La percezione del movimento
description
Transcript of La percezione del movimento
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La percezione del movimento
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La selettività neurale per il movimento
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Il detettore (parziale) di Reichardt
PreferitaNulla
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Il detettore (completo) di Reichardt
+ -
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M M
Movie
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L’illusione dell’insegna dei barbieri
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demo
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V1
MT
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Waterfall illusion (Addams, 1834)
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Positional motion aftereffect (PMAE)
Snowden (1998) Curr. Biol.Nishida & Johnson (1999) Nature
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Movimento complesso: flusso ottica
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Lettura
• Morrone, M.C., Burr, D.C., and Vaina, L. (1995). Two stages of visual processing for radial and circular motion. Nature 376, 507-509.
• Morrone, M.C., Tosetti, M., Montanaro, D., Burr, D.C., Fiorentini, A., and Cioni, G. (2000). A cortical area that responds specifically to optic flow, revealed by function Magnetic Resonance Imaging. Nature Neuroscience 3, 1322-1328.
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Neural response in MSTdDuffy & Wurtz, 1991
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10 100
1
10
Mot
ion
Sen
sitiv
ity (
1+N
/S)
Radial
10 100
Rotation
10 100
1
10DCB
Translation
10 100
1
10
10 100
Stimulus Area (%)
10 100
1
10MCM
Spatial summation
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Signal-to-noise Predictions
• S α Nsectors
• σ2 α Nsectors σ α √Nsectors
• S/σ α √Nsectors
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10 100
1
10
Mot
ion
Sen
sitiv
ity (
1+N
/S)
Radial
Empty Noise
10 100
Rotation
10 100
1
10DCB
Translation
10 100
1
10
10 100
Stimulus Area (%)
10 100
1
10MCM
Spatial summation in noise
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Signal-to-noise Predictions
• S α Nsectors
• σ2 = k (constant)
• S α Nsectors
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10 100
1
10
100
Probablity summation
DCB
Con
tras
t Sen
sitiv
ity
Area (%)
10 100
1
10
100
Contrast summation
MCM
Spatial summation of contrast
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Two-stage motion analysis
Σ
Local motion detectorsContrast thresholded
Complex motionintegrator
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10 100
1
10
100
DCB
Con
tras
t Sen
sitiv
ity
Area (%)
Empty Noise
10 100
1
10
100
MCM
Spatial summation of contrast in noise
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10 100
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10
100
DCB
Con
tras
t Sen
sitiv
ity
Area (%)
Disc Det Empty Noise
10 100
1
10
100
MCM
Spatial summation of contrast in noise
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100 1000 10000
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100 1000 10000
100 1000 10000
Translation
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1000
RadialCircular
FP
LS
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10
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1000
Con
trast
Sen
sitiv
ity
Duration (ms)
Temporal summation of contrast sensitivity
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0
ttt
ttatSp
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Duration (ms)
Coh
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ce S
ensi
tivity
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10
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100 1000 10000
Translation
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FP
LS
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1
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Motion coherence sensitivity
00
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ttt
ttatSp
p
10 secs
noise signal
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100
1000
10000
coherence Contrast
Translation Circular RadialTranslation Circular Radial
Type of flow
LS
Te
mp
ora
l Int
egra
tion
(ms)
100
1000
10000
FP
Summation constants
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Segmentation has different temporal integration.
Even a weak signal embedded in noise can be seen given a long enough view
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10 100
1
10
DCB 4.5o
Mo
tio
n S
ensi
tivi
ty (
1+ N
/S)
10 100
1
10
MCM
72o
Radial Circular Trans
10 100
1
10
18o
10 100
1
10
10 100
1
10
Stimulus Area (%)10 100
1
10
Summation with large fields
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Summation with large fields in
noise1 10 100
1
10
DCB
4.5o
Mot
ion
Sen
sitiv
ity (
1+N
/S)
1 10 100
1
10
MCM
72o
1 10 100
1
10
36o
18o
1 10 100
1
10
1 10 100
1
10
1 10 100
1
10
1 10 100
1
10
1 10 100
1
10
Stimulus Area (%)
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1 10 100
0
1
2 MCMS
lope
of S
umm
atio
n F
unct
ion
Stimulus Diameter (degs)
1 10 100
0
1
2
DCB Radial Circular Trans
Spatial summation for flow is extensive
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Spatial summation of contrast sensitivity of sinusoids
Anderson and Burr, 1987
0.01 0.1 1 10 1000.01
0.1
1
10
SA HS
Su
mm
atio
n L
imit
(de
gs)
Spatial Frequency (c/deg)
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Interim Conclusions•There exists psychophysical evidence for detectors tuned to complex optical flow.
•Evidence suggest that the detectors are “second-stage” after contrast thresholding.
•Temporal summation is extensive: ~ 3 sec.
•Spatial summation is extensive, ~ 70°.
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A neural centre for optic flow?
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FLOW (30 s) NOISE (30 s)2 s 2 s 2 s 2 sInverting Direction
Rotation
Radial
Translation
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MT
Time (s)
Res
pons
e
Inverting Rotation / Inverting Noise
Continuous Rotation / Noise
Gradually Changing Flow / Noise
MC
b
a
c
d
e
f
0 60 120 1800.98
0.99
1.00
1.01
1.02
0 60 120 1800.98
0.99
1.00
1.01
1.02
0 60 120 1800.98
0.99
1.00
1.01
1.02
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0 60 120 1800.98
0.99
1.00
1.01
1.02
Continuous Translation \ Noise
Ave
rag
ed N
orm
aliz
ed R
esp
on
se
0 60 120 1800.98
0.99
1.00
1.01
1.02
Inverting Translation \ Inverting Noise
Time (s)
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Translation
Flow SB
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Experiment in dos
Biological motion
http://www.biomotionlab.ca/Demos/BMLwalker.html
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Adult plasticity: paraplegia affects perception of “biological motion”
The mirror system?(Giacomo Rizzolatti)
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Sensitivity impaired for biological motion but not contrast sensitivity for orientation
Controls
Patients
Arrighi et al., Current Biol. (2011)
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Paraplegic sensitivity worse for visual motion, especially biological
motion
3
10
100
300
30
100
1000
3000
*
Coh
eren
ce s
ensi
tivity *
**
Motion CS Static CSBM:DirectionDiscrimin
BM: Detection
TranslatingWalker
Controls Patients
**
Con
tras
t sen
sitiv
ity
Arrighi et al., Current Biol. (2011)
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The results point to shared neural circuits for production and perception of movement
– the mirror system?
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CONCLUSIONS Paraplegic adults have reduced sensitivity to
biological motion: shared neural mechanisms for perception and production of motion
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L’illusione di Ouchi
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L’illusione di Ouchi
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