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