prism adaptation: dependency on motion trajectory christian kaernbach lutz munka institut für...
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Prism Adaptation: Dependency on Motion Trajectory
Prism Adaptation: Dependency on Motion Trajectory
Christian KaernbachLutz Munka
Institut für Allgemeine PsychologieUniversität Leipzig
Douglas Cunningham
Max-Planck Institut für Biologische Kybernetik
Tübingen
Perception and ActionPerception and Action
و ت ؤظ ز كه ن غ
ج د ى
Sign TheoryHermann von Helmholtz, 1879
Object Perception
Perception as “Image”
Perception
Action
Correlation theories
Perception serves ActionJames J. Gibson, 1979
Experiments with prism gogglesExperiments with prism goggles
Fresnel prisms
www.prism-adaptation.deprism goggle set: 15 €
Perception
Action
Experiments with prism gogglesExperiments with prism goggles
و ت ؤظ ز كه ن غ
ج د Actionى
PerceptionAction
Perception
Action
Perception
???
???
Adaptation
Problem: centralrepresentation of
spatial knowledge
spatialknowledge
is distributed
Suspicion: The exact motion sequence is relevant.Martin, T.A., et al. (1996). no transfer between underhand and overhand throwing
Kitazawa et al. (1997): no transfer between fast and slow reaching
Hypothesis: The Negative Aftereffect (NAE) is greater for the adapted as compared to an alternate trajectory.
Effect of motion trajectoryEffect of motion trajectory
– Touch screen– Horizontal bar as chin rest– 72 participants,
graded randomly in 4 groups– target position central (block 2&4)
or horizontally randomized (Block 1&3)– prism goggles (Block 3) with 16.7° horizontal
shift (left-hand base)
• Block 1 „Familiarization“ with full visual feedback,20 trials (5 repetitions 4 trajectories)
• Block 2 „Pretest“ without feedback, 20 trials (54)• Block 3 „Adaptation“ with prism goggles, with full visual feedback,
80 trials (801) a single trajectory is adapted, one per group• Block 4 „Posttest“ without feedback, 20 trials (54)
ResultsResults
passive hand:Block 4 vs. Block 2 Block 4 minus Block 2
0102030
-80 -60 -40 -20 0 20 40 60
PHST PHAT
µ = 3 ± 1.8 mmµ = 1 ± 1.7 mm
-60
-50
-40
-30
-20
-10
01 2 3 4 5
AHAT
AHST
Linear(AHST)Linear(AHAT)
temporal dynamics
0102030
-80 -60 -40 -20 0 20 40 60
AHST AHAT
µ = -46 ± 2.2 mmµ = -26 ± 2.3 mm
PH passive hand ST same trajectoryAH active hand AT alternate trajectory
horizontal error [mm]
hori
zont
al e
rror
[m
m]
ResultsResults
-60
-50
-40
-30
-20
-10
01 2 3 4 5
AHAT
AHST
Linear(AHST)Linear(AHAT)
temporal dynamics
PH passive hand ST same trajectoryAH active hand AT alternate trajectory
-60
-50
-40
-30
-20
-10
01 2 3 4 5
AHAT: B234 dominantAHAT: B234 schwachAHST: B234 dominantAHST: B234 schwach
handiness
-60
-50
-40
-30
-20
-10
01 2 3 4 5
AHAT: B3 o, B4-2 uAHAT: B3 u, B4-2 oAHST: B3 o, B4-2 oAHST: B3 u, B4-2 u
above/below
familiar / unfamiliar motions
non-pref
non-pref
Discussion of first experimentDiscussion of first experiment
• no transfer of adaptation to unadapted handonly ca. 50% transfer to alternate trajectory of adapted hand
• passive decay of adaptationunfamiliar motions are affected more
adaptation seems not to depend on recalibration of proprioceptionotherwise 100% transfer to be expected.
relearning of motor scripts ?
Objection: same starting position, but slightly different end position,end position of unadapted trajectory was not adapted.
Some more experimentsSome more experiments
-59-49
-90
-60
-30
0
Neg
ativ
e A
fter
effe
ct[m
m]
same different trajectory
Interposing circular movements
-80
-51
-90
-60
-30
0
Neg
ativ
e A
fter
effe
ct [
mm
]
same differentstarting position
Varying the starting position
Some more experimentsSome more experiments
With/without weighted wrist wrap
-55-44
-90
-60
-30
0
Neg
ativ
e A
fter
effe
ct [
mm
]
same different condition
Vertical generalization
-90
-60
-30
0
Neg
ativ
e A
fter
effe
ct [
mm
]
high both low
high
medium
low
adapted
tested
Some more experimentsSome more experiments
Temporal dynamics of adaptation in block 3Alternate full/no feedback / Terminal feedback
0102030405060708090
100
0 5 10 15 20# of feedbacks
Hor
izon
tal e
rror
[m
m]
blind (alt. with full feedback)terminal feedback
ConclusionsConclusions• Adaptation does not transfer to the passive hand,
nor fully to alternate trajectories of the adapted hand.
• Adaptation of pointing performance involves mainly relearning of motor scripts.
• Spatial motor knowledge is distributed. There is no central representation of spatial motor knowledge.
Knowing where is knowing how to.
• But what about our phenomenal experience? It seems that it is not needed for direct motor actions like pointing, grasping etc.
– blindsight patients catching balls– Stratton (1897) riding bicycle with inverting goggles
with phenomenal experience still upside-down.
• What is phenomenal experience good for?It seems to be a late product of evolution, enabling us to plan alternative action schemes. Tolman, E.C. (1948). Cognitive maps in rats and men. Psychological Review, 55, 189-208.
Illusion:Spatial knowledge is
consciousuniform, central
precisemotor actions, planing
ConclusionsConclusions
• Does the proposed dissociation between two spatial representations answer the “illusion question” in the abstract of this symposium?Yes.
Under ecological conditions perception and action work hand in hand without significant discrepancies, thus leading us safely through our daily activities. However, dissociations between space perception and spatial action are also well-known: Several figural illusions (e.g. the Müller-Lyer or the Titchener/Ebbinghaus illusions) deceive perceptual judgment but exert only a marginal influence on motor behavior like pointing and grasping. The aim of the symposium is to find the causes of these dissociations and to relate them to the contributions of motor processes to perceived visual space.
Two spatial representations:I II
unconscious consciousdistributed uniform, central
precise distortedmotor actions action planing