Biomedical subjects

Alessia Tessari

Publications and source records attributed to Alessia Tessari.

7 recordsLinked to original sources

PubMed2006

Effect of learning on imitation of new actions: implications for a memory model.

The effects of learning on strategy selection in the context of action imitation have been investigated in two experiments conducted with healthy individuals. It was predicted that, once learnt, meaningless actions are processed by the cognitive system as meaningful and this new representational status might influence the process selection in action imitation. Results showed that not only were learnt meaningless actions processed in the same way as known, meaningful actions, but that they were imitated even better, probably due to their being represented only once in the episodic, long-term memory system. Our findings are interpreted in the light of a multiple route model for action imitation.

Adult↗

PubMed2005

Is handedness recognition automatic? A study using a Simon-like paradigm.

The authors used a modified Simon task (J. R. Simon, 1969) to assess the automatic recognition of handedness. Participants responded to the color of a circle in the center of the photograph of a right or a left hand, displayed in the center of the computer screen. A regular Simon effect was found for back views, whereas a reverse Simon effect was found for palm views. This pattern of results was found when the forearm was present (Experiment 2), when 1 finger at a time was rendered invisible (Experiment 3), and when the hands were connected to a body image (Experiment 4). When the hands were cut at the wrist, no effect emerged (Experiment 1). These findings suggest an automatic encoding of the relative position of the hand in relation to the body (imaginary or real) rather than the automatic encoding of handedness.

Automatism↗

PubMed2005

Common and differential neural mechanisms supporting imitation of meaningful and meaningless actions.

Neuropsychological studies indicate that, after brain damage, the ability to imitate meaningful or meaningless actions can be selectively impaired. However, the neural bases supporting the imitation of these two types of action are still poorly understood. Using PET, we investigated in 10 healthy individuals the neural mechanisms of imitating novel, meaningless actions and familiar, meaningful actions. Data were analyzed using SPM99. During imitation, a significant positive correlation (p < .05, corrected) of regional cerebral blood flow with the amount of meaningful actions was observed in the left inferior temporal gyrus only. In contrast, a significant positive correlation (p < .05, corrected) with the amount of meaningless movements was observed in the right parieto-occipital junction. The direct categorical comparison of imitating meaningful (100%) relative to meaningless (100%) actions showed differential increases in neural activity (p < .001, uncorrected) in the left inferior temporal gyrus, the left parahippocampal gyrus, and the left angular gyrus. The reverse categorical comparison of imitating meaningless (100%) relative to meaningful (100%) actions revealed differential increases in neural activity (p < .001, uncorrected) in the superior parietal cortex bilaterally, in the right parieto-occipital junction, in the right occipital-temporal junction (MT, V5), and in the left superior temporal gyrus. Increased neural activity common to imitation of meaningless and meaningful actions compared to action observation was observed in a network of areas known to be involved in imitation of actions including the primary sensorimotor cortex, the supplementary motor area, and the ventral premotor cortex. These results are compatible with the two-route model of action imitation which suggests that there are at least two mechanisms involved in imitation of actions: a direct mechanism transforming a novel action into a motor output, and a semantic mechanism, on the basis of stored memories, that allows reproductions of known actions. Our results indicate that, in addition to shared neural processes, the direct and the semantic mechanisms that underlie action imitation also draw upon differential neural mechanisms. The direct mechanism underlying imitation of meaningless actions differentially involves visuospatial transformation processes as evidenced by activation of areas belonging to the dorsal stream. In contrast, imitation of meaningful actions differentially involves semantic processing as evidenced by activation of areas belonging to the ventral stream.

Adult↗

PubMed2004

The strategic control of multiple routes in imitation of actions.

The aim of this study was to bring to the surface the strategic use of imitative processes in the context of a 2-route model: (a) direct imitation, used in reproducing new, meaningless actions, and (b) imitation based on stored semantic knowledge of familiar meaningful actions. Three experiments were carried out with healthy participants who reproduced meaningful and meaningless actions within an established time limit. The study investigated 3 factors that could potentially affect the selection of processes used for imitation: (a) the composition of the experimental list (blocked or mixed presentation), (b) the presence-absence of instructions (Experiments 1 and 2), and (c) the relative proportions of the stimuli (Experiment 3). Overall, the results suggest that each of these factors influences the selection of imitative strategies in healthy individuals with temporarily reduced capacities, as happens in the case of brain-damaged patients.

Adult↗

PubMed2002

Imitation without awareness.

Imitation is a characteristic but little-understood function of the human brain and of some higher animals. The direct matching hypothesis suggests that a specialised brain circuit is able to extract and directly copy the motor commands of another person's observed actions. Here we investigate how conscious people are of this kind of imitation. We first showed that imitation reactions are faster than simple visual reaction times, consistent with a direct matching circuit in the CNS. We next compared the perceived time of imitation reactions in 17 healthy subjects with other kinds of actions. We found a significant delay in subjects' awareness of their own imitation reactions. Thus, while imitation reactions are unusually fast, subjects are not aware of this. The brain's direct-matching circuit for imitation partly bypasses conscious awareness.

Adult↗

PubMed2002

Motor distal component and pragmatic representation of objects.

In this study, we tested whether in certain experimental conditions the distal and proximal motor components may dissociate in action imitation, and how the distal component and the object representation may interact. Experiments 1-3 were carried out using a dual task procedure in which an action span and a motor suppression were coupled. In Experiment 1, it was shown that action spans were affected more by a distal movement (e.g. distal motor suppression) than by a proximal movement (proximal motor suppression). In Experiment 2, it was demonstrated that the reduction of the action spans was not due to the distal motor suppression being more difficult than the proximal motor suppression. In Experiment 3, pantomimes were replaced with the corresponding objects and the participants were asked to mime the objects, reproducing the appropriate actions. During the presentation of the objects, the participants were engaged in a motor suppression that was performed either by the hand or by the arm. The distal motor suppression reduced the pantomime span more significantly than the proximal motor suppression. Experiment 4 showed that the spans of pantomimes of objects shown in Experiment 3 are longer when participants do not perform motor suppressions. Our results suggest that in normal subjects a difference between the distal and the proximal motor component can be observed under dual task conditions and that distal motor suppression seems to interfere both with the encoding of action and with pragmatic representation of objects.

Analysis of Variance↗

PubMed2001

Imitation of novel and well-known actions: the role of short-term memory.

Four experiments were carried out using the action span paradigm. In experiment 1 we found that well-learnt, meaningful (MF) actions were imitated better than novel, meaningless (ML) actions. In experiments 2 and 3, during the encoding of MF and ML actions, participants were required to carry out different suppression tasks. In experiment 2 we replicated the advantage of MF actions over ML actions and also found that the motor suppression shortened the action span more than the other forms of suppressions (spatial and articulatory). Action encoding and motor suppression tapping the same subsystem, temporarily holding the motor information, could explain the reduced motor span obtained in experiment 2. Two alternative explanations that could have accounted for this effect were ruled out in experiments 3 and 4. In experiment 3 we verified whether the reduction of the action span was produced by the different combination of the articulatory suppression with motor suppression or with the spatial suppression. In experiment 4, we demonstrated that the reduction was not due to the motor suppression being more difficult than the other types of suppression. The critical finding that the spans of well-learnt, MF actions are longer than those of novel, ML actions observed in experiments 1 and 2 was interpreted in terms of different processing routes engaged in the imitation of these two types of actions. MF actions can be imitated along both a semantic, indirect route and a direct route leading from the visual analysis of the action to the motor system. In contrast, the imitation of ML actions is accomplished along the direct route only.

Brain↗