Oliver Sacks vividly remembers meeting a man named Mr. MacGregor in St. Dunstan’s Hospital. MacGregor greeted Sacks and explained that other people told him that he leaned, “like the Leaning Tower of Pisa.” MacGregor walked around the room, leaning about twenty degrees to the left but insisting that he was perfectly straight. When Sacks showed MacGregor a tape of his movements, MacGregor, who’d had Parkinson’s disease in the past, immediately realized that he was leaning to one side.
Unlike the case with Jimmie G. (in which Sacks showing him his aged face), here Sacks seems to be doing the right thing by showing MacGregor a video of his lean—this is one case, in other words, in which disrupting a patient’s illusion is the ethical and helpful thing to do.
There are five main senses, Sacks notes, but there are also other ways for the mind to orient itself. One way of doing so is the vestibular system. The ears are arranged to function like carpenter’s levels—when one inner ear is higher or lower than the other, the mind senses that the body is unbalanced. But Mr. MacGregor’s case was far more complicated than a simple problem with the vestibular system. MacGregor leaned to one side because, although his vestibular, proprioceptive, and visual systems functioned normally, his mind couldn't integrate these three systems, due to the effects of Parkinson’s.
Sacks has already discussed proprioception earlier; here, he’ll discuss the vestibular system, located in the inner ears, which allows people to grasp their own orientation without relying on their five senses to do so. Much like Dr. P. in the first chapter, MacGregor suffers from a problem of perception—his brain experiences all the sensory data from the visual, vestibular, and proprioceptive systems, but can’t translate this information into normal perception.
To understand Mr. MacGregor’s condition, Sacks says, we can look to the work of the great neurologist Purdon Martin, who argued that one of the mind’s roles is to integrate sensory data from the visual, proprioceptive, and vestibular systems. People with Parkinson’s, however, lack the ability to integrate the data, meaning that they might lose their balance while doing something as simple as closing their eyes.
Parkinson’s disease causes the long-term degeneration of the nervous system—in the case of Mr. MacGregor, for instance, Parkinson’s disease renders MacGregor’s brain incapable of interpreting sensory data.
While talking with Sacks about his condition, Mr. MacGregor proposed using a level surface, his glasses, to orient himself. He and Sacks experimented with hanging a tiny pendulum on his glasses, so that he could visually assess his orientation whenever he needed to. These glasses later became popular in the hospital, since there were other Parkinson’s patients who could use them to stand and walk straight.
Like many of the chapters, this chapter ends with Sacks using unconventional means to train Mr. MacGregor to cope with his new condition. MacGregor has to rely more than usual on his five senses (in this case, sight) to determine if he’s standing straight or not, but in doing so, he regains his posture, and a semblance of a normal life.