The Experts below are selected from a list of 110295 Experts worldwide ranked by ideXlab platform
Jason B Mattingley - One of the best experts on this subject based on the ideXlab platform.
-
perceptual load influences auditory Space Perception in the ventriloquist aftereffect
Cognition, 2011Co-Authors: Ranmalee Eramudugolla, Marc R Kamke, Salvador Sotofaraco, Jason B MattingleyAbstract:A period of exposure to trains of simultaneous but spatially offset auditory and visual stimuli can induce a temporary shift in the Perception of sound location. This phenomenon, known as the 'ventriloquist aftereffect', reflects a realignment of auditory and visual spatial representations such that they approach perceptual alignment despite their physical spatial discordance. Such dynamic changes to sensory representations are likely to underlie the brain's ability to accommodate inter-sensory discordance produced by sensory errors (particularly in sound localization) and variability in sensory transduction. It is currently unknown, however, whether these plastic changes induced by adaptation to spatially disparate inputs occurs automatically or whether they are dependent on selectively attending to the visual or auditory stimuli. Here, we demonstrate that robust auditory spatial aftereffects can be induced even in the presence of a competing visual stimulus. Importantly, we found that when attention is directed to the competing stimuli, the pattern of aftereffects is altered. These results indicate that attention can modulate the ventriloquist aftereffect.
-
effects of prismatic adaptation on judgements of spatial extent in peripersonal and extrapersonal Space
Neuropsychologia, 2003Co-Authors: Nadja Berberovic, Jason B MattingleyAbstract:Recent research has shown that visuomotor adaptation to a lateral displacement of the visual field induces significant perceptual aftereffects in normal observers, and in right hemisphere patients with spatial neglect [Neuroreport 11 (2000) 1899; Nature 395 (1998) 166]. These findings suggest that adaptive realignment following prism exposure induces a bias in visual Space Perception, even in tasks that require no visually guided motor response. Given recent neurophysiological and behavioural data suggesting independent visual representations for peripersonal and extrapersonal Space, here we asked whether adaptive aftereffects extend beyond participants' immediate reaching Space to stimuli presented beyond arms' reach (i.e. in extrapersonal Space). Thirty-two participants underwent adaptive realignment to 10degrees left- or right-displacing wedge-prisms. Before and after adaptation participants performed a visual landmark task that required estimation of the midpoint of horizontal line stimuli. There was a significant rightward shift in visual midpoint judgements following adaptation to left-deviating prisms, which was evident in both peripersonal and extrapersonal Space. Paradoxically, a significant rightward shift also occurred following adaptation to right-deviating prisms, but only in extrapersonal Space. We suggest that the pattern of adaptive aftereffects observed reflects the different reference frames used by participants to perform spatial judgements in peripersonal and extrapersonal Space. We also propose that an underlying hemispheric asymmetry in the processing of spatial errors during adaptation may contribute to the direction of aftereffects in both normal observers, and in patients with unilateral lesions. (C) 2002 Elsevier Science Ltd. All rights reserved.
Giacomo Rizzolatti - One of the best experts on this subject based on the ideXlab platform.
-
two different streams form the dorsal visual system anatomy and functions
Experimental Brain Research, 2003Co-Authors: Giacomo Rizzolatti, M MatelliAbstract:There are two radically different views on the functional role of the dorsal visual stream. One considers it as a system involved in Space Perception. The other is of a system that codes visual information for action organization. On the basis of new anatomical data and a reconsideration of previous functional and clinical data, we propose that the dorsal stream and its recipient parietal areas form two distinct functional systems: the dorso-dorsal stream (d-d stream) and the ventro-dorsal stream (v-d stream). The d-d stream is formed by area V6 (main d-d extrastriate visual node) and areas V6A and MIP of the superior parietal lobule. Its major functional role is the control of actions "on line". Its damage leads to optic ataxia. The v-d stream is formed by area MT (main v-d extrastriate visual node) and by the visual areas of the inferior parietal lobule. As the d-d stream, v-d stream is responsible for action organization. It, however, also plays a crucial role in Space Perception and action understanding. The putative mechanisms linking action and Perception in the v-d stream is discussed.
-
motor and cognitive functions of the ventral premotor cortex
Current Opinion in Neurobiology, 2002Co-Authors: Giacomo Rizzolatti, Leonardo Fogassi, Vittorio GalleseAbstract:Abstract Recent data show that the ventral premotor cortex in both humans and monkeys has motor and cognitive functions. The cognitive functions include Space Perception, action understanding and imitation. The data also show a clear functional homology between monkey area F5 and human area 44. Preliminary evidence suggests that the ventral part of the lateral premotor cortex in humans may correspond to monkey area F4. A tentative map of the human lateral premotor areas founded on the reviewed evidence is presented.
-
parietal cortex from sight to action
Current Opinion in Neurobiology, 1997Co-Authors: Giacomo Rizzolatti, Leonardo Fogassi, Vittorio GalleseAbstract:Recent findings have altered radically our thinking about the functional role of the parietal cortex. According to this view, the parietal lobe consists of a multiplicity of areas with specific connections to the frontal lobe. These areas, together with the frontal areas to which they are connected, mediate distinct sensorimotor transformations related to the control of hand, arm, eye or head movements. Space Perception is not unitary, but derives from the joint activity of the fronto-parietal circuits that control actions requiring Space computation.
Vittorio Gallese - One of the best experts on this subject based on the ideXlab platform.
-
the conscious dorsal stream embodied simulation and its role in Space and action conscious awareness
PSYCHE: An Interdisciplinary Journal of Research On Consciousness, 2007Co-Authors: Vittorio GalleseAbstract:The aim of the present article is three-fold. First, it aims to show that Perception requires action. This is most evident for some types of visual percept (e.g. Space Perception and action Perception). Second, it aims to show that the distinction of the cortical visual processing into two streams is insufficient and leads to possible misunderstandings on the true nature of perceptual processes. Third, it aims to show that the dorsal stream is not only responsible for the unconscious control of action, but also for the conscious awareness of Space and action.
-
motor and cognitive functions of the ventral premotor cortex
Current Opinion in Neurobiology, 2002Co-Authors: Giacomo Rizzolatti, Leonardo Fogassi, Vittorio GalleseAbstract:Abstract Recent data show that the ventral premotor cortex in both humans and monkeys has motor and cognitive functions. The cognitive functions include Space Perception, action understanding and imitation. The data also show a clear functional homology between monkey area F5 and human area 44. Preliminary evidence suggests that the ventral part of the lateral premotor cortex in humans may correspond to monkey area F4. A tentative map of the human lateral premotor areas founded on the reviewed evidence is presented.
-
parietal cortex from sight to action
Current Opinion in Neurobiology, 1997Co-Authors: Giacomo Rizzolatti, Leonardo Fogassi, Vittorio GalleseAbstract:Recent findings have altered radically our thinking about the functional role of the parietal cortex. According to this view, the parietal lobe consists of a multiplicity of areas with specific connections to the frontal lobe. These areas, together with the frontal areas to which they are connected, mediate distinct sensorimotor transformations related to the control of hand, arm, eye or head movements. Space Perception is not unitary, but derives from the joint activity of the fronto-parietal circuits that control actions requiring Space computation.
Sergio Sheiji Fukusima - One of the best experts on this subject based on the ideXlab platform.
-
visual Perception of egocentric distance as assessed by triangulation
Journal of Experimental Psychology: Human Perception and Performance, 1997Co-Authors: Sergio Sheiji Fukusima, Jack M Loomis, A Da SilvaAbstract:Two triangulation methods for measuring perceived egocentric distance were examined. In the triangulation-by-pointing procedure, the observer views a target at some distance and, with eyes closed, attempts to point continuously at the target while traversing a path that passes by it. In the triangulation-by-walking procedure, the observer views a target and, with eyes closed, traverses a path that is oblique to the target; on command from the experimenter, the observer turns and walks toward the target. Two experiments using pointing and 3 using walking showed that perceived distance, averaged over observers, was accurate out to 15 m under full-cue conditions. For target distances between 15 and 25 m, the evidence indicates slight perceptual underestimation. Results also show that observers, on average, were accurate in imaginally updating the locations of previously viewed targets. The term visual Space (or visually perceived Space) refers to a perceptual representation of the immediate physical environment that exists independently of any of the particular spatial behaviors it helps to control. Much vision research has been devoted to establishing the functional properties of visual Space and the mechanisms that underlie it. A major goal of such research has been to characterize the mapping from physical to visual Space under different conditions of information availability, but ultimately the goal must be to predict visual Space solely in terms of its sensory inputs and internal determinants (e.g., intrinsic noise, observer assumptions, etc.). Because visual direction is perceived accurately, most Space Perception research has examined the Perception of egocentric distance (i-e., the distance from the object to the observer) and the Perception of exocentric distance (i.e., the distance between two targets lying in the same visual direction or, more generally, the distance between any two locations). Because we believe that the Perception of egocentric
-
visual Space Perception and visually directed action
Journal of Experimental Psychology: Human Perception and Performance, 1992Co-Authors: Jack M Loomis, J A Da Silva, Naofumi Fujita, Sergio Sheiji FukusimaAbstract:The results of two types of experiments are reported. In 1 type, Ss matched depth intervals on the ground plane that appeared equal to frontal intervals at the same distance. The depth intervals had to be made considerably larger than the frontal intervals to appear equal in length, with this physical inequality of equal-appearing intervals increasing with egocentric distance of the intervals (4 m-12 m). In the other type of experiment, Ss viewed targets lying on the ground plane and then, with eyes closed, attempted either to walk directly to their locations or to point continuously toward them while walking along paths that passed off to the side. Performance was quite accurate in both motoric tasks, indicating that the distortion in the mapping from physical to visual Space evident in the visual matching task does not manifest itself in the visually open-loop motoric tasks. Language: en
M Matelli - One of the best experts on this subject based on the ideXlab platform.
-
cortical connections of the inferior parietal cortical convexity of the macaque monkey
Cerebral Cortex, 2006Co-Authors: Stefano Rozzi, M Matelli, Roberta Calzavara, Abdelouahed Belmalih, Elena Borra, Georgia G Gregoriou, Giuseppe LuppinoAbstract:: We traced the cortical connections of the 4 cytoarchitectonic fields--Opt, PG, PFG, PF--forming the cortical convexity of the macaque inferior parietal lobule (IPL). Each of these fields displayed markedly distinct sets of connections. Although Opt and PG are both targets of dorsal visual stream and temporal visual areas, PG is also target of somatosensory and auditory areas. Primary parietal and frontal connections of Opt include area PGm and eye-related areas. In contrast, major parietal and frontal connections of PG include IPL, caudal superior parietal lobule (SPL), and agranular frontal arm-related areas. PFG is target of somatosensory areas and also of the medial superior temporal area (MST) and temporal visual areas and is connected with IPL, rostral SPL, and ventral premotor arm- and face-related areas. Finally, PF is primarily connected with somatosensory areas and with parietal and frontal face- and arm-related areas. The present data challenge the bipartite subdivision of the IPL convexity into a caudal and a rostral area (7a and 7b, respectively) and provide a new anatomical frame of reference of the macaque IPL convexity that advances our present knowledge on the functional organization of this cortical sector, giving new insight into its possible role in Space Perception and motor control.
-
two different streams form the dorsal visual system anatomy and functions
Experimental Brain Research, 2003Co-Authors: Giacomo Rizzolatti, M MatelliAbstract:There are two radically different views on the functional role of the dorsal visual stream. One considers it as a system involved in Space Perception. The other is of a system that codes visual information for action organization. On the basis of new anatomical data and a reconsideration of previous functional and clinical data, we propose that the dorsal stream and its recipient parietal areas form two distinct functional systems: the dorso-dorsal stream (d-d stream) and the ventro-dorsal stream (v-d stream). The d-d stream is formed by area V6 (main d-d extrastriate visual node) and areas V6A and MIP of the superior parietal lobule. Its major functional role is the control of actions "on line". Its damage leads to optic ataxia. The v-d stream is formed by area MT (main v-d extrastriate visual node) and by the visual areas of the inferior parietal lobule. As the d-d stream, v-d stream is responsible for action organization. It, however, also plays a crucial role in Space Perception and action understanding. The putative mechanisms linking action and Perception in the v-d stream is discussed.