Yarbus 1967
Le saccadi
• Servono per spostare lo sguardo,
posizionando gli oggetti di interesse sulla
fovea.
• Sono movimenti rapidi e balistici.
• Possono essere involontarie o volontarie.
• La velocità è fra 200 e 900 gradi/sec
Two problems produced
by saccades:
• Fast large-field retinal
motion.
• Continuous displacement
of retinal image.
Contrast sensitivity at saccadic velocities
Saccadic velocities:
200 - 900 deg/sc
Efference copy
Corolary discharge
Contrast Sensitivity
1000
DB
norm
sac
1000
MCM
100
100
10
10
1
1
0.01
0.1
1
10 0.01
0.1
Spatial Frequency (c/deg)
1
10
Contrast Sensitivity
1000
lum
DB
col
1000
MCM
norm
sac
100
100
10
10
1
1
0.01
0.1
1
10 0.01
0.1
Spatial Frequency (c/deg)
1
10
JF
Contrast Sensitivity
MCM
10
10
1
1
0
200
400
0
Delay (ms)
200
400
Uchikawa & Sato
Relative Sensitivity
100
Saccade
Normal
P-Cells
M-Cells
10
1
500
600
Wavelength (nm)
700
SCREEN
MIRROR
Single cell of monkey MT
30
A
10
Contrast sensitivity
Human: blank background
1
-300
30
-200
-100
0
100
200
300
-200
-100
0
100
200
300
-200
-100
0
100
200
300
B
10
Human: texture background
1
Monkey
Normalised Firing
-300
10
C
1
0.1
-300
Time (ms)
Dynamics of saccadic suppression
Psychophysics & Physiology
Dynamics of saccadic suppression
Psychophysics & Physiology
Monkey MT
Diamond et al., 2000
Diamond et al., 2000
Michael Kubischik, Bart Krekelberg Frank Bremmer
Dept.Zoology & Neurobiology, Ruhr-Univ. Bochum
In MT la selettività per
la direzione cambia
durante i movimenti
saccadici
Evidenza da imaging
A che livello riaggisce la
soppressione saccadica?
Burr, D. “Eye Movements: Keeping Vision Stable”
Current Biology 2004
Contrast Sensitiity
100
Simultaneous Masking
10
1
1
10
Mask Contrast
100
Contrast sensitivity
normal
saccade
100
100
10
10
1
1
1
Mask Contrast (%)
10
100
Stimolazione elletrica della retina
e della cortex
I blinks
(gli ammiccamenti)
Burr “Vision: in the blink of an
eye”. Current Biology, 2005
LGN
Stimulation alone
Stimulation and blinks
Blinks in the dark
Predicted visual response
V1
3
0.4
0.2
BOLD Signal (%)
Soppressione
durante il
blinking
0.0
V2
4
2
2
1
0
0
2
V3
MT
0.1
1
0.0
0
-0.1
Le aree sopresse durante il blinking
Rosso: aree visive sopresse durante il blinking
Verde: aree occulomotori sopresse durante il blinking
Two problems produced
by saccades:
• Fast large-field retinal
motion.
• Continuous displacement
of retinal image.
We make 3
saccades per
second:
Continual
displacement of
retinal
information
Horizontal error in auditory localization (deg)
Auditory localisation of visual target in dark
Leonard Matin Science 1981
30
LM
Control
Paralised
20
30
JS
20
10
10
0
0
-10
-10
-20
-20
-30
-30
-30
-20
-10
0
10
-10
0
10
Horizontal eccentricity (deg)
20
30
Von Holst und Mittelstaedt 1954
Sperry 1950
30
Position (degs)
20
F1
10
0
-10
F0
-20
-30
-200
-100
0
100
Time (ms)
F0
-30
-20
-10
F1
0
10
20
30
Apparent position (degs)
40
JR
MCM
20
40
20
Target
0
0
Fix
-20
-20
-40
-40
-200
-100
0
100
200 -200
-100
0
100
Delay from saccadic onset
200
Apparent position (degs)
40
JR
MCM
20
40
20
Target
0
0
Fix
-20
-20
-40
-40
-200
-100
0
100
200 -200
-100
0
100
Delay from saccadic onset
200
Apparent position (degs)
40
JR
MCM
20
40
20
Target
0
0
Fix
-20
-20
-40
-40
-200
-100
0
100
200 -200
-100
0
100
Delay from saccadic onset
200
Apparent position (deg)
peri-saccadic
no-saccade
MCM
40
20
JR
40
20
Targ
0
0
Fix
-20
-20
-40
-40
-40
-20
0
20
40 -40
-20
0
Real position (deg)
20
40
30
Position (degs)
20
10
F1
0
F0
-10
-20
-30
-200
-100
0
100
Time (ms)
F0
-30
-20
-10
F1
0
10
20
30
Number of bars seen
5
Isoluminant green
Black bars
HDS
MRD
5
4
4
3
3
2
2
1
1
0
0
-100
0
100
-100
0
100
Time from saccade onset (ms)
Real saccades
MCM
4
Bars seen
JR
4 bars
4
2
2
0
4
0
4
3 bars
2
2
0
4
0
4
2 bars
2
2
0
4
0
4
0 or 1 bar
2
2
0
-200 -100
0
0
100 200-200 -100
Delay (ms)
0
100 200
SCREEN
MIRROR
Simulated saccades
MCM
JR
4
4
Bars seen
4 bars
2
2
0
0
4
4
3 bars
2
2
0
0
4
4
2 bars
2
2
0
0
4
4
0 or 1 bar
2
2
0
0
-200
-100
0
100
-200
Delay (ms)
-100
0
100
Physiological correlates
to compression?
Remapping can precede the
saccade.
Stimulus in Stimulus outside Saccade brings
receptive field receptive field stimulus into
receptive field
Saccade
alone: no
stimulus
Normalized Activity
Remapping can precede the saccade
0.6
0.5
0.4
0.3
future
current
0.2
0.1
t magniture
0.0
-400
1.0
0.8
0.6
-200
0
200
Time (ms)
400
600
LIP population response
Kubischik, Krekelberg & Bremmer
Remapping in humans:
psychophysics
Adapter
Test
Adapter
Remapping in humans:
psychophysics
Melcher
Nature Neurosc.
2007
left
After-effect magniture
Remapping in humans:
psychophysics
1.0
0.8
0.6
0.4
0.2
0.0
-400
right
-200
0
200
Time (ms)
400
600
Normalized Activity
Remapping in humans and
monkeys
0.6
0.5
0.4
0.3
future
current
0.2
0.1
After-effect magniture
0.0
-400
-200
0
200
400
600
-400
-200
0
200
400
600
1.0
0.8
0.6
0.4
0.2
0.0
Time (ms)
Two Visual Streams of Processing
Goodale and Milner
Pulv
Posterior
Parietal Cortex
SC
Retina
LGNd
V1
Inferotemporal
Cortex
Ventral
Scene-parsing and
object identification
Scene-based frame
of reference
Dorsal
Visual control of
motor output
Effector-based frames
of reference
Relational metrics
Absolute metrics
Propositional
Isomorphic
Long-term
representations
Moment-to-moment
computations
“Conscious”
“Automatic”
Goodale, M.A. & Humphrey, G.K. (1998). Cognition.
Matching
Patient DF
Control
Posting
Illusions fool the eye but not the hand in
normals: Aglioti, De Souza & Goodale
L’illusione inganna l’occhio ma non
la mano (Agliotti et Goodale, 1995)
-20
-16
-12
-8
-4
0
4
8
12
16
Fixation
Target
Bar
Eye
LC Shutter
-200
-100
0
Time (ms)
100
200
20
Verbal report: shutter closed
MCM
Apparent Position (deg)
JR
20
20
10
10
0
0
-10
-10
-20
-20
-20
-10
0
10
20
-20
-10
Real Position (deg)
0
10
20
Pointing: shutter closed
MCM
Apparent Position (deg)
JR
20
20
10
10
0
0
-10
-10
-20
-20
-20
-10
0
10
20
-20
-10
Real Position (deg)
0
10
20
Pointing: shutter closed
Verbal report: shutter closed
MCM
Apparent Position (deg)
JR
20
20
10
10
0
0
-10
-10
-20
-20
-20
-10
0
10
20
-20
-10
Real Position (deg)
0
10
20
Pointing: shutter closed
Verbal report: shutter closed
Apparent Position (deg)
25
25
MCM
JR
0.92
20
20
0.75
15
15
0.08
0.10
10
10
5
5
0
0
0
5
10
15
20
25 0
5
10
15
Real Position (deg)
20
25
Pointing: eyes closed
MCM
Apparent Position (deg)
JR
20
20
10
10
0
0
-10
-10
-20
-20
-20
-10
0
10
20
-20
-10
Real Position (deg)
0
10
20
Pointing: eyes closed
Verbal: shutter closed
MCM
Apparent Position (deg)
JR
20
20
10
10
0
0
-10
-10
-20
-20
-20
-10
0
10
20
-20
-10
Real Position (deg)
0
10
20
Illusion returns when vision available
Pointing: eyes and shutter open
MCM
Apparent Position (deg)
JR
20
20
10
10
0
0
-10
-10
-20
-20
-20
-10
0
10
20
-20
-10
Real Position (deg)
0
10
20
Illusion returns when vision available
Pointing: eyes and shutter open
Verbal: shutter closed
MCM
Apparent Position (deg)
JR
20
20
10
10
0
0
-10
-10
-20
-20
-20
-10
0
10
20
-20
-10
Real Position (deg)
0
10
20
The results support the idea of
separate representations of visual
space for perception and action.
• The perceptual system is plastic and subject
to distortion during saccades.
• The action system remains veridical during
saccades (to guide eye movments).
• When both systems are available the
perceptual system dominates.