Angela Sirigu

The Mental Representation of Hand Movements After Parietal Cortex Damage

Recent neuroimagery findings showed that the patterns of cerebral activation during the mental rehearsal of a motor act are similar to those produced by its actual execution. This concurs with the notion that part of the distributed neural activity taking place during movement involves internal simulations, but it is not yet clear what specific contribution the different brain areas involved bring to this process. Here, patients with lesions restricted to the parietal cortex were found to be impaired selectively at predicting, through mental imagery, the time necessary to perform differentiated finger movements and visually guided pointing gestures, in comparison to normal individuals and to a patient with damage to the primary motor area. These results suggest that the parietal cortex is important for the ability to generate mental movement representations.

Promoting social behavior with oxytocin in high-functioning autism spectrum disorders

Social adaptation requires specific cognitive and emotional competences. Individuals with high-functioning autism or with Asperger syndrome cannot understand or engage in social situations despite preserved intellectual abilities. Recently, it has been suggested that oxytocin, a hormone known to promote mother-infant bonds, may be implicated in the social deficit of autism. We investigated the behavioral effects of oxytocin in 13 subjects with autism. In a simulated ball game where participants interacted with fictitious partners, we found that after oxytocin inhalation, patients exhibited stronger interactions with the most socially cooperative partner and reported enhanced feelings of trust and preference. Also, during free viewing of pictures of faces, oxytocin selectively increased patients’ gazing time on the socially informative region of the face, namely the eyes. Thus, under oxytocin, patients respond more strongly to others and exhibit more appropriate social behavior and affect, suggesting a therapeutic potential of oxytocin through its action on a core dimension of autism.

Movement Intention After Parietal Cortex Stimulation in Humans

Consciousness and Intention Where in the brain are our intentions formed and how do we become aware of these intentions? Desmurget et al. (p. 811; see the Perspective by Haggard) investigated the effect of direct cortical stimulation of parietal and premotor regions in patients undergoing brain surgery for tumor removal. Stimulation of the parietal lobe provoked the conscious experience of wanting to move the upper limb, lips, or tongue without any concomitant motor activity. When stimulation intensity was increased, patients believed that they had actually moved or talked, but again no muscle activity was detected. When, however, the premotor region of the frontal lobes was stimulated, real complex multijoint movements were induced. However, patients did not experience these movements as produced by a conscious internal act of will. Indeed, they were not even aware that they had moved. Increasing stimulation intensity increased the amplitude or complexity of the movement but never made it reach consciousness. Stimulation of the parietal cortex causes subjects to report having moved, even in the absence of actual motor responses. Parietal and premotor cortex regions are serious contenders for bringing motor intentions and motor responses into awareness. We used electrical stimulation in seven patients undergoing awake brain surgery. Stimulating the right inferior parietal regions triggered a strong intention and desire to move the contralateral hand, arm, or foot, whereas stimulating the left inferior parietal region provoked the intention to move the lips and to talk. When stimulation intensity was increased in parietal areas, participants believed they had really performed these movements, although no electromyographic activity was detected. Stimulation of the premotor region triggered overt mouth and contralateral limb movements. Yet, patients firmly denied that they had moved. Conscious intention and motor awareness thus arise from increased parietal activity before movement execution.

Regret and its avoidance: a neuroimaging study of choice behavior

Human decisions can be shaped by predictions of emotions that ensue after choosing advantageously or disadvantageously. Indeed, anticipating regret is a powerful predictor of future choices. We measured brain activity using functional magnetic resonance imaging (fMRI) while subjects selected between two gambles wherein regret was induced by providing information about the outcome of the unchosen gamble. Increasing regret enhanced activity in the medial orbitofrontal region, the anterior cingulate cortex and the hippocampus. Notably, across the experiment, subjects became increasingly regret-aversive, a cumulative effect reflected in enhanced activity within medial orbitofrontal cortex and amygdala. This pattern of activity reoccurred just before making a choice, suggesting that the same neural circuitry mediates direct experience of regret and its anticipation. These results demonstrate that medial orbitofrontal cortex modulates the gain of adaptive emotions in a manner that may provide a substrate for the influence of high-level emotions on decision making.

Action prediction in the cerebellum and in the parietal lobe

The ability of the central nervous system to predict motor behaviour is a central issue in experimental and computational studies of motor control. The parietal cortex and the cerebellum have been proposed to play a role in sensorimotor prediction. Here we discuss the roles of these two brain regions in various aspects of sensorimotor prediction according to results of recent empirical studies using a variety of techniques including electrophysiology, psychophysics, functional neuroimaging and the investigation of neurological patients.

A parietal-premotor network for movement intention and motor awareness

It is commonly assumed that we are conscious of our movements mainly because we can sense ourselves moving as ongoing peripheral information coming from our muscles and retina reaches the brain. Recent evidence, however, suggests that, contrary to common beliefs, conscious intention to move is independent of movement execution per se. We propose that during movement execution it is our initial intentions that we are mainly aware of. Furthermore, the experience of moving as a conscious act is associated with increased activity in a specific brain region: the posterior parietal cortex. We speculate that movement intention and awareness are generated and monitored in this region. We put forward a general framework of the cognitive and neural processes involved in movement intention and motor awareness.

The role of sensorimotor experience in object recognition : a case of multimodal agnosia

Object recognition was studied in a 19-yr-old male patient who presented severe multimodal amnesia and agnosia without significant intellectual, linguistic or perceptual deficits. Bilateral temporal lobe lesions involved medial, polar and anterior infero-temporal structures. Although visual recognition was impaired to various extents for all categories of objects, preservation of certain capacities were demonstrated. In particular, the patient was able to determine specifically how to manipulate certain objects, in spite of his incapacity to define their function or their context of utilization. It is argued that object recognition involves different processing modes such that when direct access to representations of an object is impaired, sensorimotor information activated via alternative cortical and subcortical pathways may provide a limited mechanism for recognition.

Cortical reorganization in motor cortex after graft of both hands.

Cortical organization shifts after sensory deprivation, but the reversibility of this reorganization has not been studied. Here, using functional magnetic resonance imaging (fMRI), we investigated the dynamics of cortical reorganization in a patients motor cortex before and after bilateral hand transplantation. We found that amputation-induced cortical reorganization was reversed following hand transplantation.

The neuropsychological pattern of corticobasal degeneration: Comparison with progressive supranuclear palsy and Alzheimer's disease

The pattern of cortical and subcortical neuropathologic lesions in corticobasal degeneration (CBD) should predict a specific cognitive profile in this disease.To characterize this profile and to determine its specificity by comparison with progressive supranuclear palsy (PSP) and senile dementia of the Alzheimers type (SDAT), we used an extensive neuropsychological battery assessing global efficiency, executive functions, various tests of encoding and retrieval, dynamic motor organization, and upper limb praxis. We compared the performance of patients with CBD (n equals 15) with that of controls (n equals 19) matched for age and education, and with that of patients with PSP and SDAT (15 in each group), matched for severity of dementia and depression. Patients with CBD showed: (1) a moderate global deterioration; (2) a dysexecutive syndrome similar to that of patients with PSP and more severe than in SDAT; (3) explicit learning deficits, without retention difficulties and easily compensated by using the same semantic cues at encoding and retrieval as in PSP; this was in contrast with SDAT where cued recall and recognition were also impaired; (4) disorders of dynamic motor execution (temporal organization, bimanual coordination, control, and inhibition) similar to those of patients with PSP and not in SDAT; (5) asymmetric praxis disorders (posture imitation, symbolic gesture execution, and object utilization) that were not observed in PSP or SDAT. Patients with CBD show a specific neuropsychological pattern associating a dysexecutive syndrome, likely due to degeneration of the basal ganglia and prefrontal cortex, and asymmetric praxis disorders, which might be related to premotor and parietal lobe lesions. This neuropsychological profile may help to distinguish this condition clinically from other neurodegenerative diseases. NEUROLOGY 1995;45: 1477-1483

Brain, emotion and decision making: the paradigmatic example of regret.

Human decisions cannot be explained solely by rational imperatives but are strongly influenced by emotion. Theoretical and behavioral studies provide a sound empirical basis to the impact of the emotion of regret in guiding choice behavior. Recent neuropsychological and neuroimaging data have stressed the fundamental role of the orbitofrontal cortex in mediating the experience of regret. Functional magnetic resonance imaging data indicate that reactivation of activity within the orbitofrontal cortex and amygdala occurring during the phase of choice, when the brain is anticipating possible future consequences of decisions, characterizes the anticipation of regret. In turn, these patterns reflect learning based on cumulative emotional experience. Moreover, affective consequences can induce specific mechanisms of cognitive control of the choice processes, involving reinforcement or avoidance of the experienced behavior.