Transcript Slide 1

Sensation & Perception
• Ch. 1-3: Review
© Takashi Yamauchi (Dept. of Psychology,
Texas A&M University)
Rat-man demonstration
What does this tell?
Why do we see two different things (a rat or a
man)?
• An interaction between
– attention and perception
– cognition and perception
• Tell me what you see.
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Tired
Old
Sick
Dark
Slow
Heavy
Hospital
ugly
death
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Beautiful
Young
Fresh
Fast
Energy
Juicy
Clean
cheerful
Vigorous
How come?
–Different types of physical information (air
vibration, light energy) are translated into a
common language in the brain
–  neural information
Environmental Stimuli (e.g., light energy)
Transduction
Neural Processing
Perception
Ch 1
10
• What does this circle tell you?
• How are the circle and the rat-man
demonstration related?
• Levels of analysis
– Psychological level
– Physiological level
– Single cell recording
– EEG/ERP
– PET Scan / fMRI
– What are they?
Single cell recording
PET & fMRI
fMRI Setup
• Detection
– Absolute threshold
– Difference threshold
• Can you define them?
• DL (difference threshold)
• Weber’s law
The impact of standard stimuli
• DL (difference threshold) gets larger as
the standard stimulus gets larger.
• Weber’s law
DL/S=K
• DL: difference threshold
• S: standard stimulus
• K: constant
Weber’s law
Question:
• With a standard stimulus 1 kg, John’s
difference threshold was 0.25kg. With a
standard stimulus 10kg, what would be
John’s difference threshold?
Question:
• With a standard stimulus 1 kg, John’s
difference threshold was 0.25kg. With a
standard stimulus 10kg, what would be
John’s difference threshold?
DL/S=K
DL/S=K
•DL: 0.25
•DL: ?
•S: 1
•S: 10
•K: 0.25
•K:
Magnitude estimation
• What is it?
Magnitude estimation
Magnitude estimation
Standard:
== 10
Standard:
== 100
Target: == ?
Target: == ?
Steven’s power law
• P = K S^n
P: perceived magnitude
K: constant
S: stimulus intensity
n: a power
Neurons
Dendrites
Cell body
Axon
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Neuron
Neurotransmitter
Synapse
Action potential
Dendrites
Axon
Cell body
Excitatory and inhibitory connections
Rods and cones
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Morphology
Their roles
Distribution on the retina
Their connections
Photo receptors: Rods and cones
The distribution of cones and rods
on the retina
• Cones are concentrated
mainly on the fovea.
• There are no rods on the
fovea.
• We move eyes to capture
images on the fovea.
• Convergence:
– The ratio of connections with two groups of
neurons.
– Rods vs. Ganglion cells
• 120:1
– Cones vs. Ganglion cells
• 6:1
Why does this matter?
The frequency of
action potential
The number of
action potential
emitted by a
neuron is
correlated with
Time
the intensity of
the stimulus.
0
t
0
t
Time
0
t
Time
• How do you detect there are
two separate dots (lights)?
Questions: What happens to
B?
Questions: What happens to B?
Excitatory
Inhibitory
Questions: What happens to B?
Receptive field
• The receptive field of a neuron in the
visual system is the area on the retina
that influences the firing rate (action
potential) of the neuron.
• Measuring the receptive field of a
ganglion cell
Measuring a receptive field of a
ganglion cell
Change the size of the stimulus and see
the way a ganglion cell respond
Cones
Ganglion
cell
12 3 4 5 6 7
B
=sum(B
=sum(B)
Physical stimuli
Your perception
Lateral
inhibition
Lateral inhibition
L
H
(A) (B) (C)
H
H
H
(D)
L
L
L
(a)= -h’ + h -h’
(b)= -h’ + h -l’
h
h
h
l
h’ h’ h’ h’ h’ l’
(a)
(b)
l
l
h’ l’
l’ l’
(c)
(d)
(c)= -h’ + l -l’
l’ l’
(d)= -l’ + l -l’
h>l
h’ > l’, -h’<-l’
(a)<(b), (c) <(d)
Lateral inhibition
L
H
(A) (B) (C)
H
H
H
(D)
L
L
L
(a)= -h’ + h -h’
(b)= -h’ + h -l’
h
h
h
l
h’ h’ h’ h’ h’ l’
(a)
(b)
l
l
h’ l’
l’ l’
(c)
(d)
(c)= -h’ + l -l’
l’ l’
(d)= -l’ + l -l’
h>l
h’ > l’, -h’<-l’
(a)<(b), (c) <(d)