Fróðskaparrit - 01.01.1968, Side 108

116
Motion Sickness
Fortunately there is a more important mechanism: that of
habituation. This consists of dimiinution of responces to the
repeated or continued stimuli, and helps to bring some
improvement in most people after repeated or prolonged
exposures to wave motion. Habituation must play an impor-
tant part in reducing motion sickness amongst those who
travel much and is probably the reason why children are more
prone to motion sickness tthan adults. However, habituation
is highly specific, so tthat it occurs only with regard to a precise
stimulus (Glacer et al 1959), which means that habituation to
one kind of motion will not necessarily protect against another
kind of motion. This explains why people wiho are used to
the short period acceleration in small boats, are sometimes
sick in larger ones which oscillate at longer periods and accele-
rate and descelerate at different rates. Similarly, tthose who are
good sailors in large ships are often sick in smaller boats or
aeroplanes.
An understanding of the physiological mechanisms which
have been discussed, suggests several ways of inhibiting motion
sickness. Obviously tthose who favour lying down and those
who favour standing up on deck, are both right, since lying
dawn will reduce vestibular stimulation, while standing up and
looking at the horizon will accelerate habituation and reduce
visual distortion. Equally, of course, both views are wrong
because lying down will prevent habituation, and standing
up will facilitate nausea and vomiting. From wlhat is known
about tihe influence of che brain on reflexes, it follows that
distracting and interesting activities can help to prevent motion
sickness by drawing the person’s attention from his symptoms.
Medication.
The first antiihistamine substance tto be given against motion
sickness was antisan (Mc Evedy 1949). Since chen various
antihistamine drugs have been introduced against motion sick-
ness, but tthey are not all effective.