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It is well established that attention increases the efficiency of information processing, but the neural mechanisms underlying this improvement are not fully understood. Evidence indicates that neural firing rates increase for attended stimuli, but another possibility is that attention could increase the selectivity of the neural population representing an(More)
Adaptation is a general property of almost all neural systems and has been a longstanding tool of psychophysics because of its power to isolate and temporarily reduce the contribution of specific neural populations. Recently, adaptation designs have been extensively applied in functional MRI (fMRI) studies to infer neural selectivity in specific cortical(More)
Although visual spatial attention has been shown to increase activity as measured with both fMRI and electrophysiological techniques, significant differences in the results have been shown. fMRI studies have routinely demonstrated large signal increases to an attended versus unattended stimulus in early visual areas (V1-V3) whereas some previous(More)
Two functional magnetic resonance imaging (fMRI) face viewpoint adaptation experiments were conducted to investigate whether fMRI adaptation in high-level visual cortex depends on the duration of adaptation and how different views of a face are represented in the human visual system. We found adaptation effects in multiple face-selective areas, which(More)
We used functional magnetic resonance imaging (fMRI) to measure activity in human visual cortex, including a higher object processing area, the lateral occipital complex (LOC), and primary visual cortex (V1), in response to a perceptually bistable stimulus whose elements were perceived as either grouped into a shape or randomly arranged. We found activity(More)
The human visual system has a remarkable ability to successfully operate under a variety of challenging viewing conditions. For example, our object-recognition capabilities are largely unaffected by low-contrast (e.g., foggy) environments. The basis for this ability appears to be reflected in the neural responses in higher cortical visual areas that have(More)
Visual perception involves the grouping of individual elements into coherent patterns, such as object representations, that reduce the descriptive complexity of a visual scene. The computational and physiological bases of this perceptual remain poorly understood. We discuss recent fMRI evidence from our laboratory where we measured activity in a higher(More)
The ability to remember a briefly presented scene depends on a number of factors, such as its saliency, novelty, degree of threat, or behavioral relevance to a task. Here, however, we show that the encoding of a scene into memory may depend not only on what the scene contains but also when it occurs. Participants performed an attentionally demanding target(More)
Lightness is the apparent reflectance of a surface, and it depends not only on the actual luminance of the surface but also on the context in which the surface is viewed [1-10]. The cortical mechanisms of lightness processing are largely unknown, and the role of early cortical areas is still a matter of debate [11-17]. We studied the cortical responses to(More)
The functional MRI (fMRI) response to a pair of identical, successively presented stimuli can result in a smaller signal than the presentation of two nonidentical stimuli. This "repetition effect" has become a frequently used tool to make inferences about neural selectivity in specific cortical areas. However, little is known about the mechanism(s)(More)