|
 Brain
Entrainment is the process whereby two
interacting oscillating systems, which have
different periods when they function independently,
assume the same period. The two oscillators may fall
into synchrony, but other phase relationships are
also possible.
The system with the greater frequency slows down,
and the other accelerates. Christian Huygens, a
notable physicist, coined the term entrainment after
he noticed, in 1666, that two pendulum clocks had
moved into the same swinging rhythm, and subsequent
experiments duplicated this process. Notably, the
two pendula stabilized not in synchrony, but in
antiphase. They satisfy the definition of
entrainment because they have the same period, even
though they have opposite phase. The accepted
explanation for this is that small amounts of energy
are transferred between the two systems when they
are out of phase in such a way as to produce
negative feedback. As they assume a more stable
phase relationship, the amounts of energy gradually
reduce to zero. In the realm of physics, entrainment
appears to be related to resonance.
In the study of chronobiology entrainment occurs
when rhythmic physiological or behavioral events
match their period to an environmental oscillation
(termed a zeitgeber, which is German for "timegiver").
The activity/rest (sleep) cycle is only one set of
such events that is normally entrained by
environmental cues whose period is ultimately
determined by the earth's rotation. The term
entrainment is justified because the biological
rhythms are endogenous: they persist when the
organism is isolated from periodic environmental
cues. Circadian oscillations occur even in isolated
organs, and it is believed that a master pacemaker
in the mammalian brain, the SCN (suprachiasmatic
nuclei), entrains the periphery. Such hierarchical
relationships are not the only ones possible: two or
more oscillators may couple in order to assume the
same period without either being dominant over the
other(s). This situation is analogous to Huygens'
pendulum clocks.
Products are being developed now and
will be listed soon ... please check back. |
Members Area
Affiliate Program
Join Our Mailing List
Main Page |
