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La percezione del movimento. La selettività neurale per il movimento. Il detettore (parziale) di Reichardt. Nulla. Preferita. Il detettore (completo) di Reichardt. Movie. L ’ illusione dell ’ insegna dei barbieri. demo. V1. MT. Waterfall illusion (Addams, 1834). - PowerPoint PPT Presentation
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La percezione del movimento
La selettività neurale per il movimento
Il detettore (parziale) di Reichardt
PreferitaNulla
Il detettore (completo) di Reichardt
+ -
M M
+ -
M M
Movie
L’illusione dell’insegna dei barbieri
demo
V1
MT
Waterfall illusion (Addams, 1834)
Positional motion aftereffect (PMAE)
Snowden (1998) Curr. Biol.Nishida & Johnson (1999) Nature
Movimento complesso: flusso ottica
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.
Neural response in MSTdDuffy & Wurtz, 1991
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
Signal-to-noise Predictions
• S α Nsectors
• σ2 α Nsectors σ α √Nsectors
• S/σ α √Nsectors
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
Signal-to-noise Predictions
• S α Nsectors
• σ2 = k (constant)
• S α Nsectors
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
Two-stage motion analysis
Σ
Local motion detectorsContrast thresholded
Complex motionintegrator
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
10 100
1
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
100 1000 10000
10
100
1000
100 1000 10000
10
100
1000
100 1000 10000
100 1000 10000
Translation
100 1000 10000
10
100
1000
RadialCircular
FP
LS
100 1000 10000
10
100
1000
Con
trast
Sen
sitiv
ity
Duration (ms)
Temporal summation of contrast sensitivity
00
0
ttt
ttatSp
p
100 1000 10000
Duration (ms)
Coh
eren
ce S
ensi
tivity
100 1000 10000
1
10
100
1000
100 1000 10000
Translation
100 1000 10000
1
10
100
1000RadialCircular
FP
LS
100 1000 10000
1
10
100
1000
100 1000 10000
1
10
100
1000
Motion coherence sensitivity
00
0
ttt
ttatSp
p
10 secs
noise signal
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
Segmentation has different temporal integration.
Even a weak signal embedded in noise can be seen given a long enough view
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
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 (%)
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
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)
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°.
A neural centre for optic flow?
FLOW (30 s) NOISE (30 s)2 s 2 s 2 s 2 sInverting Direction
Rotation
Radial
Translation
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
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)
Translation
Flow SB
Experiment in dos
Biological motion
http://www.biomotionlab.ca/Demos/BMLwalker.html
Adult plasticity: paraplegia affects perception of “biological motion”
The mirror system?(Giacomo Rizzolatti)
Sensitivity impaired for biological motion but not contrast sensitivity for orientation
Controls
Patients
Arrighi et al., Current Biol. (2011)
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)
The results point to shared neural circuits for production and perception of movement
– the mirror system?
CONCLUSIONS Paraplegic adults have reduced sensitivity to
biological motion: shared neural mechanisms for perception and production of motion
L’illusione di Ouchi
L’illusione di Ouchi