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Perceptual awareness and its loss in unilateral neglect and extinction
, 2001
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Is there a role of visual cortex in spatial hearing
- Eur. J. Neurosci
"... The integration of auditory and visual spatial information is an important prerequisite for accurate orientation in the environment. However, while visual spatial information is based on retinal coordinates, the auditory system receives information on sound location in relation to the head. Thus, an ..."
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The integration of auditory and visual spatial information is an important prerequisite for accurate orientation in the environment. However, while visual spatial information is based on retinal coordinates, the auditory system receives information on sound location in relation to the head. Thus, any deviation of the eyes from a central position results in a divergence between the retinal visual and the head-centred auditory coordinates. It has been suggested that this divergence is compensated for by a neural coordinate transformation, using a signal of eye-in-head position. Using functional magnetic resonance imaging, we investigated which cortical areas of the human brain participate in such auditory–visual coordinate transformations. Sounds were produced with different interaural level differences, leading to left, right or central intracranial percepts, while subjects directed their gaze to visual targets presented to the left, to the right or straight ahead. When gaze was to the left or right, we found the primary visual cortex (V1 ⁄V2) activated in both hemispheres. The occipital activation did not occur with sound lateralization per se, but was found exclusively in combination with eccentric eye positions. This result suggests a relation of neural processing in the visual cortex and the transformation of auditory spatial coordinates responsible for maintaining the perceptual alignment of audition and vision with changes in gaze direction.
2005), “Interstimulus contingency facilitates saccadic responses in a bimodal go/no-go task
- Cognitive Brain Research
"... Abstract The saccadic response to a suddenly appearing visual target stimulus is faster when an accessory auditory stimulus is presented in its spatiotemporal proximity. This multisensory facilitation of reaction time is usually considered a mandatory bottom -up process. Here, we report that it can ..."
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Abstract The saccadic response to a suddenly appearing visual target stimulus is faster when an accessory auditory stimulus is presented in its spatiotemporal proximity. This multisensory facilitation of reaction time is usually considered a mandatory bottom -up process. Here, we report that it can be modulated by the predictability of the target location provided by an accessory stimulus, thereby indicating a form of top -down processing. Subjects were asked to make a saccade in the direction of a visual target randomly appearing left or right from fixation. An accessory auditory stimulus was presented either at the same location or opposite to the target, with the probability varying over blocks of presentation. Thus, the auditory stimulus contained probabilistic information about the target location (interstimulus contingency). A certain percentage of the trials were catch trials in which the auditory accompanying stimulus (Experiment 1) or the visual target (Experiment 2) was presented alone and the subjects were asked to withhold their response. In particular with visual catch trials, varying the predictability of target location resulted in reaction time facilitation in the bimodal trials, with both high (80%) and low predictability (20%), but only when both stimuli were presented within a small time window (40 ms). As subjects could not possibly follow the task instructions in this short period explicitly, we conclude that they utilized the interstimulus contingency information implicitly, thus revealing an extremely fast involuntary top -down control on saccadic eye movements. D 2005 Elsevier B.V. All rights reserved. Classification: Neural basis of behavior; Cognition Theme: Sensory systems Topic: Multisensory
3Center for the Neural Basis of Cognition
"... of the eye movement command is thought to trigger remapping. Updating creates a stable representation of space by compensating for the displacement of objects on the retina. We hypothesized that spatial updating also occurs in humans. Behavioral results in humans and nonhuman primates have shown tha ..."
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of the eye movement command is thought to trigger remapping. Updating creates a stable representation of space by compensating for the displacement of objects on the retina. We hypothesized that spatial updating also occurs in humans. Behavioral results in humans and nonhuman primates have shown that they have similar abilities in double-step eye movement tasks that require the use of updated visual information (Baizer and Bender, 1989; Hallett and Lightstone, 1976). Moreover, the parietal lobe is critical for task performance. Humans with parietal lobe damage are unable to perform double-step tasks (Duhamel et al., 1992b; Heide et al., 1995), and parietal neurons in monkeys are specifically active in these tasks (Goldberg et al., 1990). We thus hypothesized that up-
Human Gaze Shifts to Acoustic and Visual Targets
, 2002
"... Eye and head contributions to orienting gaze shifts have been primarily studied using visual targets. Consequently, relatively little is known about the kinematics of eye and head movements in gaze shifts to acoustic targets. Although early work in nonhuman primates indicates that orienting response ..."
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Eye and head contributions to orienting gaze shifts have been primarily studied using visual targets. Consequently, relatively little is known about the kinematics of eye and head movements in gaze shifts to acoustic targets. Although early work in nonhuman primates indicates that orienting responses to acoustic and visual targets are
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"... Understanding how the cerebral cortex processes in-formation is a major aim of neurobiology today, with im-portant implications for disciplines ranging from psy-chiatry to the designing of living machines. Numerous investigative techniques at different levels are used to this end, including function ..."
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Understanding how the cerebral cortex processes in-formation is a major aim of neurobiology today, with im-portant implications for disciplines ranging from psy-chiatry to the designing of living machines. Numerous investigative techniques at different levels are used to this end, including functional brain imaging, single-unit recording, and anatomy. These techniques rapidly con-verge at the level of the cortical area, where specific physiological functions can be localized and each area exhibits distinct patterns of connectivity. The concerted action of multiple areas is thought to underlie sensory pro-cesses and cognitive functions. This has led to a major field of research that attempts to determine the position of individual areas in the overall cortical organization of in-formation flow. Work in the visual system has been par-
