In 2001, Mark Francis stumbled off a curb and fell, hitting his head and sustaining a traumatic brain injury. In the weeks after that, he noticed he wasn't perceiving the world as he used to. One day when he was trying to make a turn across two lanes of traffic, the once routine driving maneuver felt impossible. “I froze. There was too much visual movement going on—I could not keep track of it all. It was overwhelming,” says Francis, 68, a retired home remodeler from Boise, ID.
Other strange things were happening. When Francis looked at certain signs or pictures and icons on his computer, they had no meaning. “They were just artwork,” he says. Doing some online research, Francis came across a description of a condition called visual agnosia that sounded like what he was experiencing. It wasn't his eyesight that was the problem. His brain was having trouble processing what his eyes were seeing. “My ability to perceive the world went off the rails,” he says.
Agnosia is a rare neurologic condition that can manifest in different ways. In its visual form, people may be unable to recognize everyday objects such as keys or utensils, even though their vision is fine. They see the objects but have lost the ability to identify what they are or do. People with auditory agnosia can't recognize certain sounds, such as a siren or a baby crying, even though they can hear just fine. Those with a tactile form of agnosia can't recognize what they touch.
In an especially unusual form of agnosia called prosopagnosia, or face blindness, people can't recognize faces that should be familiar to them, such as those of family members or close friends. Other variations of the disorder include finger agnosia, which is the inability to distinguish one's own fingers, and motion agnosia, in which people can't perceive that an object is moving.
“Agnosia occurs as a result of brain damage through a stroke, dementia, traumatic brain injury, or perhaps even a developmental disorder,” says Marlene Behrmann, PhD, an associate professor of ophthalmology at the University of Pittsburgh who studies the condition. In some cases, agnosia may be preceded by a small stroke that may have gone unrecognized or undiagnosed. She and other researchers are trying to better understand the complex processes that occur in the brain when it collects incoming information from the senses, breaks it down, and reorganizes it so that we can then make sense of and interact with our environment. In agnosia, that “perception” is lacking in different ways, depending on the area of the damage.
In visual agnosia, the occipital region of the brain may be damaged; auditory agnosia may be caused by injury in the temporal region. Those regions “contain the pathways and machinery that connect sight and sound to the parts of the brain that interpret that information,” says Vijay Ramanan, MD, PhD, assistant professor of neurology at Mayo Clinic in Rochester, MN, who focuses on cognitive/behavioral neurology. But he adds that “the brain is highly integrated and complex, so nothing happens in isolation.”
Learning to Adapt
To diagnose agnosia, determine its underlying cause, and chart a way forward, doctors perform a thorough evaluation, including a neurologic examination and possibly other diagnostic tests such as a CT scan, an MRI, or a lumbar puncture. Patients can then work with occupational and physical therapists and social workers as needed to develop adaptive techniques. Someone with visual agnosia, for instance, might learn to keep objects in the same spot all the time, use labels, and stay organized, says Dr. Ramanan.
Besides categorizing agnosia by what sense is involved (visual, auditory, tactile), researchers also classify cases as apperceptive or associative, says Roy H. Hamilton, MD, FAAN, a behavioral neurologist at the University of Pennsylvania and president of the Society for Behavioral and Cognitive Neurology. In apperceptive agnosia, the brain is unable to reconstruct incoming sensory information so that it can be perceived. “In associative agnosia, you can put the information together, but you still can't recognize what you've got. It is perception stripped of meaning,” says Dr. Hamilton.
Agnosia is not itself a disease, Dr. Hamilton explains—it's a symptom of a neurologic problem, such as stroke, head trauma, or neurodegeneration. He sometimes sees people with visual agnosia resulting from a progressive and degenerative disease called posterior cortical atrophy, which damages the region in the back of the brain where visual and spatial information is processed.
An early sign of agnosia is thinking your eyesight is going bad because you can't find ordinary objects, such as keys. People often see an ophthalmologist first and are fitted for eyeglasses, says Dr. Hamilton. But glasses won't make a difference, since the problem of agnosia lies in the brain, not the eyes.
“The reality we perceive is not simply a reflection of the world as it exists but rather the composite of what our brains are able to process,” says Dr. Hamilton. “We can have radically different impressions of the world if our brains are just a little different.”
Much of what is known about visual agnosia (and to some extent the auditory and tactile forms) comes from case studies in which people with the condition undergo a series of tests during which they are asked to name and differentiate among objects, in real form or pictures. Each study participant also undergoes brain imaging to locate the area of damage, whether from a stroke or other trauma. The use of functional MRI allows scientists to examine activity in the subjects' brains when they are asked to name objects.
Effects Vary
People with visual agnosia are usually able to identify real, three-dimensional objects better than drawings or photographs, says Erez Freud, PhD, a neurocognitive scientist at York University in Toronto. In some cases, they may incorrectly name an object but say it is something else that's similar in shape. For instance, they may identify an image as a lamp instead of a mushroom, or a snake instead of a pretzel. In some cases, they can roughly reproduce a drawing of an image even though they can't identify it.
“It's a life-altering deficit,” Dr. Freud says. “People with agnosia cannot make sense of their visual environment even though their eyes are okay.” Drs. Freud and Behrmann studied the case of a man who developed visual agnosia after a cardiac problem deprived his brain of oxygen. On a visit to the man's home in rural Pennsylvania, Dr. Freud had breakfast with him and observed that he was unable to distinguish between a fork and a knife. It wasn't until the man touched the tines of the fork that he understood what it was, says Dr. Freud. Although the man was baffled by ordinary objects, he could take walks unaided through the woods near his home.
Another research participant developed visual agnosia after being exposed to carbon monoxide when she was 34. She performed poorly on tests involving black-and-white drawings of objects, but her abilities improved with the addition of color and surface texture to the pictures. “People with visual agnosia do better with more realistic objects because they have more cues to support their impaired visual processing systems,” Dr. Freud says.
Mark Francis says visual agnosia continues to affect his daily life, often in unexpected ways. He has trouble with websites that use pictograms and icons instead of text to help users navigate the sites, and emojis are indecipherable. One time he rented a car with a dashboard that was mostly images; he had no idea what the various indicators meant. He says the “visual chaos” he experiences caused him to retire early and go on disability because he felt he couldn't drive his work truck safely. He wishes technology could be more accommodating of problems like his.
“There are no easy treatments for these conditions, and they don't seem to just go away,” says Dr. Behrmann. Until scientists discover a cure or an effective treatment, she adds, people with agnosia will depend mostly on adaptive strategies to cope with their limitations. In some cases, treating the underlying condition—whether it's a stroke, a brain injury, or an infection—may improve or resolve the agnosia. Otherwise, help from health care personnel and physical and occupational therapists can lessen its impact.
