| Popis: |
Macaque monkeys can be trained to use a rake to retrieve out of reach food. This model offers an opportunity to understand how cortical neurons function during the acquisition of tool use. Three critical issues need to be tested: first, does the use of tools by naïve monkeys result in long-term changes in the cortical network that controls skilled hand use? Second, since the ventral premotor (area F5) and primary motor cortex (M1) have been shown to be particularly important for shaping the hand to grip particular objects, how does activity in these areas modulate during tool use, and how does this compare to activity during a precision grip task? Finally, since the rake task involves close observation of the experimenter’s movements, how do mirror neurons function during tool use? Using voxel based morphometry and structural MRI it was identified that learning to use a rake results in structural changes in the superior temporal sulcus, right second somatosensory area and right intraparietal sulcus, but was not detectable in either M1 or F5. Recording the activity of identified pyramidal tract neurons (PTNs) in M1 and F5 demonstrated that a majority of PTNs showed clear modulation for both the precision grip and rake tasks. M1 PTNs displayed direction-related tuning in their discharge, both during the rake task and in preparation for it. Conversely, F5 neurons showed less directionrelated activity, consistent with the more goal-related nature of F5 activity. In the mirror task, two distinct populations of mirror PTNs in M1 and F5 were encountered: ‘classic’ mirror neurons, which increased their activity when observing movement and suppression mirror neurons which decreased their activity during action observation. It was demonstrated that some of these neurons were active early in the rake task as the experimenter placed the reward prior to the monkey’s raking action. |
