Cornell Medical College Advances
By HERMAN ROSEN, M.D.
Learn to Distinguish Speech Sounds While Asleep
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
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.
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
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.#
Herman Rosen is Clinical Professor of Medicine at Weill Cornell
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