1,721,051 research outputs found
Haptic information differentially interferes with visual analysis in reaching-grasping control and in perceptual processes
No full textWe used an interference paradigm in order to study integration between haptic and visual information in motor control and in perceptual analysis. Subjects either reached and grasped a visually presented sphere or matched its size with their left hand while manipulating with their right hand another sphere whose size could be smaller or greater. In four experiments haptic analysis of the manipulated sphere could be either automatically incorporated with or explicitly dissociated from visual analysis. In a fifth experiment reaching-grasping and matching were executed with the right hand, whereas manipulation was executed with the left hand. Manipulation with the right hand influenced finger shaping during grasping with the left hand when the sizes of the two objects were different. Interference was observed mainly in those experiments in which haptic analysis could be automatically integrated with visual analysis. In the matching task, no effect was observed. Finally, manipulation with the left hand did not produce any interference effect on reaching-grasping and matching executed by the right hand. The results of the present study suggest that somesthetic information is integrated with visual information only in sensorimotor transformations. In addition, they support the notion that the left hemisphere together with the right hemisphere is involved in the control of left hand reaching-grasping movements
Influence of automatic word reading on motor control
No full textWe investigated the possible influence of automatic word reading on processes of visuo-motor transformation. Six subjects were required to reach and grasp a rod on whose visible face the word 'long' or 'short' was printed. Word reading was not explicitly required. In order to induce subjects to visually analyse the object trial by trial, object position and size were randomly varied during the experimental session. The kinematics of the reaching component was affected by word presentation. Peak acceleration, peak velocity, and peak deceleration of arm were higher for the word 'long' with respect to the word 'short'. That is, during the initial movement phase subjects automatically associated the meaning of the word with the distance to be covered and activated a motor program for a farther and/or nearer object position. During the final movement phase, subjects modified the braking forces (deceleration) in order to correct the initial error. No effect of the words on the grasp component was observed. These results suggest a possible influence of cognitive functions on motor control and seem to contrast with the notion that the analyses executed in the ventral and dorsal cortical visual streams are different and independent
Verbal and pragmatic coding
No full textPlanning reaching and grasping an object requires selective computation of extrinsic (i.e. distance) and intrinsic (i.e. size) object properties, respectively. However, the mechanism for this selection can be partially effective in this process, and nonrelevant object attributes can be used. An experiment was carried out to test whether linguistic information on object properties, as well as sensorial object information, could be automatically involved in movement planning. Subjects were required to reach and grasp a wooden bar, that could have two sizes and could be placed at two spatial positions. An Italian word, either lungo (long) or corto (short) was written on the external face of the object. No analysis of the word was required to the subjects. Results showed that arm velocity was higher for farther object position. In addition, the word influenced arm velocity. Faster reaching movements were found for stimuli with the word lungo with respect to stimuli with the word corto. In other words, the subjects planned a movement as if the stimuli with the word lungo were positioned farther than the stimuli with the word corto. This finding indicates that high-level coding are automatically involved in the analysis of object attributes, as distance. We conclude that in human behaviour the verbal representation is may be related to pragmatic object representation. This may support the notion of the correspondence between praxic and linguistic functions, shown by neuropsychological studies
Implicit visual analysis in handedness recognition
No full textIn the present study, we addressed the problem of whether hand representations, derived from the control of hand gesture, are used in handedness recognition. Pictures of hands and fingers, assuming either common or uncommon postures, were presented to right-handed subjects, who were required to judge their handedness. In agreement with previous results (Parsons, 1987, 1994; Gentilucci, Daprati, & Gangitano, 1998), subjects recognized handedness through mental movement of their own hand in order to match the posture of the presented hand. This was proved by a control experiment of physical matching. The new finding was that presentation of common finger postures affected responses differently from presentation of less common finger postures. These effects could be not attributed to mental matching movements nor related to richness in hand-finger cues useful for handedness recognition. The results of the present study are discussed in the context of the notion that implicit visual analysis of the presented hands is performed before mental movement of one's hand takes place (Parsons, 1987; Gentilucci et al., 1998). In this process, hand representation acquired by experience in the control and observation of one's and other people's hand gestures is used. We propose that such an immediate recognition mechanism belongs to the class of mental processes which are grouped under the name of intuition, that is, the processes by which situations or people's intentions are immediately understood, without conscious reasoning
Visual illusions and the control of children arm movements
No full textThe aim of the present study was to determine whether children like adults (Gentilucci M, Chieffi S, Daprati E, Saetti MC, Toni
I. Visual illusion and action. Neuropsychologia 1996;34:369–76; Gentilucci M, Daprati E, Gangitano M, Toni I. Eye position
tunes the contribution of allocentric and egocentric information to target localisation in human goal directed arm movements.
Neurosci Lett 1997;222:123–6) are influenced by visual illusions when they transform visual information in motor command.
Children and adults pointed to a shaft extremity of the Mu ̈ ller-Lyer configurations, as well as to an extremity of a control
configuration. Movements were executed in two experimental conditions. In the vision condition subjects saw both the stimulus
and their hand before and during movement. In the no vision (memory) condition subjects saw the stimulus and their hand before, but not during movement. Movement started 5 s after vision was precluded. The Mu ̈ ller-Lyer illusion affected pointing kinematics of both children and adults. As found previously (Gentilucci M, Chieffi S, Daprati E, Saetti MC, Toni I. Visual illusion and action. Neuropsychologia 1996;34:369–76; Gentilucci M, Daprati E, Gangitano M, Toni I. Eye position tunes the contribution
of allocentric and egocentric information to target localisation in human goal directed arm movements. Neurosci Lett
1997;222:123–6), subjects undershot and overshot the shaft extremity of the closed and of the open configuration, respectively.
The illusion effect was greater in the no vision than in the vision condition. These results show that in children like in adults the
system underlying visual perception in an object-centered frame of reference and that involved in motor control functionally
interact with each other. Although the processes of target localisation were the same, the transformation of target position
information in a sequence of motor patterns was different in children from that in adults. Even if both children and adults
lengthened duration of the deceleration phase in the vision condition, only adults shortened duration of the acceleration phase in order to maintain constant movement time (Viviani P, Schneider R. A developmental study of the relationship between geometry
and kinematics in drawing movements. J Exp Psychol 1991;17:198–218). This result suggests that children are yet unable to co-ordinate temporally acceleration with deceleration phase
Impaired control of an action after supplementary motor area lesion: A case study
No full textThe kinematics of the action formed by reaching-grasping an object and placing it on a second target was studied in a patient who suffered from an acute vascular left brain lesion, which affected the Supplementary Motor Area proper (SMA-proper) (Matelli M, Luppino G. Thalamic input to mesial and superior area 6 in the macaque monkey. Journal of Comparative Neurology 1996;372:59-87, Matelli M, Luppino G, Fogassi L, Rizzolatti G. Thalamic input to inferior area 6 and area 4 in the macaque monkey. Journal of Comparative Neurology 1989;280:468-488), and in five healthy control subjects. The reach kinematics of the controls was affected by the positions of both the reaching-grasping and the placing targets (Gentilucci M, Negrotti A, Gangitano M. Planning an action. Experimental Brain Research 1997;115:116- 28). In contrast, the reach kinematics of the patient was affected only by the position of the reaching-grasping target. By comparing these results with those previously found in Parkinson's disease patients executing the same action (Gentilucci M, Negrotti A. Planning and executing an action in Parkinson's disease patients. Movement Disorders 1999;1:69-79, Gentilucci M, Negrotti A. The control of an action in Parkinson's disease. Experimental Brain Research 1999;129:269-277), we suggest that the anatomical 'motor' circuit formed by SMA-proper (see above), Basal Ganglia (BG) and Thalamus (Alexander GE, Crutcher MD. Functional architecture of basal ganglia circuits: neural substrates of parallel processing. Trends in the Neurosciences 1990;13:266-271, Hoover JE, Strick PL. Multiple output channels in the basal ganglia. Nature 1993;259:819-821) may be involved in the control of actions: SMA-proper assembles the sequence of the action, whereas BG updates its parameters and stores them. (C) 2000 Elsevier Science Ltd
Right-handers and left-handers have different representations of their own hand
No full textThe visual control of our own hand when dealing with an object and the observation of interactions between other people's hand and objects can be involved in the construction of internal representations of our own hand, as well as in hand recognition processes. Therefore, a different effect on handedness recognition is expected when subjects are presented with hands holding objects with either a congruent or an incongruent type of grip. Such an experiment was carried out on right-handed and left-handed subjects. We expected that the different degree of lateralisation in motor activities observed in the two populations [J. Herron, Neuropsychology of left-handedness, Academic Press, New York, 1980.] could account for the construction of different internal hand representations. As previously found [L.M. Parsons, Imaged spatial transformations of one's hands and feet, Cogn. Psychol., 19 (1987) 178-241.], in order to identify handedness, subjects mentally rotated their own hand until it matched with the presented one. This process was confirmatory, being preceded by an implicit visual analysis of the target hand. Presentation of hands holding objects with congruent or incongruent types of grip influenced handedness recognition at different stages in right-handed and left-handed subjects. That is, the mental rotation stage was affected in right-handed subjects, whereas the initial phase of implicit hand analysis was affected in left-handed subjects. We suggest that in handedness recognition, left-handers relied more on a pictorial hand representation, whereas right-handers relied more on a pragmatic hand representation, probably derived from experience in the control of their own movements. The use of different hand representations may be due to differential activation of temporal and premotor areas
Visual distractors differentially interfere with the reaching and grasping components of prehension movements
No full textIn the present study we addressed the issue of how an object is visually isolated from surrounding cues when a reaching-grasping (prehension) movement towards it is planned. Subjects were required to reach and grasp an object presented either alone or with a distractor. In five experiments, different degrees of elaboration of the distractor were induced by varying: (1) the position of the distractor (central or peripheral); (2) the time when the distractor was suppressed (immediately or delayed, with respect to stimulus presentation); and (3) the type of distractor analysis (implicit or explicit). In addition, we tested whether the possible effects of the distractor on reaching-grasping were due to the use of an allocentric reference centered on it. This was obtained by comparing the effects of the distractor with those of a stimulus, the target of a placing movement successive to the reaching-grasping. The results of the five experiments can be summarized as follows. The necessary condition for an interference effect on both the reaching and the grasping components was the central presentation of the distractor. When the information on the distractor could be immediately suppressed, an interference effect was observed only on the grasp component. In the case of delayed suppression, an effect was found on the reaching component. Finally, when an overt analysis of the distractor was required, the interference effect disappeared. Two main conclusions have been drawn from the results of the present study. First, comparison between properties of the target and surrounding cues is performed by two independent processes for reaching and grasping an object. The process for the grasp relies more on allocentric cues than that for the reach. Second, when surrounding stimuli are automatically analyzed during visual search of the target, the process of visuo-motor transformation can incorporate their features into the target. In contrast, overt analysis of surrounding stimuli is performed separately from that of the target. Finally, the data of the present study are discussed in support of the premotor theory of attention
Planning and executing sequential motor acts in Parkinson Disease
No full textMany experimental evidences highlighted that Parkinson Disease (PD) patients are particularly impaired in performing a sequence of movements. In the present experiment we focused to study how PD patients plan and execute an action constituted by the sequence of reaching-grasping an object (first motor act) and placing it on a second target (second motor act). We wished to determine whether properties of the target of the second motor act influenced the kinematics of first motor act. The results showed that PD patients modified, as the controls, the initial ballistic phase of reaching according to variation of second target position (object extrinsic properties). In particular, peak acceleration was higher for farther position of the second target. However, in the subsequent phase the patients, differently from the controls, modified their reaching kinematics removing the effects of second target distance. In other words the patients re-programmed the reaching component by taking into account only properties of the first target. This effect was obtained by varying the duration of the acceleration phase. These results indicate that PD patients are able to compute the general program of an action that takes into account extrinsic properties of the final target. However, this program decays during its execution inducing premotor areas to reprogram it. This finding provides a further evidence of the role of the basal ganglia as structure involved in the storing motor program and in controlling the action
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