Remembering Smell (6 page)

A theory of consciousness may seem far removed from an explanation of smell dysfunction, but what if the dysfunction fills one's brain with fake smells? What do these sensations say about the nature of reality? Are they sensations at all? Could the smells be perceptions, meaning that they originate in the mind, not at the periphery, where the damage started? Scientists have shown that tinnitus, a persistent ringing, buzzing, or other sound in the ears that occurs in the absence of any external stimulus, can be a phantom sensation. They're trying to figure out how the peripheral machinery—those tiny bones in the ear—and the high brain collaborate to produce this symptom.

Tinnitus can be worse than annoying. For people who constantly hear cats screeching, cars honking, or bombs going off, tinnitus can even lead to suicide. Whatever zapped my sense of smell—and I was convinced that it was Zicam and not a cold—seemed to have caused a chain reaction. The limbic system, which responds to odors instantly, added to the confusion by drenching in fear that mother of all brain maps, the one that blends input from all brain regions to create a single conscious perception.

D
R. CUSHING'S COMPARISON
of phantosmia to phantom limb syndrome—"the brain is trying to compensate for the lost or damaged body part"—had me wondering if that was literally true.

Johannes Frasnelli treats smell-i mpaired patients in Germany. He reported that more than 60 percent of his patients with smell dysfunction had smell hallucinations, and many of these patients also suffered from depression. His American colleague Don Leopold advises ENTs on how to treat smell dysfunction. Leopold urges doctors to pay close attention when patients mention weird odors. This isn't so easy. Only 5 to 10 percent of phantosmia victims admit to having these sensations. This is because "symptoms were not taken seriously by their general practitioner [or] their families." In other words, the patient assumes he's either nuts or acting like a baby.

"Among smell pathologies," wrote psychologist and fragrance consultant Avery Gilbert in his book
What the Nose Knows
, "the most appalling is cacosmia, in which everything smells like shit." My world smelled like shit, puke, burning flesh, and rotten eggs. Not to mention smoke, chemicals, urine, and mold. My brain had truly outdone itself. If it was acting on the theory that, as with childhood fears, it was best to let the bad stuff out of the dark closet and stare it in the face, I could only offer my congratulations.

Cacosmia belongs to the phantosmia family of smells; that is, smells that have no outside source.
Parosmia
refers to bizarre distortions of
actual
odors. The smell molecules are there, but their chemical formulas are misinterpreted somewhere between the receptor sheet and the central brain. It's not always clear when phantosmia is really parosmia, or vice versa. Neuroscientist Johannes Frasnelli thinks parosmia is likely a peripheral malfunction while phantosmia denotes a central problem, such as schizophrenia or epilepsy. Phantosmia victims often report a single odor, while parosmia offers a more varied repertoire. My own symptoms put me in the parosmia camp, but I'd been diagnosed with phantosmia. You see the problem. No one really knew what I had.

With both disorders, the smells may be interpreted as familiar scents until the victim understands that the smells are not real. The fact is, the smells aren't identical to anything. That they're novel may be why people find them noxious. Novelty is always off-putting to the brain. Threatening.

Specific anosmia
is the label applied to the syndrome in which a person can't smell a specific thing, such as urine, leather, or musk, but other odors come through loud and clear.
Hyposmia
means weakened smell, usually caused by the aging process. The opposite (extremely rare) condition is called
hyperosmia.
It was the subject of a chapter in Oliver Sacks's
The Man Who Mistook His Wife for a Hat.
A medical student blamed his bout of heightened smell on a drug he'd used to keep himself awake. The affliction made him able to smell as keenly as dogs, he said, and he found himself behaving like a dog, following his nose instead of his eyes and thinking brain. While this was a nuisance, he enjoyed his supercharged smeller immensely while it lasted. Oh, to be a dog again!

I continued to think of my own hallucinations as a kind of phantom limb syndrome (PLS) of the nasal cavity. My nose and brain were trying to compensate for my loss of smell function, as Dr. Cushing had suggested. My brain was becoming hysterical because my olfactory alert system had gone on the blink.
I can't find you and I need you!
And by the way,
don't touch that food!

PLS is a brain anomaly—an exception to the rule. Thousands of amputees in the two world wars suffered phantom limb pain. Their symptoms were attributed to shell shock. Even today, unrelated symptoms—phantom pains and emotional distress—are often regarded as being part of the same thing: mental illness. We now call shell shock posttraumatic stress disorder, a more dignified and suitable term.

The power of smell is being harnessed to help soldiers re-cover from PTSD. A California psychologist who was deeply moved by the experiences of Iraq war veterans haunted by things they saw or did in the confusion of a guerrilla war devised a treatment. Victims were repeatedly exposed in safe surroundings to olfactory memory triggers such as the smell of burning flesh, diesel, and gunpowder, and the odor images eventually came unstuck from the memories. Eventually the smells lost their potency. They were unable to summon the emotional havoc on their own.

Traumatized amputees who come home from war sometimes attribute their PTSD symptoms not to their wartime experiences but to the phantom pains they can't understand or remedy. They are fortunate to have doctors who know that phantom sensations are real, and awful, entirely capable of making one feel crazed and out of control. PLS symptoms range from an unsettling sense that the detached limb is still there to searing sensations similar to electric shocks. Oliver Sacks described a diabetic amputee who, bedeviled by phantom sensations, complained that his doctors should have cut the nerves to the leg, then put the leg in a cast, and then, "when the feeling wasn't there,
then
cut it off! Get rid of the feeling, get rid of the idea,
then
get rid of the thing itself!" Surely this would have prevented "this damn phantom."

The man was right.

Oliver Sacks has covered the gamut of what he calls disorders of mental imaging. He had a patient who was so devastated when he lost his sense of smell after a fall that he willed it back. This belief that he could smell again—part conscious, part unconscious—intensified with time. Sacks wrote in
The Man Who Mistook His Wife for a Hat
that "he snuffs and smells the 'spring,' [calling up] a smell-memory or smell-picture so intense that he can almost deceive himself, and deceive others, into believing that he truly smells it."

Like this man's made-up smells, the odor in my brain was fake. But its origins had more in common with visual agnosia, the subject of that book's title story about the wife-turned-hat. This patient's brain sent occasional faulty pictures to his visual cortex. In the doctor's office, he tried to put his wife's head on his head, thinking it was his hat.

This question of what is real and what isn't was the topic of Sacks's third book,
A Leg to Stand On.
I read the whole book in one sitting. It tells how Sacks himself lost all sense of "connection" to a leg after an injury damaged its muscle and nerve tissue. This confounding experience threw all his assumptions about perception into the ditch. He became anxious and then morbidly depressed, and he turned to philosophy to anchor him and to poetry and music to restore his emotional equilibrium and faith in a beautiful, knowable, and reliable reality. He decided that the German philosopher Immanuel Kant had it right: human reality exists only to the extent that it conforms to the brain's ability to observe cause and effect; anything beyond that, such as who or what made us, is beyond our ken.

Later Sacks reversed himself. In a lengthy footnote attached to
Leg's
third printing, he told of having read new theories based in part on revelations about brain function. He'd been influenced by the philosopher Thomas Kuhn, who believed that "facts are not like pebbles waiting to be picked up on the beach." Instead facts become facts based on "the viewer's theoretical viewpoint."

Well before Kuhn, the Irish philosopher George Berkeley wrote in 1710, "Light and colours, heat and cold, extension and figures—in a word, the things we think and feel—what are they but so many sensations, notions, ideas?"

What has lately been nudging scientists as well as philosophers in Berkeley's direction is the recognition that human perception presents each of us with a world more complex and varied than a mere merging of neuron patterns created in the sensory system could make possible. As abundant as receptor proteins are, the stimuli they gather cannot, on their own, create experience. The step that philosophers call binding (and that Richard Axel calls binding problem number two) must involve inputs from other brain regions that store memory and emotion. It's only when an outside event such as the loss of smell or of a limb disturbs this central binding—Axel puts all such anomalies under the umbrella category of "nonbinding"—that one gets a glimpse of how subjective and illusory reality actually is.

Experiments done in European labs found that psychosis could be induced in a subject by temporarily confusing his visual cortex with optical illusions (for example, researchers placed mirrors in such a way that they created the illusion the subject was somewhere he was in fact not). Brain scientist Vilayanur'S. Ramachandran of the University of California at San Diego wondered if the technique could also be used to trick the brain into believing all was well.

Sure enough, it worked. An amputee suffering from phantom limb pain was placed in front of a mirror that reflected back his image but with his missing limb restored. Unable to tell the reflected image from the real thing, his brain assumed the missing arm was now back and stopped pestering it. Mirrors have been effective in treating Iraq war veterans' PLS. One young soldier was driving a Humvee when a roadside bomb blew off his right leg above the knee. Soon after surgery, he was harassed by phantom sensations he likened to electric shocks. Narcotics did not relieve the pain. Nothing did. His doctors persuaded the soldier to join an experiment at Walter Reed Army Medical Center in Washington, D.C., that used mirror techniques. Reluctantly, he agreed. In the study, twenty-two amputees who had each lost a leg or a foot and were experiencing phantom limb pain were divided into three groups. Each member of the first group viewed a mirror in which he saw a reflected image of his intact limb; members of the second group viewed a covered mirror; and those in the third group were trained in mental imaging. After four weeks, all the mirror-therapy patients reported a significant decrease in symptoms (though some experienced intense feelings of grief on looking in the mirror and seeing themselves as they used to be). The soldier who'd lost his leg to the roadside bomb was in the first group, and his pain was gone after just a few sessions.

Neuroscientists now know where his pains were coming from. They were concocted from living memories and delivered via the nerve endings in the leg stump. When the brain tried to move the absent limb, the result was an abnormal neural pattern experienced as searing pain. But why are phantom feelings so nasty? Is it because the senses—touch and smell, among others—are the first line of defense against the outside world? The default response to a sense's absence is negative (sharp pains, foul smells) because no other logical explanation is available.

Writer and physician Atul Gawande describes a woman who had spent eleven years scratching a constant itch on the left side of her scalp until she scratched right through her skull and into her brain and its fluid began to drip out of the wound. The itch had started with a case of shingles that left the scalp numb. The more she scratched, the worse the itch became. After treating her with everything from creams to tranquilizers to brain surgery that severed nerves to the scalp, her doctors concluded that the itch was a central problem. The woman's brain was compensating for the numb scalp, replacing the absent sensations with sensations that felt, as Gawande put it, like "armies of ants" crawling all over the spot. Like olfactory hallucinations, the itch is not only torturous; it's constant. Gawande's profile of the woman tormented by this inner itch concludes with neuroscientist Ramachandran figuratively scratching his own scalp as he ponders what possible mirror techniques could produce the elaborate visual lie needed to finally turn off the woman's itch switch.

My phantom-smelling brain would have to be tricked—
trick
was the exact word Dr. Cushing used—into thinking all was well, just like the brains of the patients in Dr. Ramachandran's mirror experiment. But amitriptyline is a drug, not a mirror. And for all its magic-trick aspects, mirror therapy is fairly straightforward. There's still no explanation for why an antidepressant quiets the olfactory din of phantosmia beyond this: the drug just happens to bind with the receptors in the high brain that control the behavior of the misfiring synapses.

Neuroscientist Antonio Damasio explained phantom sensations as secondary brain maps made by "reconstruction through the process of recall of a previously acquired memory that kicks in when the primary maps go offline." This only applies to hearing, vision, and touch, all of which depend on a sense of the body to work properly. Smell is fundamentally different, and its connections are much more broadly dispersed in the brain because of the olfactory system's great age. Richard Axel is not alone in believing that smell is the primary sense; it has influenced human development in a profound way. But how (and why) does it continue to wield power and influence?

I asked Johannes Frasnelli if he thought phantosmia and phantom limb syndrome had anything beyond phantom sensations in common, if my mind (not the receptor sheet) could be deliberately distorting reality so that I'd smell warning odors, such as rotten food and burning flesh. I told him about my experience and asked how he explained phantosmia to his patients. Phantosmia is uncanny, I added.