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Biomedical subjects

J Decety

Publications and source records attributed to J Decety.

At least 19 recordsLinked to original sources
PubMed2003

Modulating the experience of agency: a positron emission tomography study.

This study investigated agency, the feeling of being causally involved in an action. This is the feeling that leads us to attribute an action to ourselves rather than to another person. We were interested in the effects of experimentally modulating this experience on brain areas known to be involved in action recognition and self-recognition. We used a device that allowed us to modify the subject's degree of control of the movements of a virtual hand presented on a screen. Four main conditions were used: (1) a condition where the subject had a full control of the movements of the virtual hand, (2) a condition where the movements of the virtual hand appeared rotated by 25 degrees with respect to the movements made by the subject, (3) a condition where the movements of the virtual hand appeared rotated by 50 degrees, and (4) a condition where the movements of the virtual hand were produced by another person and did not correspond to the subject's movements. The activity of two main brain areas appeared to be modulated by the degree of discrepancy between the movement executed and the movement seen on the screen. In the inferior part of the parietal lobe, specifically on the right side, the less the subject felt in control of the movements of the virtual hand, the higher the level of activation. A reverse covariation was observed in the insula. These results demonstrate that the level of activity of specific brain areas maps onto the experience of causing or controlling an action. The implication of these results for understanding pathological conditions is discussed.

Adult↗
PubMed2003

The detection of contingency and animacy from simple animations in the human brain.

Contingencies between objects and people can be mechanical or intentional-social in nature. In this fMRI study we used simplified stimuli to investigate brain regions involved in the detection of mechanical and intentional contingencies. Using a factorial design we manipulated the 'animacy' and 'contingency' of stimulus movement, and the subject's attention to the contingencies. The detection of mechanical contingency between shapes whose movement was inanimate engaged the middle temporal gyrus and right intraparietal sulcus. The detection of intentional contingency between shapes whose movement was animate activated superior parietal networks bilaterally. These activations were unaffected by attention to contingency. Additional regions, the right middle frontal gyrus and left superior temporal sulcus, became activated by the animate-contingent stimuli when subjects specifically attended to the contingent nature of the stimuli. Our results help to clarify neural networks previously associated with 'theory of mind' and agency detection. In particular, the results suggest that low-level perception of agency in terms of objects reacting to other objects at a distance is processed by parietal networks. In contrast, the activation of brain regions traditionally associated with theory of mind tasks appears to require attention to be directed towards agency and contingency.

Adolescent↗
PubMed2002

A PET exploration of the neural mechanisms involved in reciprocal imitation.

Imitation is a natural mechanism involving perception-action coupling which plays a central role in the development of understanding that other people, like the self, are mental agents. PET was used to examine the hemodynamic changes occurring in a reciprocal imitation paradigm. Eighteen subjects (a) imitated the actions of the experimenter, (b) had their actions imitated by the experimenter, (c) freely produced actions, or (d) freely produced actions while watching different actions made by the experimenter. In a baseline condition, subjects simply watched the experimenter's actions. Specific increases were detected in the left STS and in the inferior parietal cortex in conditions involving imitation. The left inferior parietal is specifically involved in producing imitation, whereas the right homologous region is more activated when one's own actions are imitated by another person. This pattern of results suggests that these regions play a specific role in distinguishing internally produced actions from those generated by others.

Adult↗
PubMed2002

Does visual perception of object afford action? Evidence from a neuroimaging study.

Positron emission tomography (PET) was used to explore the neural correlates of a potential involvement of motor representation during the perception of visually presented objects with different tasks. The main result of this study was that the perception of objects, irrespective of the task (judgement of the vertical orientation, motor imagery, and silent generation of the noun or of the corresponding action verb), versus perception of non-objects, was associated with rCBF increases in a common set of cortical regions. The occipito-temporal junction, the inferior parietal lobule, the SMA-proper, the pars triangularis in the inferior frontal gyrus, the dorsal and ventral precentral gyrus were engaged in the left hemisphere. The ipsilateral cerebellum was also involved. These activations are congruent with the idea of an involvement of motor representation already during the perception of object and thus provide neurophysiological evidence that the perception of objects automatically affords actions that can be made toward them. Besides this common set of cortical areas, each task engaged specific regions.

Adult↗
PubMed2001

Is perceptual anticipation a motor simulation? A PET study.

A large body of psychophysical evidence suggests that perception of human movement is constrained by the observer's motor competence. PET measurements of regional cerebral blood flow were performed in eight healthy subjects who were requested, in a forced-choice paradigm, to anticipate the outcome of a single moving dot trajectory depicting the beginning of either mechanical, pointing, or writing movements. Selective activation of the left premotor cortex and of the right intraparietal sulcus was associated with visual anticipation of pointing movements while the left frontal operculum and superior parietal lobule were found to be activated during anticipation of writing movements. These results are discussed in the perspective that the motor system is part of a simulation network, which is used to interpret perceived actions.

Adolescent↗
PubMed2001

How the brain perceives causality: an event-related fMRI study.

Detection of the causal relationships between events is fundamental for understanding the world around us. We report an event-related fMRI study designed to investigate how the human brain processes the perception of mechanical causality. Subjects were presented with mechanically causal events (in which a ball collides with and causes movement of another ball) and non-causal events (in which no contact is made between the balls). There was a significantly higher level of activation of V5/MT/MST bilaterally, the superior temporal sulcus bilaterally and the left intraparietal sulcus to causal relative to non-causal events. Directing attention to the causal nature of the stimuli had no significant effect on the neural processing of the causal events. These results support theories of causality suggesting that the perception of elementary mechanical causality events is automatically processed by the visual system.

Adult↗
PubMed2001

Functional anatomy of execution, mental simulation, observation, and verb generation of actions: a meta-analysis.

There is a large body of psychological and neuroimaging experiments that have interpreted their findings in favor of a functional equivalence between action generation, action simulation, action verbalization, and perception of action. On the basis of these data, the concept of shared motor representations has been proposed. Indeed several authors have argued that our capacity to understand other people's behavior and to attribute intention or beliefs to others is rooted in a neural, most likely distributed, execution/observation mechanism. Recent neuroimaging studies have explored the neural network engaged during motor execution, simulation, verbalization, and observation. The focus of this metaanalysis is to evaluate in specific detail to what extent the activated foci elicited by these studies overlap.

Brain Mapping↗
PubMed2001

Does perception of biological motion rely on specific brain regions?

Perception of biological motions plays a major adaptive role in identifying, interpreting, and predicting the actions of others. It may therefore be hypothesized that the perception of biological motions is subserved by a specific neural network. Here we used fMRI to verify this hypothesis. In a group of 10 healthy volunteers, we explored the hemodynamic responses to seven types of visual motion displays: drifting random dots, random dot cube, random dot cube with masking elements, upright point-light walker, inverted point-light walker, upright point-light walker display with masking elements, and inverted point-light walker display with masking elements. A gradient in activation was observed in the occipitotemporal junction. The responses to rigid motion were localized posteriorly to those responses elicited by nonrigid motions. Our results demonstrate that in addition to the posterior portion of superior temporal sulcus, the left intraparietal cortex is involved in the perception of nonrigid biological motions.

Adult↗
PubMed2001

Different brain correlates for watching real and virtual hand actions.

We investigated whether observation of actions reproduced in three-dimensional virtual reality would engage perceptual and visuomotor brain processes different from those induced by the observation of real hand actions. Participants were asked to passively observe grasping actions of geometrical objects made by a real hand or by hand reconstructions of different quality in 3D virtual reality as well as on a 2D TV screen. We found that only real actions in natural environment activated a visuospatial network including the right posterior parietal cortex. Observation of virtual-reality hand actions engaged prevalent visual perceptual processes within lateral and mesial occipital regions. Thus, only perception of actions in reality maps onto existing action representations, whereas virtual-reality conditions do not access the full motor knowledge available to the central nervous system.

Adult↗
PubMed2001

Effect of subjective perspective taking during simulation of action: a PET investigation of agency.

Perspective taking is an essential component in the mechanisms that account for intersubjectivity and agency. Mental simulation of action can be used as a natural protocol to explore the cognitive and neural processing involved in agency. Here we took PET measurements while subjects simulated actions with either a first-person or a third-person perspective. Both conditions were associated with common activation in the SMA, the precentral gyrus, the precuneus and the MT/V5 complex. When compared to the first-person perspective, the third-person perspective recruited right inferior parietal, precuneus, posterior cingulate and frontopolar cortex. The opposite contrast revealed activation in left inferior parietal and somatosensory cortex. We suggest that the right inferior parietal, precuneus and somatosensory cortex are specifically involved in distinguishing self-produced actions from those generated by others.

Acoustic Stimulation↗
PubMed2000

Motor imagery in normal subjects and in asymmetrical Parkinson's disease: a PET study.

OBJECTIVE: To investigate, using PET and H2(15)O, brain activation abnormalities of patients with PD during motor imagery. To determine whether motor imagery activation patterns depend on the hand used to complete the task. BACKGROUND: Previous work in PD has shown that bradykinesia is associated with slowness of motor imagery. METHODS: The PET study was performed in eight patients with PD with predominantly right-sided akinesia, and in eight age-matched control subjects, all right-handed. Regional cerebral blood flow was measured by PET and H2(15)O while subjects imagined a predetermined unimanual externally cued sequential movement with a joystick with either the left or the right hand, and during a rest condition. RESULTS: In normal subjects, the prefrontal cortex, supplementary motor area (SMA), superior parietal lobe, inferior frontal gyrus, and cerebellum were activated during motor imagery with either the left or the right hand. Contralateral primary motor cortex activation was noted only when the task was imagined with the right (dominant) hand, whereas activation of the dorsolateral prefrontal cortex was observed only during imagery with the left hand. In patients with PD, motor imagery with the right ("akinetic") hand was characterized by lack of activation of the contralateral primary sensorimotor cortex and the cerebellum, persistent activation of the SMA, and bilateral activation of the superior parietal cortex. Motor imagery with the left ("non-akinetic") hand was also abnormal, with lack of activation of the SMA compared with controls. CONCLUSIONS: In patients with PD with predominantly right-sided akinesia, brain activation during motor imagery is abnormal and may appear even with the less affected hand. In normal subjects, brain activation during motor imagery depends on the hand used in the imagined movement.

Adult↗
PubMed2000

Overactivation of primary motor cortex is asymmetrical in hemiparkinsonian patients.

Regional cerebral blood flow (rCBF) was measured using PET and H2(15)O in Parkinson's disease (PD) patients with predominantly right-sided akinetic-rigid symptoms and in control subjects during the execution of an externally cued motor task either with the left or the right hand. During the execution of the task with the left, non-akinetic, hand, cerebral activation in PD patients appeared similar to that of controls. Activated areas were the primary motor cortex, premotor cortex, parietal cortex and cerebellum. When the task was executed with the right, akinetic, hand cerebral activation in PD patients differed from that of controls subjects. The most important change was a bilateral activation of the primary motor cortex. We conclude that overactivation of primary motor cortex is asymmetrical in hemiparkinsonian patients.

Adult↗
PubMed2000

New aspects of motion perception: selective neural encoding of apparent human movements.

Perception of apparent motion operates somewhat differently for objects and human figures. Depending on the interstimulus interval, the latter d may give rise to either perception of a direct path (i.e. biologically impossible) or indirect path (i.e. biologically possible). Here, PET was used to investigate whether a change in brain activity accompanies this perceptual shift. We found neural encoding of apparent motion to be a function of the intrinsic properties of the stimulus presented (object vs human) as well as the kind of human movement path perceived (biomechanically possible vs impossible). Motor and parietal cortex were only involved for possible motion which suggests that these regions are selectively activated to process actions which conform to the capabilities of the observer.

Adult↗
PubMed2000

A PET investigation of the attribution of intentions with a nonverbal task.

Several authors have demonstrated that theory of mind is associated with a cerebral pattern of activity involving the medial prefrontal cortex. This study was designed to determine the cerebral regions activated during attribution of intention to others, a task which requires theory-of-mind skills. Eight healthy subjects performed three nonverbal tasks using comic strips while PET scanning was performed. One condition required subjects to attribute intentions to the characters of the comic strips. The other two conditions involved only physical logic and knowledge about objects' properties: one condition involved characters, whereas the other only represented objects. The comparison of the attribution of intention condition with the physical logic with characters condition was associated with rCBF increases in the right middle and medial prefrontal cortex including Brodmann's area (BA) 9, the right inferior prefrontal cortex (BA 47), the right inferior temporal gyrus (BA 20), the left superior temporal gyrus (BA 38), the left cerebellum, the bilateral anterior cingulate, and the middle temporal gyri (BA 21). The comparison of the physical logic with characters condition and the physical logic without characters condition showed the activation of the lingual gyri (BA 17, 18, 19), the fusiform gyri (BA 37), the middle (BA 21) and superior (BA 22, 38) temporal gyri on both sides, and the posterior cingulate. These data suggest that attribution of intentions to others is associated with a complex cerebral activity involving the right medial prefrontal cortex when a nonverbal task is used. The laterality of this function is discussed.

Adult↗
PubMed1999

MRI measurement of the functional blood flow changes in a large superficial vein draining the motor cortex.

In this study, phase-contrast MR techniques are applied in order to measure the blood flow changes induced by a motor task in a large superficial vein draining the motor cortex. The measurements were applied to six healthy volunteers, in motor rest conditions and during performance of a motor task. The latter consisted of sequential finger-to-thumb opposition. The task was actually executed and mentally simulated. Significant blood flow increases were found when changing from from mental simulation to actual execution of the motor task (increases ranging between 1.6 and 10.3 ml/min, i.e. 9% and 45%, respectively) and from resting conditions to actual execution of the motor task (increases ranging between 1.7 and 14.0 ml/min, i.e. 32% and 72%, respectively).

Adult↗
PubMed1999

Human brain activity related to the perception of spatial features of objects.

The role of the parietal cortex in visuospatial analysis of object was investigated by cerebral blood flow measurements in seven objects using positron emission tomography. Data were acquired while subjects performed a matching task requiring the discrimination of simultaneously presented objects based on one of their spatial properties. Three properties were studied separately during three scanning conditions repeated twice:surface orientation, principal axis orientation, and size. Scans were also obtained during a sensorimotor control task (similar visual stimulation, same motor action, voluntary saccades toward each object) as well as during rest (no stimulation, eyes closed). Compared to rest, the three property matching tasks showed the same pattern of activation: the whole occipital lobe, the right intraparietal sulcus (IPS), and the right occipitotemporal (OT) junction. Compared to the control condition, only right IPS and OT junction were significantly activated during discrimination of the spatial properties. The IPS focus was located between the superior parietal lobule and the angular gyrus, and the OT activation overlapped the posterior part of the inferior temporal gyrus and the middle occipital gyrus. These results indicate that discrimination of spatial attributes requires the activation of both the parietal and the temporal cortices of the right hemisphere and provide further evidence that the IPS plays a critical role in visuospatial analysis of objects.

Adult↗
PubMed1999

Neural mechanisms subserving the perception of human actions.

Our ability to generate actions and to recognize actions performed by others is the bedrock of our social life. Behavioral evidence suggests that the processes underlying perception and action might share a common representational framework. That is, observers might understand the actions of another individual in terms of the same neural code that they use to produce the same actions themselves. What neurophysiological evidence, if any, supports such a hypothesis? In this article, brain imaging studies addressing this question are reviewed and examined in the light of the functional segregation of the perceptual mechanisms subtending visual recognition and those used for action. We suggest that there are not yet conclusive arguments for a clear neurophysiological substrate supporting a common coding between perception and action.

Journal Article↗