Biomedical subjects

U Castiello

Publications and source records attributed to U Castiello.

At least 55 records · Page 3Linked to original sources

PubMed1994

Parkinson's disease: reorganization of the reach to grasp movement in response to perturbation of the distal motor patterning.

This study assessed the kinematic changes to the reach to grasp movement in response to a perturbation of object size in 15 Parkinson's disease (PD) and 15 control subjects. For non-perturbed trials subjects reached 35 cm to grasp and lift either an illuminated small (0.7 cm) or large (8 cm) diameter cylinder. For perturbed trials (20%), illumination shifted unexpectedly from the small to the large or from the large to the small cylinder at the onset of the reach. For Condition One trials subjects were given no instructions as to which grasp to use. With perturbation, they thus naturally changed grasp from precision grip to whole hand prehension or vice versa. The results for the PD subjects indicated a slowness at the transition from one to another grasp. This contrasted to the smooth transitions when perturbation required only a change of grasp aperture (precision grip--Condition Two; whole hand prehension--Condition Three). PD subjects thus showed dysfunction in the suppression/activation of different grasp programs rather than deficits in the on-line modification of an operating program.

Aged↗

PubMed1994

Orienting the finger opposition space during prehension movements.

Two experiments are reported that examined the act of prehension when subjects were asked to grasp with their thumb and index finger pads an elongated object resting horizontally on a surface and placed at different orientations with respect to the subject. In Experiment 1, the pad opposition preferences were determined for the six angles of orientation examined. For angles of 90 degrees (object parallel to frontal plane) or less, no rotation of the wrist (pronation) was used; for angles 110 degrees or greater, pronation was systematically employed to reorient the finger opposition space. Only one angle, 100 degrees , produced any evidence of ambiguity in how to grasp the object: Approximately 60% of these grasps involved pronation and 40% did not. Using the foregoing grasp preference data, in Experiment 2 we examined the kinematics of the wrist and elbow trajectories during prehension movements directed at an object in different orientations. Movement time, time to peak acceleration, velocity, and deceleration were measured. No kinematic differences were observed when the object orientation either required (110 degrees ) or did not require (80 degrees ) a pronation. By contrast, if the orientation was changed at the onset of the movement, such that an unpredicted pronation had to be introduced to achieve the grasp, kinematics were affected: Movement time was increased, and the time devoted to deceleration was lengthened. These data are interpreted as evidence that when natural prehension occurs, pronation can be included in the motor plan without affecting the movement kinematics. When constraints are imposed on the movement execution as a consequence of a perturbation, however, the introduction of a pronation component requires kinematic rearrangement.

Journal Article↗

PubMed1994

Reach to grasp: changes with age.

This study provides the first known kinematic assessment of the reach-to-grasp movement in elderly subjects. Twelve subjects (aged 60-71) were compared to gender-matched younger subjects (aged 18-25). Subjects reached 35 cm to grasp either a small (0.7 cm) or a large (8 cm) diameter cylinder. Precision grip was naturally adopted for the small cylinder, and whole hand prehension for the large cylinder. The displacements of active infrared markers (wrist and hand) were recorded with an Optotrak system. Movement initiation time, movement duration, and kinematic parameters of the reach-and-grasp components were computed. Older subjects showed slower, longer movements with a prolonged approach phase. However, the patterning and coordination of this movement, with respect to the utilization of a precision grip or whole hand prehension, were similar for both groups. Subtle changes with age thus appear to reflect a strategy that develops to compensate for deterioration in other systems such as visual or proprioceptive.

Adolescent↗

PubMed1993

The bilateral reach to grasp movement.

This study investigated the kinematic organization of bilateral reach to grasp movements. In Experiment 1 non-homologous bilateral movements were performed. One limb reached to grasp an object using whole hand prehension; the contralateral limb simultaneously reached to grasp an object using precision grip. Corresponding unilateral movements were assessed. Movement duration for each limb in the bilateral condition was similar. However, with earlier temporal settings for peak wrist acceleration and velocity, the limb performing precision grip showed a longer approach (deceleration) phase to the object. Unilateral precision grip movements showed a longer movement duration and deceleration phase than unilateral whole hand prehension movements. In Experiment 2 homologous bilateral movements were assessed. Both limbs performed either a reach and whole hand prehension or a reach and precision grip. Again the precision grip movements showed longer movement and deceleration times. Experiment 3 consisted of bilateral non-homologous pointing movements and a pointing movement with one limb while reaching to grasp with the contralateral limb. It was found that the earlier temporal settings of peak acceleration and velocity with the precision grip limb of the non-homologous bilateral task (Expt. 1) were largely due to the performance of distal grasping actions. It is concluded that a kinematic parameterization which is independent to each limb is evident for bilateral tasks which require functionally independent actions.

Adolescent↗

PubMed1993

The reach to grasp movement of blind subjects.

The importance of vision for the processing and coordination of the transport and manipulation components of a reach to grasp movement was assessed. Four blind volunteers (two men, two women; aged 25-40) were compared with matched control groups: (1) blindfolded and (2) full vision. Subjects reached 20 or 30 cm for a large or small diameter (6 cm or 0.7 cm, respectively) cylinder. For condition 1 trials they were given no instruction as to the type of grasp to adopt; for condition 2 they were instructed to consistently use a precision grip; while for condition 3 they were required to use whole had prehension. Blind subjects demonstrated a double grip pattern and either a low-velocity phase (20 cm) or a double transport movement (30 cm). However, their pattern of prehension with respect to intrinsic (size) and extrinsic (distance) cylinder properties was similar to that of the control groups. Grip aperture was appropriately scaled and, when greater precision was required, deceleration time was prolonged. Temporal coupling was evident between the two components. It was concluded that experience of vision is not necessary for the coordination or patterning of the basic reach to grasp movement. It does allow, however, for a movement consisting of only one opening and closing of the hand.

Acceleration↗

PubMed1993

Reach to grasp: the natural response to perturbation of object size.

This study assessed the reach to grasp movement and its adaptive response to a perturbation of object size. In blocked trials, subjects (n = 12) were instructed to reach 35 cm to grasp and lift a small- (0.7 cm) or large-diameter (8 cm) cylinder. Under an unconstrained condition (condition 1), no instructions as to the type of grasp to adopt were given. Subjects thus naturally used a precision grip (PG) for the small cylinder and whole hand prehension (WHP) for the large cylinder. Under condition 2, subjects were instructed to utilize a PG for grasps of both the large and small cylinders. For condition 3, the instruction was to use WHP irrespective of object size. Kinematic organization was determined with analysis of the recordings of active markers placed on the wrist, thumb, and three fingers. For condition 1 the results showed a temporal arrangement of both components (transport and manipulation) which differed from that of conditions 2 and 3. In perturbed trials, illumination shifted from the small to large cylinder or vice versa. With condition 1, subjects automatically switched from one grasp to another with no or little increase of movement duration. This was generally achieved by an earlier temporal setting of peak wrist deceleration. For conditions 2 and 3, where a change of aperture was required, movement duration was prolonged without adaptation of earlier transport component parameters. It is concluded that the adaptive responses to a change of distal patterning also affect the organization of the proximal component. Assessment of grasps constrained by instructions may lead to interpretations of central control of the reach to grasp movement which differ from those obtained by assessing more natural prehensile patterns.

Adolescent↗

PubMed1993

Generalized representation of handwriting: evidence of effector independence.

Previous analyses of writing data have provided qualitative evidence of temporal and spatial similarities across muscle effectors. In order to further explore the notion of effector independence in handwriting a single case study approach was adopted that employed quantitative analyses. A left-handed individual who lost his left hand and forearm in an automobile accident and wore a myoelectric arm was tested. After his accident he learned to write with the right hand developing this skill for 8 years. Once he was fitted with the myoelectric arm he began again to write with the left hand. Thus, the acquired writing patterns of both hands reflect two well-learned skills which utilize different muscle effectors. Wright's NAME-EQUATION paradigm (1990) was utilized which required the subject to write his name and the equation X + Y = Z with the dominant, non-dominant hand and the elbow of the dominant arm. A control subject was also tested. For the subject wearing a myoelectric arm (primary subject), kinematic and handwriting analysis revealed astonishing similarities between the different effectors tested. For the control subject, the obtained results showed that as the effectors changed so did the handwriting kinematics. The collective findings support the hypothesis that motor programs, the directives that guide skilled movement, can be generalized across different effectors, but only after considerable practice.

Adult↗

PubMed1993

A kinematic study of the reach to grasp movement in a subject with hemiParkinson's disease.

The kinematic organization of a reach to grasp movement in a left hemiParkinson subject is compared to that of a control subject. Subjects used the right and left limbs to reach 15, 27 or 40 cm for the grasp of cylinders of 0.7 or 8 cm diameter. In general, the kinematics of the affected limb of the hemiParkinson subject differed from that of the unaffected limb. However, for both arms the hemiParkinson subject showed a delay in the onset of the manipulation component. The subtle dysfunction in the activation of near-simultaneous or sequential movements is thus bilateral, despite unilateral clinical symptomatology.

Aged↗

PubMed1993

Perturbation of the grasp component of a prehension movement in a subject with hemiParkinson's disease.

The response to perturbation of the manipulation component during prehension was assessed for both hands of a hemiParkinson and of a Control subject. With perturbed trials, the hemiParkinson showed the same pattern as the Control: a reorganization of kinematic parameters and no increase of movement time. However, for both limbs of the hemiParkinson subject there was a transition phase from precision grip to whole hand prehension--this was more pronounced for the affected limb. The manipulation component did not show a delay of activation [2]. Thus the global dysfunction in the performance of sequential movement patterns was related to aspects of task predictability.

Aged↗

PubMed1993

Temporal dissociation of the prehension pattern in Parkinson's disease.

This study assesses the reach to grasp movement of eight Parkinson and eight control subjects. The reach was of either 15, 27.5 or 40 cm. The grasp was either of a small (0.7 cm) or a large diameter (8 cm) dowel. When comparing Parkinson to control subjects, no differences were found in the regulation of movement parameters according to changes in object distance or size. However, for Parkinson's disease patients the onset of the manipulation component was delayed with respect to the onset of the transport component. It is proposed that this reflects a deficit in the simultaneous or sequential implementation of different segments of a complex movement.

Aged↗

PubMed1992

Does the type of prehension influence the kinematics of reaching?

Kinematic studies have indicated that when a subject reaches to grasp an object, the movement consists of two primary components: (a) a transport phase whereby the hand is brought towards the object and (b) a grip phase whereby the hand changes shape in anticipation of the grasp. Using a visual perturbation paradigm, we investigated the effect of different grip component strategies upon the transport phase. The distal strategy was determined by the size of the object to be grasped: for the small object (1.5 cm o.d.) subjects naturally adopted a precision grip between the index finger and thumb; for the large object (6 cm o.d.) subjects used a whole hand prehensile grip. During 20% of the reaching trials the perturbation was introduced by unexpectedly changing the object size. The results showed that corrections to the distal program in response to the perturbation were preceded by changes in the deceleration phase of the proximal component. The data supported previous findings of two visuo-motor channels for this prehensile movement but indicated that when unanticipated shifts of only the distal program are required, both channels show modifications.

Acceleration↗

PubMed1992

Temporal coupling between transport and grasp components during prehension movements: effects of visual perturbation.

The temporal coupling between the transport and grasp components of prehension movements was investigated through two experiments. In Experiment 1, six normal subjects were required to reach and grasp each of three spheres located at three different distances (Blocked trials). In Experiment 2, a visual perturbation paradigm was used in which the location of the object to be reached and grasped could change at the beginning of arm movement (Perturbed trials). The same subjects participated in both experiments. Kinematics of wrist trajectory (transport component) and of distance between thumb and index finger (grasp component) were analyzed. The results of Experiment 1 showed that the two components could be temporally coupled during their time course. In Experiment 2, the visual perturbation affected both the components, but different times were required by each component to reorganize the movement towards the new target. These different times caused the decoupling of those events that appeared synchronized in Experiment 1. Finally, evidence was found to suggest that planning of grip formation takes into account not only the perceived characteristics of the object, but also the time planned by the transport component to reach the object.

Acceleration↗

PubMed1992

Splitting focal attention.

The study was based on the inverse relationship between the effect of attention on reaction time (RT) and the size of the area over which focal attention is allocated. Independent occurrence of this in 2 locations in the opposite hemifields would be evidence of attention splitting. In Experiment 1, in which the 2 locations were denoted by empty boxes, there was an inverse relationship between size of the stimulated box and RT. Experiment 2 replicated the finding with different stimulation conditions. In Experiment 3, no relationship was found between RT and length of a cuing line. In Experiment 4, in which attention was manipulated by central cues, there was an effect of box size on valid and neutral trials but not invalid trials. Observers could split focal attention and manipulate simultaneously 2 independent attentional foci on objects located in the opposite hemifields.

Adult↗

PubMed1991

Influence of different types of grasping on the transport component of prehension movements.

The main aim of the present study was to clarify whether different types of grasping may affect the transport component of prehension movements. To this purpose two experiments were carried out. In the first experiment the kinematics of arm movements (transport and manipulation components) were studied in eight normal subjects instructed to reach and grasp different objects located either 20 or 30 cm from their hand. The objects employed required two different types of grip: prehension with the whole hand and prehension with the index finger and the thumb (precision grip). In the second experiment subjects were instructed to point to the same objects employed in the first experiment. This experiment served as a control for the precision requirements related to the object size. The results showed that, once the precision requirements were taken into account, the transport component remained unmodified with the different types of grip. The time course of the manipulation component and its temporal relations with the transport component changed with the type of grasping. The maximal hand aperture was reached earlier in the precision grip than in the whole hand prehension and the temporal coupling with the transport component was weaker in the former condition than in the latter. The data are interpreted as further evidence in favour of independence between the transport and the manipulation "channels".

Adolescent↗

PubMed1991

Temporal dissociation of motor responses and subjective awareness. A study in normal subjects.

The aim of the present study was to examine the timing of different responses given simultaneously to a single event, the sudden displacement of a visual object occurring at the onset of the grasping movement directed at that object. The subjects were requested to correct their movement in order to reach accurately for the object and to signal the time at which they became aware of its displacement by a simple vocal utterance (Tah!). The onset of the motor adjustment was measured using kinematic landmarks obtained from the hand trajectory. Movements executed during trials where the object was displaced had an earlier peak in acceleration (107 ms) than movements executed during control trials (120 ms). By contrast, the vocal signal occurred 420 ms following object displacement, that was more than 300 ms after the onset of the motor correction. Control experiments were performed in order to verify the influence of possible interferences between the two tasks. Motor corrections performed without vocal utterance had the same timing as when the vocal signal was produced. Vocal signals produced in response to object's displacements but in the absence of reaching movements had the same latency as when movements were performed. We conclude from these results that the two responses were generated independently of each other. Assuming that the vocal responses in this experiment did signal the subject's awareness, the observed delay between motor corrections and these responses suggests that neural activity must be processed during a significant and quantifiable amount of time before it can give rise to conscious experience. This dissociation between motor responses and awareness in normal subjects is discussed in the light of clinical cases where overt behaviour and conscious experience are dissociated by cerebral lesions.

Awareness↗

PubMed1991

Measuring time to awareness.

The timing of two simultaneous responses to one single visual event, namely the sudden subjective expansion of a real object occurring at the onset of a reaching movement, was measured in normal subjects. The motor response was represented by the earliest sign of correction in trajectory of the movement. The subjective report was represented by a vocal utterance that the subjects were instructed to emit when they became aware of the change in appearance of the object. The subjective report lagged the motor response by 150 ms. Control experiments ruled out a possible interference between the two responses. It is concluded that this temporal dissociation reflects a duality of neural pathways involved in processing object-related information.

Awareness↗

PubMed1991

[Effect of age on the orientation of attention: effect of changing the interval between signal and stimulus].

The purpose of the experiment was to examine the effect of aging on spatial attention. One of two possible locations, horizontally arranged, was cued. The subject had to respond to the onset of a visual stimulus, wherever it appeared. The task demand was to orient attention to the stimulated location before producing a response, or to reorient it if the position is not the cued one. Younger and older adults showed the same response pattern, despite the overall slowing down of response presented by the latter.

Adolescent↗

PubMed1991

[Kinematic study of the temporal coupling between the components of transport and manipulation during reaching and grasping movements].

In this study the temporal coupling between transport and manipulation components of prehension movements was tested. For this purpose two experiments were carried out. In Experiment 1 six normal subjects were required to reach and grasp one of three spheres located at three different distances (Blocked trials). In Experiment 2 a visual perturbation paradigm was used in which the location of the object to be reached and grasped could change at onset of arm movement (Perturbed trials). The results of this study exclude a temporal coupling between events of transport and manipulation components. On the contrary they suggest that manipulation component organizes its time course having information about the time required to reach the object.

Animals↗