Mistakes that affect others: an fMRI study on processing of own errors in a social context.

In social contexts, errors have a special significance and often bear consequences for others. Thinking about others and drawing social inferences in interpersonal games engages the mentalizing system. We used neuroimaging to investigate the differences in brain activations between errors that affect only agents themselves and errors that additionally influence the payoffs of interaction partners. Activation in posterior medial frontal cortex (pMFC) and bilateral insula was increased for all errors, whereas errors that implied consequences for others specifically activated medial prefrontal cortex (mPFC), an important part of the mentalizing system. The results demonstrate that performance monitoring in social contexts involves additional processes and brain structures compared with individual performance monitoring where errors only have consequences for the person committing them. Taking into account how one's behavior may affect others is particularly crucial for adapting behavior in interpersonal interactions and joint action.

Spatial and effector processing in the human parietofrontal network for reaches and saccades.

It is generally accepted that interactions between parietal and frontal cortices subserve the visuomotor processing for eye and hand movements. Here, we used a sequential-instruction paradigm in 3-T functional MRI to test the processing of effector and spatial signals, as well as their interaction, as a movement is composed and executed in different stages. Subjects prepared either a saccade or a reach following two successive visual instruction cues, presented in either order. One cue instructed which effector to use (eyes, right hand); the other signaled the spatial goal (leftward vs. rightward target location) of the movement. During the first phase of the prepared movement, after cueing of either goal or effector information, we found significant spatial goal selectivity but no effector specificity along the parietofrontal network. During the second phase of the prepared movement, when both goal and effector information were available, we found a large overlap in the neural circuitry involved in the planning of eye and hand movements. Gradually distributed along this network, we observed clear spatial goal selectivity and limited, but significant, effector specificity. Regions in the intraparietal sulcus and the dorsal premotor cortex were selective to both goal location and motor effector. Taken together, our results suggest that the relative weight of spatial goal and effector selectivity changes along the parietofrontal network, depending on the status of the movement plan.

Cerebral correlates of motor imagery of normal and precision gait.

We have examined the cerebral structures involved in motor imagery of normal and precision gait (i.e., gait requiring precise foot placement and increased postural control). We recorded cerebral activity with functional magnetic resonance imaging while subjects imagined walking along paths of two different widths (broad, narrow) that required either normal gait, or exact foot placement and increased postural control. We used a matched visual imagery (VI) task to assess the motor specificity of the effects, and monitored task performance by recording imagery times, eye movements, and electromyography during scanning. In addition, we assessed the effector specificity of MI of gait by comparing our results with those of a previous study on MI of hand movements. We found that imagery times were longer for the narrow path during MI, but not during VI, suggesting that MI was sensitive to the constraints imposed by a narrow walking path. Moreover, MI of precision gait resulted in increased cerebral activity and effective connectivity within a network involving the superior parietal lobules, the dorsal precentral gyri, and the right middle occipital gyrus. Finally, the cerebral responses to MI of gait were contiguous to but spatially distinct from regions involved in MI of hand movements. These results emphasize the role of cortical structures outside primary motor regions in imagining locomotion movements when accurate foot positioning and increased postural control is required.

Integration of target and effector information in the human brain during reach planning.

To plan a reaching movement, the brain must integrate information about the location of the target with information about the limb selected for the reach. Here, we applied rapid event-related 3-T fMRI to investigate this process in human subjects (n = 16) preparing a reach following two successive visual instruction cues. One cue instructed which arm to use; the other cue instructed the location of the reach target. We hypothesized that regions involved in the integration of target and effector information should not only respond to each of the two instruction cues, but should respond more strongly to the second cue due to the added integrative processing to establish the reach plan. We found bilateral regions in the posterior parietal cortex, the premotor cortex, the medial frontal cortex, and the insular cortex to be involved in target-arm integration, as well as the left dorsolateral prefrontal cortex and an area in the right lateral occipital sulcus to respond in this manner. We further determined the functional properties of these regions in terms of spatial and effector specificity. This showed that the posterior parietal cortex and the dorsal premotor cortex specify both the spatial location of a target and the effector selected for the response. We therefore conclude that these regions are selectively engaged in the neural computations for reach planning, consistent with the results from physiological studies in nonhuman primates.

Motor imagery of gait: a quantitative approach.

Motor imagery (MI) is widely used to study cognitive aspects of the neural control of action. Prior studies were mostly centred on hand and arm movements. Recently a few studies have used imagery tasks to explore the neurophysiology of human gait, but it remains unclear how to ascertain whether subjects actually perform imagery of gait as requested. Here we describe a new experimental protocol to quantify imagery of gait, by behaviourally distinguishing it from visual imagery (VI) processes and by showing its temporal correspondence with actual gait. Fourteen young healthy subjects performed two imagery tasks and an actual walking (AW) task. During both imagery tasks subjects were sitting on a chair and faced a computer screen that presented photographs of walking trajectories. During one task (MI), subjects had to imagine walking along the walking trajectory. During the other task (VI), subjects had to imagine seeing a disc moving along the walking trajectory. During the AW task, subjects had to physically walk along the same walking trajectory as presented on the photographs during the imagery tasks. We manipulated movement distance by changing the length of the walking trajectory, and movement difficulty by changing the width of the walking trajectory. Subjects reported onset and offset of both actual and imagined movements with a button press. The time between the two button presses was taken as the imagined or actual movement time (MT). MT increased with increasing path length and decreasing path width in all three tasks. Crucially, the effect of path width on MT was significantly stronger during MI and AW than during VI. The results demonstrate a high temporal correspondence between imagined and AW, suggesting that MI taps into similar cerebral resources as those used during actual gait. These results open the possibility of using this protocol for exploring neurophysiological correlates of gait control in humans.

Does egocentric mental rotation elicit sex differences?

Mental rotation tests traditionally show a male performance advantage. Some neuroimaging studies have reported sex-specific cortical activation patterns during mental rotation. However, these experiments used abstract stimuli and some studies did not systematically exclude performance as a confounding variable. The mental rotation of hands and hand-related objects, compared to abstract objects, is known to evoke an egocentric motor strategy. In this study, we used fMRI to explore potential gender-specific cortical activation patterns for the mental rotation of hands and tools in a sample with an adequate and equal performance for men and women. We found a common neural substrate for men and women comprising superior parietal lobe, dorsolateral premotor cortex, and extrastriate occipital areas, compatible with an egocentric motor strategy for the mental rotation of hands and tools. Sex differences were modest and limited to the mental rotation of hands. Women recruited more left ventral premotor cortex, which could imply that women rely more on imitation or use more perceptual comparisons. Men, on the other hand, drafted more the lingual gyrus, possibly referring to more extensive semantic or early visual processing. We conclude that men and women use a very similar motor strategy during egocentric mental rotation with a potential gender-specific accent.