Fun_People Archive
16 Mar
Weird research result

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From: Peter Langston <psl>
Date: Thu, 16 Mar 100 10:07:01 -0800
To: Fun_People
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Subject: Weird research result

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From: shivers@ai.mit.edu

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NEW SCIENTIST (2000 Mr 11, p. 6), Mind numbing:  Lose your bite and you
could lose your memory (based on an article in Behavioural Brain Biology,
vol. 108, p. 145).

TITLE:  Mind numbing:  Lose your bite and you could lose your memory

    A GOOD pair of dentures may fend off dementia.  Thats the message from
Japanese researchers, who say that chewing helps prevent memory loss as we
grow old.
    New memories are briefly stored in the hippocampus, a brain area
critical for learning.  But as we age, hippocampal cells start to
deteriorate and our short-term memory gets worse.  Elderly people with
missing teeth often chew less, too, and some studies have suggested that
bad memory and tooth loss might be linked.

    To put this idea to the test, Minoru Onozuka of the Gifu University
School of Medicine in Japan and his colleagues looked at mice that have
been genetically altered so they rapidly develop signs of human ageing,
such as hair loss, cataracts and failing memory.  Onozuka extracted the
molar teeth of some mice, so they could still eat, but couldnt chew.
    The memories of the mice were then tested in a water maze.  Young mice
quickly learned to find a hidden platform, regardless of whether they had
molars missing or not, and old mice with a full set of teeth performed only
slightly worse.  But the old molarless mice couldnt remember how to find
the platform, consistently heading out into the pool in the wrong direction.
Looking at their hippocampi suggested why:  essential cells called glia
had deteriorated far more than usual.

    The findings suggest that chewing is essential to preserve our ability
to form memories in old age.  To pursue this, Onozuka used magnetic
resonance imaging (MRI) to study brain activity while people were chewing.
The task causes an increase in hippocampal signals, he says.
    But how exactly chewing stimulates the mind remains a mystery.  We
don't touch the mechanism,admits Onozuko.  We need more experiments.

    Joyce Wau, a specialist in ageing at the Molecular Medicine Centre at
Edinburgh University, finds the work fascinating.  She thinks that chewing
improves our memories by reducing stress.  After all, humans often chew
gum to help with stress relief.
    The hippocampus helps control levels of stress hormones in the blood,
she says.  So if older people chew less, their stress levels might rise
enough to cause a decline in short-term memory.

SOURCE:  Behavioural Brain Research (vol 108, pp 145-55):  Impairment of
spatial memory and changes in astroglial responsiveness following loss of
molar teeth in aged SAMP8 mice, by Minoru Onozuka, Kazuko Watanabe, Sachio
Nagasaki, Yifa Jiang, Satoru Ozono, Katsuhiro Nishiyama, Toshio Kawase,
Nobuyuki Karasawa, Ikuko Nagatsu.
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