Biomedical subjects

Umberto Castiello

Publications and source records attributed to Umberto Castiello.

At least 19 recordsLinked to original sources

PubMed2006

Adjusting reach to lift movements to sudden visible changes in target's weight.

People can adjust their reach-to-grasp movements online to sudden changes in the spatial properties of a target. We investigated whether they can also do this when a non-spatial property, weight, suddenly changes. Guiding your movement by using visual cues about an object's weight depends heavily on experience and is expected to be processed by the (slow) ventral stream rather than the (fast) 'online control' dorsal stream. In the first experiment, participants reached out and lifted an object with an expected or an unexpected weight. As predicted, there was an effect of expected weight on the time between the end of the reaching phase and the object's lift-off. In the second experiment, the object sometimes visibly changed weight after the participants had started their movement. The lifting time did not depend on whether the object had changed weight. Thus, participants can make online adjustments to a visually indicated change in weight. These results are interpreted as being contrary to existing theories of online control.

Adult↗

PubMed2006

Different action patterns for cooperative and competitive behaviour.

The aim of the present study is to elucidate the influence of context on the kinematics of the reach-to-grasp movement. In particular, we consider two basic modes of social cognition, namely cooperation and competition. In two experiments kinematics of the very same action - reaching-to-grasp a wooden block - were analyzed in two different contexts provided by a cooperative task and competitive task. For the 'cooperation' tasks two participants were required to reach and grasp their respective objects and to cooperate to join the two objects in specific configurations in the middle of the working surface. For the 'competition' tasks, the two participants had to compete to place their own object first in the middle of the working surface. Results revealed specific kinematic patterns for cooperation and competition which were distinct from similar actions performed by each participant in isolation. Further, during the cooperation tasks, a high level of correlation between key kinematical parameters of the two participants was found. In accordance with evidence from neuroimaging, developmental and social psychology our results suggest the existence of motor patterns which reflect the intention to act in a social context.

Adult↗

PubMed2006

Transfer of interfered motor patterns to self from others.

Previous behavioural and neuroimaging data on humans demonstrated that kinematics and the level of brain activity vary according to whether participants reach towards and grasp a target object presented in isolation or flanked by a distractor object. Here we seek to explore whether a differential activation can be revealed by the mere observation of another person grasping an object in isolation or alongside a distractor. To this end we used event-related functional magnetic resonance imaging to localize neural activity related to action observation that was influenced by the presence of a distractor object. We found that observing a human model reaching-to-grasp a three-dimensional target alongside a distractor elicits a differential level of activation in a network of areas typically involved during action observation: the dorsal sectors of the premotor cortex and the inferior frontal gyrus. Whereas our previous understanding of the human action observation system has been restricted to actions directed to single objects, we provide compelling evidence that areas within this network modulate with respect to the context in which the observed action takes place. This may prove to be a fundamental process for our understanding of how others' actions can be represented at a neural level.

Adult↗

PubMed2005

Effects of end-goal on hand shaping.

The aim of the present study was to determine whether hand shaping was affected by planning of an action subsequent to object contact. Ten subjects (5 females and 5 males, ages 19-33) were requested to reach toward and grasp a convex object between the thumb and the four fingers of the right hand and to perform one of the following actions: 1) lift up the object; 2) insert the object into a niche of a similar shape and size as the object, or 3) insert the object into a rectangular niche much larger than the object. Flexion/extension at the metacarpal-phalangeal and proximal interphalangeal joints of all digits were measured using resistive sensors embedded in a glove. Although all experimental conditions required grasping the same object, we found different covariation patterns among finger joint angles across conditions. Gradual preshaping of the hand occurred only when planning object lift or when the end-goal required object placement into the tight niche. In contrast, for the larger niche, gradual preshaping was not evident for the ring and the little finger. Further, reaching movements were faster for movements ending with the larger niche than for the other movement conditions. The present results suggest that hand shaping takes into account end-goal in addition to object geometry. We discuss these findings in the context of forward internal models that allow the prediction of the sensorimotor consequences of motor commands in advance to their execution.

Adult↗

PubMed2005

Failure to read motor intentions from gaze in children with autism.

A core feature of autism is the abnormal use of gaze to attribute mental states to others, and thus to predict others' behaviour. An untested idea is whether this dysfunction is confined to mental states having a propositional content, such as beliefs and desire or extends to motor intentional states which allow one to make inferences about the actions of others. This study used kinematics to examine the ability to use gaze to inform one about the motor states of another in normal and autistic children. In each trial two participants, a model and an observer, were seated facing each other at a table. In three experimental blocks the model was requested to grasp a stimulus, to gaze towards the same stimulus, and to gaze away from the stimulus without performing any action. The task for the observer was to grasp the stimulus after having watched the model perform her task. We observed that normal children showed facilitation effects in terms of movement speed following the observation of the model grasping or simply gazing at the object. In contrast, autistic children did not show any evidence of facilitation in these conditions. Neither normal nor autistic children showed evidence of facilitation when the model's gaze was not directed towards the stimulus. These findings demonstrate that, in contrast to normal children, children with autism fail to use information from the model's action or gaze to plan their subsequent action, and that in autism the inability to use of another person's gaze produces a lack of understanding of the motor intention of others.

Adolescent↗

PubMed2005

An object-centred reference frame for control of grasping: effects of grasping a distractor object on visuomotor control.

Previous evidence based on perceptual integration and arbitrary responses suggests extensive cross-modal links in attention across the various modalities. Attention typically shifts to a common location across the modalities, despite the vast differences in their initial coding of space. An issue that remains unclear is whether or not these effects of multisensory coding occur during more natural tasks, such as grasping and manipulating three-dimensional objects. Using kinematic measures, we found strong effects of the diameter of a grasped distractor object on the aperture used to grasp a target object at both coincident and non-coincident locations. These results suggest that interference effects can occur between proprioceptive and visuomotor signals in grasping. Unlike other interference effects in cross-modal attention, these effects do not depend on the spatial relation between target and distractor, but occur within an object-based frame of reference.

Adolescent↗

PubMed2005

Effects of an orientation illusion on motor performance and motor imagery.

Although the effect of visual illusions on overt actions has been an area of keen interest in motor performance, no study has yet examined whether illusions have similar or different effects on overt and imagined movements. Two experiments were conducted that compared the effects of an orientation illusion on an overt posture selection task and an imagined posture selection task. In Experiment 1 subjects were given a choice of grasping a bar with the thumb on the left side or right side of the bar. In Experiment 2 subjects were instructed to only imagine grasping the bar while remaining motionless. Subjects then reported which side of the bar their thumb had been placed in imagined grasping. Both the overt selection and imagined selection tasks were found to be sensitive to the orientation illusion, suggesting that similar visual information is used for overt and imagined movements, with both being sensitive to an orientation illusion. The results are discussed in terms of the visual processing and representation of real and imagined actions.

Brain↗

PubMed2005

Effects of increasing visual load on aurally and visually guided target acquisition in a virtual environment.

The aim of the present study is to investigate interactions between vision and audition during a target acquisition task performed in a virtual environment. We measured the time taken to locate a visual target (acquisition time) signalled by auditory and/or visual cues in conditions of variable visual load. Visual load was increased by introducing a secondary visual task. The auditory cue was constructed using virtual three-dimensional (3D) sound techniques. The visual cue was constructed in the form of a 3D updating arrow. The results suggested that both auditory and visual cues reduced acquisition time as compared to an uncued condition. Whereas the visual cue elicited faster acquisition time than the auditory cue, the combination of the two cues produced the fastest acquisition time. The introduction of secondary visual task differentially affected acquisition time depending on cue modality. In conditions of high visual load, acquiring a target signalled by the auditory cue led to slower and more error-prone performance than acquiring a target signalled by either the visual cue alone or by both the visual and auditory cues.

Adolescent↗

PubMed2005

The neuroscience of grasping.

People have always been fascinated by the exquisite precision and flexibility of the human hand. When hand meets object, we confront the overlapping worlds of sensorimotor and cognitive functions. We reach for objects, grasp and lift them, manipulate them and use them to act on other objects. This review examines one of these actions--grasping. Recent research in behavioural neuroscience, neuroimaging and electrophysiology has the potential to reveal where in the brain the process of grasping is organized, but has yet to address several questions about the sensorimotor transformations that relate to the control of the hands.

Animals↗

PubMed2005

Reaching in children with and without developmental coordination disorder under normal and perturbed vision.

The aim of this study is to describe the reaching action of children with developmental coordination disorder (DCD) and to investigate whether their use of visual feedback during the time course of this action differs from that of normally developing children. Fifty-two children subdivided into 2 age bands (7-8 and 9-10 years) within 2 groups (with and without DCD) participated in this experiment. They were asked to reach for a target positioned either ipsilaterally or contralaterally to the reaching hand in 2 visual conditions: a condition where vision was unrestrained (normal vision) and a condition where they wore glasses with prismatic lenses (perturbed vision). An analysis of the experimental data indicates that the trajectories followed by the DCD group were longer and more curved than those of the control group. Further, the deceleration times were longer for the DCD group than for the normally developing children. The introduction of the prismatic lenses supports the idea that the use of visual feedback by children with DCD may be different from that in children without DCD.

Age Factors↗

PubMed2004

The human premotor cortex is 'mirror' only for biological actions.

Previous work has shown that both human adults and children attend to grasping actions performed by another person but not necessarily to those made by a mechanical device. According to recent neurophysiological data, the monkey premotor cortex contains "mirror" neurons that discharge both when the monkey performs specific manual grasping actions and when it observes another individual performing the same or similar actions. However, when a human model uses tools to perform grasping actions, the mirror neurons are not activated. A similar "mirror" system has been described in humans, but whether or not it is also tuned specifically to biological actions has never been tested. Here we show that when subjects observed manual grasping actions performed by a human model a significant neural response was elicited in the left premotor cortex. This activation was not evident for the observation of grasping actions performed by a robot model commanded by an experimenter. This result indicates for the first time that in humans the mirror system is biologically tuned. This system appears to be the neural substrate for biological preference during action coding.

Adult↗

PubMed2004

Differential effects of cast shadows on perception and action.

In two experiments we investigated the effects of cast shadows on different real-life tasks. In experiment 1, participants were required to make a speeded verbal identification of the target object (perceptual task), whereas in experiment 2 participants were required to reach for and grasp the target object (motor task). In both experiments real three-dimensional (3-D) objects were presented, one at a time, either with their own natural cast shadow (congruent condition) or with the cast shadow of a different object (incongruent condition). Shadows were cast either to the left or to the right of the object. We asked whether the features of the shadow (ie whether it is congruent or incongruent with the object, and whether it is cast to the left or to the right of the object) could influence perception and action differently. Results showed that cast shadows did not influence identification of real 3-D objects (experiment 1), but they affected movement kinematics, producing distractor-like interference, particularly on movement trajectory (experiment 2). These findings suggest a task-dependent influence of cast shadows on human performance. In the case of object-oriented actions, cast shadows may represent further affordances of the object, and as such compete for the control of the action.

Adult↗

PubMed2004

Comparing effects of 2-D and 3-D visual cues during aurally aided target acquisition.

The aim of the present study was to investigate interactions between vision and audition during a visual target acquisition task performed in a virtual environment. In two experiments, participants were required to perform an acquisition task guided by auditory and/or visual cues. In both experiments the auditory cues were constructed using virtual 3-D sound techniques based on nonindividualized head-related transfer functions. In Experiment 1 the visual cue was constructed in the form of a continuously updated 2-D arrow. In Experiment 2 the visual cue was a nonstereoscopic, perspective-based 3-D arrow. The results suggested that virtual spatial auditory cues reduced acquisition time but were not as effective as the virtual visual cues. Experiencing the 3-D perspective-based arrow rather than the 2-D arrow produced a faster acquisition time not only in the visually aided conditions but also when the auditory cues were presented in isolation. Suggested novel applications include providing 3-D nonstereoscopic, perspective-based visual information on radar displays, which may lead to a better integration with spatial virtual auditory information.

Adolescent↗

PubMed2003

Binding personal and extrapersonal space through body shadows.

Shadows in visual scenes can have profound effects on visual perception. Here we have found that visual distracters distant from the body interfere with human spatial discrimination of tactile targets at a hand, particularly when the shadow of the stimulated hand stretches toward them in extrapersonal space. These findings suggest that shadows cast by a person's own body parts can bridge the gap between personal and extrapersonal space.

Adult↗

PubMed2003

Shadows in the brain.

The aims of the present study were to investigate whether the processing of an object shadow occurs implicitly, that is without conscious awareness, and where physically within the human brain shadows are processed. Here we present neurological evidence, obtained from studies of brain-injured patients with visual neglect, that shadows are implicitly processed and that this processing may take place within the temporal lobe. Neglect patients with lesions that do not involve the right temporal lobe were still able to process shadows to optimize object shape perception. In contrast, shadow processing was not found to be as efficient in neglect patients with lesions that involve the right temporal lobe.

Aged↗

PubMed2003

The reach-to-grasp movement in children with autism spectrum disorder.

Autism is associated with a wide and complex array of neurobehavioural symptoms. Examination of the motor system offers a particularly appealing method for studying autism by providing information about this syndrome that is relatively immune to experimental influence. In this article, we considered the relationship between possible movement disturbance and symptoms of autism and introduced an experimental model that may be useful for rehabilitation and diagnostic purposes: the reach-to-grasp movement. Research is reviewed that characterizes kinematically the reach-to-grasp movement in children with autism compared with age-matched 'controls'. Unlike the age-matched children, autistic children showed differences in movement planning and execution, supporting the view that movement disturbances may play a part in the phenomenon of autism.

Autistic Disorder↗

PubMed2003

Motor facilitation following action observation: a behavioural study in prehensile action.

Previous research has shown that the observation of actions and the execution of actions activate common neural systems. More recently, we have presented data showing that action observation of prehension primes subsequent execution (Castiello, Lusher, Mari, Edwards, & Humphreys, 2002). In the current paper we examined action priming under conditions in which the size of the prime did not predict the size of the target (only 20% of trials were valid). We demonstrated reliable priming under these conditions, consistent with the effect occurring automatically. In addition, we show priming even when observers saw just the object rather than the object and a reaching action on the prime trial. We discuss the findings in relation to the role of mirror neurons and object affordances.

Adolescent↗

PubMed2003

The human temporal lobe integrates facial form and motion: evidence from fMRI and ERP studies.

Physiological studies in humans and monkeys indicate that the posterior temporal cortex is active when viewing the movements of others. Here we tested the premise that this region integrates form and motion information by presenting both natural and line-drawn displays of moving faces and motion controls where motion was continuously presented in the same part of the visual field. The cortex in and near the STS and on the fusiform gyrus (FG) responded to both types of face stimuli, but not to the controls, in a functional magnetic resonance imaging study in 10 normal subjects. The response in the STS to both types of facial motion was equal in magnitude, whereas in the FG the natural image of the face produced a significantly greater response than that of the line-drawn face. In a subsequent recording session, the electrical activity of the brain was recorded in the same subjects to the same activation task. Significantly larger event-related potentials (ERPs) to both types of moving faces were observed over the posterior temporal scalp compared to the motion controls at around 200 ms postmotion onset. Taken together, these data suggest that regions of temporal cortex actively integrate form and motion information-a process largely independent of low-level visual processes such as changes in local luminance and contrast.

Adult↗