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PubMed2001

The cortical motor system.

The cortical motor system of primates is formed by a mosaic of anatomically and functionally distinct areas. These areas are not only involved in motor functions, but also play a role in functions formerly attributed to higher order associative cortical areas. In the present review, we discuss three types of higher functions carried out by the motor cortical areas: sensory-motor transformations, action understanding, and decision processing regarding action execution. We submit that generating internal representations of actions is central to cortical motor function. External contingencies and motivational factors determine then whether these action representations are transformed into actual actions.

Animals↗
PubMed2002

Viewing lip forms: cortical dynamics.

Viewing other persons' actions automatically activates brain areas belonging to the mirror-neuron system (MNS) assumed to link action execution and observation. We followed, by magnetoencephalographic cortical dynamics, subjects who observed still pictures of lip forms, on-line imitated them, or made similar forms in a self-paced manner. In all conditions and in both hemispheres, cortical activation progressed in 20-70 ms steps from the occipital cortex to the superior temporal region (where the strongest activation took place), the inferior parietal lobule, and the inferior frontal lobe (Broca's area), and finally, 50-140 ms later, to the primary motor cortex. The signals of Broca's area and motor cortex were significantly stronger during imitation than other conditions. These results demonstrate that still pictures, only implying motion, activate the human MNS in a well-defined temporal order.

Adult↗
PubMed2004

Neural circuits underlying imitation learning of hand actions: an event-related fMRI study.

The neural bases of imitation learning are virtually unknown. In the present study, we addressed this issue using an event-related fMRI paradigm. Musically naive participants were scanned during four events: (1) observation of guitar chords played by a guitarist, (2) a pause following model observation, (3) execution of the observed chords, and (4) rest. The results showed that the basic circuit underlying imitation learning consists of the inferior parietal lobule and the posterior part of the inferior frontal gyrus plus the adjacent premotor cortex (mirror neuron circuit). This circuit, known to be involved in action understanding, starts to be active during the observation of the guitar chords. During pause, the middle frontal gyrus (area 46) plus structures involved in motor preparation (dorsal premotor cortex, superior parietal lobule, rostral mesial areas) also become active. Given the functional properties of area 46, a model of imitation learning is proposed based on interactions between this area and the mirror neuron system.

Adult↗
PubMed2003

Why are smiles contagious? An fMRI study of the interaction between perception of facial affect and facial movements.

In human communication there is often a close relationship between the perception of an emotionally expressive face and the facial response of the viewer himself. Whereas perception and generation of facial expressions have been studied separately with functional imaging methods, no studies exist on their interaction. We combined the presentation of emotionally expressive faces with the instruction to react with facial movements predetermined and assigned. fMRI was used in an event related design to examine healthy subjects while they regarded happy, sad, or neutral faces and were instructed to simultaneously move the corners of their mouths either (a). upwards or (b). downwards, or (c). to refrain from movement. The subjects' facial movements were recorded with an MR-compatible video camera. Movement latencies were shortened in congruent situations (e.g. the presentation of a happy face and combined with upward movements) and delayed in non-congruent situations. Dissonant more than congruent stimuli activated the inferior prefrontal cortex and the somatomotor cortex bilaterally. The congruent condition, in particular when seeing a happy face, activated the medial basotemporal lobes (hippocampus, amygdala, parahippocampal region). We hypothesize that this region facilitates congruent facial movements when an emotionally expressive face is perceived and that it is part of a system for non-volitional emotional facial movements.

Adult↗
PubMed2002

Motor and cognitive functions of the ventral premotor cortex.

Recent data show that the ventral premotor cortex in both humans and monkeys has motor and cognitive functions. The cognitive functions include space perception, action understanding and imitation. The data also show a clear functional homology between monkey area F5 and human area 44. Preliminary evidence suggests that the ventral part of the lateral premotor cortex in humans may correspond to monkey area F4. A tentative map of the human lateral premotor areas founded on the reviewed evidence is presented.

Anatomy, Comparative↗
PubMed2002

Cognitive motor control: spatial and temporal aspects.

Cognitive motor control refers to processes that blend cognitive and motor functions in a seamless, interwoven fashion. Such functions evolve in space and time at various levels of complexity. This article focuses on conceptual issues regarding spatial and temporal aspects of motor control as well as on methods suitable for extracting information from neuronal ensembles.

Animals↗
PubMed2003

An interference effect of observed biological movement on action.

It has been proposed that actions are intrinsically linked to perception and that imagining, observing, preparing, or in any way representing an action excites the motor programs used to execute that same action. There is neurophysiological evidence that certain brain regions involved in executing actions are activated by the mere observation of action (the so-called "mirror system;" ). However, it is unknown whether this mirror system causes interference between observed and simultaneously executed movements. In this study we test the hypothesis that, because of the overlap between action observation and execution, observed actions should interfere with incongruous executed actions. Subjects made arm movements while observing either a robot or another human making the same or qualitatively different arm movements. Variance in the executed movement was measured as an index of interference to the movement. The results demonstrate that observing another human making incongruent movements has a significant interference effect on executed movements. However, we found no evidence that this interference effect occurred when subjects observed a robotic arm making incongruent movements. These results suggest that the simultaneous activation of the overlapping neural networks that process movement observation and execution infers a measurable cost to motor control.

Adult↗
PubMed1999

Chimps ape man.

Explore the source record for details and available documents.

Adult↗
PubMed2003

When the self represents the other: a new cognitive neuroscience view on psychological identification.

There is converging evidence from developmental and cognitive psychology, as well as from neuroscience, to suggest that the self is both special and social, and that self-other interaction is the driving force behind self-development. We review experimental findings which demonstrate that human infants are motivated for social interactions and suggest that the development of an awareness of other minds is rooted in the implicit notion that others are like the self. We then marshall evidence from functional neuroimaging explorations of the neurophysiological substrate of shared representations between the self and others, using various ecological paradigms such as mentally representing one's own actions versus others' actions, watching the actions executed by others, imitating the others' actions versus being imitated by others. We suggest that within this shared neural network the inferior parietal cortex and the prefrontal cortex in the right hemisphere play a special role in the essential ability to distinguish the self from others, and in the way the self represents the other. Interestingly, the right hemisphere develops its functions earlier than the left.

Awareness↗
PubMed2004

Inferring false beliefs from the actions of oneself and others: an fMRI study.

The ability to make judgments about mental states is critical to social interactions. Simulation theory suggests that the observer covertly mimics the activity of the observed person, leading to shared states of mind between the observer and the person observed. We tested this hypothesis by investigating the neural networks activated while subjects watched videos of themselves and of others lifting a box, and judged the beliefs of the actors about the weight of the box. A parietal premotor circuit was recruited during action perception, and the activity started earlier when making judgments about one's own actions as opposed to those of others. This earlier activity in action-related structures can be explained by simulation theory on the basis that when one observes one's own actions, there is a closer match between the simulated and perceived action than there is when one observes the actions of others. When the observers judged the actions to reflect a false belief, there was activation in the superior temporal sulcus, orbitofrontal, paracingulate cortex and cerebellum. We suggest that this reflects a mismatch between the perceived action and the predicted action's outcomes derived from simulation.

Brain Mapping↗
PubMed2002

History of the first synthesis of 2-deoxy-2-fluoro-D-glucose the unlabeled forerunner of 2-deoxy-2-[18F]fluoro-D-glucose.

The history of the first successful synthesis of 2-deoxy-2-fluoro-D-glucose (19FDG) is described. In many aspects, this substance imitates the behavior of naturally occurring glucose. For example, it is transported into the cells and is converted to the corresponding 6-phosphate by the enzyme hexokinase in a manner similar to glucose. Due to the presence of the fluorine atom at C-2, however, this phosphate derivative does not undergo further glycolysis but is metabolically trapped in the cell. Thanks to these properties, eight years after the synthesis of 19FDG, its 18F-labeled derivative was successfully used with positron emission tomography (PET).

Journal Article↗
PubMed1987

The analysis of marital interaction in cross-sectional twin data.

The effects on twin data of social interaction between spouses is examined. When social interaction leads to an increase in marital resemblance (eg through reciprocal imitation), the variance of married individuals is increased, compared to the variance of unmarried individuals. Furthermore, the expected correlations between concordant married twin pairs will be lower than the expected correlations between concordant unmarried twin pairs, with the discordant twin correlations being intermediate in value. It is therefore possible, in principle, to detect the effects of marital interaction without using either longitudinal data or data on spouse pairs. However, to be detectable in twin data, marital interaction must be strong, or must exhibit marked asymmetry of effects between males and females. Genotype x environment interaction can also produce heterogeneity of correlation between concordant married, discordant, and concordant unmarried twin pairs, when genetic and environmental effects interact with marital status. However, this will usually produce increased estimates of the genetic component of variance in unmarried twins, whereas marital interaction produces increased genetic variance in married twins.

Environment↗
PubMed2002

Performance of gesture in children with and without DCD: effects of sensory input modalities.

This study aimed to investigate the extent to which gesture performance depends on input modality and whether gestural development patterns differ in children with and without developmental coordination disorder (DCD). Therefore, development of limb gesture was studied in 140 children--105 control children (94 males, 11 females) and in 35 children with DCD (29 males, six females) divided into three age bands: 5 to 6 years, 7 to 8 years, and 9 to 10 years. Transitive gestural skills were investigated through four input modalities: Imitation, Visual plus Tactile, Visual, and Verbal. Results indicate that limb gestural skills in normally developing children follow a progressive maturation pattern: Imitation, Visual plus Tactile, and visual routes appear to mature before the verbal route and appear to be available earlier to enable the child to perform a correct gesture. The performance of children with DCD throughout the four modalities suggested a general maturational delay. When gestures were required through the Verbal modality, there was a specific deficit in using sensory-motor information and in integrating it into a motor representation. In the Verbal modality, children with DCD performed consistently worse than their control peers and the difference in performance tended to increase rather than improve with age.

Age Factors↗
PubMed2007

Nature of motor imitation problems in school-aged males with autism: how congruent are the error types?

This case-comparison study explores the underlying mechanisms of imitation problems in school-aged males with autism. Analysis of congruent error types in their imitation performance was made and compared with appropriate comparisons. Fifty-five males (eight low-functioning with autism: mean age 6y 2mo [SD 7.6mo]; 13 low-functioning with learning disabilities: mean age 6y 3mo [SD 2.8mo]; 17 high-functioning with autism: mean age 8y 9mo [SD 11mo]; and 17 typically developing: mean age 8y 8mo [SD 11.6mo]) were assessed on 18 single gestures and six sequences of hand postures. Imitation performance was videotaped for blind scoring on 21 possible errors by two independent observers. Results revealed that in both groups with autism, imitation required far more effort (more attempts) than in the comparison groups and was less precise (more spatial errors). Typical for low-functioning participants with autism was their less mature imaginary grip in transitive gestures. Typical for high-functioning participants with autism was their preference for immature mirror-image imitations. These observations support the assumption that the underlying mechanisms in motor imitation problems are linked more to the action production system and less to the action conceptual system or to behavioural problems. We postulate that the action production system is delayed rather than deficient.

Autistic Disorder↗
PubMed1999

Development of an instrument to measure manual praxis.

The purpose of this study was to develop an instrument to measure manual praxis by assessing areas of function considered important in learning and planning movement; use of tools, imitation of gesture, and motor sequencing. Participants included 362 healthy children aged between 3 and 12 years. Their parents completed a questionnaire on hand skills. Performance on all tasks improved with age. However, transitive gestures reached an early ceiling effect at around 5 years of age. Assessment of manual praxis from the parental questionnaire correlated with the child's directly measured competency during a test of object use (P<0.01) but not with the ability to imitate transitive gestures or enact a motor sequence with a 'novel' task. Children from schools where a higher number were eligible for free school meals because of low family income had more difficulty with imitation of gesture and motor sequencing to verbal and picture commands (P<0.001, P<0.05, P<0.05). They were neither disadvantaged in tool use nor in appreciation of extracorporeal space. The pattern of errors made in tool use and motor sequencing differed from those described in adults with acquired dyspraxia. These results suggest that assessment of manual praxis in clinical populations should include tool use, imitation of gesture, and motor sequencing and that they should not necessarily be regarded as measuring a unitary function.

Age Factors↗
PubMed1988

The Werther effect after television films: new evidence for an old hypothesis.

In this study it was possible to prove the Werther effect in suicides after watching fictional models for the first time. A twice-broadcast (1981, 1982) six-episode weekly serial showing the railway suicide of a 19-year-old male student provided a quasi-experimental ABABA design to investigate differential effects of suicide imitation. Imitation effects were most clearly observable in the groups whose age and sex were closet to those of the model. Over extended periods (up to 70 days after the first episode), the number of railway suicides increased most sharply among 15- to 19-year-old males (up to 175%); the effect steadily decreased in the older age groups, so that no effect was observable for males over 40 years and females over 30 years. Also, the imitation effects remained detectable for longer periods in the groups closest in age to the model. The increases observed after the first and second broadcast for males aged less than 30 years closely corresponded with the respective audience figures for the two showings.

Adolescent↗