Silvia Stefanini

Spoken and gestural production in a naming task by young children with Down syndrome

Lexical production in children with Down syndrome (DS) was investigated by examining spoken naming accuracy and the use of spontaneous gestures in a picture naming task. Fifteen children with DS (range 3.8-8.3 years) were compared to typically developing children (TD), matched for chronological age and developmental age (range 2.6-4.3 years). Relative to TD children, children with DS were less accurate in speech (producing a greater number of unintelligible answers), yet they produced more gestures overall and of these a significantly higher percentage of iconic gestures. Furthermore, the iconic gestures produced by children with DS accompanied by incorrect or no speech often expressed a concept similar to that of the target word, suggesting deeper conceptual knowledge relative to that expressed only in speech.

Execution and observation of bringing a fruit to the mouth affect syllable pronunciation

Kinematic analysis of lip and voice spectrum analysis were used to assess the influence of both execution and observation of arm–mouth‐related actions on speech production. In experiments 1 and 2 participants brought either a cherry or an apple to their mouth and either pronounced the syllable BA (experiment 1) or emitted a nonspeech‐related vocalization (experiment 2). In the other three experiments participants observed arm actions performed by the experimenter and pronounced the syllable BA. In experiment 3, they observed the action of bringing the cherry or apple to the mouth. In experiments 4 and 5, they observed a pantomime of the same action performed by the experimenter with his own arm (experiment 4) or with a nonbiological arm (experiment 5). The results showed that the formant 2 of the vowel ‘a’ increased when participants executed the bringing‐to‐the‐mouth act with the apple or observed its execution or pantomime with the experimenters arm (experiments 1, 3 and 4). In contrast, no modification in the vowel formants was found during a nonspeech‐related vocalization (experiment 2) and during observation of an action with a nonbiological arm (experiment 5). Finally, the opening of the lips was larger when the participant brought the apple rather than the cherry to the mouth and pronounced BA (experiment 1). Taken together, the results of the present study suggest that the execution and observation of the bringing‐to‐the‐mouth action activate a mouth articulation posture (probably due to the act of food manipulation with the mouth) which selectively influences speech production. They support the idea that the system involved in speech production shares and may derive from the neural substrate which is involved in the control of arm–mouth interactions and, in general, of arm actions.

Co-speech gestures in a naming task: Developmental data

Few studies have explored the development of the gesture-speech system after the two-word stage. Aim of the present study is to examine developmental changes in speech and gesture use, in the context of a simple naming task. Fifty-one children (age range: 2;3–7;6) were divided into five age groups and requested to name pictures representing objects, actions, or characteristics. In the context of a naming task that requires only the production of a single word, children produced pointing and representational gestures together with spoken responses. Pointing was the most frequent gesture produced by all groups of children. Among representational gestures, action gestures were more frequent than size and shape gestures. In addition, gesture production declined as a function of increasing age and spoken lexical competence. Results are discussed in terms of the links between action, gesture, and language, and the ways in which these may change developmentally.

Action observation and speech production: study on children and adults.

The present study aimed to determine whether observation of upper limb actions selectively influences speech production. We compared the effects on children with those on adults, hypothesizing that action observation is used by children for speech learning. Children and adults observed an actor either grasping a cherry or an apple, or bringing the same fruits to his mouth. They pronounced the syllable/ba/ at the end of the action. In a control experiment, children and adults executed the two bringing-to-the-mouth actions, still pronouncing/ba/. As previously found ([Euro. J. Neurosci., 17 (2003) 179]; [Euro. J. Neurosci., 19 (2004) 192]), the observed kinematics of the action, which were different according to the fruit size, influenced lip shaping kinematics and voice formants. In addition, the effect was selective for the action since the observations of actions such as grasping and bringing-to-the-mouth affected formant 1 and formant 2 in the voice spectra, respectively. The effects on speech were greater in the children than in the adults. By contrast, the effects on lip shaping did not differ between the two groups. Effects similar to those found for action observation were found for action execution in spite of a different arm kinematics between children and adults. The results of the present study are discussed according to the hypothesis that action observation induces in the viewer action recognition and activation of the successive mouth act (probably grasping-with-the-mouth when observing grasping-with-the-hand and chewing when observing bringing-to-the-mouth). This subsequently seems to affect characteristics peculiar to the emitted vowel. This mechanism might have been used by humans to transfer a primitive arm gesture communication system from the arm to the mouth and may be further used by children for speech learning.

Grasping an object naturally or with a tool: are these tasks guided by a common motor representation?

The aim of the present study was to determine whether kinematic parameters of the grasping motor act are controlled independently of the biomechanical features of the grasping effector. With this purpose in mind, we compared grasping movements performed naturally or using a tool. The tool consisted of two mechanical fingers whose opening and closing phases required squeezing (flexion of the biological fingers) and releasing (extension of the biological fingers) of a handle, respectively. The forces required for opening and closing the mechanical fingers were, respectively, greater and smaller than those used to grasp the objects naturally. In a control experiment the participants grasped with their thumb and index finger the same objects grasped with the tool. The kinematics of the mechanical and biological fingers as well as those of the arm in the two experiments were compared with each other. Grasping an object with the tool showed some kinematic characteristics strikingly similar to those of the natural grasp, whereas others were different. Like the natural grasp, the tool grasp consisted of a finger opening and closing phase. The scaling of both peak velocity of aperture and maximal aperture of the mechanical fingers as a function of object size was the same as that of the biological fingers. In contrast, the tool grasp differed from the natural one for the temporal aspects of the movement. Finally, the initial reach (i.e. the acceleration phase) was poorly influenced by the tool use whereas the final reach (i.e. the deceleration phase) was lengthened and more sensitive to object size. We discuss the results of the present study as being in favour of the hypothesis that some features of the grasp motor representation are coded in cortical areas independently of the used effector. In addition, they suggest a partial independence between the reach and the grasp components.

Early movement impairments in a patient recovering from optic ataxia.

Since Balints first description, optic ataxia has been considered as a pure visuomotor impairment produced by a lesion of the posterior parietal cortex. Beyond general agreement on the parietal involvement in visually guided behaviour, the exact role of the dorsal posterior parietal cortex in the temporal aspects of visuomotor control remains unclear. Recent evidence has indicated a specific involvement of the parietal cortex in the on-line visual guidance of movement. Here, we report the motor performance of, GT, a patient recovering from an optic ataxia due to a right focal lesion of the dorsal posterior parietal cortex. When asked to reach and grasp, with his left contralesional hand, different sized objects, located at different positions from his body, GT showed an apparently complete recovery from optic ataxia. However, the early kinematic aspects of GTs prehension movement were not normally tuned either by intrinsic or extrinsic visual properties of objects. At variance with both an age-matched control group and a neurological patient with a right internal capsule lesion and no sign of optic ataxia, GTs latencies to peak wrist acceleration and peak velocity were not modulated by object location. A similar defective pattern was present in GTs grasping component where, despite the sparing of the classical scaling of grip aperture, object size did not modulate the peak velocity of grip aperture. These results constitute evidence that the posterior region of the dorsal parietal cortex, besides playing a role in the on-line control of movement execution may also be involved in the programming of early kinematics parameters.

A Developmental Study on Children's Capacity to Ascribe Goals and Intentions to Others.

The capacity to ascribe goals and intentions to others is a fundamental step in child cognitive development. The aim of the present study was to assess the age at which these capabilities are acquired in typically developing children. Two experiments were carried out. In the first experiment, 4 groups of children (age range = 3 years 2 months-7 years 11 months) were shown pictures representing hand-object interactions and asked what the individual was doing (what task) and why (why task). In the why task, observed handgrip could be either congruent with the most typical action performed with that object (e.g., to drink in the case of a mug) or corresponding to the act of putting away the object. In the second experiment, children saw pictures showing a handgrip either within a context suggesting the most typical use of the object or its being put away. Results showed that by 3-4 years, children are able to state the goal relatedness of an observed motor act (what understanding), whereas the ability to report the intention underlying it (why understanding) is a later and gradual acquisition, reaching a high performance by 6-7 years. These results, besides their intrinsic value, provide an important baseline for comparisons with studies on developmental disorders, also highlighting the relevance of distinguishing what and why understanding.

Types of prehension in children with Williams–Beuren syndrome: A pilot study

As part of a more extensive research program investigating cognitive, linguistic and motor skills in children with Williams – Beuren syndrome (WBS) we made some preliminary observations of prehension movements. Eight children, in a restricted age range (9 – 11 years), took part in the pilot study. We individuated and classified three types of prehension in two different tasks: the Developmental Test of Visual-Motor Integration (VMI) for assessing perceptual and motor skills, and the Movement Assessment Battery for Children (M-ABC) for assessing manual dexterity. Sixteen typically developing children, individually matched with WBS children, were also assessed, resulting in two different comparison groups: 8 children were matched for mental age and 8 for chronological age. A peculiar type of prehension (referred to as the “lateral grip”) was used by all children with WBS, but was only rarely observed in the comparison groups. These findings can contribute to a better description of motor development in children with WBS and to a better understanding of their visuospatial difficulties.