1,721,063 research outputs found
Hemispheric metacontrol and cerebral dominance in healthy individuals investigated by means of chimeric faces
No full textCerebral dominance and hemispheric metacontrol were investigated by testing the ability of healthy participants to match chimeric, entire, or half faces presented tachistoscopically. The two hemi-faces compounding chimeric or entire stimuli were presented simultaneously or asynchronously at different exposure times. Participants did not consciously detect chimeric faces for simultaneous presentations lasting up to 40 ms. Interestingly, a 20 ms separation between each half-chimera was sufficient to induce detection of conflicts at a conscious level. Although the presence of chimeric faces was not consciously perceived, performance on chimeric faces was poorer than on entire- and half-faces stimuli, thus indicating an implicit processing of perceptual conflicts. Moreover, the precedence of hemispheric stimulation over-ruled the right hemisphere dominance for face processing, insofar as the hemisphere stimulated last appeared to influence the response. This dynamic reversal of cerebral dominance, however, was not caused by a shift in hemispheric specialization, since the level of performance always reflected the right hemisphere specialization for face recognition. Thus, the dissociation between hemispheric dominance and specialization found in the present study hints at the existence of hemispheric metacontrol in healthy individuals. (c) 2005 Elsevier B.V. All rights reserved
Sport performance: Motor expertise and observational learning in sport.
No full text27-Sport Performance from Part V1-Shared Representation in Applied Contexts
Virtual lesion of ventral premotor cortex impairs visual perception of biomechanically possible but not impossible actions
No full textSingle-pulse transcranial magnetic stimulation (TMS) studies show that action observation facilitates the onlooker's cortico-spinal system supporting the notion of motor mirroring. Repetitive transcranial magnetic stimulation (rTMS) over ventral premotor cortex (vPMc) impairs visual discrimination of body actions. Although studies suggest that the action observation-execution matching system may map only actions that belong to the observer's motor repertoire, we demonstrated comparable motor and premotor facilitation during observation of biomechanically possible as well as impossible actions. It has also been shown that seeing impossible body movements activates the extrastriate body area (EBA). Using event-related rTMS, we sought to determine whether vPMc and EBA are actively involved in the visual discrimination of actions performed through biomechanically possible or impossible kinematics and of their biomechanical plausibility. Stimulation of vPMc impaired discrimination of possible actions while leaving intact the discrimination of biomechanically impossible actions and of biomechanical plausibility. No effect of EBA rTMS on any type of action processing was found. Thus, vPMc is crucial for discrimination of the goal of actions that can be actually performed suggesting that this area is involved in the visual processing of goal-directed actions
Magnetic stimulation of extrastriate body area impairs visual processing of nonfacial body parts
No full textFunctional magnetic resonance imaging indicates that observation of the human body induces a selective activation of a lateral occipitotemporal cortical area called extrastriate body area (EBA) [1]. This area is responsive to static and moving images of the human body and parts of it, but it is insensitive to faces and stimulus categories unrelated to the human body [1, 2]. With event-related repetitive transcranial magnetic stimulation, we tested the possible causal relation between neural activity in EBA and visual processing of body-related, nonfacial stimuli. Facial and noncorporeal stimuli were used as a control. Interference with neural activity in EBA induced a clear impairment, consisting of a significant increase in discriminative reaction time, in the visual processing of body parts. The effect was selective for stimulus type, because it affected responses to nonfacial body stimuli but not to noncorporeal and facial stimuli, and for locus of stimulation, because the effect from the interfering stimulation of EBA was absent during a corresponding stimulation of primary visual cortex. The results provide strong evidence that neural activity in EBA is not only correlated with but also causally involved in the visual processing of the human body and its parts, except the face
Action anticipation and motor resonance in elite basketball players
No full textWe combined psychophysical and transcranial magnetic stimulation studies to investigate the dynamics of action anticipation and its underlying neural correlates in professional basketball players. Athletes predicted the success of free shots at a basket earlier and more accurately than did individuals with comparable visual experience (coaches or sports journalists) and novices. Moreover, performance between athletes and the other groups differed before the ball was seen to leave the model's hands, suggesting that athletes predicted the basket shot's fate by reading the body kinematics. Both visuo-motor and visual experts showed a selective increase of motor-evoked potentials during observation of basket shots. However, only athletes showed a time-specific motor activation during observation of erroneous basket throws. Results suggest that achieving excellence in sports may be related to the fine-tuning of specific anticipatory 'resonance' mechanisms that endow elite athletes' brains with the ability to predict others' actions ahead of their realization
Long- and short-term plastic modeling of action prediction abilities in volleyball
No full textAthletes show superior abilities not only in executing complex actions, but also in anticipating others' moves. Here, we explored how visual and motor experiences contribute to forge elite action prediction abilities in volleyball players. Both adult athletes and supporters were more accurate than novices in predicting the fate of volleyball floating services by viewing the initial ball trajectory, while only athletes could base their predictions on body kinematics. Importantly, adolescents assigned to physical practice training improved their ability to predict the fate of the actions by reading body kinematics, while those assigned to the observational practice training improved only in understanding the ball trajectory. The results suggest that physical and observational practice might provide complementary and mutually reinforcing contributions to the superior perceptual abilities of elite athletes. Moreover, direct motor experience is required to establish novel perceptuo-motor representations that are used to predict others' actions ahead of realization
Representation of body identity and body actions in extrastriate body area and ventral premotor cortex
Full text linkAlthough inherently linked, body form and body action may be represented in separate neural substrates. Using repetitive transcranial magnetic stimulation in healthy individuals, we show that interference with the extrastriate body area impairs the discrimination of bodily forms, and interference with the ventral premotor cortex impairs the discrimination of bodily actions. This double dissociation suggests that whereas extrastriate body area mainly processes actors' body identity, premotor cortex is crucial for visual discriminations of actions
The Spiritual Brain: Selective Cortical Lesions Modulate Human Self-Transcendence
No full textThe predisposition of human beings toward spiritual feeling, thinking, and behaviors is measured by a supposedly stable personality trait called self-transcendence. Although a few neuroimaging studies suggest that neural activation of a large fronto-parieto-temporal network may underpin a variety of spiritual experiences, information on the causative link between such a network and spirituality is lacking. Combining pre- and post-neurosurgery personality assessment with advanced brain-lesion mapping techniques, we found that selective damage to left and right inferior posterior parietal regions induced a specific increase of self-transcendence. Therefore, modifications of neural activity in temporoparietal areas may induce unusually fast modulations of a stable personality trait related to transcendental self-referential awareness. These results hint at the active, crucial role of left and right parietal systems in determining self-transcendence and cast new light on the neurobiological bases of altered spiritual and religious attitudes and behaviors in neurological and mental disorders
Motor facilitation during action observation: Topographic mapping of the target muscle and influence of the onlooker's posture
No full textTranscranial magnetic stimulation (TMS) studies report that viewing a given action performed by a model activates the neural representation of the onlooker's muscles that are activated during the actual execution of the observed action. Here we sought to determine whether this mirror observation-execution facilitation reflects only muscular specificity or whether it is also influenced by postural congruency between onlooker/model body parts. We recorded motor potentials evoked by single-pulse TMS from the first dorsal interosseous (FDI) and abductor digiti minimi (ADM) muscles during observation of the right index and little finger abduction/adduction movements of models who kept their hands in a palm-down or palm-up position. Moreover, in different experiments observers kept their right hand palm down or palm up. Selective motor facilitation was observed during observation of movements that map the motor function of the targeted muscles, regardless of the posture of the observed hand. Modulation of FDI, however, was obtained only when participants kept their hand palm down; by contrast, modulation of ADM was obtained only when participants kept their hand palm up. Interestingly, electromyographic recordings showed that FDI is mostly active when index abduction/adduction movements are performed in the palm-down position, whereas ADM is mostly active when little finger abduction/adduction movements are performed in the palm-up position. Results show that the influence of the onlooker's hand posture is comparable in action execution and observation, thus indicating a fine-grain functional correspondence between these two processes
Motor facilitation of the human cortico-spinal system during observation of bio-mechanically impossible movements
No full textNeurophysiological and neuroiniaging studies in the human and the monkey brain indicate that links between action observation and execution are much tighter than previously believed. Indeed, the mere observation of movements performed by other individuals brings about a clear increase in activity in specific fronto-parietal neural networks (mirror system). Here, we report a series of four single-pulse transcranial magnetic stimulation studies of the motor system, which show that observation of index and little finger movements brings about a facilitation of potentials recorded from muscles that would be involved in the actual execution of the observed action. Remarkably, however, a clear representational selectivity was found also during observation of bio-mechanically impossible index or little finger movements. Thus, in movement observation tasks, the human cortico-spinal system reacts similarly to the vision of bio-mechanically possible and impossible movements but it is able to detect which muscle would be involved in the actual execution of the observed movement. Importantly, this system may be more related to coding body part movements than precisely simulating their execution. (c) 2005 Elsevier Inc. All rights reserved
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