As a temporary New Yorker, I am experiencing firsthand the endless stimuli begging for attention on the streets of this great city. Take an imaginary stroll down the avenue of your choosing. Envision the crosswalks, cars, poles, pets, people, and tourists (yes, people and tourists are different obstacles) that you must dodge to get where you are going. Needless to say, the ability to pay attention is much more than a convenient attribute—it is, in fact, necessary for survival.
In our society, if you struggle to pay attention, we prod you to “focus!” If the problem persists, a doctor may diagnose you with Attention Deficit Disorder (ADD). ADD is far from a doomsday diagnosis, and with appropriate treatment it can be easily managed. But imagine if your inability to pay attention were so pervasive that you couldn’t attend to anything—anything at all—in one-half of your surroundings. This is the case for a small subset of the population suffering from hemispatial neglect, a disabling condition colloquially known as “left neglect.”
Individuals suffering from left neglect cannot process stimuli from one-half of the world and, as a natural consequence, neglect that side of the world entirely. This condition usually results from a stroke. Consider for a moment how this might affect your daily life. When totally ignoring the left side of your body, you would shave only the right side of your beard, or apply makeup to only the right side of your face. To be clear, left neglect is unrelated to vision—a patient with left neglect may also have 20-20 eyesight.
Patients who present with symptoms of left neglect may be asked to draw a clock. If suffering from the disorder, the patient will draw only one-half of the clock. Many times a patient will use only one sleeve of a jacket or not touch the food on one half of a dinner plate. In severe cases, a person might ignore large objects or even people speaking to them if the speaker is positioned to the person’s left side. To further complicate matters, the patient has limited insight into his or her condition. Individuals suffering from left neglect think drawings are complete, beards are completely shaven, and make-up is evenly applied.
Left neglect results from damage to the parietal cortex of the brain’s right hemisphere, meaning the injury is opposite of the resulting disability. Right neglect isn’t as much of a concern in the clinical world. A patient may have an injury on the left side of his brain, but there are many “back up” circuits available to compensate for the disability. Your right parietal cortex isn’t so lucky; once damaged, it must undergo professional long-term rehabilitation in the hopes of regaining full function.
The good news is that neuroscientists are working hard to discover and implement effective treatments for these patients. Some of the widely accepted therapies include continually instructing patients to gaze into the neglected space, almost forcing their attention, and stimulating appendages on the neglected side.
Recently, some doctors and scientists began exploring the use of direct brain stimulation on the non-injured side of the brain. This approach hinges on the theory that the healthy side of the brain is overstimulated after a stroke and this effect may contribute to the neglect. No therapies have proven perfect for this population, however.
So next time you are a little distracted on a city street, think twice about what that really means, and be thankful that your jacket is covering both shoulders.
Hemispatial neglect: Subtypes, neuroanatomy, and disability.
Buxbaum LJ, Ferraro MK, Veramonti T, Farne A, Whyte J, Ladavas E, Frassinetti F, Coslett HB.
Neurology. 2004; (5):749-56.
A behavioral analysis of spatial neglect and its recovery after stroke.
Jennifer Rengachary, Biyu J. He, Gordon L. Shulman, and Maurizio Corbetta
Front Hum Neurosci. 2011; 5: 29.
Rehabilitation approaches to hemineglect.
The Neurological Institute of New York, Columbia University Medical Center, New York, 10032, USA.