Biomedical subjects

M Gangitano

Publications and source records attributed to M Gangitano.

At least 19 recordsLinked to original sources

PubMed2002

Segregation of areas related to visual working memory in the prefrontal cortex revealed by rTMS.

The functional organization of working memory (WM) in the human prefrontal cortex remains unclear. Storage and processing functions might be segregated in ventral and dorsal areas of the prefrontal cortex, respectively. If so, storage functions might be spared, irrespective of informational domain, following damage or dysfunction in dorsolateral areas. Alternatively, WM and prefrontal function in general might be segregated according to informational domains (e.g. spatial versus object-based information). In the present study we used repetitive transcranial magnetic stimulation (rTMS) to directly test these competing hypotheses. We applied rTMS to transiently and selectively disrupt the function of the dorsomedial, dorsolateral or ventral prefrontal cortex in normal human volunteers performing either a spatial or a face-recognition delayed-response task. Performance in the spatial task was impaired by rTMS of the dorsomedial prefrontal cortex. Performance in the face-recognition (non-spatial) task was impaired by rTMS of the ventral prefrontal cortex. Transient disruption of the dorsolateral prefrontal cortex affected performance in both tasks. These findings provide evidence of domain-specific segregation of WM functions in widely separated areas of prefrontal cortex.

Adult↗

PubMed2001

Modulation of spinal cord excitability by subthreshold repetitive transcranial magnetic stimulation of the primary motor cortex in humans.

Repetitive transcranial magnetic stimulation (rTMS) allows the modulation of intra-cortical excitability and may therefore affect the descending control of spinal excitability. We applied rTMS at subthreshold intensity and 1 Hz frequency for 10 min to the left primary motor cortex representation of the flexor carpi radialis muscle (FCR) in 10 subjects and assessed the H and M responses to median nerve stimulation before and after the rTMS. Following rTMS, H wave thresholds significantly reduced by approximately 20%. Maximal H but not M wave amplitude significantly increased over the baseline, so that H/M amplitude ratio was increased by 41%. Sham stimulation did not induce any noticeable change in M or H waves. Slow rTMS might facilitate monosynaptic spinal cord reflexes by inhibiting the cortico-spinal projections modulating spinal excitability.

Adult↗

PubMed2001

Grammatical distinctions in the left frontal cortex.

Selective deficits in producing verbs relative to nouns in speech are well documented in neuropsychology and have been associated with left hemisphere frontal cortical lesions resulting from stroke and other neurological disorders. The basis for these impairments is unresolved: Do they arise because of differences in the way grammatical categories of words are organized in the brain, or because of differences in the neural representation of actions and objects? We used repetitive transcranial magnetic stimulation (rTMS) to suppress the excitability of a portion of left prefrontal cortex and to assess its role in producing nouns and verbs. In one experiment subjects generated real words; in a second, they produced pseudowords as nouns or verbs. In both experiments, response latencies increased for verbs but were unaffected for nouns following rTMS. These results demonstrate that grammatical categories have a neuroanatomical basis and that the left prefrontal cortex is selectively engaged in processing verbs as grammatical objects.

Adolescent↗

PubMed2001

Phase-specific modulation of cortical motor output during movement observation.

The effects of different phases of an observed movement on the modulation of cortical motor output were studied by means of transcranial magnetic stimulation (TMS). A video-clip of a reaching-grasping action was shown and single TMS pulses were delivered during its passive observation. Times of cortical stimulation were related to the phases of the shown movement, locking them to the appearance of specific kinematic landmarks. The amplitude of the motor evoked potentials (MEPs) induced by TMS in the first dorsal interosseus (FDI) muscle was modulated by the amount of the observed finger aperture. The presence of such an effect is consistent with the notion of a mirror neuron system in premotor areas that couples action execution and action observation also in terms of temporal coding.

Acoustic Stimulation↗

PubMed2001

Influence of stimulus color on the control of reaching-grasping movements.

This kinematic study aimed to determine whether color is a stimulus property involved in the control of reaching-grasping movements. Subjects reached and grasped a target-object, located either on the right or on the left of the subject's midline. A distractor, placed along the subject's midline, could be randomly presented. The colors, i.e., both chromaticity (red and green stimuli were presented) and lightness, of the target and distractor were varied in experiment 1. Only stimulus lightness and only stimulus chromaticity were varied in experiments 2 and 3, respectively. In experiment 4 subjects matched with their thumb and index finger the size of the target-stimuli presented in experiment 1. Chromaticity (experiments 1 and 3) of the target and distractor influenced grasp, but not reach. Maximal finger aperture was larger during grasping the red than the green target. Data collected in the matching task (experiment 4) confirmed a trend to overestimate the red target and to underestimate the green one. During grasp, hand shaping was influenced by distractor chromaticity when it was different from target chromaticity. Distractor lightness affected reach, but not grasp (experiments 1 and 2). Reach was slower when the distractor was lighter and arm trajectory veered away from it. The results of the present study suggest that color, that is the ensemble of chromaticity and lightness, is a stimulus property involved in the control of reaching-grasping. The different effects of target color on reach and grasp support the notion that intrinsic object properties, such as color, affect grasp more than reach. In addition, the different effects of distractor chromaticity and lightness on reach and grasp confirm that target-objects are visually extracted from surrounding cues by means of different processes, according to the required motor response.

Adult↗

PubMed2001

Visual illusions and the control of children arm movements.

The 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 Müller-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 Müller-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.

Acceleration↗

PubMed2001

Intracortical inhibition and facilitation in human facial motor area: difference between upper and lower facial area.

OBJECTIVE: To investigate the intracortical inhibitory and excitatory systems in the motor cortical representation of upper and lower facial muscles. METHODS: Paired-pulse transcranial magnetic stimulation (TMS) was applied to 7 healthy volunteers, with the interstimulus interval (ISI) between the conditioning stimulus (CS) and test stimulus, varied from 1 to 20 ms. CS was set at 90% of motor threshold. Muscle evoked potentials (MEPs) were recorded from first dorsal interosseus (FDI), orbicularis oculi (o. oculi) and mentalis muscles. RESULT: TMS evoked MEPs in o. oculi on both ipsi- and contralateral sides in all subjects. In the paired-pulse study, MEP amplitude in the mentalis decreased at short ISIs of 1-3 ms, followed by increases at 12-20 ms. These effects were similar to those in the FDI. O. oculi did not show a distinct inhibitory period at short ISIs and facilitation at long ISIs was detected but was significantly less than in FDI and mentalis. In o. oculi, there was no significant difference between the effects of ipsilateral and contralateral CS on the MEPs. CONCLUSION: The bi-hemispheric control of volitional movement and the modulation from brainstem projections appear to markedly influence intracortical inhibitory and excitatory systems in the motor cortical representation of o. oculi.

Adult↗

PubMed2001

Grasp with hand and mouth: a kinematic study on healthy subjects.

Neurons involved in grasp preparation with hand and mouth were previously recorded in the premotor cortex of monkey. The aim of the present kinematic study was to determine whether a unique planning underlies the act of grasping with hand and mouth in humans as well. In a set of four experiments, healthy subjects reached and grasped with the hand an object of different size while opening the mouth (experiments 1 and 3), or extending the other forearm (experiment 4), or the fingers of the other hand (experiment 5). In a subsequent set of three experiments, subjects grasped an object of different size with the mouth, while opening the fingers of the right hand (experiments 6-8). The initial kinematics of mouth and finger opening, but not of forearm extension, was affected by the size of the grasped object congruently with the size effect on initial grasp kinematics. This effect was due neither to visual presentation of the object, without the successive grasp motor act (experiment 2) nor to synchronism between finger and mouth opening (experiments 3, 7, and 8). In experiment 9 subjects grasped with the right hand an object of different size while pronouncing a syllable printed on the target. Mouth opening and sound production were affected by the grasped object size. The results of the present study are discussed according to the notion that in an action each motor act is prepared before the beginning of the motor sequence. Double grasp preparation can be used for successive motor acts on the same object as, for example, grasping food with the hand and ingesting it after bringing it to the mouth. We speculate that the circuits involved in double grasp preparation might have been the neural substrate where hand motor patterns used as primitive communication signs were transferred to mouth articulation system. This is in accordance with the hypothesis that Broca's area derives phylogenetically from the monkey premotor area where hand movements are controlled.

Adult↗

PubMed2000

Language and motor control.

We investigated the possible influence of automatic word reading on processes of visuo-motor transformation. Subjects reached and grasped an object on which the following Italian words were printed: "VICINO" (near) or "LONTAN" (far) on an object either near or far from the agent (experiments 1, 2); PICCOLO (small) or "GRANDE" (large) on either a small or a large object (experiment 4); and "ALTO" (high) or "BASSO" (low) on either a high or a low object (experiment 5). The kinematics of the initial phase of reaching-grasping was affected by the meaning of the printed words. Namely, subjects automatically associated the meaning of the word with the corresponding property of the object and activated a reach and/or a grasp motor program influenced by the word. No effect on initial reach kinematics was observed for words related to object properties not directly involved in reach control (experiment 3). Moreover, in all the experiments, the presented words poorly influenced perceptual judgement of object properties. In experiments 5-7, the effects of the Italian adjectives "ALTO" (high) and "BASSO" (low) on reaching-grasping control were compared with those of the Italian adverbs "SOPRA" (up) and "SOTTO" (down). Adjectives influenced visual analysis of target-object properties, whereas adverbs more directly influenced the control of the action. We suggest that these effects resemble the structure of a sentence, where adjectives are commonly referred to nouns, and adverbs to verbs. In other words, class of words and, in a broad sense, grammar influenced motor control. The results of the present study show that cognitive functions such as language can affect visuo-motor transformation. They are discussed according to the notion that a strict relation between language and motor control exists, and that the frontal cortex can be involved in interactions between automatic word reading and visuo-motor transformation.

Adolescent↗

PubMed2000

Impaired control of an action after supplementary motor area lesion: a case study.

The 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.

Acceleration↗

PubMed2000

Recognising a hand by grasp.

The present study aimed to demonstrate that motor representations are used to recognise biological stimuli. In three experiments subjects were required to judge laterality of hands and forearms presented by pictures. The postures of the hands were those assumed when holding a small, medium and large sphere. In experiment 1, the sphere held in hand was presented, whereas in experiment 2 it was absent. In experiment 3, the same images, showing holding-a-sphere hands, as in experiment 1 were presented, but without forearm. In all experiments one finger of each hand could be absent. In experiment 1 recognition time was longer for those hand postures for which the corresponding grasping motor acts required more accuracy. This was confirmed by a control experiment (experiment 4), in which subjects actually grasped the spheres. Absence of fingers did not influence right-left hand recognition. However, the absence of target object in experiment 2, and of forearm in experiment 3 reduced the effects of the type of holding on hand laterality recognition. The results of the present study indicate that grasp representations are used to recognise hand laterality. In particular, the visual description of how hand and object interact in space (the opposition space [M.A. Arbib, Programs, schemas and neural networks for control of hand movement: beyond the RS frameworks, in: M. Jeannerod (Ed.), Attention and Performance XIII: Motor Representation and Control, Lawrence Erlbaum, Hillsdale, NJ, 1990, 111-138; M.A. Arbib, T. Iberall, D. Lyons, Coordinated control programs for movements of the hand, in: A.W. Goodman, I. Darian-Smith (Eds.), Hand function and the neocortex, Springer, Berlin, 1985, pp. 135-170]) and the anchoring of the hand to the agent are the features of the grasp representations used in hand-recognition processes. The data are discussed according to the more general notion that motor representations are automatically extracted in the process of intuiting situations, or people's intentions. These motor representations, which are compared with those of other people, contain concrete information on the actions (the motor program) by which a situation is created and on the aim of the agents executing those actions.

Adult↗

PubMed1998

Haptic information differentially interferes with visual analysis in reaching-grasping control and in perceptual processes.

We 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.

Adult↗

PubMed1998

Implicit visual analysis in handedness recognition.

In 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.

Adult↗

PubMed1998

Visual distractors differentially interfere with the reaching and grasping components of prehension movements.

In 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.

Adult↗

PubMed1998

Right-handers and left-handers have different representations of their own hand.

The 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.

Adult↗

PubMed1998

Influence of automatic word reading on motor control.

We 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.

Acceleration↗

PubMed1997

Eye position tunes the contribution of allocentric and egocentric information to target localization in human goal-directed arm movements.

Subjects were required to point to the distant vertex of the closed and the open configurations of the Müller-Lyer illusion using either their right hand (experiment 1) or their left hand (experiment 2). In both experiments the Müller-Lyer figures were horizontally presented either in the left or in the right hemispace and movements were executed using either foveal or peripheral vision of the target. According to the illusion effect, subjects undershot and overshot the vertex location of the closed and the open configuration, respectively. The illusion effect decreased when the target was fixated and when the stimulus was positioned in the right hemispace. These results confirm the hypothesis that both egocentric and allocentric information are combined in order to encode target position in space. When movements are directed to foveal targets, decreasing effects of allocentric cues, as shown by decreasing the illusion effect, could be due to enhanced efficiency of the egocentric system. That is, information on eye position when target is fixated can be used to precisely establish its spatial relations with the body. In addition, a more accurate analysis of allocentric information is hypothesized when the target is positioned in the left hemispace. In other words, our data confirm the notion that the right cerebral hemisphere is involved in space representation.

Adult↗

PubMed1997

Tactile input of the hand and the control of reaching to grasp movements.

The role of tactile information of the hand in the control of reaching to grasp movements was investigated. The kinematics of both reaching (or transport) and grasp components were studied in healthy subjects in two experimental conditions. In one condition (control condition) subjects were required to reach and grasp an object that could have two sizes and that could be located at two distances from the viewer. In the other condition (anaesthesia condition) the same movements were executed, but anaesthesia was provided to the subjects' fingertips. In both conditions vision of the hand was prevented during movement. Anaesthesia affected mainly the kinematics of the first phase of grasping, that is, the finger-opening phase. This phase was lengthened and maximal finger aperture increased. In contrast, the duration of the successive phase (finger-closure) was poorly modified. The reaching component was also impaired by anaesthesia. Although the total extent of hand path and the spatial relations between the finger aperture and closure phases did not change between the two conditions, hand path variability increased. This occurred during transport deceleration phase and after the increase in variability of finger path. In addition, the whole movement was slowed down. The results of the present experiment suggest that tactile signals at the beginning and at the end of movement can be used to compute grasp time and to optimise grasp temporal parameters. Alternatively, signals from tactile receptors can be involved in encoding the position sense of the fingers. When this input is lacking, the control of grasp and in particular that of finger-opening phase can be impaired. Finally, the effect of the grasp impairment on the reaching component supports the notion that the coordination between reaching and grasping involves the whole temporal course of the two components.

Adult↗