Unformatted text preview: neuron up to that
,
p two time points, viewed to:
and the underlying in bans, this
responses
2i
hesis that density functions. These functions describe
1 at Bethe process is stopped and a decision is rendered for h .
sensory time point, given that h is true. If the weight of evidence reaches the barrier ,
that “two This is the expected outcome when h is true. If the weight of evidence reaches B (not shown), a decision for h is issued in error.
1
rtex. We
(Recall) Equation 4, 1is the logistic function (here using
.
(4)
Pr(h m)
t, that is
neither
which,speed. Higher barriers meant that 1968; 1 and10 B1975; Luce, 1986; Ratcliff and
like
le
tween accuracy and
Link
Heath,
ght, when more evidence was e ). Unlike in turn, implied Rouder, 1998; Stone, 1960; Usher and McClelland, 2001;
base accumulated, which, in Equation 4, however, the probability
1 0 0 1 1 1 1 1 0 Pr(x,yh1) 994). Thus, neural activity in these areas
Banburismus Performed by Neurons
ncoded, noisy evidence that the brain
Neuron
where
304
SpeedAccuracy Tradeoff
o decide which hypothesis was most
Neuron
304 1 (x ) 1 2 2 (y √1 2 ) 0 2 2 P(Correct)
QPredicted Effect of Barrier Height
Accuracy
y Signals to Turing’s
Figure 3.
2
2
1
on Speed, Accuracy, and Reward Rate in a
Figure 3. Predicted Effect of
DirectionDiscrimination Task Barrier Height
nce
on Speed, Accuracy, and Reward Rate in
The calculations assume that an experiment a
2
DirectionDiscrimination (see
uses six levels ofthe Task text for dedifficulty
is assume common variance, 1 and
consider categorical decisions about
The (A) Accuracy.
that an experiment
tails). calculations The probability of a coruses six levels of difficulty all text for derect choice averaged across(see six motion
x Accuracy. The function of barrier
gnals by formulating quantities like Tutails). (A)and y, respectively, under h1, and
strengths is plotted as a probability of a correct choice averaged ensures six deciheight. A higher barrieracross all that motion
strengthsbased on aas a xweight of evi .
vidence that are m...
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 Spring '08
 LEWIS
 Banburismus

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