Representation of the observer’s predicted outcome value in mirror and nonmirror neurons of macaque F5 ventral premotor cortex

Both the populations of F5 mirror neurons and nonmirror neurons represent the predicted value of an outcome resulting from the observation of a grasping action. Value-dependent motivation, arousal, and attention directed at the observed action do not provide a better explanation for this representation. The population activity’s metric suggests an optimal scaling of value representation to task setting.

Anatomical Plasticity of the Distal Forelimb Projection of the Ventral Premotor Cortex Four weeks After Primary Motor Cortex Injury

Brain injury affecting the isocortical frontal cortex is a common pathological occurrence. Many patients report severe deficits to functions of daily living. However, there is a variable degree of motor recovery that occurs with some individuals recovering astounding degrees of motor recovery while others have not. This variability has led researchers into investigating the possible mechanisms for this variability. Recently, several non-human primate studies have shed light on the possibility of spared, ipsilesional motor area taken over the lost function to the damaged cortex. Unfortunately, these studies have focused on long-term adaption ranging from 5months to one year post injury. In this present study, we are the first use rigorous stereological quantification to show that significant neuroplastic changes in the form of changes to neuroanatomical connections between distant cortical area occurs at a very early time point of 4 weeks post injury. Much like the Dancause study in 2005, we found that ishemic damage to the distal forelimb area (DFL) of the primary motor cortex (M1) induced plastic changes between the DFL of the ventral premotor cortex (PMv) and area 1/2 of the somatosensory cortex. Indeed, we found a nearly 2 fold increase in the number of boutons between PMV and area 1/2. Additionally, labeled fibers from PMv change direction from their normal termination within M1 and traveled in a ventral posterior direction toward the somatosensory cortex. Also of interest, several labeled fibers actually traveled through the glial scar of M1 toward the somatosensory cortex. These data demonstrate that a massive neuroplastic response has occurred following an ischemic insult to the DFL of M1. These data may suggest that the brain may be undergoing an attempt to re-establish a degree of motor and or sensory control to compensate for the lost function due to the injury.

Movement initiation and grasp representation in premotor and primary motor cortex mirror neurons

Pyramidal tract neurons (PTNs) within macaque rostral ventral premotor cortex (F5) and primary motor cortex (M1) provide direct input to spinal circuitry and are critical for skilled movement control, but surprisingly, can also be active during passive action observation. We recorded from single neurons, including identified PTNs in the hand and arm area of primary motor cortex (M1) (n=189), and in premotor area F5 (n=115) of two adult male macaques, while they executed, observed, or simply withheld (NoGo) reach-to-grasp and hold actions. We found that F5 maintains a more sustained, similar representation of grasping actions during both execution and observation. In contrast, although some M1 neurons mirrored during the grasp and hold, M1 population activity during observation contained signatures of a withholding state. This suggests that M1 and its output may dissociates signals required for the initiation of movement from those associated with the representation of grasp in order to flexibly guide behaviour.Significance StatementVentral premotor cortex (area F5) maintains a similar representation of grasping actions during both execution and observation. Primary motor cortex and its outputs dissociate between movement and non-movement states.

Predictive coding account of action perception: Evidence from effective connectivity in the Action Observation Network

Visual perception of actions is supported by a network of brain regions in the occipito-temporal, parietal, and premotor cortex in the primate brain, known as the Action Observation Network (AON). Although there is a growing body of research that characterizes the functional properties of each node of this network, the communication and direction of information flow between the nodes is unclear. According to the predictive coding account of action perception, this network is not a purely feedforward system but has feedback connections through which prediction error signals are communicated between the regions of the AON. In the present study, we investigated the effective connectivity of the AON in an experimental setting where the human subjects’ predictions about the observed agent were violated, using fMRI and Dynamical Causal Modeling (DCM). We specifically examined the influence of the lowest and highest nodes in the AON hierarchy, pSTS and ventral premotor cortex, respectively, on the middle node, inferior parietal cortex during prediction violation. Our DCM results suggest that the influence on the inferior parietal node is through a feedback connection from ventral premotor cortex during perception of actions that violate people’s predictions.

Grasping Neurons in the Ventral Premotor Cortex of Macaques Are Modulated by Social Goals

Although it is established that F5 neurons can distinguish between nonsocial goals such as bringing food to the mouth for eating or placing it in a container, it is not clear whether they discriminate between social and nonsocial goals. Here, we recorded single-unit activity in the ventral premotor cortex of two female macaques and used a simple reach-to-grasp motor task in which a monkey grasped an object with a precision grip in three conditions, which only differed in terms of their final goal, that is, a subsequent motor act that was either social (placing in the experimenter's hand [“Hand” condition]) or nonsocial (placing in a container [“Container” condition] or bringing to the mouth for eating [“Mouth” condition]). We found that, during the execution of the grasping motor act, the response of a sizable proportion of F5 motor neurons was modulated by the final goal of the action, with some having a preference for the social goal condition. Our results reveal that the representation of goal-directed actions in ventral premotor cortex is influenced by contextual information not only extracted from physical cues but also from cues endowed with biological or social value. Our study suggests that the activity of grasping neurons in the premotor cortex is modulated by social context.