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16. Motor Actions and Tool Use > 16-8. Summary - Pg. Vol4-192

192 the cerebellum The final study mentioned here was one in which monkeys were trained to use a rake to obtain food rewards. All three monkeys tested (monkeys E, N, and F) learned to use the rake within the 14-day training period. Monkeys E and F used their right hand to rake and their left hand to retrieve the food reward. Monkey N used both hands to both rake and retrieve the food. They were examined repeat- edly in a 4-T scanner for a six-week period: two weeks of habituation to the task, two weeks of intensive daily training, and a two-week post-training period. As task performance improved, structural MRI scans revealed significant increases in the signal intensity of gray matter in the cerebral cortex. These increases were the most significant in the right superior temporal sulcus, right second somatosensory area, and right intraparietal sulcus, with less significant increases in these same regions of the left hemisphere. Interestingly, signal increases were also observed in the white matter of the bilateral cerebellar hemispheres in lobule V (Quallo et al., 2009). An observed enhancement of structural MRI signals indicated an increase in the volume of gray and/or white matter. What really underlies the just-described cerebellar enhancement is still unknown, but it is in keeping with long-lasting plas- ticity in cerebellar circuits that play a role in cerebellar learning. 16-8 Summary Neuronal mechanisms for motor actions have been studied by unit recording of Purkinje cell discharge in monkeys and brain imaging in monkeys and humans. Mirror neurons in the premotor cortex appear to be a part of the neuronal systems controlling motor actions. To advance further, it will be particularly important to find neural substrates of the psychological concepts of body schema and motor schema. Complex motor actions such as an actor's performance on the stage typi- cally integrate movements with perceptual and conceptual behavior. This indicates that neural mechanisms for motor actions must involve both motor and cognitive domains, as discussed in the next chapter.