January 18, 2006
New findings have large implications
for explaining drug addiction
Daily Science Writer
Although the omnipresent "sweet tooth" might not
exist, University researchers have discovered a special
region of the brain that generates pleasure responses,
which could be linked to your craving for sweets.
Findings for a project led by biopsychology Prof.
Kent Berridge and research associate Susana Pecina,
which were released last month, indicate that the brain
has specialized neural receptors in its different regions
that control how much a person will like or want some-
Researchers previously believed that the only mech-
anism involved in generating a pleasure response were
electrically active cells known as neurons that release
dopamine in the brain.
But Berridge said the nucleus accumbens, a region
located in the front of the brain, contains a zone that
plays a major role in creating a pleasure response.
"Our current result pinpoints the opioid pleasure-
generating machinery in the brain's nucleus accum-
bens," Berridge said
In the pleasure zone of the nucleus accumbens, neu-
rotransmitters known as opioids are used as messengers
to stimulate neurons.
To determine which section of the brain was linked
to pleasure, researchers injected drugs that resemble
the opiod neurotransmitter into specific regions of rats'
brains, and observed the animals' facial expressions,
The researchers labeled the facial expressions as
either "liking" or "disliking." Facial expressions such
as tongue protrusions indicated liking, while responses
that looked like grimaces indicated disliking. Pecina
said these expressions were a good measure because
they are homologous across species.
Scientists were originally unclear as to the exact
lqcation of this pleasure zone and if the sensation of
"liking" was connected to the feeling of "wanting." But
the discovery shows that the "liking" sensation is iso-
lated only in a small zone of the nucleus accumbens.
Researchers make an important distinction between
the two different responses. They define "wanting"
as the desire to obtain a substance that would satiate
the individual, and "liking" as the inmediate feeling
associated with obtaining a substance. Because their
research shows that the "liking" response is generat-
ed in a separate region than the "wanting" response,
Berridge said this suggests that "wanting" could hypo-
thetically occur without the "liking" sensation. For "Our goal is to specify exactly which brain systems
example, a heroin addict could technically want to use generate the pleasure reaction and apply it to the sensa-
the substance, without necessarily liking the feeling, tion, and how they do it," Berridge said.
due to a change in the neural pathways. Unusual activation in this system could in principle produce
Berridge said if this is true, researchers may have a pathologically excessive 'wants' for a particular reward that
better idea of how drug addiction works. fails to be matched by equally high 'likes'," Berridge said.
According to Berridge, the opioid "wanting" region
might take signals from the dopamine "wanting" region
and send them to the rest of the brain:
Pecina says that the future of this research lies in bet-
ter understanding the neural connections that control
the pleasure reaction.
Scientists have used X-ray
light to measure a black hole
By Chad Brenner
For the Daily
Black holes aren't so elusive anymore.
University scientists have recently-found a way to
quantify the mass, spin and space around a certain
type of black hole by examining shifts in X-ray light
The result was presented last week at the Ameri-
can Astronomical Society meeting in Washington by
Massachusetts Institute of Technology Prof. Jeroen
Homan and his team of researchers which include
University astronomy Prof. Jon Miller.
Miller said the significance of this finding con-
firms that a black hole's gravity alters the frequency
He added that the finding is a direct result of how
black holes distort space and time - a four-dimen-
sional metric that Einstein dubbed "spacetime."
A black hole forms when a star has used up its
energy sources. Because the star no longer has the
power required to support its mass, the star implodes
and concentrates all of its mass into a point. The star
then collapses on itself, generating a gravitational
pull strong enough that light cannot escape from it.
In the absence of a black hole, the space-time
dimension can be thought of as a flat plane. But
in the presence of a black hole's massive gravi-
tational pull, spacetime looks like a bowling ball
resting on a trampoline. The ball forces the flat
surface of the trampoline to drop, resulting in a
significant change in shape.
Similarly, the shape of spacetime around a black
hole changes in time as the black hole spins through
space. Originally, scientists could only theorize that
any fast frequency light that passes by the black hole
would undergo a change that corresponds to the
warped environment around the black hole. Using
NASA's Rossi X-ray Timing Explorer, the research
team identified X-ray patterns around a black hole
first observed in 1996. After observing the same
frequencies in two separate experiments, nine years
apart, Miller suggests that something fundamental is
occurring with the black hole.
Moreover, because of the high improbability of
two exact frequency spectrums appearing over time
FRESNO, Calif. - Under legal
pressure, a rural school district yes-
terday canceled an elective philoso-
phy course on "intelligent design."
A group of parents had sued the
El Tejon school system last week,
accusing it of violating the consti-
tutional separation of church and
state with "Philosophy of Design,"
a high school course taught by a
minister's wife that advanced the
However, some activists contend-
ed that Jones's ruling opened the
door to teaching intelligent design
in philosophy or religion classes.
The settlement in the El Tejon
school district was announced just
before a federal judge was sched-
uled to hold a hearing on whether
to halt the class midway through
the monthlong winter term.
All five of the cash-strapped dis-
IMAGE COURTESY OF UM-NEWS SERVICE
The black hole (shown left) called GRO 11655-440 is about 6.5 times as massive as the sun.
Recent data may help scientists to find ways to measure the mass and spin of black holes.
notion that life
is so complex it
must have been
created by some
kind of higher
agreed to halt
the course at
tain High next
week and said
it would never
again offer a
"course that pro-
motes or endors-
a strong signal
to school dis-
tricts across the
country that they
an alternative to
they do so in a
"This sends a
strong signal to
country that they
as an alternative
- Ayesha N. Khan
Legal Director for Ameri-
cans United for Separa-
tion of Church and State
voted to settle
said Pete Car-
ton, the dis-
The class start-
ed Jan. 3 with
said the sub-
ject was proper
for a philoso-
phy class. But
videos that pre-
theories as sci-
of Los Angeles
nts from a dozen
from the black hole, the research team could finally
confirm that black holes alter light frequencies.
As a mass becomes more and more concentrat-
ed in a black hole, the corresponding gravitational
force increases and, therefore, so does the speed at
which matter can escape this force, a rate known
as escape velocity.
The area where the escape velocity is active is called
the event horizon, a theoretical sphere that can be
drawn around every black hole. Any particle or matter
that finds itself within the event horizon cannot escape
without a velocity greater than the speed of light. Out-
side the event horizon, light can still escape, but the
black hole's gravity will slightly alter the light's fre-
quency spectrum. It is this altered light that the Rossi
X-ray Timing Explorer observed and allowed the team
to hypothesize about a recurring pattern.
From a distance from about 100 miles beyond the
event horizon, matter can easily orbit a black hole.
As the matter moves through an orbit, it comes in
contact with gravitational waves in spacetime that
are created by the black hole. The matter then expe-
riences a precise shift in position similar to a boat
rocking on the ocean that is suddenly struck by
a large wave. The magnitude of these space-time
waves corresponds to intrinsic properties of the black
hole, namely mass and spin. Not all black holes have
matter orbiting them, so the research team could not
measure the mass and spin of just any black hole. But
the team was able to study a black hole where gas
was falling toward it.
Miller said as the gas would fall in orbit towards the
black hole, the temperature in the gas would increase
and emit X-ray light, which could be observed and
analyzed according to its power spectrum.
After the initial frequency recordings from
1996 to 1997, the gas source became depleted.
However, nine years later, gas was again falling
into orbit around the black hole and "the black
hole was still singing the same tune," Homan
said. At this time, scientists increased their obser-
vations of the system, measuring the shifts in the
gas position through X-ray frequencies. The team
also went through the first archival recordings of
gas falling into the orbit of the black hole and took
the same measurements.
"Measurements were made possible by analyz-
ing the system for a few hours a day over several
months through the black hole's bright phase,"
Miller said. "The significance of this finding is
the observation that fast frequencies were altered
by the gravity of the black hole."
science class or a
in the Tehachapi
75 miles north
draws 500 studer
humanities class," said Ayesha N.
Khan, legal director for Americans
United for Separation of Church and
State, which represented the parents.
In a landmark lawsuit, Ameri-
cans United successfully blocked
the Dover, Penn., school system last
month from teaching intelligent
design alongside evolution in high
school biology classes. U.S. Dis-
trict Judge John E. Jones III ruled
that intelligent design is religion
masquerading as science.
Sharon Lemburg, a social stud-
ies teacher and soccer coach who
taught "Philosophy of Design,"
defended the course in a letter to
the weekly Mountain Enterprise.
"I believe this is the class that the
Lord wanted me to teach," she
Similar battles over intelligent
design are being fought in Georgia
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