Reprint of: Visual processing of words in a patient with visual form agnosia: A behavioural and fMRI study.

Patient D.F. has a profound and enduring visual form agnosia due to a carbon monoxide poisoning episode suffered in 1988.

Visual processing of words in a patient with visual form agnosia: a behavioural and fMRI study.

Patient D.F. has a profound and enduring visual form agnosia due to a carbon monoxide poisoning episode suffered in 1988.

The role of temporal synchrony as a binding cue for visual persistence in early visual areas: an fMRI study.

We examined the role of temporal synchrony-the simultaneous appearance of visual features-in the perceptual and neural processes underlying object persistence. When a binding cue (such as color or motion) momentarily exposes an object from a background of similar elements, viewers remain aware of the object for several seconds before it perceptually fades into the background, a phenomenon known as object persistence. We showed that persistence from temporal stimulus synchrony, like that arising from motion and color, is associated with activation in the lateral occipital (LO) area, as measured by functional magnetic resonance imaging.

Dissociable neural mechanisms for determining the perceived heaviness of objects and the predicted weight of objects during lifting: an fMRI investigation of the size-weight illusion.

In size-weight (SW) illusions, people learn to scale their fingertip forces for lifting small and big objects of equal weight even though they fail to learn perceptually that both objects have the same weight. The question then arises as to what the separate neural mechanisms are for determining the perceived heaviness of objects and the predicted weight of these objects during lifting. To answer this question, we used fMRI to first identify areas that code for the size, weight, and density of objects using an adaptation paradigm.

fMRI reveals greater within- than between-hemifield integration in the human lateral occipital cortex.

Early visual areas within each hemisphere (V1, V2, V3/VP, V4v) contain distinct representations of the upper and lower quadrants of the contralateral hemifield. As receptive field size increases, the retinotopy in higher-tier visual areas becomes progressively less distinct. Using functional magnetic resonance imaging (fMRI) to map the visual fields, we found that an intermediate level visual area, the lateral occipital region (LO), contains retinotopic maps with a contralateral bias, but with a combined representation of the upper and lower visual field.

The neural correlates of change detection in the face perception network.

A common view is that visual processing within the ventral visual stream is modulated by attention and awareness. We used fMRI adaptation to investigate whether activation in a network of brain regions involved with face recognition--namely the fusiform face area (FFA), occipital face area (OFA) and right superior temporal sulcus (rSTS)--was modulated by physical changes to face stimuli or by observers' awareness of the changes. We sequentially presented two matrices of four faces.

Independent processing of form, colour, and texture in object perception.

Most investigations of object recognition have focused on the form rather than the material properties of objects. Nevertheless, knowledge of the material properties of an object (via its surface cues) can provide important information about that object's identity. In this study, we used Garner's speeded-classification task to explore whether or not the processing of form and the processing of surface properties are independent.

Task-related laterality effects in the lateral occipital complex.

Using functional imaging, we investigated the effects of two different tasks on activation in the lateral occipital complex (LOC). Alternating blocks of intact and scrambled objects were presented. In one task, subjects responded when an object repeated (matching task).

Hierarchical attention in discriminating objects at different levels of specificity.

An implicit assumption of studies in the attentional literature has been that global and local levels of attention are involved in object recognition. To investigate this assumption, a divided attention task was used in which hierarchical figures were presented to prime the subsequent discrimination of target objects at different levels of category identity (basic and subordinate). Target objects were identified among distractor objects that varied in their degree of visual similarity to the targets.

Perceptual continuity and the emergence of perceptual persistence in the ventral visual pathway.

Perceptual continuity is an important aspect of our experience of the visual world. In this study, we focus on an example of perceptual continuity involving the maintenance of figure-ground segregation despite the removal of binding cues that initiated the segregation. Fragmented line drawings of objects were superimposed on a background of randomly oriented lines.

Electrophysiological correlates of object categorization: back to basics.

The time course of visual object categorization as a function of electrophysiological activity in the brain was investigated using a variant of the "oddball" design. Category level was manipulated by sequentially presenting subordinate, basic or superordinate target objects among a variety of non-target objects. It was found that superordinate categorizations were performed more quickly and differentiated from basic level categorizations in amplitude early in visual processing (320-420 ms).

The role of axes of elongation and symmetry in rotated object naming.

Many theorists have postulated that axes of elongation and/or symmetry play an important role in the recognition of objects. In this paper, evidence is presented that mitigates this claim from independent assessments of the effects of axes of elongation or symmetry on the time to name rotated line drawings of common objects. This conclusion was further supported in a stronger test in which both of these variables were orthogonally controlled, the aspect ratio of elongation was manipulated,and only objects that were completely geometrically symmetrical or asymmetrical were used.