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Biomedical subjects

U Castiello

Publications and source records attributed to U Castiello.

At least 19 recordsLinked to original sources
PubMed2000

Dopaminergic effects on the implicit processing of distractor objects in Parkinson's disease.

The aim of the present study was to assess the effects of dopaminergic medication on the selection-for-action mechanisms in Parkinson's disease (PD). PD subjects were tested after not having taken medication for at least 12 h ("Off' state) and then retested 1-2 h after medication ("On" state). A three-dimensional kinematic system (ELITE, BTS, Italy) was used to record reach-to-grasp movements to a target object placed at a reaching distance of 30 cm. The target was presented alone or in the presence of distractor objects, which could be of either the same size (compatible distractor) or a different size (incompatible distractor). PD subjects in the Off state were significantly more affected by the presence of the incompatible distractor than in the On state. These results indicate that dopaminergic medication is of benefit in reducing interference effects when distractor objects evoke motor programs that differ from the motor program elicited by the target. Results are discussed in light of the role played by the striatal and mesocortical dopaminergic systems for response selection in basal ganglia disorders.

Adult↗
PubMed2000

The reach-to-grasp movement in Parkinson's disease before and after dopaminergic medication.

The aim of the present study was to assess the effects of dopaminergic medication on the organisation of the reach-to-grasp movement in Parkinson's disease. A three-dimensional kinematic system (ELITE, B/T/S Italy) was used to record reach-to-grasp movements to objects of either small (0.7 cm) or large (8 cm) diameter placed at a reaching distance of either 20 or 30 cm. Vision of the reaching limb and target was also manipulated. Parkinson's disease participants (N = 14) were assessed in 'OFF' (12 h without medication) and 'ON' (1-2 h post-administration of medication) states. In the 'ON' state, movement duration and the time spent in arm deceleration were significantly less than in the 'OFF' state. The amplitudes of peak reaching velocity, acceleration and deceleration were all higher in the 'ON' than in the 'OFF' state. Further, in the 'ON' state, the acceleration profile no longer exhibited small irregular adjustments, the number of significant correlations between parameters measured from the transport and manipulation components was greater, and the movement was more direct in both the mediolateral horizontal and vertical planes. These results indicate that dopaminergic medication is of benefit in reducing bradykinesia and in fine-tuning kinematic parameterisation of a selected reach-to-grasp action.

Adult↗
PubMed2000

Interference from distractors in reach-to-grasp movements.

Descriptions of interference effects from non-relevant stimuli are extensive in visual target detection and identification paradigms. To explore the influence of features of non-relevant objects on reach-to-grasp movements, we instructed healthy normal controls to reach for and pick up a cylinder (target) placed midsagittally 30 cm from the starting position of the hand. In Experiment 1, the target was presented alone, or accompanied by a narrower, wider, or same-size distractor positioned to the left or right of the target. In Experiment 2, the target was presented alone or accompanied by a distractor, which was slanted at a different orientation to the target. Reflective markers were placed on the wrist, thumb, and index finger of the right hand, and infra-red light-detecting cameras recorded their displacement through a calibrated 3-dimensional working space. Kinematic parameters were derived and analysed. Consistent changes in the expression of peak velocity, acceleration, and deceleration were evident when the distractor was narrower or wider than the target. The impact of the orientation of the distractor, conversely, was not marked. We discuss the results in the context of physiological findings and models of selective attention.

Adult↗
PubMed1999

Modulation of unilateral neglect as a function of direction of object motion.

Unilateral neglect is a disorder involving difficulty in attending to the side of space contralesional to brain injury. Two recent experiments have shown that task-irrelevant background motion reduces neglect on line bisection tasks; however, task-relevant motion has not been assessed. We investigated the effect of task-relevant object motion on left neglect using a moving cube presented on a computer screen. Subjects responded to cued corners of the cube as it moved across the screen. Direction of cube motion had a significant impact on the magnitude of neglect. Responses to left hemispace targets appearing on a leftward moving cube were equal to patients' fastest responses. In contrast, responses to left hemispace targets appearing on a rightward moving cube were the slowest of all responses. These results demonstrate that contralesional object motion is capable of normalising neglect patients' detection of contralesional targets.

Adult↗
PubMed1999

The reach-to-grasp movement in Parkinson's disease: response to a simultaneous perturbation of object position and object size.

This study assessed the adaptive response of the reach-to-grasp movement of 12 Parkinson's disease (PD) and 12 control subjects to a simultaneous perturbation of target object location and size. The main aim was to test further the reported dysfunction of PD subjects in the simultaneous activation of movement components. Participants were required to reach 30 cm to grasp a central illuminated cylinder of either small (0.7 cm) or large (8 cm) diameter. For a small percentage of trials (20/100) a visual perturbation was introduced unexpectedly at the onset of the reaching action. This consisted of a shift of illumination from the central cylinder to a cylinder of differing diameter, which was positioned 20 degrees to the left (n = 10) or to the right (n = 10). The subject was required to grasp the newly illuminated cylinder. For the Parkinson's disease subject group, the earliest response to this 'double' perturbation was in the parameter of peak reaching acceleration, which was on average 50 ms earlier for 'double' perturbed than for non-perturbed trials. The grasp component response followed more than 500 ms after the earliest transport response. For the control subjects initial signs of a response to the 'double' perturbation were seen almost simultaneously in the transport parameter of peak arm deceleration, and in the manipulation parameter of maximum grip aperture, but these changes were not evident until more than 400 ms after movement onset. These results indicate that the basal ganglia can be identified as part of a circuit which is involved in the integration of parallel neutral pathways, and which exercise flexibility in the degree to which these components are 'coupled' functionally. With basal ganglia dysfunction the activation of integration centres that at first gate the flow of information to the parallel channels of reach and grasp seems inefficient.

Adult↗
PubMed1999

Sudden and gradual presentation of distractor objects: differential interference effects.

In solving the selection-for-action problem, it is believed that attentional mechanisms enable dominance of target over non-target objects. However, under some conditions, information from non-target objects "interferes" with the action to a relevant target. We investigated the possibility that this interference may result when the irrelevant object activates a specific subset of visuomotor pathways. Participants reached to grasp three-dimensional stimuli while actively attending to a nearby flanker object. The means by which the flanker was presented was manipulated. This relevant object was illuminated either abruptly or gradually. The parvocellular pathway in early visual processing is equally activated in both conditions. The magnocellular pathway is strongly activated by abrupt presentation and weakly activated with gradual presentation of the flanker object. Kinematics of the reach-to-grasp action to the target showed signs of interference only in the sudden illumination condition. This suggests a dissociation between dorsal and ventral cortical streams in terms of relevance for action. Our data suggests that this effect is not due to early visual-pathway differences, but instead reveals a property of a transient object-based visual attention mechanism.

Adult↗
PubMed1999

Covert orienting and focusing of attention in children with attention deficit hyperactivity disorder.

Performance on the covert visuo-spatial attentional functions of orienting and focusing by a group of ADHD children (n = 20) was compared to that of age and sex-matched control children. In Experiment 1, responses were given to cued targets at valid and invalid locations. In Experiment 2, responses were given to targets presented in small, medium-sized or large visual field locations. For both experiments, the hypotheses that reaction times of ADHD children would be greater than those of control children and that performance would be asymmetrical, were supported. For Experiment 1, ADHD children showed bilaterally greater 'benefits' from having directed attention to the cued location and greater 'costs' in having to relocate the attentional focus than controls. In Experiment 2, the hypothesis that the function of focusing attention by ADHD children may show breakdown in the usual pattern of an increase in reaction time with focus area was partly supported by the finding of similar reaction times to targets presented in medium-sized and large regions of the left visual hemifield. These results have been interpreted as reflecting a stronger anchorage of attention by ADHD children upon a cued location and an inability to shift covert attention easily to an alternative location. The breakdown of the focusing function suggests adoption of similar time response sets across focus area size by the more compromised right hemisphere.

Attention↗
PubMed1999

Semantic category interference effects upon the reach-to-grasp movement.

In the present study the kinematics of the reach-to-grasp movement towards a target object in the presence of distractors was investigated. Three experiments were conducted. In the first experiment, there were three conditions, (a) the target alone, (b) the target presented with a distractor object that was semantically similar to the target and (c) the target presented with a distractor object that was semantically different from the target. The same conditions were repeated for the second experiment but the size of the distractors were also manipulated. For the third experiment the target was presented with a distractor object that was semantically different from the target but similar in shape. In the first experiment interference effects were observed in kinematic parameters of the grasp, but not for the reach component when the target and the distractor were semantically different. In the second and the third experiment, similar results were found. Results are discussed in terms of conflicting processing between objects pertaining to different semantic categories.

Adolescent↗
PubMed1999

Mechanisms of selection for the control of hand action.

Most attention research has viewed selection as essentially a perceptual problem, with attentional mechanisms required to protect the senses from overload. Although this might indeed be one of several functions that attention serves, the need for selection also arises when one considers the requirement of actions rather than perception. This review examines recent attempts to determine the role played by selective mechanisms in the control of action. Recent studies looking at reach-to-grasp responses to target objects in the presence of distracting objects within a three-dimensional space are discussed. The manner in which motor aspects of the reach-to-grasp response might be influenced by distractors is also highlighted, rather than merely addressing the perceptual consequences of distractors. The studies reviewed here emphasize several factors highlighting the importance of studying selective processes within three-dimensional environments from which attention and action have evolved.

Journal Article↗
PubMed1998

Upper limb movement differentiation according to taxonomic semantic category.

The size or shape of an object, its perceptual features, determine the patterning of an arm and hand action involving that object. Little is known about the role played by the taxonomic semantic attributes of an object for perceptuomotor processing. In this study we investigated whether the semantic relationship between two target stimuli influences the kinematics of a bilateral reach-to-grasp action. The results showed that reach-to-grasp movements preceding the action of putting living-thing pairs together were faster, and showed earlier settings of reach and grasp temporal parameters, than movements involving pairs of non-living things. It is hypothesized that this reflects the recruitment of different categorical perceptuomotor pathways.

Adult↗
PubMed1998

Reach to grasp: the response to a simultaneous perturbation of object position and size.

This study assessed the reach to grasp movement and its adaptive response to a simultaneous perturbation of object location and size. The aim was to clarify the means by which integration between the neural pathways modulating transport and manipulation is achieved. Participants (n = 11) were required to reach 30 cm to grasp a central illuminated cylinder of either small (0.7 cm) or large (8 cm) diameter. For a small percentage of trials (20/100) a visual perturbation was introduced unexpectedly at the onset of the reaching action. This consisted of a shift of illumination from the central cylinder to a cylinder of differing diameter (large in session A; small in session B) that was positioned 20 degrees to the left (n = 10 trials) or to the right (n = 10) of the central cylinder. The subject was required to grasp the newly illuminated cylinder. Movement duration for these "double" (position and size) perturbed trials was much longer than those of control trials to the central cylinder (session A: by an average of 250 ms; session B: 180 ms), and the increased values were much greater than those reported previously in "single" perturbation studies where either size or location of the object was perturbed. Initial signs of a response to the "double" perturbation were seen almost simultaneously in the transport parameter of peak arm deceleration and in the manipulation parameter of maximum grip aperture, but these changes were not evident until more than 400 ms after movement onset, a response onset much later than that found in "single" perturbation studies. It is proposed that the visual change resultant from the double perturbation activates integration centres that at first gate the flow of information to the parallel channels of transport and manipulation. Following processing of this information, these centres act to instigate a synchronised and coordinated response in both components. These results add support to the existence of neural centres dedicated to the integration of parallel neural pathways, and which exercise flexibility in the degree to which these components are "coupled" functionally.

Adaptation, Physiological↗
PubMed1998

Attentional coding for three-dimensional objects and two-dimensional shapes. Differential interference effects.

The role played by the attentional mechanisms that enable dominance of relevant objects over distractor objects was investigated by measuring changes in the kinematics of the reach-to-grasp movement. Subjects reached towards three-dimensional (3D) stimuli while attention was diverted towards distracting information consisting of either two-dimensional (2D) projected shapes or 3D objects. Movement kinematics were influenced to a greater degree when a secondary task was performed involving a 3D object rather than a 2D projected shape. When the distractor was 3D, both the reaching and the grasping components were altered but, when it was 2D only, the reaching component was modified. It is suggested that, when attention is directed towards a distractor, it is associated with interference in the kinematics of the action towards the target. Further, the nature and dimensions of the distractor selectively influence the reach or the grasp component of a prehension movement.

Adult↗
PubMed1998

Kinematic analysis of the reach to grasp movement in Parkinson's and Huntington's disease subjects.

This experiment investigates the kinematic characteristics of the reach to grasp movement of Parkinson's and Huntington's disease subjects under two different experimental conditions. In the first condition subjects were required to perform the movement at a normal speed, while in the second condition they were required to perform the movement as fast as possible. Results showed that the kinematic parameterization of movement in Parkinson's disease subjects did not differ from that of age-matched control subjects for both the normal and the fast condition. However, the performances of Huntington's disease subjects appeared to be different when compared to the other two groups. Differences were mainly related to Huntington's disease patients' inability to properly define the temporal features of the movements.

Adult↗
PubMed1998

The effect of unilateral posteroventral pallidotomy on the kinematics of the reach to grasp movement.

OBJECTIVE: To assess postoperative effects of unilateral posteroventral pallidotomy on the organisation of upper limb movement. METHODS: A three dimensional kinematic system (ELITE, B/T/S/ Italy) was used to record reach to grasp movements to objects of either small (0.7 cm) or large (8 cm) diameter placed at a reaching distance of either 20 or 30 cm. Four patients with Parkinson's disease were assessed in "off" (12 hours without medication) and "on" (1 hour after administration of medication) preoperatively and postoperatively. RESULTS: Duration of the movement and the time spent in arm deceleration were significantly reduced after surgery. However, movement patterning according to object size was adversely affected. Postoperatively, all four patients showed an abnormal pattern of a longer movement duration, and three showed a longer time of reaching arm deceleration, for reach to grasp movements to the large object than for those to the small object. CONCLUSION: Posteroventral pallidotomy seems to be beneficial in reducing bradykinesia of upper limb movements but may have "costs" to movement patterning, particularly for reach to grasp movements to objects of differing sizes. This study raises interesting questions about the role of the globus pallidus interna in coordinating stimulus bound visual information with appropriate motor patterning.

Aged↗
PubMed1998

Prehension movements and perceived object depth structure.

This study asked the question, "Will the motor pattern to a perceived two-dimensional (2-D) object differ from that same object when it is perceived as three dimensional (3-D)?" Subjects were required to reach and grasp an apple that could appear to be 2-D or 3-D. Two experimental sessions were conducted. In Condition A, the apple was initially perceived to be 2-D, but, for 20% of trials, it suddenly shifted to a 3-D apple at movement onset. In Condition B, the apple was initially perceived to be 3-D, but, for 20% of trials, it suddenly shifted to a 2-D silhouette of the same apple. For control trials, subjects grasped the perceived 2-D apple as if it were a disc (82%), and they grasped the 3-D apple, as they would a normal apple, with a whole-hand grasp (86%). For Condition A perturbed trials, there was a rapid change from a 2-D precision grip to a 3-D whole-hand prehension, whereas the converse was true for the opposite perturbation. Peak acceleration was anticipated for Condition A perturbed trials but not for Condition B perturbed trials. These results indicate that the motor patterns we use in interacting with an object are strongly influenced by the way we perceive the object in real time, and that object affordances, such as dimension, can override the influence exerted by existing representations.

Adult↗
PubMed1998

Dissociation of covert and overt spatial attention during prehension movements: selective interference effects.

In four experiments, the influence of distractor objects on the temporal evolution of the reach-to-grasp movement toward a target object (an apple) was examined. In the first experiment, the distractor was another apple, which moved laterally behind the target and occasionally changed direction toward the target, thus becoming the to-be-grasped object. In the second and third experiments, the distractor was a stationary piece of fruit, which sometimes became the to-be-grasped object because of a change in illumination. The fourth experiment was a combination of the first two experiments. In all cases, selective interference effects on the transport and manipulation components were observed only when attention to the distractor was covert rather than overt. It is proposed that covert visuospatial attention selects information about distracting but potentially important stimuli, such that a registration of significance is accomplished without the need to process all available information.

Adult↗
PubMed1997

Arm and mouth coordination during the eating action in humans: a kinematic analysis.

The kinematic characteristics of the eating action in humans were assessed. Ten subjects were asked to bring to the mouth pieces of cheese of different sizes (0.7 cm and 2 cm). The pattern of mouth aperture with respect to the size of the food was similar to that found for grasping differently sized objects with the hand. Mouth aperture was appropriately scaled and the time of maximum aperture was reached earlier for the smaller than for the larger piece of cheese. The deceleration phase of the arm was prolonged when the small piece of cheese had to be brought to the mouth with respect to when the large piece of cheese had to be brought to the mouth. Temporal coupling between the time of maximum peak deceleration and the maximum mouth aperture was found in seven of the ten subjects. Taken together these preliminary results suggest that coordinated actions are subserved by the use of a common coordinating schema independently from the effectors involved.

Adult↗