Letters

Cursor cortex

"Mind over matter" (SN: 8/28/99, p. 142) reviews the state of the art in brain-computer interfacing. I am the inventor of the neurotrophic electrode and project director at Neural Signals Inc. for the effort that involves implanting this electrode into the brains of locked-in patients. I appear with Dr. Bakay and the patient JR in the photograph in the article.

The article's last section addresses the concern that following paralysis, the brain's usual responses are distorted and thus would not be appropriate for communication. In our present patient, evidence suggests that the implanted brain becomes devoted to control of the cursor. We call this area the "cursor cortex." If this holds true in subsequent patients, it implies that implantation can be performed, perhaps in any part of the brain, without fear of functional loss.

Philip R. Kennedy
Neural Signals Inc.
Atlanta, Ga.
http://www.NeuralSignals.com

On plants and parkinsonism

"Tropical fruits linked to parkinsonism" (SN: 7/31/99, p. 69) needs a minor revision. The story refers to research that suggests a link between the so-called Guam syndrome of parkinsonlike symptoms and the consumption of sago palm. It is not sago palm (Metroxylon sagu) but rather the superficially similar cycad tree (Cycas circinalis) that has aroused suspicion.

Sago palms are true palms. They are known in insular Southeast Asia but are not native to Guam. Cycad trees are not palms at all. Because they have fronds, though, they have been popularly lumped into the palm family.

It is well known that cycad seeds contain a toxin that causes all kinds of neurological problems, but this toxin can be rinsed out if you have plenty of time and fresh water. Could eating inadequately rinsed cycad-seed flour have caused the rash of cases of "Guam syndrome" (known on Guam as "lytico" and "bodig")? That is the question.

Mary McCutcheon
George Mason University
Fairfax, Va.

Yes, the cycad tree is a prime suspect in Guam syndrome. We referred to it as "a sago palm" for brevity, but it is commonly called, and rightfully so, the "false sago palm." —N. Seppa

With only 5,000 diagnosed sufferers in the United States, progressive supranuclear palsy (PSP) needs all the publicity it can get. But your article describes this brain disease inaccurately. It is not "a mild paralysis that causes trunk and neck rigidity" but a relentlessly progressive, poorly treatable condition leading to death, usually within 10 years, with neck rigidity and major impairments of balance, swallowing, speech, eye movement, and, eventually, intellect. We hope that recent advances in the understanding of why tau protein accumulates in degenerating brain cells in PSP may soon lead to preventative therapy.

Lawrence I. Golbe
Society for PSP
New Brunswick, N.J.

We relied on dictionary definitions of PSP, which called it "a mild form of paralysis" and included trunk rigidity in PCP's description. —N. Seppa

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