CEREBELLAR ACTIVITY RELATED TO ACQUISITION OF
INTERNAL MODELS OF A NOVEL TOOL: IMPLICATIONS FROM AN FMRI STUDY ON HUMAN
SUBJECTS USING A COMPUTER MOUSE FOR THE FIRST TIME.
H. Imamizu*1, S. Miyauchi2, T. Tamada1,
T. Yoshioka1 and M. Kawato,1,3 1ERATO KDB, Kyoto, Japan; 2Communications
Research Lab., Hyogo, Japan; 3ATR Human Information Processing Research
Labs.
We applied functional MRI to compare the cerebellar activities in human subjects who use a computer mouse for the first time (novice subjects) with the cerebellar activities in subjects skilled with using the mouse (skilled subjects). A task for the subjects was to move a computer mouse so that the cursor would follow a randomly moving target on the screen in test periods while it was to pursue the moving target with their eyes and without hand or mouse movements in baseline periods. We used a correlation analysis to find regions that produced higher MR signals during the test periods than during the baseline periods. Results indicated that 1) when skilled subjects used the mouse, anterior parts of the cerebellum were active ipsilaterally to the used hand, and 2) when the novice subjects used the mouse, lateral posterior parts of the cerebellum were active bilaterally in addition to the anterior parts. Past neruophysiological and computational studies postulated that the anterior cerebellum acquires internal models that mimic the input-output properties of the musculoskeletal systems and that it contributes to rapid and smooth motor control. Thus, the activities in the anterior cerebellum are expected to be correlated to the hand movements. We already found the lateral posterior activities when the skilled subjects learned how to use a novel mouse in which a relationship between the mouse and its corresponding cursor was systematically altered in our previous studies (e.g., Imamizu et al., 1997, NeuroImage 5:S598). Based on this result, we have proposed a hypothesis that an internal model of the novel tool is acquired in the lateral posterior parts of the cerebellum. Results of the current study support this hypothesis by showing that the lateral posterior cerebellum plays an important role in acquiring an internal model of a general tool, i.e., an ordinal computer mouse, when the tool is novel to the subjects.