Leonardo Fogassi

From monkey mirror neurons to primate behaviours: possible 'direct' and 'indirect' pathways.

The discovery of mirror neurons (MNs), deemed to be at the basis of action understanding, could constitute the potential solution to the ‘correspondence problem’ between ones own and others action that is crucial for of imitative behaviours. However, it is still to be clarified whether, and how, several imitative phenomena, differing in terms of complexity and cognitive effort, could be explained within a unified framework based on MNs. Here we propose that MNs could differently contribute to distinct imitative behaviours by means of two anatomo-functional pathways, subjected to changes during development. A ‘direct mirror pathway’, directly influencing the descending motor output, would be responsible for neonatal and automatic imitation. This proposal is corroborated by some new behavioural evidences provided here. During development, the increased control of voluntary movements and the capacity to efficiently suppress automatic motor activation during action observation assign to the core MNs regions essentially perceptuo-cognitive functions. These functions would be exploited by an ‘indirect mirror pathway’ from the core regions of the MN system to prefrontal cortex. This latter would play a key role in parsing, storing and organizing motor representations, allowing the emergence of more efficient and complex imitative behaviours such as response facilitation and true imitation.

Randomized Trial of Observation and Execution of Upper Extremity Actions Versus Action Alone in Children With Unilateral Cerebral Palsy

Background. The properties of the mirror neuron system suggest a new type of upper limb (UL) rehabilitation in children with unilateral cerebral palsy (UCP), based on observation of action therapy followed by execution of a variety of observed movements (AOT). Objective. We tested the effects of AOT in the Upper Limb Children Action Observation Training (UP-CAT) trial. Methods. In a randomized, evaluator-blinded, block-designed trial, 24 UCP children with mild to moderate hand impairment were assigned to 2 groups. The experimental group observed, 1 hour per day for 3 consecutive weeks, video sequences of unimanual or bimanual goal-directed actions and subsequently executed observed actions with the hemiparetic UL or both ULs. The control group performed the same actions in the same order as the experimental sample, but had watched computer games. The Assisting Hand Assessment (AHA) scale was the primary outcome measure; the Melbourne assessment and ABILHAND-Kids were secondary ones. Outcomes were assessed at 1 week (T1), 8 weeks (T2), and 24 weeks (T3) after the end of the training. Results. The experimental group improved more (P = .008) in score changes for the AHA at the primary endpoints T1 (P = .008), T2 (P = .019), and T3 (P = .049). No between-group significant changes were found for ABILHAND-Kids or Melbourne assessment. Conclusions. UP-CAT improved daily UL activities in UCP children, suggesting a new rehabilitation approach based on a neurophysiological model of motor learning.

Neurological Principles and Rehabilitation of Action Disorders: Computation, Anatomy, and Physiology (CAP) Model

This chapter outlines the basic computational, anatomical, and physiological (CAP) principles underlying upper-limb actions, such as reaching for a cup and grasping it or picking up a key, inserting it into a lock, and turning it.

Individual and social learning processes involved in the acquisition and generalization of tool use in macaques.

Macaques can efficiently use several tools, but their capacity to discriminate the relevant physical features of a tool and the social factors contributing to their acquisition are still poorly explored. In a series of studies, we investigated macaques ability to generalize the use of a stick as a tool to new objects having different physical features (study 1), or to new contexts, requiring them to adapt the previously learned motor strategy (study 2). We then assessed whether the observation of a skilled model might facilitate tool-use learning by naive observer monkeys (study 3). Results of study 1 and study 2 showed that monkeys trained to use a tool generalize this ability to tools of different shape and length, and learn to adapt their motor strategy to a new task. Study 3 demonstrated that observing a skilled model increases the observers manipulations of a stick, thus facilitating the individual discovery of the relevant properties of this object as a tool. These findings support the view that in macaques, the motor system can be modified through tool use and that it has a limited capacity to adjust the learnt motor skills to a new context. Social factors, although important to facilitate the interaction with tools, are not crucial for tool-use learning.

The extended features of mirror neurons and the voluntary control of vocalization in the pathway to language

Abstract In this book it has been proposed that the mirror system can be a scaffold for building a language-ready brain, because of its property of matching action observation with action execution, a feature that can correspond to the “parity” requirement for communication. In this commentary we will first emphasize two properties of mirror neurons and motor cortex that may have contributed to language: the generalization of the property of understanding action goals and the capacity to decode the goal of action sequences. Then we will propose, based on recent behavioural and neurophysiological data in monkeys, that the vocalization in non-human primates could have reached a partial voluntary control, thus contributing to the emergence of a communicative system relying on the coordination of gestures and utterances.

Action observation network in childhood: A comparative fMRI study with adults

Very little is known about the action observation network and the mirror neuron system (AON/MNS) in children and its age-related properties compared with those observed in adults. In the present fMRI study we explored the activation of areas belonging to the AON/MNS in children and adults during observation of complex hand-grasping actions, as compared to observation of simple grasping acts executed with the left and the right hand, seen from a first person perspective. The results indicate that during the action observation tasks in children there was activation of a cortical network similar to that found in adults, including the premotor cortex, the posterior part of the inferior frontal gyrus and the posterior parietal lobe. However, the activation in children was more widespread and showed a higher inter-subject variability compared with adults. Furthermore, the activated network seems more lateralized to the left hemisphere in adults and more bilateral in children, with a linear growth of lateralization index as a function of age. Finally, in children the activation in the anterior intraparietal cortex (AIP) of each hemisphere was higher during observation of the contralateral hand (hand identity effect) and during the observation of complex actions relative to simple grasping acts, confirming the role of AIP for action-related hand identity previously described in adults. These results support the assumption that structure and size of action representations are sensitive to mechanisms of development and show physiological plasticity. These properties of the AON/MNS could constitute a powerful tool for spontaneous reorganization and recovery of motor deficits after brain injury in children and in adults, as well as for specific rehabilitation programmes.

Toward automated electrode selection in the electronic depth control strategy for multi-unit recordings

Multi-electrode arrays contain an increasing number of electrodes. The manual selection of good quality signals among hundreds of electrodes becomes impracticable for experimental neuroscientists. This increases the need for an automated selection of electrodes containing good quality signals. To motivate the automated selection, three experimenters were asked to assign quality scores, taking one of four possible values, to recordings containing action potentials obtained from the monkey primary somatosensory cortex and the superior parietal lobule. Krippendorffs alpha-reliability was then used to verify whether the scores, given by different experimenters, were in agreement. A Gaussian process classifier was used to automate the prediction of the signal quality using the scores of the different experimenters. Prediction accuracies of the Gaussian process classifier are about 80% when the quality scores of different experimenters are combined, through a median vote, to train the Gaussian process classifier. It was found that predictions based also on firing rate features are in closer agreement with the experimenters assignments than those based on the signal-to-noise ratio alone.

Reorganization of the Action Observation Network and Sensory-Motor System in Children with Unilateral Cerebral Palsy: An fMRI Study

Little is known about the action observation network (AON) in children with unilateral cerebral palsy (UCP). Using fMRI, we aimed to explore AON and sensory-motor network (SMN) in UCP children and compare them to typically developed (TD) children and analyse the relationship between AON (re-)organization and several neurophysiological and clinical measures. Twelve UCP children were assessed with clinical scales and transcranial magnetic stimulation (TMS). For the fMRI study, they underwent a paradigm based on observation of complex and simple object-manipulation tasks executed by dominant and nondominant hand. Moreover, UCP and TD children carried out a further fMRI session to explore SMN in both an active motor and passive sensory task. AON in the UCP group showed higher lateralization, negatively related to performances on clinical scales, and had greater activation of unaffected hemisphere as compared to the bilateral representation in the TD group. In addition, a good congruence was found between bilateral or contralateral activation of AON and activation of SMN and TMS data. These findings indicate that our paradigm might be useful in exploring AON and the response to therapy in UCP subjects.