Alexander C Huk

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We performed a series of functional magnetic resonance imaging experiments to divide the human MT+ complex into subregions that may be identified as homologs to a pair of macaque motion-responsive visual areas: the middle temporal area (MT) and the medial superior temporal area (MST). Using stimuli designed to tease apart differences in retinotopic(More)
Both the speed and the accuracy of a perceptual judgment depend on the strength of the sensory stimulation. When stimulus strength is high, accuracy is high and response time is fast; when stimulus strength is low, accuracy is low and response time is slow. Although the psychometric function is well established as a tool for analyzing the relationship(More)
Decision-making often requires the accumulation and maintenance of evidence over time. Although the neural signals underlying sensory processing have been studied extensively, little is known about how the brain accrues and holds these sensory signals to guide later actions. Previous work has suggested that neural activity in the lateral intraparietal area(More)
Several fMRI studies have reported MT+ response increases correlated with perception of the motion aftereffect (MAE). However, attention can strongly affect MT+ responses, and subjects may naturally attend more to the MAE than control trials without MAE. We found that requiring subjects to attend to motion on both MAE and control trials produced equal(More)
How do neurons in a decision circuit integrate time-varying signals, in favor of or against alternative choice options? To address this question, we used a recurrent neural circuit model to simulate an experiment in which monkeys performed a direction-discrimination task on a visual motion stimulus. In a recent study, it was found that brief pulses of(More)
Physiological models of visual motion processing posit that 'pattern-motion cells' represent the direction of moving objects independent of their particular spatial pattern. We performed fMRI experiments to identify neuronal activity in the human brain selective for pattern motion. A protocol using adaptation to moving 'plaid' stimuli allowed us to separate(More)
A photograph of an action can convey a vivid sense of motion. Does the inference of motion from viewing a photograph involve the same neural and psychological representations used when one views physical motion? In this study, we tested whether implied motion is represented by the same direction-selective signals involved in the perception of real motion.(More)
Three experiments are reported concerning the texture density aftereffect. The experiments address the question of how visual texture density information is encoded by examining patterns of transfer between different textures. In the first two experiments, it is shown that manipulation of spatial frequency and orientation information does not affect the(More)
How does the primate visual system encode three-dimensional motion? The macaque middle temporal area (MT) and the human MT complex (MT+) have well-established sensitivity to two-dimensional frontoparallel motion and static disparity. However, evidence for sensitivity to three-dimensional motion has remained elusive. We found that human MT+ encodes two(More)
Popular hemodynamic brain imaging methods, such as blood oxygen-level dependent functional magnetic resonance imaging (BOLD fMRI), would benefit from a detailed understanding of the mechanisms by which oxygen is delivered to the cortex in response to brief periods of neural activity. Tissue oxygen responses in visual cortex following brief visual(More)