Prism Adaptation
Prism Adaptation

Example
Prism Adaptation
Place yoked prism (base left or right) OU
 Subject makes motor responses
 Measure how quickly adaptation occurs
 Take prism off to measure after-effect

Prism Adaptation
The adaptation phase is where the motor
system adapts to a new visuospatial
coordinates created by the yoked prisms.
 The aftereffect is a method to measure
the amount of adaptation that has taken
place once the prisms have been
removed.

Prism adaptation
Parietal cortex
 Cerebellum
 Motor cortex

Prism Adaptation
Held Experiment (1965)
 Plasticity of the visual system
 Depends on interaction between the motor
and visual systems

Ruiz & Diaz (1999)
Subjects throw ball at a target 2 meters
away
 Baseline, adapt to prism, after-effect
 Investigated adaptation by number of
throws and amount of prism

Prism Adaptation
10, 20 and 30 prism diopters of prism
power
 Varied number of throws 3, 6, 9, 13, 25

Prism Adaptation

Conclusions
 Larger
prism power leads to greater
displacement on first throw and increases the
number of throws needed to adapt
 Aftereffect depends on the number of visual
motor interactions (throws) not on wearing
time.
 Aftereffect does not have the same magnitude
as the adaptation
Prism Adaptation in Neglect
Patients
Can we use prism adaptation to aid
patients with left side neglect?
 http://www.youtube.com/watch?v=B89qYu9Ov8&feature=related

Prism Adaptation in Neglect
Patients
Frassinetti et al 2002 Brain
 13 right brain injury patients
 Half the patients where in a control group
 Wore base left prism that shifted the field
10 degrees (34 cm viewing distance)

Prism Adaptation in Neglect
Patients
Pointed to objects in a box-similar to Held
paradigm
 2 sessions a day for 2 weeks
 The after effect lasts much longer in these
patients (6 to 12 hours)

Frassinett et al Study

Conclusions
 Treatment
resulted in long term effects
 Treatment transferred to a wide variety of
skills
 Do not need awareness of the condition for
improvements to occur. Bottom up task
Why?

Neurological correlates of prism adapation
 Cerebellum
 Posterior
parietal cortex
 Motor cortex
Possible Theories

Effect balance between right and left
parietal areas
 In
neglect patient may force them to attend to
right hemisphere information