Biomedical subjects

Maurizio Gentilucci

Publications and source records attributed to Maurizio Gentilucci.

14 recordsLinked to original sources

PubMed2006

Imitation during phoneme production.

Does listening to and observing the speaking interlocutor influence phoneme production? In two experiments female participants were required to recognize and, then, to repeat the string-of-phonemes /aba/ presented by actors visually, acoustically and audiovisually. In experiment 1 a male actor presented the string-of-phonemes and the participants' lip kinematics and voice spectra were compared with those of a reading control condition. In experiment 2 female and male actors presented the string-of-phonemes and the lip kinematics and the voice spectra of the participants' responses to the male actors were compared with those to the female actors (control condition). In both experiments 1 and 2, the lip kinematics in the visual presentations and the voice spectra in the acoustical presentations changed in the comparison with the control conditions approaching the male actors' values, which were different from those of the female participants and actors. The variation in lip kinematics induced changes also in voice formants but only in the visual presentation. The data suggest that both features of the lip kinematics and of the voice spectra tend to be automatically imitated when repeating a string-of-phonemes presented by a visible and/or audible speaking interlocutor. The use of imitation, in place of the usual lip kinematics and vocal features, suggests an automatic and unconscious tendency of the perceiver to interact closely with the interlocutor. This is in accordance with the idea that resonant circuits are activated by the activity of the mirror system, which relates observation to execution of arm and mouth gestures.

Adult↗

PubMed2006

From manual gesture to speech: a gradual transition.

There are a number of reasons to suppose that language evolved from manual gestures. We review evidence that the transition from primarily manual to primarily vocal language was a gradual process, and is best understood if it is supposed that speech itself a gestural system rather than an acoustic system, an idea captured by the motor theory of speech perception and articulatory phonology. Studies of primate premotor cortex, and, in particular, of the so-called "mirror system" suggest a double hand/mouth command system that may have evolved initially in the context of ingestion, and later formed a platform for combined manual and vocal communication. In humans, speech is typically accompanied by manual gesture, speech production itself is influenced by executing or observing hand movements, and manual actions also play an important role in the development of speech, from the babbling stage onwards. The final stage at which speech became relatively autonomous may have occurred late in hominid evolution, perhaps with a mutation of the FOXP2 gene around 100,000 years ago.

Animals↗

PubMed2006

Repetitive transcranial magnetic stimulation of Broca's area affects verbal responses to gesture observation.

The aim of the present study was to determine whether Broca's area is involved in translating some aspects of arm gesture representations into mouth articulation gestures. In Experiment 1, we applied low-frequency repetitive transcranial magnetic stimulation over Broca's area and over the symmetrical loci of the right hemisphere of participants responding verbally to communicative spoken words, to gestures, or to the simultaneous presentation of the two signals. We performed also sham stimulation over the left stimulation loci. In Experiment 2, we performed the same stimulations as in Experiment 1 to participants responding with words congruent and incongruent with gestures. After sham stimulation voicing parameters were enhanced when responding to communicative spoken words or to gestures as compared to a control condition of word reading. This effect increased when participants responded to the simultaneous presentation of both communicative signals. In contrast, voicing was interfered when the verbal responses were incongruent with gestures. The left stimulation neither induced enhancement on voicing parameters of words congruent with gestures nor interference on words incongruent with gestures. We interpreted the enhancement of the verbal response to gesturing in terms of intention to interact directly. Consequently, we proposed that Broca's area is involved in the process of translating into speech aspects concerning the social intention coded by the gesture. Moreover, we discussed the results in terms of evolution to support the theory [Corballis, M. C. (2002). From hand to mouth: The origins of language. Princeton, NJ: Princeton University Press] proposing spoken language as evolved from an ancient communication system using arm gestures.

Adult↗

PubMed2005

Automatic audiovisual integration in speech perception.

Two experiments aimed to determine whether features of both the visual and acoustical inputs are always merged into the perceived representation of speech and whether this audiovisual integration is based on either cross-modal binding functions or on imitation. In a McGurk paradigm, observers were required to repeat aloud a string of phonemes uttered by an actor (acoustical presentation of phonemic string) whose mouth, in contrast, mimicked pronunciation of a different string (visual presentation). In a control experiment participants read the same printed strings of letters. This condition aimed to analyze the pattern of voice and the lip kinematics controlling for imitation. In the control experiment and in the congruent audiovisual presentation, i.e. when the articulation mouth gestures were congruent with the emission of the string of phones, the voice spectrum and the lip kinematics varied according to the pronounced strings of phonemes. In the McGurk paradigm the participants were unaware of the incongruence between visual and acoustical stimuli. The acoustical analysis of the participants' spoken responses showed three distinct patterns: the fusion of the two stimuli (the McGurk effect), repetition of the acoustically presented string of phonemes, and, less frequently, of the string of phonemes corresponding to the mouth gestures mimicked by the actor. However, the analysis of the latter two responses showed that the formant 2 of the participants' voice spectra always differed from the value recorded in the congruent audiovisual presentation. It approached the value of the formant 2 of the string of phonemes presented in the other modality, which was apparently ignored. The lip kinematics of the participants repeating the string of phonemes acoustically presented were influenced by the observation of the lip movements mimicked by the actor, but only when pronouncing a labial consonant. The data are discussed in favor of the hypothesis that features of both the visual and acoustical inputs always contribute to the representation of a string of phonemes and that cross-modal integration occurs by extracting mouth articulation features peculiar for the pronunciation of that string of phonemes.

Acoustic Stimulation↗

PubMed2005

Speech and gesture share the same communication system.

Humans speak and produce symbolic gestures. Do these two forms of communication interact, and how? First, we tested whether the two communication signals influenced each other when emitted simultaneously. Participants either pronounced words, or executed symbolic gestures, or emitted the two communication signals simultaneously. Relative to the unimodal conditions, multimodal voice spectra were enhanced by gestures, whereas multimodal gesture parameters were reduced by words. In other words, gesture reinforced word, whereas word inhibited gesture. In contrast, aimless arm movements and pseudo-words had no comparable effects. Next, we tested whether observing word pronunciation during gesture execution affected verbal responses in the same way as emitting the two signals. Participants responded verbally to either spoken words, or to gestures, or to the simultaneous presentation of the two signals. We observed the same reinforcement in the voice spectra as during simultaneous emission. These results suggest that spoken word and symbolic gesture are coded as single signal by a unique communication system. This signal represents the intention to engage a closer interaction with a hypothetical interlocutor and it may have a meaning different from when word and gesture are encoded singly.

Adult↗

PubMed2004

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.

Adolescent↗

PubMed2004

Early movement impairments in a patient recovering from optic ataxia.

Since Balint's 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.

Aged↗

PubMed2004

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.

Adult↗

PubMed2004

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 experimenter's 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.

Adult↗

PubMed2003

Object motor representation and language.

Results of kinematic studies on the control of the reaching-grasping motor act (Gentilucci 2003, Exp Brain Res 149:395-400) suggest that grasp is guided by a single motor representation, which codes all the possible types of interactions with the objects. Neuroimaging studies in humans (Chao and Martin 2000, Neuroimage 12:478-484; Grabowski et al. 1998, Neuroimage 7:232-243; Grafton et al. 1997, Neuroimage 6:231-236; Martin et al. 1995, Science 270:102-105) suggest that these representations are coded in the premotor cortex and are automatically activated when naming the object or viewing it without the execution of an overt action. If an object motor representation is accessed by language, naming of object properties related to sensory-motor transformation can automatically influence the object motor representation. This hypothesis was verified by behavioural experiments (Gentilucci and Gangitano 1998, Eur J Neurosci 10:752-756; Gentilucci et al. 2000, Exp Brain Res 133:468-490; Glover and Dixon 2002, Exp Brain Res 146:383-387), which showed that automatic reading (and probably silent naming; MacLeod 1991, Psychol Bull 109:163-203) of adjectives related to object properties analysed for planning the reaching-grasping motor act influenced the control of the arm movement. In a new study it was determined whether the class of a word can be a factor selectively influencing motor control. Participants were required to reach for and grasp an object located either on the right or on the left, and to place it on the opposite side. Either a verb ("place" SPOSTA versus "lift" ALZA) or an adjective ("lateral" LATERALE versus "high" ALTO) was printed on the target. A greater influence of the verbs than of the adjectives was observed on the kinematics of the action. In particular, when the verb ALZA was printed on the object, hand-path height and vertical component of arm velocity were higher than when the adjective ALTO was presented on the object. The data support the hypothesis that the object motor representation is mainly coded in terms of possible interactions with the object.

Adult↗

PubMed2003

Object familiarity affects finger shaping during grasping of fruit stalks.

In experiment 1 participants reached and grasped equal green stalks of a green apple and a red strawberry. Stability of the two fruits was equalized by fixing the fruits on the table plane where they were reached for and grasped. The results confirmed that finger shaping was influenced by the size of the fruit body (Gentilucci 2002). Finger shaping was larger when grasping the apple stalk than the strawberry stalk. In addition, deceleration phase lengthened when reaching to grasp the strawberry stalk. In experiment 2 participants reached for and grasped equal wooden matches substituting the stalks of the same apple and strawberry presented in experiment 1. No effect of the fruit body was observed on grasping and reaching the matches. This result excluded that the closeness of the stalk to the fruit body was responsible for the interference effect observed in experiment 1. In experiment 3 participants reached for and grasped equal green stalks of an apple and a strawberry of the same red colour. The same results as in experiment 1 were found. They excluded that a grouping effect due to the same green colour of the stalk and the apple body was responsible for the interference effect observed in experiment 1. Results are discussed as further support of the hypothesis that an object is globally analysed when interacting with it, and familiarity, i.e. the way by which a familiar object is commonly grasped, strongly influences all the other possible interactions with it.

Adult↗

PubMed2003

Finger control in the tripod grasp.

The present study aimed to determine whether grasping is based on either (1) synchronous finger movements producing stereotyped types of grasp, or (2) independently controlled finger movements producing variable final finger postures. Participants reached for and grasped sphere-shaped objects of three sizes. They were allowed to select three different grasp configurations: a "pinch" grip (thumb and index finger), a "middle" grip (thumb and middle finger) and a "tripod" grip (thumb and index plus middle finger). Object distance from the subject was varied in order to verify whether finger control and final finger postures varied according to the degree of accuracy required by target object distance. All the participants always selected the tripod grip when reaching for the large and medium size objects. The pinch grip was used by half of the participants when reaching for the small object, but only in 17% of the trials. Target object distance did not appear to influence the type of selected grip. The tripod grip was found to consist of two different components: an aperture component (opening and closing the gap between the thumb and opposition finger) and a finger separation component (increasing and decreasing the gap between the index and middle fingers). The timing of the aperture component was the same for the index and middle fingers. In contrast, the timing of the finger separation was weakly coupled with the aperture components. Moreover, the relative spatial position among the three fingers during and at the end of grasp varied according to object size. When grasping the large object, both the index finger and the middle finger were in opposition to the thumb. In contrast, when grasping the small object, the index finger was less in opposition to the thumb with respect to the middle finger. The final spatial position of the thumb relative to the starting position was independent of object size, whereas those of the index and middle fingers varied with object size. The results support the notion that grasp is accomplished by using two virtual fingers formed by the thumb and one or more other fingers that synchronously open and close on the object along the opposition space [Arbib 1990; in: Jeannerod M (ed) Attention and performance XIII: motor representation and control. Lawrence Erlbaum, Hillsdale, pp 111-138]. This suggests a degree of coupling between the control of the virtual fingers.

Adult↗

PubMed2003

Grasp observation influences speech production.

Subjects pronounced either the syllable 'BA' or 'GA' while observing motor acts of hand grasp directed to objects of two sizes (experiment 1). Kinematics of lip aperture and amplitude spectrum of voice were influenced by the observation of the different grasp kinematics depending on the size of the target objects. Specifically, both lip aperture and voice peak amplitude were greater when the observed hand grasp was directed to the large object. Two control experiments ruled out that the different arm velocity when reaching objects varying in size (experiment 2), and overt visual analysis of the target-object (experiment 3), affected lip movement and voice emission. Results provide behavioural evidence in favour of the hypothesis that the system involved in observation (and preparation) of grasp movements partially shares the cortical areas involved in speech production.

Adult↗

PubMed2002

Object motor representation and reaching-grasping control.

The following two competing hypotheses were tested in the present study. Is grasp guided by multiple representations of a single object, each of which codes a different grasp motor act according to the physical properties of that item? Conversely, is grasp guided by a single representation that codes all the possible affordances enabled by the object? Subjects reached different objects, but the object part used by subjects to grasp them was identical. In experiments 1 and 2, two familiar objects (fruits) which varied for size and shape were presented. Subjects grasped their stalks whose size and shape were equal. In experiments 3-7 the presented objects were geometrical solids, which varied, respectively, for weight, volume, intrinsic height, centre of mass and shape. Nevertheless, in all experiments the object portion where subjects' fingers grasped it had the same physical features. Finally, experiment 8 was a control experiment in which subjects reached and grasped equal handles of bells of the same shape, but different size. Volume, shape, and familiarity of the object influenced the grasp kinematics, even if the features of the grasped object part did not change. Variation in intrinsic object height and weight influenced final reach kinematics. Variation in centre of mass influenced neither grasp nor reach kinematics. Data are discussed in support of the hypothesis that a single object motor representation, which codes all the object affordances, is involved in grasp kinematic implementation.

Adult↗