Weill Cornell Medical College Advances
EDITED By HERMAN ROSEN, M.D.

Newborns Learn to Distinguish Speech Sounds While Asleep

The old idea of putting foreign-language cassettes under your baby’s crib, or playing Mozart on the stereo to help the baby learn, is based on studies that are “largely anecdotal,” says Dr. Amir Raz, at the Sackler Institute for Developmental Psychobiology of Weill Cornell Medical College. But now, Dr. Amir and eleven Finnish scientists have carried out a study that shows that babies less than a week old can learn to distinguish between speech sounds by hearing them while they are asleep. The results, published recently in the journal Nature, may one day lead to innovations in the nursery.

The investigators, led by Dr. Marie Cheour of Turku, Finland, studied 45 newborns, all less than one week old. Fifteen were in an experimental group, and 15 were in each of two control groups. The babies had electrodes placed on their scalps, and speakers near their heads gently played a randomized sequence of two similar Finnish vowel sounds as they slept. Through the electrodes, a computer measured how well the brain distinguishes between the two sounds, without requiring the subject to perform any behavior (or even to be awake).

In the first, hour-long session, held in the evening, the experimental group and the two control groups all showed no recognition of the two sounds. Over the following night, for between two-and-a-half and five hours, the experimental group had a “training” session of exposure to the two sounds. One control group did not have this exposure, and the other control group heard two different sounds. Then, in the morning, all three groups underwent another hour-long testing session. The results were that, after the overnight training, the experimental group had learned to distinguish between these two vowels in Finnish speech.

The two control groups, however, still showed no recognition. Moreover, when the two sounds were presented to the experimental group at a different pitch, the experimental group was still able to distinguish between them. And, when the experimental group underwent a third session on the following evening, it retained its ability to distinguish between the two sounds, showing that the effect “lasted for some time.” The authors write, “We have shown that newborns can assimilate auditory information while they are sleeping, suggesting that this route to learning may be more efficient in neonates than it is generally thought to be in adults.”

Dr. Raz says that a big question that remains to be answered is whether this learning while asleep can carry over any effects to the waking state. That is next on the research agenda. He says that it is possible the effect may prove to be like that of a dream in adults —which we experience intensely while we are asleep, but which we often half-forget upon waking up, and which does not have any important effect. But he suspects there will be some carry-over effect.

Another question still to be answered is, up to what age do children retain this ability to learn while asleep? This study is preliminary, but it could lead to several potentially significant consequences.

How Tubercle Bacillus Evades the Body’s Immune System

One of the challenges posed by the tubercle bacillus, which causes tuberculosis (TB), is to understand how the bacillus, once it infects tissue, persists for a lifetime despite the attack of the body’s immune system. Mycobacterium tuberculosis (Mtb) survives despite prolonged forces that the immune system uses to kill many other invading pathogens. Dr. Carl Nathan and others at Weill Cornell Medical College have now found that Mtb defends itself against destruction by using a “bucket brigade” of proteins –including two proteins involved in essential metabolism.

“This may be the first known instance in which essential metabolic enzymes also support antioxidant defenses,” the authors write in their web-based pre-publication issue of Science. They add, “one or more [of these proteins] may hold interest as a drug target for tuberculosis.”

Mtb infects one-third of the people in the world, five to ten percent of them will eventually develop the disease. Before 1952, when the first effective anti-tuberculosis drug was introduced, there was about a 50% mortality rate from the disease. Today TB is still the leading cause of death from bacterial infection, about 3 million dying of it each year. AIDS makes TB worse. Moreover some Mtb strains have developed resistance to existing drugs.

The article describes the discovery of new functions for three proteins, which together with a fourth protein, act sequentially in a “bucket brigade” to block the human immune system’s macrophage cells which act to destroy invading bacteria. The Mtb uses proteins already present in human cells along with unique versions of proteins of its own. Thus if a drug could be found that blocks the tubercle bacillus’ proteins, it could make the pathogen more susceptible to destruction by the immune system, without harming the body’s own cells. Dr. Nathan also suggests that interfering with these enzymes might cripple Mtb’s ability to build its unusually thick and hard to penetrate cell wall, thus further exposing it to medicines and to the immune system’s “killer” cells.#

Dr. Herman Rosen is Clinical Professor of Medicine at Weill Cornell Medical College.

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