“The Brain, Reimagined,” by Douglas Fox, concerns work by physicists Thomas Heimburg and Andrew D. Jackson, who argue that signals in neurons are conveyed by mechanical waves of expansion and contraction of the cell membrane rather than by electrical spikes, or action potentials, as described by British researchers Alan Hodgkin and Andrew Huxley.

Heimburg's contention is described as being that the Hodgkin-Huxley model is simply wrong. It is astonishing that he would not accept a compromise between the two models. Given, for example, the Hodgkin-Huxley equations' long-standing success in describing action potentials, this argument would require addressing how the new mechanism accounts for the observations of the old. The list of questions could be quite long, and there are several I would ask at a minimum. Among them are how Heimburg's model accounts, quantitatively, for the increased velocity of conduction in myelinated axons and the mechanism by which it leads to transmission across a chemical synapse.

DOUGLAS A. EAGLES via e-mail

Fox hints at the possibility that a voltage pulse in a neuron will initiate a mechanical deformation and that a mechanical pulse will generate a voltage. This sounds similar to the way that changes in electric and magnetic fields generate each other to produce a propagating electromagnetic wave. Is it possible that the interaction of electrical and mechanical effects is actually required for neurons to function?

PETER SOCHACKI Schaumburg, Ill.

FOX REPLIES: Heimburg, Jackson and their colleagues spent years assembling evidence to place their theory on a sound physics foundation. But Eagles raises a fair point that the theory does not currently explain why myelination increases the speed of nerve pulses or how a mechanical pulse might trigger neurotransmitter release at a synapse. These questions will have to be addressed for the mechanical-wave theory to gain broader credibility. Doing that will almost certainly require that biologists step in to continue the work that physicists have begun.

I would agree with Sochacki: if a mechanical wave is indeed part of nerve conduction, then it seems plausible that the mechanical and electrical signals might entrain and reinforce each other. Lipid membranes have been around since the origin of life, and it appears reasonable to suspect that ion channel proteins, which nestle inside the membranes, have perhaps evolved to not simply tolerate those nanoscale forces but to harness them.


Lydia Denworth reports on novel ideas and technology used for “Preventing Suicide.” As a psychiatrist and researcher, I would like to emphasize that although formal training in how to detect and manage suicide can be very helpful, it is unlikely to reach all of those who potentially work with troubled individuals. A more straightforward option is to become comfortable discussing topics related to suicidal ideation and behavior.

If you are exposed to someone with any risk of suicide, being open to hearing what the person has to say and listening are typically enough to prevent an attempt and create an opportunity for progress, such as a referral to a mental health specialist. Denworth says that 95 percent of young people in a survey indicated that they wanted to be asked about suicide risk. People prefer to live and, if given the chance, without sensing reluctance from the listener, will discuss suicidal thoughts.


Denworth writes that “the pain and hopelessness that lead a person to want to die can be anticipated, addressed and ameliorated.” Yet one of the techniques she describes is to match “suicide-related images—blood, wounds and knives—with aversive pictures of snakes, spiders, and the like.” Programming the emotional mind to feel fear or disgust at the means of killing oneself makes no more difference to a patient's suffering than preventing suicide by strapping someone to a bed. Am I the only one who finds it disturbing that a doctor thinks it is acceptable to inflict this kind of emotional conditioning?

R. ALLEN GILLIAM Longwood, Fla.


“Flashes in the Night,” by Duncan Lorimer and Maura McLaughlin, discusses the observation and search for fast radio bursts from the distant universe. The article brought back a memory from my days as an undergraduate assistant working on the 300-foot radio telescope in Green Bank, W. Va., in 1968.

Green Bank is in a radio-quiet area, but the local farmers used equipment that the telescope could detect. It was easy to distinguish these signals because they didn't shift four minutes every day, as do the radio sources we were interested in. But one puzzling signal showed up most days at the same sidereal time. We identified it as coming from the noisy starter in a co-worker's car as he showed up for his observing run, four minutes later each day. Perhaps we would have called the signal a peryton had we known more about mythology. Instead, in keeping with the designations in the Third Cambridge Catalogue of Radio Sources, we named the source after the driver's initials: 3C-MMD.

ALAN KARP Palo Alto, Calif.


Having retired from designing software systems, I was not a bit surprised by David Pogue's assessment of the sorry state of dashboard controls in “Automotive Touch Screens Are Awful” [TechnoFiles].

I was often struck by the utter arrogance of engineers in my profession when it came to creating user interfaces (UIs). It seemed that the main objective in designing a UI was to produce the cleverest newfangled gadget, without regards to legacy or familiarity on the part of the target users, who were never consulted. Completely forgotten was the idea that a UI should be easily mastered by the most technologically inept operator. I suppose we should be thankful that the steering wheel hasn't yet been replaced by arrows on a touch screen.



I am fascinated by Aditee Mitra's “The Perfect Beast,” which describes “mixotrophic” plankton, which can use solar energy like plants but can also hunt and eat prey.

The idea that one plankton specializes in preying on a different one makes me wonder if there are any indications of types that attack environmentally damaging species, such as the “toxic Karlodinium” or “ecologically damaging, green Noctiluca” cited in the article, and if it would thus be possible to encourage growth of the more desirable species in areas prone to blooms of the undesirable ones.

EDWARD J. JAGO via e-mail


“The Perfect Beast,” by Aditee Mitra, includes a photograph of a microorganism incorrectly described as Ceratium (Tripos) furca. Although the source of the image had identified it as that species, an expert review clarified that it shows a member of the genus Protoperidinium.