Dissociation is neurological mode activated in case of immediate mortal danger. Animals use it also. For example, when cat catches mouse, mouse goes in dissociation mode because he believes cat will kill him. So he plays dead. Movement stops, breathing diminishes, blood goes from limbs to vital organs, digestion and urination slows down.
Dopamine is being inhibited by adrenaline. Now, mouse doesn’t fake dissociation, he really can’t move his body. Eventually, if cat looses interest in half dead, dissociated mouse, she goes away. Suddenly, mouse’s brain declares the threat is gone and terminates dissociation. Mouse is alive and mobile again.
Similarly, recovery from Parkinson’s occurs when one’s brain declares it is safe after all and thus terminates dissociation. Some do it in small steps, day by day, some on the other hand, do it more swiftly, in one or two strokes.