The recording of mirror neurons during tool use confirmed that this distinct set of visuomotor neurons has the same goal-relatedness as the other F5 purely motor neurons.
The present findings, by proving the goal-relatedness of F5 neurons, provide a very strong empirical validation to this proposal. The evidence, however, in favor of this assumption was rather indirect and based on nonsystematic studies.
#CHIMPANZEE HAND AXE CODE#
This suggestion was based on the assumption that neurons in F5 code the goal of motor acts. It has been suggested that the activation of F5 mirror neurons during the observation of motor acts allows the observer to understand the goal of the observed action ( 24). The capacity to learn tool use appears, therefore, to be based on two elements: the goal-centered organization of primate motor cortex and an appropriate interaction with the external world.įinally, it is well known that in area F5 there is a distinct set of neurons that discharge both during the execution and the observation of actions done by others (mirror neurons refs. As a consequence, the neurons that control hand closure are selected first, and those that control hand opening are selected subsequently. After learning to use the reverse pliers, the opposite connections, reinforced by the success of the tool-mediated motor acts, prevail. In a natural setting, daily interactions with objects reinforce the connections that lead to the desired goal, thus selecting first those neurons that control hand opening and then those that control hand closure. 15), would also send a corollary discharge to the goal-related F5 and F1g neurons. These movement-related neurons, besides sending their output to the spinal cord ( 20, 21) (see also ref. This correct movement selection may be accounted for if one admits that goal-related F5 and F1g neurons are synaptically connected with two different sets of motor cortex neurons controlling the opening and the closing of the hand, respectively. What could be the mechanism that allows a transformation of a goal into appropriate movements even when an opposite sequence of movements is necessary to achieve the goal? Our findings show that, after learning, the correct movement selection occurred immediately as soon as the monkey grasped one or the other type of pliers. Unit 199: peak force, averaged across 10 trials, 3.9 N and 9.3 N with normal and reverse pliers, respectively. Unit 210: peak force, averaged across 10 trials, 2.8 N and 10.2 N with normal and reverse pliers, respectively. With reverse pliers ( Lower), the neuron started to fire during the hand closure (trace down), reaching its maximum during hand opening.
Unit 199 ( Right) started to fire in normal pliers ( Upper) condition during hand opening (trace up), reaching its maximum at the beginning of the hand closure. With normal pliers ( Upper), Unit 210 ( Left) began to fire during hand closure (trace down), reaching the maximum at approximately the moment in which the food was grasped with the reverse pliers ( Lower), this unit started to fire with the hand opening (trace up), also reaching its maximum when the food was grasped. The values shown on the vertical axes indicate the potentiometer-measured voltage.
Trace down indicates that the hand closes, and the distance between handles decreases, whereas trace up indicates that the hand opens, and the distance between handles increases. The traces below each histogram indicate the instantaneous hand position (average of the voltage changes values occurred during neuronal recording) recorded with the potentiometer and expressed as a function of the distance between the pliers handles. Both rasters and histograms are aligned with the end of the grasping closure phase (asterisks). Rasters and histograms (10 trials) illustrate the neurons' discharge recorded during grasping with normal pliers ( Upper) and reverse pliers ( Lower). Activity of two neurons recorded in area F5.
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