If the probability of outcome is different, for example if there

is a 50 chance of raining today, it will change the metrics.

So, in this case, it makes sense, from normative perspective to take an umbrella.

So, the idea is that during the

decision making process we integrate probabilities of outcomes.

And the values of outcome so its called expected utility theory.

This is very influential normal to economic theory so just as

we pay attention to the probabilities and the values of our outcomes.

So, this is very influential theory but of course as we know from

the number of behavioral economic studies this theories doesn't explain.

Our behavior, our decisions perfectly well.

There are very serious deviations from the predictions of this theory.

But, this theory nicely captures that we integrate

probabilities and values during the decisions we make.

So how to investigate, the process of

integration of probabilities and values in our brains.

We can use paradigms suggested by Brian Kinutson word so here

at the beginning of the trial, subject can see a cue

and vertical line codes the magnitude of the expiatory word and

horizontal line codes the probability of the expiatory word, so here.

We can investigate how brain process expected probabilities, and expect the

three words of how braids integrates both aspects through the decision making.

So, subject has to press the button when

the white square is presented from the screen.

And in this case, to indicate the subject can actually

get a very high reward was a very high probability.

So as you see, at the end of this trial, the subject collected $5.

So what Brian Knutson found, that nucleus accumbens really could expected values.

So, activity of the eventual straight of the

circumference is proportional correlates with the expected values.

As you see on the right slide, activity of nucleus accumbens, perhaps not

ideally correlated with expected value, but still

correlates with expected value in certain way.

So, it looks like nucleus accumbens codes

expected values during the decision making process.

We can actually investigate the same

aspects of decision making using different paradise.

For example, in this case participants play cards and then

one case on the left, participant can guess where

the red card is located so subject in the

first case can open four cards and in this case can correctly predicted where

the red card is located on the right side of this slide you can

see another condition when subject can only open one

card and guess where the red card is located.

With this manipulation, we can actually manipulate the probability of outcome.

In the first case, there was a high probability

to get positive outcomes, then in the second place.

We can also manipulate the amount of money subject expects to get during this game.

So with this game, this paradigm, we can make

a look what is going inside the nucleus accumbens.

So here, you see that activity of nucleus accumbens

is proportional to the expected magnitude of the reward.

On the right side of the slide you see that nucleus

accumbens particularly strongly activated when subject

is expecting to get higher reward.

At the bottom of this slide you'll see that

also nucleus accumbens reacts to the probability of the outcome.

So, activity of the nucleus accumbens is particularly strong

when subject expect to get rewards with highest probability.

So actually, the same region encodes probabilities and values.

If we will make a look to this map of the activity of the nucleus accumbens, you see

that different regions' coding probabilities and reward magnitudes

are presented here by different colors and this regions are overlapped.

Look.

So, overall it looks like nucleus accumbens

is involved into the calculation of utility.

It processes expected rewards.

So, it actually estimates the probability of the outcome.

And it also estimates their amount of values related to the outcomes.

So, we can make some intermediate conclusions

about the functional role of the nucleus accumbens.

So, first of all, as I suggested, from neuroeconomic perspective, our values

are simply the firing grades of certain neural populations.

So, it looks like nucleus accumbens code anticipated gains.

Anticipated gains magnitude during the decision making.

And also looks like, that certain neural populations of nucleus accumbens.

The code expected magnitude of the reward.

In some populations, code probability of getting the reward.

So, it looks like, this is a key region for the calculation of the expected

utility during the decision making

process.

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