Suggestive evidence for a forward model of the arm in the monkey motor cortex

To test an idea that neurons in the motor cortex encodes a future state of the arm, we constructed a plausible model using arm state-related variables to explain neuronal activity, and applied a multiple linear regression analysis. We found that the model fit was fairly good with a mean determination coefficient of 0.57 for analyzed 231 neurons and that neuronal activity preceded the actual movement of the arm with 66 ms on average. Presuming that the brain follows optimal feed back control theory, these findings suggest that the motor cortex may contain a forward model of the arm.