Wednesday, June 27, 2018
Anonymous Promises Action Over Immigration & Child Separation
https://www.youtube.com/watch?v=G70pj4OeoBo
Ajit Pai Insists “Public Opinion is Not Against Us” on Net Neutrality
https://www.youtube.com/watch?v=gFz15iHO-KQ
Is Europe's New Military 'Intervention Force' a Message to Trump?
https://www.youtube.com/watch?v=2oBTgSseeIY
Computational model analysis reveals serotonin speeds learning
Study
provides insight into the role of serotonin in neural plasticity
June
26, 2018
Sainsbury
Wellcome Centre
A
new computational-model reveals that serotonin, one of the most widespread
chemicals in the brain, can speed up learning.
A
new computational-model designed by researchers at UCL based on data from the
Champalimaud Centre for the Unknown reveals that serotonin, one of the most
widespread chemicals in the brain, can speed up learning.
Serotonin
is thought to mediate communications between neural cells and play an essential
role in functional, and dysfunctional, cognition. For a long time, serotonin
has been recognized as a major target of antidepressants
(selective-serotonin-reuptake-inhibitor (SSRIs) that are used to treat various
psychiatric conditions, such as depression, obsessive-compulsive-disorder and
forms of anxiety. However, serotonin in humans, and other animals, is
associated with a bewildering variety of aspects of cognition and
decision-making, including punishment, reward and patience.
The
new results, published in Nature Communications today, provide
additional illumination. In the article, Kiyohito Iigaya and Peter Dayan at
Gatsby Computational Neuroscience Unit and the Max Planck UCL Centre for
Computational Psychiatry and Ageing Research at UCL, analysed data collected by
their collaborators, Madalena Fonseca and Masayoshi Murakami, led by Zachary
Mainen at the Champalimaud Centre for Unknown in Portugal.
In
the experiments, mice were trained to choose one of the two targets to receive
water rewards. Mice continually had to learn which of the targets was more
rewarding, as the reward rates changed without warning. Crucially, sometimes
serotonin release in the brain was temporarily boosted in mice with genetically
modified serotonin neurons by a technique called optogenetics, allowing the
effects of serotonin on learning to be assessed.
Iigaya
built a computational account of mice behaviour based on reinforcement learning
principles, which are widely used in machine-learning and AI. Iigaya found that
the learning rate, i.e. how fast the modelled mice learn, was modulated by
serotonin stimulation. He compared trials with and without stimulation of
serotonin neurons, and observed that the learning rate was significantly faster
when stimulation was delivered, meaning that boosting serotonin sped up
learning in mice.
The
authors also found that when mice made decisions in very quick succession, they
followed a simple strategy called 'win-stay lose-switch', in which they
repeated a choice if it had just been rewarded, and switched to the other
choice if it had not been rewarded. Serotonin stimulation did not affect these
fast choices. However, on subset of trials, when animals acted slowly and took
a long time in-between trials, their decisions did not follow the simple
win-stay lose-switch rule. Instead, the mice made decisions based on a longer
history of rewards, which was well-characterized by a reinforcement learning
account. Serotonin stimulation only affected this slow learning system.
Importantly,
the authors found that this slow system tracked reward outcomes every trial,
even when the choices were made by the fast, win-stay lose-switch, system.
Thus, the effects of the serotonin stimulation to boost the slow system became
apparent only occasionally, when the animals spent a long time before making
decisions. The authors believe that the way that multiple decision-systems mask
each other might explain why scientists have had difficulty in constructing a
comprehensive theory as to how serotonin affects learning and decision-making.
The
authors conclude: "Our results suggest that serotonin boosts [brain]
plasticity by influencing the rate of learning. This resonates, for instance,
with the fact that treatment with an SSRI can be more effective when combined
with so-called cognitive behavioral therapy, which encourages the breaking of
habits in patients."
Substantial
clinical research shows that SSRI treatment is often most effective if combined
with cognitive-behavioural-therapy (CBT). The goal of CBT is to change
maladaptive thinking and behaviour actively, through sessions that are designed
for patients to (re)learn their way to think and behave. However, scientists
have had limited understanding of how and why SSRI and CBT work together for
treatments. The new findings point to a possible functional link between the
two, with serotonin boosting the learning inherent to CBT, providing clues as
to one of the roles that this neuromodulator plays in the treatment of
psychiatric disorders.
Story
Source:
Materials
provided by Sainsbury
Wellcome Centre. Note: Content may be edited for style and length.
Journal
Reference:
Kiyohito
Iigaya, Madalena S. Fonseca, Masayoshi Murakami, Zachary F. Mainen, Peter
Dayan. An effect of serotonergic stimulation on learning rates for rewards
apparent after long intertrial intervals. Nature Communications, 2018; 9
(1) DOI: 10.1038/s41467-018-04840-2
Is Ocasio-Cortez Win a Black Swan Event?
By Rob Kall
Black swan is the name of
Nassim Nicholas Taleb's best-selling book (millions sold) and it could be used
to describe Alexandria Ocasio-Cortez's upset defeat of incumbent Democrat Joe
Crowley.
Taleb characterizes a black
swan event as having three characteristics:
The event is a surprise (to
the observer).
The event has a major effect.
After the first recorded
instance of the event, it is rationalized by hindsight, as if it could have
been expected; that is, the relevant data were available but unaccounted for in
risk mitigation programs. The same is true for the personal perception by
individuals.
For at least 1400 years black
swans were believed not to exist. The term "black swan" was used to
describe something non-existent. Then, a whole lot of them were discovered in
Australia.
Nassim Nicholas Taleb's hugely
successful book argues that black swan events often play major roles in
history, citing 9/11 and the invention of the internet as examples.
I believe it is reasonable to
characterize Ocasio-Cortez's win as a black swan event. That means that it
could play a major role in history. It could open the sluice gates to
Berniecrat victories and defeats of old-school Clinton DLC corporatist
Democrats.
Over the coming days, the
Pelosi-led powers that be will surely do as Taleb describes, and rationalize
this beautiful black swan event, just as early critics of the computer said it
could only be of interest to a handful of businesses.
Ocasio-Cortez, through her
victory has opened a door that could see throngs of victorious progressive
candidates swell through. Let's hope it happens soon enough, before the current
Democratic leaders destroy the opportunity for victory that Donald Trump and
his GOP sycophants have served up on a plate.
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