early visual cortex. Here, we show that the nHRFs are not inverted versions of the corresponding pHRFs. The nHRF has complex dynamics that varied significantly with eccentricity. The results also show shift-invariant temporal linearity does not hold for the NBR.

scholarly journals Rewarding Feedback After Correct Visual Discriminations Has Both General and Specific Influences on Visual Cortex

2010 ◽  
Vol 104 (3) ◽  
pp. 1746-1757 ◽  
Author(s):  
R. S. Weil ◽  
N. Furl ◽  
C. C. Ruff ◽  
M. Symmonds ◽  
G. Flandin ◽  
...  
Keyword(s):  
Visual Cortex ◽  
Visual Stimuli ◽  
Blood Oxygen Level Dependent ◽  
Blood Oxygen Level ◽  
Neural Basis ◽  
Correct Performance ◽  
Visual Events ◽  
Visual Areas ◽  
Improved Performance ◽  
Time Point

Reward can influence visual performance, but the neural basis of this effect remains poorly understood. Here we used functional magnetic resonance imaging to investigate how rewarding feedback affected activity in distinct areas of human visual cortex, separating rewarding feedback events after correct performance from preceding visual events. Participants discriminated oriented gratings in either hemifield, receiving auditory feedback at trial end that signaled financial reward after correct performance. Greater rewards improved performance for all but the most difficult trials. Rewarding feedback increased blood-oxygen-level-dependent (BOLD) signals in striatum and orbitofrontal cortex. It also increased BOLD signals in visual areas beyond retinotopic cortex, but not in primary visual cortex representing the judged stimuli. These modulations were seen at a time point in which no visual stimuli were presented or expected, demonstrating a novel type of activity change in visual cortex that cannot reflect modulation of response to incoming or anticipated visual stimuli. Rewarded trials led on the next trial to improved performance and enhanced visual activity contralateral to the judged stimulus, for retinotopic representations of the judged visual stimuli in V1. Our findings distinguish general effects in nonretinotopic visual cortex when receiving rewarding feedback after correct performance from consequences of reward for spatially specific responses in V1.

Orientation Anisotropies in Human Visual Cortex

2010 ◽  
Vol 103 (6) ◽  
pp. 3465-3471 ◽  
Author(s):  
Damien J. Mannion ◽  
J. Scott McDonald ◽  
Colin W. G. Clifford
Keyword(s):  
Visual Image ◽  
Cortical Activity ◽  
Blood Oxygen Level Dependent ◽  
Sinusoidal Grating ◽  
Natural Environments ◽  
Blood Oxygen ◽  
Fundamental Operation ◽  
Blood Oxygen Level ◽  
Visual Areas ◽  
Dependent Activity

Representing the orientation of features in the visual image is a fundamental operation of the early cortical visual system. The nature of such representations can be informed by considering anisotropic distributions of response across the range of orientations. Here we used functional MRI to study modulations in the cortical activity elicited by observation of a sinusoidal grating that varied in orientation. We report a significant anisotropy in the measured blood-oxygen level-dependent activity within visual areas V1, V2, V3, and V3A/B in which horizontal orientations evoked a reduced response. These visual areas and hV4 showed a further anisotropy in which increased responses were observed for orientations that were radial to the point of fixation. We speculate that the anisotropies in cortical activity may be related to anisotropies in the prevalence and behavioral relevance of orientations in typical natural environments.

scholarly journals fMRI of the rod scotoma elucidates cortical rod pathways and implications for lesion measurements

2015 ◽  
Vol 112 (16) ◽  
pp. 5201-5206 ◽  
Author(s):  
Brian Barton ◽  
Alyssa A. Brewer
Keyword(s):  
Blood Oxygen Level Dependent ◽  
Cortical Reorganization ◽  
Blood Oxygen Level ◽  
Short Term ◽  
Traumatic Lesion ◽  
Electrophysiological Studies ◽  
Short Term Adaptation ◽  
Early Visual Cortex ◽  
Dependent Signal

Are silencing, ectopic shifts, and receptive field (RF) scaling in cortical scotoma projection zones (SPZs) the result of long-term reorganization (plasticity) or short-term adaptation? Electrophysiological studies of SPZs after retinal lesions in animal models remain controversial, because they are unable to conclusively answer this question because of limitations of the methodology. Here, we used functional MRI (fMRI) visual field mapping through population RF (pRF) modeling with moving bar stimuli under photopic and scotopic conditions to measure the effects of the rod scotoma in human early visual cortex. As a naturally occurring central scotoma, it has a large cortical representation, is free of traumatic lesion complications, is completely reversible, and has not reorganized under normal conditions (but can as seen in rod monochromats). We found that the pRFs overlapping the SPZ in V1, V2, V3, hV4, and VO-1 generally (i) reduced their blood oxygen level-dependent signal coherence and (ii) shifted their pRFs more eccentric but (iii) scaled their pRF sizes in variable ways. Thus, silencing, ectopic shifts, and pRF scaling in SPZs are not unique identifiers of cortical reorganization; rather, they can be the expected result of short-term adaptation. However, are there differences between rod and cone signals in V1, V2, V3, hV4, and VO-1? We did not find differences for all five maps in more peripheral eccentricities outside of rod scotoma influence in coherence, eccentricity representation, or pRF size. Thus, rod and cone signals seem to be processed similarly in cortex.

scholarly journals Enhanced attentional gain as a mechanism for generalized perceptual learning in human visual cortex

2014 ◽  
Vol 112 (5) ◽  
pp. 1217-1227 ◽  
Author(s):  
Anna Byers ◽  
John T. Serences
Keyword(s):  
Visual Cortex ◽  
Perceptual Learning ◽  
Broad Class ◽  
Sensory Information ◽  
Large Set ◽  
Human Visual Cortex ◽  
Visual Areas ◽  
Early Visual Cortex ◽  
Response Profiles ◽  
Sensory Responses

Learning to better discriminate a specific visual feature (i.e., a specific orientation in a specific region of space) has been associated with plasticity in early visual areas ( sensory modulation) and with improvements in the transmission of sensory information from early visual areas to downstream sensorimotor and decision regions ( enhanced readout). However, in many real-world scenarios that require perceptual expertise, observers need to efficiently process numerous exemplars from a broad stimulus class as opposed to just a single stimulus feature. Some previous data suggest that perceptual learning leads to highly specific neural modulations that support the discrimination of specific trained features. However, the extent to which perceptual learning acts to improve the discriminability of a broad class of stimuli via the modulation of sensory responses in human visual cortex remains largely unknown. Here, we used functional MRI and a multivariate analysis method to reconstruct orientation-selective response profiles based on activation patterns in the early visual cortex before and after subjects learned to discriminate small offsets in a set of grating stimuli that were rendered in one of nine possible orientations. Behavioral performance improved across 10 training sessions, and there was a training-related increase in the amplitude of orientation-selective response profiles in V1, V2, and V3 when orientation was task relevant compared with when it was task irrelevant. These results suggest that generalized perceptual learning can lead to modified responses in the early visual cortex in a manner that is suitable for supporting improved discriminability of stimuli drawn from a large set of exemplars.

Feature- and Object-Based Attentional Modulation in the Human Visual System

2014 ◽  
Author(s):  
Miranda Scolari ◽  
Edward F. Ester ◽  
John T. Serences
Keyword(s):  
Object Representation ◽  
Spatial Location ◽  
Task Demands ◽  
System P ◽  
Object Based ◽  
Single Feature ◽  
Neuroimaging Data ◽  
Feature Based ◽  
Colour Feature ◽  
And Control

To increase efficiency, sensory systems process only a subset of available inputs in accord with the behavioural goals of the observer. The mechanisms that support the prioritization of relevant over irrelevant stimuli, referred to collectively as selective attention, can operate on the basis of spatial location (space-based attention), low-level visual features (e.g. orientation or colour; feature-based attention), or holistic objects (object-based attention). This chapter reviews human behavioural, electrophysiological, and neuroimaging data pertaining to the effects and control of the latter two mechanisms. Based on an increasingly rich literature spanning several decades, the authors argue that even though feature- and object-based attention are often treated as independent mechanisms, they should instead be described along a single continuum in which the information selected for prioritized processing (whether it be a single feature or a holistic object representation) is flexibly dictated by task demands.

scholarly journals A quantitative framework for motion visibility in human cortex

2018 ◽  
Author(s):  
Daniel Birman ◽  
Justin L Gardner
Keyword(s):  
Blood Oxygen Level Dependent ◽  
Perceptual Decision Making ◽  
Blood Oxygen Level ◽  
Neural Basis ◽  
Visual Areas ◽  
Motion Contrast ◽  
Dot Motion ◽  
Human Participants ◽  
Cortical Regions ◽  
Sensory Neural

AbstractDespite the central use of motion visibility to reveal the neural basis of perception, perceptual decision making, and sensory inference there exists no comprehensive quantitative framework establishing how motion visibility parameters modulate human cortical response. Random-dot motion stimuli can be made less visible by reducing image contrast or motion coherence, or by shortening the stimulus duration. Because each of these manipulations modulates the strength of sensory neural responses they have all been extensively used to reveal cognitive and other non-sensory phenomenon such as the influence of priors, attention, and choice-history biases. However, each of these manipulations is thought to influence response in different ways across different cortical regions and a comprehensive study is required to interpret this literature. Here, human participants observed random-dot stimuli varying across a large range of contrast, coherence, and stimulus durations as we measured blood-oxygen-level dependent responses. We developed a framework for modeling these responses which quantifies their functional form and sensitivity across areas. Our framework demonstrates the sensitivity of all visual areas to each parameter, with early visual areas V1-V4 showing more parametric sensitivity to changes in contrast and V3A and MT to coherence. Our results suggest that while motion contrast, coherence, and duration share cortical representation, they are encoded with distinct functional forms and sensitivity. Thus, our quantitative framework serves as a reference for interpretation of the vast perceptual literature manipulating these parameters and shows that different manipulations of visibility will have different effects across human visual cortex and need to be interpreted accordingly.

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