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Publications (138)
The current study aims to explore one factor that likely contributes to these statistical regularities, familiarity. Are highly familiar stimuli perceived more readily? Previous work showing effects of familiarity on perception have used recognition tasks, which arguably tap into post-perceptual processes. Here we use a perceptual task that does no...
EEG alpha power varies under many circumstances requiring visual attention. However, mounting evidence indicates that alpha may not only serve visual processing, but also the processing of stimuli presented in other sensory modalities, including hearing. We previously showed that alpha dynamics during an auditory task vary as a function of competit...
EEG alpha power varies under many circumstances requiring visual attention. However, mounting evidence indicates that alpha may not only serve visual processing, but also the processing of stimuli presented in other sensory modalities, including hearing. We previously showed that alpha dynamics during an auditory task vary as a function of competit...
Previous work has claimed that canonical viewpoints of objects are more readily perceived than noncanonical viewpoints. However, all of these studies required participants to identify the object, a late perceptual process at best and arguably a cognitive process (Pylyshyn, 1999). Here, we extend this work to early vision by removing the explicit ne...
In the face of multiple sensory streams, there may be competition for processing resources in multimodal cortical area devoted to establishing representations. In such cases, alpha oscillations may serve to maintain the relevant representations and protect them from interference, whereas theta band activity may facilitate their updating when needed...
In the face of multiple sensory streams, there may be competition for processing resources in multimodal cortical area devoted to establishing representations. In such cases, alpha oscillations may serve to maintain the relevant representations and protect them from interference, whereas theta oscillations may facilitate their updating when needed....
Visual suppression by single-pulse transcranial magnetic stimulation (sTMS) has been attributed to interruptions of either feedforward or feedback activity in the visual stream. The relative timing of the C1 event related potential (ERP) and of the TMS suppression, taken from separate studies, supports an interruption of feedback. Here we probe the...
Inherent correlations between visual and semantic features in real-world scenes make it difficult to determine how different scene properties contribute to neural representations. Here, we assessed the contributions of multiple properties to scene representation by partitioning the variance explained in human behavioral and brain measurements by th...
Inherent correlations between visual and semantic features in real-world scenes make it difficult to determine how different scene properties contribute to neural representations. Here, we assessed the contributions of multiple properties to scene representation by partitioning the variance explained in human behavioral and brain measurements by th...
Research on the neural correlates of consciousness (NCC) has implicated an assortment of brain regions, ERP components, and network properties associated with visual awareness. Recently, the P3b ERP component has emerged as a leading NCC candidate. However, typical P3b paradigms depend on the detection of some stimulus change, making it difficult t...
Traditional models of recognition and categorization proceed from registering low-level features, perceptually organizing that input, and linking it with stored representations. Recent evidence, however, suggests that this serial model may not be accurate, with object and category knowledge affecting rather than following early visual processing. H...
A number of regions in the human brain are known to be involved in processing natural scenes, but the field has lacked a unifying framework for understanding how these different regions are organized and interact. We provide evidence from functional connectivity and meta-analyses for a new organizational principle, in which scene processing relies...
Recently there has been dramatic improvement in computer-vision object recognition. In the 2015 ImageNet challenge, the best performing model (GoogLeNet) had a top-5 classification accuracy of 93%, a 20% improvement over 2010. This increase is due to the continued development of convolutional neural networks (CNN). Despite these advances, it's uncl...
A number of regions in the human brain are known to be involved in processing natural scenes, but the field has lacked a unifying framework for understanding how these different regions are organized and interact. We provide evidence from functional connectivity and meta-analyses for a new organizational principle, in which scene processing relies...
Peripherally presented stimuli evoke stronger activity in scene-processing regions than foveally presented stimuli, suggesting that scene understanding is driven largely by peripheral information. We used functional MRI to investigate whether functional connectivity evoked during natural perception of audiovisual movies reflects this peripheral bia...
Understanding human–object interactions is critical for extracting meaning from everyday visual scenes and requires integrating
complex relationships between human pose and object identity into a new percept. To understand how the brain builds these
representations, we conducted 2 fMRI experiments in which subjects viewed humans interacting with ob...
The purpose of categorization is to identify generalizable classes of objects whose members can be treated equivalently. Within a category, however, some exemplars are more representative of that concept than others. Despite long-standing behavioral effects, little is known about how typicality influences the neural representation of real-world obj...
Although the authors do a valuable service by elucidating the pitfalls of inferring top-down effects, they overreach by claiming that vision is cognitively impenetrable. Their argument, and the entire question of cognitive penetrability, seems rooted in a discrete, stage-like model of the mind that is unsupported by neural data.
How do we know that a kitchen is a kitchen by looking? Traditional models posit that scene categorization is achieved through recognizing necessary and sufficient features and objects, yet there is little consensus about what these may be. However, scene categories should reflect how we use visual information. Therefore, we test the hypothesis that...
Categories create cognitively useful generalizations by leveraging the correlational structure of the world. Although classic cognitive studies have shown that object categories have both intrinsic hierarchical structure (entry-level effects, Rosch et al., 1976), as well as graded typicality structure (Rosch, 1973), relatively little is known about...
How do we know that a kitchen is a kitchen by looking? Here we start with the intuition that although scenes consist of visual features and objects, scene categories should reflect how we use category information. In our daily lives, rather than asking ourselves whether we are in (for example) a "beach" scene, we tend to use scene category informat...
Research on visual scene understanding has identified a number of regions involved in processing natural scenes, but has lacked a unifying framework for understanding how these different regions are organized and interact. We propose a new organizational principle, in which scene processing relies on two distinct networks at the edge of visual cort...
Binocular rivalry occurs when incompatible images are presented simultaneously but separately to each eye. Perceptual dominance reverses over time such that one image temporarily dominates perception, while the other image is suppressed. Prior research has shown that presenting brief probes to the suppressed eye can cause a rapid switch in perceptu...
Size-contrast illusions are processed in the ventral stream of the occipitotemporal cortex and the dorsal stream of the parietal cortex. Greater interactions between these two regions are associated with stronger illusions. The present study tests if visual percepts (phosphenes) induced by TMS of the occipital and parietal cortices are also suscept...
Objects can be simultaneously categorized at multiple levels of specificity ranging from very broad ("natural object") to very distinct ("Mr. Woof"), with a mid-level of generality (basic level: "dog") often providing the most cognitively useful distinction between categories. It is unknown, however, how this hierarchical representation is achieved...
Although we are able to rapidly understand novel scene images, little is known about the mechanisms that support this ability. Theories of optimal coding assert that prior visual experience can be used to ease the computational burden of visual processing. A consequence of this idea is that more probable visual inputs should be facilitated relative...
A common goal in biological sciences is to model a complex web of connections using a small number of interacting units. We present a general approach for dividing up elements in a spatial map based on their connectivity properties, allowing for the discovery of local regions underlying large-scale connectivity matrices. Our method is specifically...
A common goal in biological sciences is to model a complex web of connections using a small number of interacting units. We present a general approach for dividing up elements in a spatial map based on their connectivity properties, allowing for the discovery of local regions underlying large-scale connectivity matrices. Our method is specifically...
A common goal in biological sciences is to model a complex web of connections using a small number of interacting units. We present a general approach for dividing up elements in a spatial map based on their connectivity properties, allowing for the discovery of local regions underlying large-scale connectivity matrices. Our method is specifically...
How do we know that a kitchen is a kitchen by looking? Relatively little is
known about how we conceptualize and categorize different visual environments.
Traditional models of visual perception posit that scene categorization is
achieved through the recognition of a scene's objects, yet these models cannot
account for the mounting evidence that hu...
Our perceptions are guided both by the bottom-up information entering our
eyes, as well as our top-down expectations of what we will see. Although
bottom-up visual processing has been extensively studied, comparatively little
is known about top-down signals. Here, we describe REVEAL (Representations
Envisioned Via Evolutionary ALgorithm), a method...
A number of influential theories posit that visual awareness relies not only on the initial, stimulus-driven (i.e., feedforward) sweep of activation but also on recurrent feedback activity within and between brain regions. These theories of awareness draw heavily on data from masking paradigms in which visibility of one stimulus is reduced due to t...
Intertrial effects such as priming of pop-out (PoP) often occur for task-irrelevant dimensions as well as task-relevant dimensions, though to a weaker extent. Here we test the hypothesis that increased priming for task-relevant dimensions is due to greater passive build-up of priming for the task-relevant dimension rather than to an active filterin...
A growing number of studies find that we can select independently from the right and left hemifields, prompting some to suggest separate resources in the two hemispheres. Here we report an experiment suggesting that competition between representations, rather than exhaustion of resources, underlies these effects. Subjects searched a briefly display...
Inter-subject registration of cortical areas is necessary in functional imaging (fMRI) studies for making inferences about equivalent brain function across a population. However, many high-level visual brain areas are defined as peaks of functional contrasts whose cortical position is highly variable. As such, most alignment methods fail to accurat...
Binocular rivalry occurs when disparate images are shown simultaneously but separately to each eye. Perceptually dominant images reverse over time, with one image temporarily dominating perception while the other is suppressed. Probes presented to the suppressed eye are typically seen by participants and tend to cause perception to shift to the sup...
A long-standing core question that has remained unanswered in cognitive science is: Do different modalities (pictures, words, sounds, smells, tastes and touch) access a common store of semantic information? Although different modalities have been shown to activate a shared network of brain regions, this does not imply a common representation, as th...
New large-scale studies using fMRI and dMRI have begun to reveal the fine-scale functional and anatomical connectome of the human brain. We have developed a new approach for understanding these massive datasets, allowing us to discover and visualize how connectivity changes over the entire cortical surface. Given a matrix describing the functional...
Masked priming effects are taken as evidence that behavior can be influenced by information that does not reach our phenomenal awareness and hence serves as a dissociation between perception and awareness. Priming with unseen stimuli in studies using metacontrast masking procedure are well established, while priming in object-substitution masking (...
The ventral attentional network (VAN) is thought to drive "stimulus driven attention" [e.g., Asplund, C. L., Todd, J. J., Snyder, A. P., & Marois, R. A central role for the lateral prefrontal cortex in goal-directed and stimulus-driven attention. Nature Neuroscience, 13, 507-512, 2010; Shulman, G. L., McAvoy, M. P., Cowan, M. C., Astafiev, S. V., T...
![Schematic of the experiment procedures (a,b) and results (c) from [13]....](publication/260876294/figure/fig1/AS:203041388142597@1425420247460/Schematic-of-the-experiment-procedures-a-b-and-results-c-from-13-This_Q320.jpg)
What is the relationship between attention and conscious awareness? Awareness sometimes appears to be restricted to the contents of focused attention, yet at other times irrelevant distractors will dominate awareness. This contradictory relationship has also been reflected in an abundance of discrepant research findings leading to an enduring contr...
We investigated the dynamics of brain processes facilitating conscious experience of external stimuli. Previously, we proposed that alpha (8-12 Hz) oscillations, which fluctuate with both sustained and directed attention, represent a pulsed inhibition of ongoing sensory brain activity. Here we tested the prediction that inhibitory alpha oscillation...
Transcranial magnetic stimulation (TMS) applied over the occipital lobe approximately 100 ms after the onset of a stimulus decreases its visibility if it appears in the location of the phosphene. Because phosphenes can also be elicited by stimulation of the parietal regions, we asked if the same procedure that is used to reduce visibility of stimul...
The purpose of categorization is to identify generalizable classes of objects whose members can be treated equivalently. Within a category, however, some exemplars are more representative of that concept than others. Despite long-standing behavioral effects, little is known about how typicality influences the neural representation of real-world obj...
Human observers can rapidly categorize natural images, but the mechanism behind this ability is still unknown. Some models posit that categorization is aided by the use of internal representations, deployed in a top-down manner to constrain visual input. What is the content of these representations? Although internal representations have been obtai...
When transcranial magnetic stimulation (TMS) is applied over occipital cortex approximately 80-100 ms after the onset of a stimulus its visibility is decreased. The location of the occipital stimulation is typically selected by first determining where on the scalp TMS results in an experience of a phosphene. Recently it has been shown that phosphen...
It is commonly said that tall people look thinner. Here, we asked whether an illusion exists such that the taller of two equally wide stimuli looks thinner, and conversely whether the thinner of two equally tall stimuli looks taller. In five experiments, participants judged the horizontal or vertical extents of two identical bodies, rectangles, or...
The perceptual load theory of attention proposes that the degree to which visual distractors are processed is a function of the attentional demands of a task-greater demands increase filtering of irrelevant distractors. The spatial configuration of such filtering is unknown. Here, we used steady-state visual evoked potentials (SSVEPs) in conjunctio...
Both perceptual load theory and dilution theory purport to explain when and why task-irrelevant information, or so-called distractors are processed. Central to both explanations is the notion of limited resources, although the theories differ in the precise way in which those limitations affect distractor processing. We have recently proposed a neu...
Within the range of images that we might categorize as a “beach”, for example, some will be more representative of that category than others. Here we first confirmed that humans could categorize “good” exemplars better than “bad” exemplars of six scene categories and then explored whether brain regions previously implicated in natural scene categor...
The Parahippocampal Place Area (PPA) has traditionally been considered a homogeneous region of interest, but recent evidence from both human studies and animal models has suggested that PPA may be composed of functionally distinct subunits. To investigate this hypothesis, we utilize a functional connectivity measure for fMRI that can estimate conne...
Functional connectivity patterns are known to exist in the human brain at the millimeter scale, but the standard fMRI connectivity measure only computes functional correlations at a coarse level. We present a method for identifying fine-grained functional connectivity between any two brain regions by simultaneously learning voxel-level connectivity...
Rhythmic events are common in our sensory world. Temporal regularities could be used to predict the timing of upcoming events, thus facilitating their processing. Indeed, cognitive theories have long posited the existence of internal oscillators whose timing can be entrained to ongoing periodic stimuli in the environment as a mechanism of temporal...
Identifying the relationships between objects in a scene is a fundamental goal in scene understanding. It is known that two interacting objects are perceptually grouped (Green & Hummel, 2006), and that interacting objects evoke greater activity in the lateral occipital complex (LOC) compared to noninteracting objects (Kim & Biederman, 2011). Howeve...
Objects can be described at multiple taxonomic levels; i.e. Fluffy is simultaneously a tabby, a cat, an animal, and a living organism. Yet, some descriptions are more basic than others (in this case: 'cat') in that they are generated first and maximize within-category similarity (Rosch 1976). Despite numerous behavioral findings confirming this obs...
People can selectively maintain task-relevant features of items in visual working memory (Woodman & Vogel, 2008), but can they effectively ignore task-irrelevant features of an attended item? And, if so, does the ability to ignore irrelevant feature dimensions correlate with visual short-term memory (VSTM) capacity? Participants performed a priming...
Discovering functional connectivity between and within brain regions is a key concern in neuroscience. Due to the noise inherent in fMRI data, it is challenging to characterize the properties of individual voxels, and current methods are unable to flexibly analyze voxel-level connectivity differences. We propose a new functional connectivity method...
Single-cell and fMRI experiments indicate that task-relevant features are enhanced globally across the visual field (VF). Moreover, this global feature-based attention can spread to task-irrelevant features of the attended object. Here we ask whether a task-irrelevant feature, by virtue of being bound to a task-relevant feature, can also be enhance...
The Oppel-Kundt illusion (OKI) consists of the perception of a filled space as larger than an empty space of the same size. Here, we used a modified version of that illusion composed of a gradient of vertical lines whose spacing decreased progressively from one side to the other: space is expected to be perceived as larger where the lines are more...
How visual content is represented in neuronal population codes and how to analyze such codes with multivariate techniques.
Vision is a massively parallel computational process, in which the retinal image is transformed over a sequence of stages so as to emphasize behaviorally relevant information (such as object category and identity) and deemphasi...
Alpha oscillations have an inhibitory influence on visual processing and fluctuate with both sustained and directed attention. We have proposed a role for these 8–12 Hz oscillations as a pulsed inhibition of ongoing brain activity, given that alpha’s inhibitory influence fluctuates as a function of its phase. An important prediction of this theory...
The perceptual load theory of attention proposes that the degree to which visual distractors are processed is a function of the perceptual demands of a task - greater perceptual demands result in increased distractor filtering. Here, we used steady-state visual evoked potentials (SSVEPs) to investigate the distribution of load-induced attentional f...
Transcranial magnetic stimulation (TMS) is a widely used experimental and clinical technique that directly induces activity in human cortex using magnetic fields. However, the neural mechanisms of TMS-induced activity are not well understood. Here, we introduce a novel method of imaging TMS-evoked activity using a non-invasive fast optical imaging...
Directing attention to a visual item enhances its representations, making it more likely to guide behavior (Corbetta et al. 1991). Attention is thought to produce this enhancement by biasing suppressive interactions among multiple items in visual cortex in favor of the attended item (e.g., Desimone and Duncan 1995; Reynolds and Heeger 2009). We ask...
Background / Purpose:
In a previous fMRI study, we showed that attending to multidimensional objects (i.e. containing color and direction of motion) enhances the neural response to features of the attended object across the visual field, both for task-relevant and task-irrelevant dimensions.In the current experiment, we investigated whether there...
