Magdalena Kegel
June 21, 2016
Poor decision-making
processes — common enough among patients with Parkinson’s disease —
may contribute to the movement difficulties that characterize the disease,
a view that redefines Parkinson’s as more than a movement disorder. The
findings may also lead to new discoveries of early disease markers,
improving chances of halting brain degeneration at an early stage.
Perceptual decisions are often a
mix between available sensory information and previous experiences. Determining
if there is enough time to cross the street when you see a car approaching
might be easy if the car is close. But if a person spots the car at a distance,
stored memories of earlier crossings integrate with the new sensory
information, to interpret the car’s speed and estimate the safety of a
crossing.
Exploring how people with early
stage Parkinson’s disease approach decisions, a research team at the University of California, Los Angeles
discovered that perceptual decision-making is only problematic for patients
when the sensory information is weak and previous experiences need to be part
of forming a decision.
Either there are no banners, they
are disabled or none qualified for this location!
Both patients and healthy controls
in the study had to make decisions based on visual information that varied
in its degrees of ambiguity. Findings demonstrated that when
patients had to rely on their memory, they had a hard time integrating memory
and visual information, and a tough time making decisions, even when
researchers verbally instructed them.
But when these same patients were
exposed to situations where the sensory information was strong,
they arrived at decisions as easily as healthy people. The
study, Patients with
Parkinson’s Disease Show Impaired Use of Priors in Conditions of Sensory
Uncertainty,” was published in the journal Current
Biology.
Drawing parallels between
decision-making and movement, scientists realized their findings might explain
why patients with Parkinson’s find it so difficult to initiate movement,
even when treated with dopamine-increasing drugs. When assisted by strong
sensory information, such as horizontal lines on the floor that a patient
can follow, problems in initiating movement are less severe, with less
shuffling and better gait.
“This tells us that the problem
for people with Parkinson’s disease is not walking per se, but rather in
generating the walking pattern without the assistance of sensory information,”
Michele Basso, the study’s senior author and a professor at UCLA’s Semel
Institute for Neuroscience and Human Behavior, said in a news release.
“The patients with Parkinson’s
disease in our study were impaired only when they had to rely on memory
information to guide their actions. We believe this fundamental problem of
decision-making in the absence of sufficient sensory information may be what is
underlying some of the movement disorder symptoms,” said Basso.
These findings contribute to a
view — growing in popularity — that Parkinson’s disease is not merely a
movement disorder.
“Parkinson’s disease has long been
seen as purely a motor problem, limited mostly to a section of the brain called
the basal ganglia and a neurotransmitter called dopamine that is not produced
at sufficient levels,” Basso said.
“The field is realizing that
Parkinson’s disease is a multisystem disease that probably involves many brain
areas and neurotransmitter systems,” she said. “Our finding suggests that
the dysfunction we uncovered may actually be unrelated to dopamine. New efforts
by us and others are geared at finding out which other brain areas and
neurotransmitters are involved, and how.”
Basso and her team noted that
impaired decision-making was not helped by dopamine medication. They also
highlighted that all the patients studied were in early disease stages,
indicating there might be other biological markers of early stage disease,
not related to disrupted dopamine signaling.
The research team now hopes to
identify such factors — a discovery that promises to be a huge step
forward for early treatment, given that once people become symptomatic, the
brain has already suffered substantial damage.
As a part of this process, the
researchers will now repeat the decision-making experiments while scanning the brains
of both patients and healthy controls to identify factors involved in impaired
decision-making processes.
http://parkinsonsnewstoday.com/2016/06/21/impaired-decision-making-processes-in-parkinsons-movement-difficulties/
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