NARRATOR: Tepotzlan,
Mexico, October, 2011.
Here, just 50 miles
from Mexico City,
shamans from all over
North and South America
gather to commemorate the
region's long tradition
of shamanic healing.
Throughout the
three-day celebration,
these modern-day medicine
men engage in sacred dances,
rhythmic chanting,
and drumming--
all methods that shamans use
to connect with other realms.
But why?
Do these practices
really effect a change
within the shamans
that allows them
to communicate with
beings that are otherwise
beyond our perception?
 In many shamanic
traditions, shamans
have special tools
that allow them
to access the spirit world.
Among the most
important of these
tools are the shaman's drum
and/or the shaman's rattle.
These are rhythm
instruments that beat out
a particular rhythm
that allow the shaman
to enter into trance
and to journey
to the world of spirits.
 We see this rapid, very
steady rhythm on the drum
as being a central tool of
shamans being able to open up
the doors of the mind,
giving voice to the unseen
realms of the cosmos.
NARRATOR: Is it
merely coincidence
that shamans all over the
world share the belief
that by repeating certain
rhythmic movements and sounds,
they can communicate
with other realms?
Or might this ancient
practice produce
a real physiological change
in the shamans themselves?
 There's a neurological
explanation for this.
One of the ways that we
can alter our consciousness
is through rhythmic movement.
So throughout the world, you see
many traditions in which people
communicate with the gods
by spinning, by dancing,
by doing something rhythmic.
NARRATOR: At the University of
California in San Francisco,
neuroscientist Dr. Adam Gazzaley
is performing experiments using
3D gaming technology to actually
track how drumming affects
the human brain Participants
wear virtual reality goggles
and experience both visual
and auditory rhythms.
ADAM GAZZALEY: We feel that if
we have a participant learn how
to entrain with different
rhythms through game mechanics,
we could strengthen the
rhythms of the brain
and lead to better performance,
better cognition, better
memory, better attention.
And so we're
recording in real time
what's going on in her brain.
You could have a rhythm going
on that you're listening to,
and your brain has its
own natural rhythms.
The entrainment
would be that they'd
become locked in time such
that they follow each other.
We're sort of at the gateway
of this frontier now.
