In some cases they performed the movement under normal vision, but in other cases the monkey saw the exact opposite hand movement produced by a reversing prism
: When it reached to the right, it saw a reach movement to the left.
Reversal prism experiment: subjects followed the same procedure as previously described, except that during PRI they wore dove reversing prisms. The critical feedback difference between the 20-diopter displacing wedge prism and the reversing prism is as follows: Both prisms led to a 40 cm rightward optical displacement, and to overcome that error in both conditions participants have to make 40 cm leftward corrections.
Significant negative correlations were found between errors in SWM and the adaptation magnitudes of the reversing prism (r = -0.49, p = 0.001) and the displacement prism (r = -0.38, p = 0.01).
Since the evaluation of these processes requires the implementation of a strategic approach during the reversing prism, then its influence could be larger than during the procedural learning, which does not require further cognitive processing .
While the error reduction in response to perturbations produced by wedge prisms is carried primarily by procedural visuomotor recalibration, the correction following dove reversing prisms is largely the result of strategic corrections [9, 31, 32].
Participants viewed the target through the window which had either a clear crystal, a 20-diopter wedge prism that produces a lateral deviation of light to the right, or right-left dove reversing prisms that flip the visual image around the midline.
A successful realignment process with reversing prisms would require the brain to reverse the feedback rule used to update motor commands .