Biomedical subjects

Alessia Tessari

Publications and source records attributed to Alessia Tessari.

3 recordsLinked to original sources

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↗