researchers at Humboldt University of
Berlin have been trying to find out what
happens in the brain when we're tickled
in 1999 scientists found young rats also
vocalize when they're tickled
are they actually laughing what does a
rat's voice sound like
the typical hearing range of a human is
20 Hertz to 20 kilohertz rats vocalize
at 20 to 100 kilohertz they make long
calls at 22 kilohertz when they're
scared or annoyed and when they're happy
they make short calls at 50 kilohertz
for example when they interact with
other rats and they are given food a bit
like when human voices go higher when
we're excited or having fun so here's
the sound a rat makes if you tickle its
back
the sound has been converted to a lower
frequency that we humans can hear but
the source frequency is mainly 50
kilohertz
apparently the rat likes being tickled
not just because of the frequency of its
calls but because when the tickling
stops the rat doesn't turn away but
looks to see where the hand has gone
rats recognize the researcher's hand as
their Playmate and approach the hand to
be tickled more
eventually they start chasing the hand
rapidly while vocalizing at 50 kilohertz
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signals from the body surface reach a
brain area called the somatosensory
cortex like a map of the entire body
with distinct regions for each body part
trunk
front legs
back legs the researcher tickled the
rats and measured the activity in the
trunk region which is the most ticklish
part of a rat's body
here is the activity of neurons in the
trunk region when a rat is tickled
thin vertical lines indicate electrical
activity in the neuronal cells
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[Music]
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signals from the trunk are being sent to
this brain region
does this neural activity represent
ticklishness
if it is the case activation of these
neurons without actually tickling the
body must be enough for the rat to feel
ticklish to test it the researcher
stimulated the neurons electrically
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foreign
calls at 50 kilohertz when its brain is
stimulated
thus the researcher found out that
ticklishness is represented by activity
of the neurons in the somatosensory
cortex
I am worried that a lot of these guys
are disappearing and nowhere else on
Earth does this organism exist you have
to go to the backs of valleys or distant
Ridge lines or isolated mountain ranges