This idea of internal models as representations within the central nervous system that simulate the naturally occurring transformations between sensory signals and motor commands has become a central theoretical framework to the understanding of the neural control of movement [25], [26].
However, for earlier presentations of the stop-signal (>152 ms), there was a greater chance that the inhibition process could at least start before descending motor commands had been triggered.
During movement generation, the neural activations are currently only taken into account at the level of motor programs, since the decision to choose a motor schema is made by higher levels and motor commands have unambiguous relations to the associated motor programs.
In other words, the two viewing conditions did not differ much for short stop-signal intervals because at these times the inhibition process triggered by the stop-signal (see [ 23]) could not be finished before the descending motor commands had already been released.
For instance, the visual go-signal needs to be transformed into a motor command that has to be based on a visuospatial memory of where the target objects are in space and what to do with them.
Typically, learning the mapping from sensory inputs X to a motor command U has been conceptualized as a mapping U = ∑ i w i g i (X ), where g i are so-called basis functions and w i are the adjustable parameters of the mapping [2, 6, 15, 16].
We consider that the efferent copy of the motor command during action planning has a double function: first, it contributes to motor prediction (internal forward model); second, it anticipates the metabolic changes (ANS activation) produced by the upcoming movement.
Mechanical considerations indicate that without a modification of the motor command, contact force would have continued to increase due to the increasing spatial distance between the tangent surface and the expected curved path.
However, the motor and somatosensory pathways function in an overlapping manner: the somatosensory cortex sends efference copies of sensory commands to motor cortex prior to the motor command, and the motor cortex has inhibitory connections with the somatosensory cortex to modulate the somatosensory input [57].
