Biomedical subjects

Umberto Castiello

Publications and source records attributed to Umberto Castiello.

29 records · Page 2Linked to original sources

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↗

PubMed2003

Understanding other people's actions: intention and attention.

This study investigated the extent to which observation of an action performed by a human actor or a robotic arm may kinematically prime the performance of an observer subsequently required to perform a similar action. In Experiment 1, an actor reached for a target presented in isolation or flanked by a distractor object. Subsequently, an observer was required to perform a similar action toward the target object, but always in the absence of the distractor. The kinematics of both the human actor and the observer were affected by the presence of the distractor. Unexpectedly, similar effects were found in the observer's kinematics during the trials in which the actor was seated in front of the observer but no action was demonstrated (catch trials). Results from 4 subsequent experiments suggest that the motor intentions of the actor can be inferred by monitoring his or her gaze. To support this conclusion, results are discussed in terms of recent work spanning many disciplines involved in combining gaze direction and body movements.

Adult↗

PubMed2003

A cross-modal interference effect in grasping objects.

The aim of the present paper was to investigate how the kinematics of a hand reaching toward a visual target would be influenced by haptic and proprioceptive input from an unseen distractor actively grasped in the other, nonreaching hand. The main results were that the amplitude of maximum grip aperture was smaller and the time to maximum grip aperture was earlier when the distractor was smaller than the target. The interference effect from the distractor was similar for both hands as they reached. Furthermore, results from a vibrating-distractor condition for passive tactile input revealed that the interference effects were evident only when the distractor was actively grasped. We suggest that neural processing of proprioceptive and tactile information relevant to distractor size produced the observed interference effects. We also emphasize the importance of active manipulation of the distractor stimulus in eliciting such interference effects.

Adult↗

PubMed2002

Posterior parietal cortex control of reach-to-grasp movements in humans.

The aim of the present study was to ascertain the neural correlates for the integration of visual information with the control of the reach-to-grasp action in the healthy human brain. Nine adult subjects (18-38 years; four females and five males) were scanned using functional magnetic resonance imaging while reaching-to-grasp a three-dimensional target. Results demonstrated differential activation of the parietal cortices according to the number of potential targets to be taken into account before movement initiation and the variability of target location. Comparing conditions where a target object that can appear at an unpredictable location with conditions where the target object appears at a predictable location revealed activations in the left superior parietal lobule, the left parieto-occipital sulcus and the right intraparietal sulcus. Results are discussed in terms of visual selective attention and action planning.

Adolescent↗

PubMed2002

Neuropsychological evaluation of deficits in executive functioning for ADHD children with or without learning disabilities.

This study investigates multiple aspects of executive functioning in children with attention deficit/hyperactivity disorder (ADHD). These areas include attentional components, impulsiveness, planning, and problem solving. The rationale of the study is based on neurophysiological studies that suggest frontal lobe dysfunction in ADHD. As frontal lobe functioning is related to abilities in executive control, ADHD is hypothesised to be associated with deficits in various areas of executive functioning. The specific effect of comorbidity of learning disability (LD) was also investigated. Eighty-three children with ADHD and 29 age-matched controls (age 7-13) participated in the study. A battery of neuropsychological tests was utilized to evaluate specific deficits in speed of processing, selective attention, switching attention, sustained attention, attentional capacity, impulsiveness, planning and problem solving. Findings indicated that children with ADHD have slower verbal responses and sustained attention deficit. Deficits in selective attention and attentional capacity observed were largely related to the presence of LD. No specific deficit associated with ADHD or the comorbidity of LD was identified in switching attention, impulsiveness, planning, and problem solving. These results revealed that ADHD is not associated with a general deficit in executive functioning. Instead, ADHD is related to a specific deficit in regulation for attentional resources. The importance of isolating the deficit related to LDs for examining the specific deficit associated with ADHD is highlighted. Results also emphasised the importance of isolating the effect of lower level of abilities (e.g., speed of processing) and the utilization of specific definition for the examination of executive functions.

Attention↗