Visuo-Motor Relationships: Plasticity and Development Read: Rosenbaum Chapters 2, 6 + may.doc

Ability to adapt to new relationships requires cerebellum

Problem of sensory-motor coordination: How do we relate the visual and motor worlds? For reaching, a visual signal about location must be transformed into a command to the arm and hand muscles. This is not innate, but must be learnt during development, and maintained through adulthood.

Evidence that visuo-motor coordination must be learnt during development. Evidence: Kittens given visual experience without opportunity for movement, and motor experience without vision, don’t learn how to control their movements using vision. Correlating the two is necessary (Held & Hein study).

Held & Hein Role of Experience in Development of Visuo-motor coordination Both kittens get visual experience and motor experience K1. Visual experience correlated with motor commands/proprioceptive feedback/vision of limbs K2. Gets both, but uncorrelated. Kitten 2 -abnormal visuo- motor coordination. 1 2

If he saw an object on the right he would reach with his right hand and discover he should have reached with his left. He could not feed himself very well, could not tie his shoelaces, and found himself severely disoriented. His image of his own body became severely distorted. At times he felt his head had sunk down between his shoulders,and when he moved his eyes and head the world slid dizzyingly around. As time went by Stratton achieved more effective control of his body. If he saw an object on the right he would reach with his left hand. He could accomplish normal tasks like eating and dressing himself. His body image became almost normal and when he moved his eyes and head the world did not move around so much. He began to feel as though his left hand was on the right, and his right hand on the left. If this new location of his body was vivid, the world appeared right side up, but sometimes he felt his body was upside down in a visually right-side-up world. After removing the prisms, he initially made incorrect reaching movements. However, he soon regained normal control of his body. Adaptation to different relation between vision and movement. George Stratton –Wore inverting lens for 8 days

Adaptation to different relation between vision and movement. George Stratton –Wore inverting lens for 8 days –Believed that we learn visual directions by associating visual experiences with other forms of sensory feedback (e.g. proprioceptive). –Alternatively… Adaptation results from learning the correlation between vision and actively generated motor commands (Held, 1965).

Why do we need to retain plasticity for new visuo-motor relationships? 1. Need to adjust to changes in body size during development. 2. Need to adjust to damage/aging. 3. Need to adjust to environmental changes eg ice, loads etc. 4. Need to learn arbitrary mappings for tool use etc. 5. Need to acquire new motor skills. 6. Visuo-motor coordination is a computationally difficult problem for the brain. Need flexibility to correct errors.

Lab 3: adaptation to visuo-motor transformations Expt 1 – Adaptation to visuo-motor transformations of different magnitudes. Expt 2.- Effect of stimulus manipulations on response latency

Expt 1 – Adaptation to visuo-motor transformations of different magnitudes. What is the visuo-motor latency? We get two estimates – horizontal and vertical. These are probably very Similar.

time X position

Rotational Transformation mouse cursor angle θ θ = 0, 45, 90, 135, 180 degrees

Does error change over time as the subject adapts? Small increase in error for 45 and 90 deg – reduced error after 20 trials. Big initial error for 135 and 180 deg – close to baseline after 20 trials.

Plot error versus transformation angle for trial = 1 and trial = 20 to view the data another way.

Not much effect on latency for 45 and 90 deg. Big increase in latency for 135 and 180 deg – still present after 20 trials.

Can also plot V lag or H lag versus transformation angle for Trial 1 and Trial 20 messy

Measure 10 trials, get means and standard errors of Horizontal lag, Vertical lag, and avg error. Questions: Is H lag different from V lag? For an individual S you can test for a difference using an independent samples T test using two groups of 10 trials. For the class, we can test using a matched pairs t-test (using mean for each S)

Components of visuo-motor latency: Stimulus processing Transformation of sensory to motor signals Production of motor response. Two manipulations of the stimulus – spatial frequency and contrast Expect faster to detect Horizontal change than a vertical change

Brighter lights lead to a faster response Contrast or brightness changes should lead to reduced latencies.

Vertical lag is longer than Horizontal lag. Low contrast lag is longer than high contrast lag. Not much change over trials For individual S data use t tests to compare H and V lag and also to compare low and high contrast lag.

Error is greater for low contrast and gets smaller over trials. Can use a t test for individual S data for low vs high contrast

Photoreceptor response to light