Many object-related actions can be recognized by their sound. We found neurons in monkey premotor cortex that discharge when the animal performs a specific action and when it hears the related sound. Most of the neurons also discharge when the monkey observes the same action. These audiovisual mirror neurons code actions independently of whether these actions are performed, heard, or seen. This discovery in the monkey homolog of Broca's area might shed light on the origin of language: audiovisual mirror neurons code abstract contents—the meaning of actions—and have the auditory access typical of human language to these contents.

Many object-related actions can be recognized both by their sound and by their vision. Here we describe a population of neurons in the ventral premotor cortex of the monkey that discharge both when the animal performs a specific action and when it hears or sees the same action performed by another individual. These 'audiovisual mirror neurons' therefore represent actions independently of whether these actions are performed, heard or seen. The magnitude of auditory and visual responses did not differ significantly in half the neurons. A neurometric analysis revealed that based on the response of these neurons, two actions could be discriminated with 97% accuracy.

The capacity to use tools is a fundamental evolutionary achievement. Its essence stands in the capacity to transfer a proximal goal (grasp a tool) to a distal goal (e.g., grasp food). Where and how does this goal transfer occur? Here, we show that, in monkeys trained to use tools, cortical motor neurons, active during hand grasping, also become active during grasping with pliers, as if the pliers were now the hand fingers. This motor embodiment occurs both for normal pliers and for ''reverse pliers,'' an implement that requires finger opening, instead of their closing, to grasp an object. We conclude that the capacity to use tools is based on an inherently goal-centered functional organization of primate cortical motor areas.neurophysiology ͉ tool use ͉ goal coding ͉ motor act

In the ventral premotor cortex of the macaque monkey, there are neurons that discharge both during the execution of hand actions and during the observation of the same actions made by others (mirror neurons). In the present study, we show that a subset of mirror neurons becomes active during action presentation and also when the final part of the action, crucial in triggering the response in full vision, is hidden and can therefore only be inferred. This implies that the motor representation of an action performed by others can be internally generated in the observer's premotor cortex, even when a visual description of the action is lacking. The present findings support the hypothesis that mirror neuron activation could be at the basis of action recognition.

Umilta MA, Brochier T, Spinks RL, Lemon RN. Simultaneous recording of macaque premotor and primary motor cortex neuronal populations reveals different functional contributions to visuomotor grasp. J Neurophysiol 98: 488 -501, 2007. First published February 28, 2007 doi:10.1152/jn.01094.2006. To understand the relative contributions of primary motor cortex (M1) and area F5 of the ventral premotor cortex (PMv) to visually guided grasp, we made simultaneous multiple electrode recordings from the hand representations of these two areas in two adult macaque monkeys. The monkeys were trained to fixate, reach out and grasp one of six objects presented in a pseudorandom order. In M1 326 task-related neurons, 104 of which were identified as pyramidal tract neurons, and 138 F5 neurons were analyzed as separate populations. All three populations showed activity that distinguished the six objects grasped by the monkey. These three populations responded in a manner that generalized across different sets of objects. F5 neurons showed object/grasp related tuning earlier than M1 neurons in the visual presentation and premovement periods. Also F5 neurons generally showed a greater preference for particular objects/grasps than did M1 neurons. F5 neurons remained tuned to a particular grasp throughout both the premovement and reach-to-grasp phases of the task, whereas M1 neurons showed different selectivity during the different phases. We also found that different types of grasp appear to be represented by different overall levels of activity within the F5-M1 circuit. Altogether these properties are consistent with the notion that F5 grasping-related neurons play a role in translating visual information about the physical properties of an object into the motor commands that are appropriate for grasping, and which are elaborated within M1 for delivery to the appropriate spinal machinery controlling hand and digit muscles.

The COVID-19 pandemic has dramatically changed the nature of our social interactions. In order to understand how protective equipment and distancing measures influence the ability to comprehend others’ emotions and, thus, to effectively interact with others, we carried out an online study across the Italian population during the first pandemic peak. Participants were shown static facial expressions (Angry, Happy and Neutral) covered by a sanitary mask or by a scarf. They were asked to evaluate the expressed emotions as well as to assess the degree to which one would adopt physical and social distancing measures for each stimulus. Results demonstrate that, despite the covering of the lower-face, participants correctly recognized the facial expressions of emotions with a polarizing effect on emotional valence ratings found in females. Noticeably, while females’ ratings for physical and social distancing were driven by the emotional content of the stimuli, males were influenced by the “covered” condition. The results also show the impact of the pandemic on anxiety and fear experienced by participants. Taken together, our results offer novel insights on the impact of the COVID-19 pandemic on social interactions, providing a deeper understanding of the way people react to different kinds of protective face covering.

During object grasp, a coordinated activation of distal muscles is required to shape the hand in relation to the physical properties of the object. Despite the fundamental importance of the grasping action, little is known of the muscular activation patterns that allow objects of different sizes and shapes to be grasped. In a study of two adult macaque monkeys, we investigated whether we could distinguish between EMG activation patterns associated with grasp of 12 differently shaped objects, chosen to evoke a wide range of grasping postures. Each object was mounted on a horizontal shuttle held by a weak spring (load force 1-2 N). Objects were located in separate sectors of a "carousel," and inter-trial rotation of the carousel allowed sequential presentation of the objects in pseudorandom order. EMG activity from 10 to 12 digit, hand, and arm muscles was recorded using chronically implanted electrodes. We show that the grasp of different objects was characterized by complex but distinctive patterns of EMG activation. Cluster analysis shows that these object-related EMG patterns were specific and consistent enough to identify the object unequivocally from the EMG recordings alone. EMG-based object identification required a minimum of six EMGs from simultaneously recorded muscles. EMG patterns were consistent across recording sessions in a given monkey but showed some differences between animals. These results identify the specific patterns of activity required to achieve distinct hand postures for grasping, and they open the way to our understanding of how these patterns are generated by the central motor network.

The selectivity for object-specific grasp in local field potentials (LFPs) was investigated in two awake macaque monkeys trained to observe, reach out, grasp and hold one of six objects presented in a pseudorandom order. Simultaneous, multiple electrode recordings were made from the hand representations of primary motor cortex (M1) and ventral premotor cortex (area F5). LFP activity was well developed during the observation and hold periods of the task, especially in the beta-frequency range (15-30 Hz). Selectivity of LFP activity for upcoming grasp was rare in the observation period, but common during stable grasp. The majority of M1 (90 of 92) and F5 (81of 97) sites showed selectivity for at least one frequency, which was maximal in the beta range but also present at higher frequencies (30 -50 Hz). When the LFP power associated with grasp of a specific object was large in the beta-frequency range, it was usually of low power in the higher 30 -50 Hz range, and vice-versa. Simple hook grips involving flexion of one or more fingers were associated with large beta power, whereas more complex grips involving the thumb (e.g., precision grip) were associated with small beta power. At many M1 sites, there was a highly significant inverse relationship between the tuning of spikes (including those of identified pyramidal tract neurons) and beta-range LFP for different grasps, whereas a positive correlation was found at higher frequencies (30 -50 Hz). High levels of beta LFP and low pyramidal cell spike rate may reflect a common mechanism used to control motor set during different types of grasp.