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Neural encoding and functional interactions underlying pantomimed movements
No full textPantomimes are a unique movement category which can convey complex information about our intentions in the absence of any interaction with real objects. Indeed, we can pretend to use the same tool to perform different actions or to achieve the same goal adopting different tools. Nevertheless, how our brain implements pantomimed movements is still poorly understood. In our study, we explored the neural encoding and functional interactions underlying pantomimes adopting multivariate pattern analysis (MVPA) and connectivity analysis of fMRI data. Participants performed pantomimed movements, either grasp-to-move or grasp-to-use, as if they were interacting with two different tools (scissors or axe). These tools share the possibility to achieve the same goal. We adopted MVPA to investigate two levels of representation during the planning and execution of pantomimes: (1) distinguishing different actions performed with the same tool, (2) representing the same final goal irrespective of the adopted tool. We described widespread encoding of action information within regions of the so-called "tool" network. Several nodes of the network-comprising regions within the ventral and the dorsal stream-also represented goal information. The spatial distribution of goal information changed from planning-comprising posterior regions (i.e. parietal and temporal)-to execution-including also anterior regions (i.e. premotor cortex). Moreover, connectivity analysis provided evidence for task-specific bidirectional coupling between the ventral stream and parieto-frontal motor networks. Overall, we showed that pantomimes were characterized by specific patterns of action and goal encoding and by task-dependent cortical interactions
Visual features of an observed agent do not modulate human brain activity during action observation
No full textRecent neuroimaging evidence in macaques has shown that the neural system
underlying the observation of hand actions performed by others (i.e., "action
observation system") is modulated by whether the observed action is performed by
a person in full view or an isolated hand (i.e., type of view manipulation).
Although a human homologue of such circuit has been identified, whether in humans
the neural processes involved in this capacity are modulated by the type of view
remains unknown. Here we used functional magnetic resonance imaging (fMRI) to
investigate whether the "action observation system", with specific reference to
the ventral premotor cortex, responds differentially depending on type of view.
We also tested this manipulation within regions of the human brain showing
overlapping activity for both the observation and the execution of action
("mirror" regions). To this end, the same subjects were requested to observe
grasping actions performed under the two types of view (observation conditions)
or to perform a grasping action (execution condition). Results from whole-brain
analyses indicate that overlapping activity for action observation and execution
was evident in a broad network of areas including parietal, premotor and temporal
cortices. Activity within such network was evident for both the observation of a
person in full view or an isolated hand, but it was not modulated by the type of
view. Similarly, results from region of interest (ROI) analyses, performed within
the ventral premotor cortex, did confirm that this area responded in a similar
fashion following the observation of either an isolated hand or an entire model
acting. These findings offer novel insights on what the "action observation" and
the "mirror" systems visually code and how the processing underlying such coding
may vary across species. Further, they support the hypothesis that action goal is
amongst the main determinants for the revelation of action observation activity,
and to the existence of a broad system involved in the simulation of action
Resting‐State Functional Interactions Between the Action Observation Network and the Mentalizing System
No full textAn object for an action, the same object for other actions: effects on hand shaping
No full textObjects can be grasped in several ways due to their physical properties, the context surrounding the object, and the goal of the grasping agent. The aim of the present study was to investigate whether the prior-to-contact grasping kinematics of the same object vary as a result of different goals of the person grasping it. Subjects were requested to reach toward and grasp a bottle filled with water, and then complete one of the following tasks: (1) Grasp it without performing any subsequent action; (2) Lift and throw it; (3) Pour the water into a container; (4) Place it accurately on a target area; (5) Pass it to another person. We measured the angular excursions at both metacarpal-phalangeal (mcp) and proximal interphalangeal (pip) joints of all digits, and abduction angles of adjacent digit pairs by means of resistive sensors embedded in a glove. The results showed that the presence and the nature of the task to be performed following grasping affect the positioning of the fingers during the reaching phase. We contend that a one-to-one association between a sensory stimulus and a motor response does not capture all the aspects involved in grasping. The theoretical approach within which we frame our discussion considers internal models of anticipatory control which may provide a suitable explanation of our results. © 2007 Springer-Verlag
Distractor objects affect fingers' angular distances but not fingers' shaping during grasping
No full textThe aim of the present study was to determine whether and how hand shaping was
affected by the presence of a distractor object adjacent to the to-be-grasped
object. Twenty subjects were requested to reach towards and grasp a 'convex' or a
'concave' object in the presence or absence of a distractor object either of the
same or different shape than the target object. Flexion/extension at the
metacarpal-phalangeal (MCP) and proximal interphalangeal joints of all digits,
and abduction angle between digits were measured by resistive sensors embedded in
a glove. The results indicate robust interference effects at the level of reach
duration and the extent of fingers' abduction angles together with changes at the
level of a single joint for the thumb. No distractor effects on individual
fingers' joints except for the MCP of the middle and little fingers were found.
These findings suggest that the presence of distractor object affects hand
shaping in terms of fingers' abduction angles, but not at the level of 'shape
dependent' fingers' angular excursions. Furthermore, they support the importance
of the thumb for the guidance of selective reach-to-grasp movements. We discuss
these results in the context of current theories proposed to explain the object
selection processes underlying the control of hand action
An object for an action, the same object for other actions: Effects on hand shaping
No full textObjects can be grasped in several ways due to their physical properties, the
context surrounding the object, and the goal of the grasping agent. The aim of
the present study was to investigate whether the prior-to-contact grasping
kinematics of the same object vary as a result of different goals of the person
grasping it. Subjects were requested to reach toward and grasp a bottle filled
with water, and then complete one of the following tasks: (1) Grasp it without
performing any subsequent action; (2) Lift and throw it; (3) Pour the water into
a container; (4) Place it accurately on a target area; (5) Pass it to another
person. We measured the angular excursions at both metacarpal-phalangeal (mcp)
and proximal interphalangeal (pip) joints of all digits, and abduction angles of
adjacent digit pairs by means of resistive sensors embedded in a glove. The
results showed that the presence and the nature of the task to be performed
following grasping affect the positioning of the fingers during the reaching
phase. We contend that a one-to-one association between a sensory stimulus and a
motor response does not capture all the aspects involved in grasping. The
theoretical approach within which we frame our discussion considers internal
models of anticipatory control which may provide a suitable explanation of our
results
Mirror neurons in humans: Consisting or confounding evidence?
No full textThe widely known discovery of mirror neurons in macaques shows that premotor and parietal cortical areas are not only involved in
executing one’s own movement, but are also active when observing the action of others. The goal of this essay is to critically evaluate the
substance of functional magnetic resonance imaging (fMRI) and positron emission tomography (PET) studies whose aim has been to
reveal the presence of a parallel system in humans. An inspection of this literature suggests that there is relatively weak evidence for
the existence of a circuit with ‘mirror’ properties in humans, such as that described in monkeys
Distractor objects affect fingers’ angular distances but not fingers’shaping during grasping
No full textThe aim of the present study was to determine
whether and how hand shaping was affected by
the presence of a distractor object adjacent to the tobe-
grasped object. Twenty subjects were requested to
reach towards and grasp a ‘convex’ or a ‘concave’ object
in the presence or absence of a distractor object
either of the same or different shape than the target
object. Flexion/extension at the metacarpal-phalangeal
(MCP) and proximal interphalangeal joints of all digits,
and abduction angle between digits were measured
by resistive sensors embedded in a glove. The results
indicate robust interference effects at the level of reach
duration and the extent of fingers’ abduction angles
together with changes at the level of a single joint for
the thumb. No distractor effects on individual fingers’
joints except for the MCP of the middle and little fingers
were found. These findings suggest that the presence
of distractor object affects hand shaping in terms
of fingers’ abduction angles, but not at the level of
‘shape dependent’ fingers’ angular excursions. Furthermore,
they support the importance of the thumb
for the guidance of selective reach-to-grasp movements.
We discuss these results in the context of current
theories proposed to explain the object selection
processes underlying the control of hand action
Do dorsolateral and dorsomedial pathways interact? Investigating parieto-frontal connectivity during a prehension task: a TMS-fMRI study
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