In the 1960s, surgeon Robert White experimented with a surgical procedure which would transplant a head from one monkey to another. After 3 years of experiments, the surgery was “successfully” completed.
When the surgery was complete and the monkey came out of the anaesthetic it could move it’s facial muscles, it could be fed and follow movements with it’s eyes. Of course, with a severed spinal cord it was paralysed from the neck down, but the operation was considered a success.
[Viewer discretion is advised if you are squeamish about bizarre surgical procedures and weird medical tests...]