Does face-selective cortex show a left visual field bias for centrally-viewed faces?

The left half of a centrally-viewed face contributes more strongly to recognition performance than the right. This left visual field (LVF) advantage is typically attributed to an untested assumption that face-selective cortex in the right hemisphere (RH) exhibits a contralateral bias, even for centrally-viewed faces. We tested the validity of this assumption using a behavioral measure of the LVF advantage and an fMRI experiment that measured laterality of face-selective cortex and neural contralateral bias.

Does right hemisphere superiority sufficiently explain the left visual field advantage in face recognition?

The tendency to perceive the identity of the left half of a centrally viewed face more strongly than that of the right half is associated with visual processing of faces in the right hemisphere (RH). Here we investigate conditions under which this well-known left visual field (LVF) half-face advantage fails to occur. Our findings challenge the sufficiency of its explanation as a function of RH specialization for face processing coupled with LVF-RH correspondence.

Functionally Separable Font-invariant and Font-sensitive Neural Populations in Occipitotemporal Cortex.

Reading relies on the rapid visual recognition of words viewed in a wide variety of fonts. We used fMRI to identify neural populations showing reduced fMRI responses to repeated words displayed in different fonts ("font-invariant" repetition suppression). We also identified neural populations showing greater fMRI responses to words repeated in a changing font as compared with words repeated in the same font ("font-sensitive" release from repetition suppression).

Embedded word priming elicits enhanced fMRI responses in the visual word form area.

Lexical embedding is common in all languages and elicits mutual orthographic interference between an embedded word and its carrier. The neural basis of such interference remains unknown. We employed a novel fMRI prime-target embedded word paradigm to test for involvement of a visual word form area (VWFA) in left ventral occipitotemporal cortex in co-activation of embedded words and their carriers.

Visual recognition of mirrored letters and the right hemisphere advantage for mirror-invariant object recognition.

Unlike most objects, letter recognition is closely tied to orientation and mirroring, which in some cases (e.g., b and d), defines letter identity altogether.

Object width modulates object-based attentional selection.

Visual input typically includes a myriad of objects, some of which are selected for further processing. While these objects vary in shape and size, most evidence supporting object-based guidance of attention is drawn from paradigms employing two identical objects. Importantly, object size is a readily perceived stimulus dimension, and whether it modulates the distribution of attention remains an open question.

An fMRI study of visual hemifield integration and cerebral lateralization.

The human brain integrates hemifield-split visual information via interhemispheric transfer. The degree to which neural circuits involved in this process behave differently during word recognition as compared to object recognition is not known. Evidence from neuroimaging (fMRI) suggests that interhemispheric transfer during word viewing converges in the left hemisphere, in two distinct brain areas, an "occipital word form area" (OWFA) and a more anterior occipitotemporal "visual word form area" (VWFA).

Distinct effects of contour smoothness and observer bias on visual persistence.

Stable object perception relies on persistent yet temporary neural representations under constantly fluctuating stimulus conditions. The mechanisms by which such representations are formed and maintained are not fully understood but presumably involve interplay between early and higher tier visual cortical mechanisms. Some neurophysiological models of feature binding in early visual cortex predict persistent contour perception under certain stimulus conditions.

Sex differences in the human visual system.

This Mini-Review summarizes a wide range of sex differences in the human visual system, with a primary focus on sex differences in visual perception and its neural basis. We highlight sex differences in both basic and high-level visual processing, with evidence from behavioral, neurophysiological, and neuroimaging studies. We argue that sex differences in human visual processing, no matter how small or subtle, support the view that females and males truly see the world differently.

Atypical Asymmetry for Processing Human and Robot Faces in Autism Revealed by fNIRS.

Deficits in the visual processing of faces in autism spectrum disorder (ASD) individuals may be due to atypical brain organization and function. Studies assessing asymmetric brain function in ASD individuals have suggested that facial processing, which is known to be lateralized in neurotypical (NT) individuals, may be less lateralized in ASD. Here we used functional near-infrared spectroscopy (fNIRS) to first test this theory by comparing patterns of lateralized brain activity in homologous temporal-occipital facial processing regions during observation of faces in an ASD group and an NT group.

Visual Cortical Representation of Whole Words and Hemifield-split Word Parts.

Reading requires the neural integration of visual word form information that is split between our retinal hemifields. We examined multiple visual cortical areas involved in this process by measuring fMRI responses while observers viewed words that changed or repeated in one or both hemifields. We were specifically interested in identifying brain areas that exhibit decreased fMRI responses as a result of repeated versus changing visual word form information in each visual hemifield.

Spatiotemporal Form Integration: sequentially presented inducers can lead to representations of stationary and rigidly rotating objects.

Objects in the world often are occluded and in motion. The visible fragments of such objects are revealed at different times and locations in space. To form coherent representations of the surfaces of these objects, the visual system must integrate local form information over space and time.

The lemon illusion: seeing curvature where there is none.

Curvature is a highly informative visual cue for shape perception and object recognition. We introduce a novel illusion-the Lemon Illusion-in which subtle illusory curvature is perceived along contour regions that are devoid of physical curvature. We offer several perceptual demonstrations and observations that lead us to conclude that the Lemon Illusion is an instance of a more general illusory curvature phenomenon, one in which the presence of contour curvature discontinuities lead to the erroneous extension of perceived curvature.

The Dynamic Ebbinghaus: motion dynamics greatly enhance the classic contextual size illusion.

The Ebbinghaus illusion is a classic example of the influence of a contextual surround on the perceived size of an object. Here, we introduce a novel variant of this illusion called the Dynamic Ebbinghaus illusion in which the size and eccentricity of the surrounding inducers modulates dynamically over time. Under these conditions, the size of the central circle is perceived to change in opposition with the size of the inducers.

Inter-element orientation and distance influence the duration of persistent contour integration.

Contour integration is a fundamental form of perceptual organization. We introduce a new method of studying the mechanisms responsible for contour integration. This method capitalizes on the perceptual persistence of contours under conditions of impending camouflage.

Haptic shape processing in visual cortex.

Humans typically rely upon vision to identify object shape, but we can also recognize shape via touch (haptics). Our haptic shape recognition ability raises an intriguing question: To what extent do visual cortical shape recognition mechanisms support haptic object recognition? We addressed this question using a haptic fMRI repetition design, which allowed us to identify neuronal populations sensitive to the shape of objects that were touched but not seen. In addition to the expected shape-selective fMRI responses in dorsal frontoparietal areas, we observed widespread shape-selective responses in the ventral visual cortical pathway, including primary visual cortex.

Double representation of the wrist and elbow in human motor cortex.

Movements of the fingers, hand and arm involve overlapping neural representations in primary motor cortex (M1). Monkey M1 exhibits a core-surround organisation in which cortical representation of the hand and fingers is surrounded by representations of the wrist, elbow and shoulder. A potentially homologous organisation in human M1 has only been observed in a single study, a functional MRI (fMRI) study by [J.

Structural salience and the nonaccidentality of a Gestalt.

We perceive structure through a process of perceptual organization. Here we report a new perceptual organization phenomenon-the facilitation of visual grouping by global curvature. Observers viewed patterns that they perceived as organized into collections of curves.

Figure-ground representation and its decay in primary visual cortex.

We used fMRI to study figure-ground representation and its decay in primary visual cortex (V1). Human observers viewed a motion-defined figure that gradually became camouflaged by a cluttered background after it stopped moving. V1 showed positive fMRI responses corresponding to the moving figure and negative fMRI responses corresponding to the static background.

Face inversion reduces the persistence of global form and its neural correlates.

Face inversion produces a detrimental effect on face recognition. The extent to which the inversion of faces and other kinds of objects influences the perceptual binding of visual information into global forms is not known. We used a behavioral method and functional MRI (fMRI) to measure the effect of face inversion on visual persistence, a type of perceptual memory that reflects sustained awareness of global form.

Equal degrees of object selectivity for upper and lower visual field stimuli.

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.

Subjective agency and awareness of shared actions.

Voluntary actions and their distal effects are intimately related in conscious awareness. When an expected effect follows a voluntary action, the experience of the interval between these events is compressed in time, a phenomenon known as 'intentional binding' (IB). Current accounts of IB suggest that it serves to reinforce associations between our goals and our intention to attain these goals via action, and that IB only occurs for self-generated (i.

The conscious experience of action and intention.

The neural signals that give rise to our experience of the actions we perform are not well understood. Obhi et al. (Cognition 110:65-73, 2009) proposed that both efferent and re-afferent signals contribute to the conscious awareness of intentional actions.

On the surprising salience of curvature in grouping by proximity.

The authors conducted 3 experiments to explore the roles of curvature, density, and relative proximity in the perceptual organization of ambiguous dot patterns. To this end, they developed a new family of regular dot patterns that tend to be perceptually grouped into parallel contours, dot-sampled structured grids (DSGs). DSGs are similar to the dot lattices used to study grouping by proximity, except that only one of the potential organizations is rectilinear; the others are curvilinear.