Development of Reach and Grasp Flashcards
How do newborns track an object?
Using saccadic eye movements.
Track objects well by 3 months and use head and eye movements together by 5 months
How do children locate targets?
At birth a baby can move attention from one object to another.
As they mature they go through period of “obligatory looking” but they are able to disengage from object again by about 4 months.
What about smooth pursuit eye movements at birth?
Limited smooth pursuit at birth.
Improves at 6 weeks.
What is timeline for eye-head-hand coordination?
2 months: head and arm strongly coupled
Over next 2 months: head and arm uncouple, allows for more flexibility
By 4 months: infants gain trunk postural stability, providing stable base for emergence of reaching
What does rudimentary reaching skills (pre- reaching) look like in newborn-3 months?
Newborn: moves arm when visually fixated on an object, open hand
2 months: frequency of reaching decreases, hand fisted
3 months: frequency of reaching increases, hand open, infants acquire skill in aiming movements and become realistic in their reaching
How are reaching movements triggered?
Visually triggered
What does infant reaching look like from 4 months to 9 months?
4-5 months: reaching occurs in several steps, bimanual reaching may dominate, elbow may be locked, final approach is awkward, reaching becomes visually guided
6 months: reaching becomes smoother (fewer steps), unilateral reaching may begin, elbow is used
8-9 months: coordinated/complementary bimanual reaching (transfers objects), controlled release
What does reaching look like at end of first year?
visually guided reaching diminishes
initiate reaching using ballistic strategy to aim hand at target and then switch to a feedback strategy to make corrective movements for grasping
How does reaching change throughout childhood?
Changes little from 9 months to 7 years.
5 year olds: ballistic strategies, lots of feedforward
7 year olds: constantly monitor and control their reaches with closed loop strategy (lots of visual feedback)
9-11 years old: combine strategies to improve efficiency and reduce amount of attention required
What are intrinsic factors that influence reaching in infancy?
Age, experience, postural control, developmental delay
What are extrinsic factors influencing reaching in infancy?
Task demands/extrinsic factors
Vision
Coordination
What does rudimentary grasp look like from 0-3 months?
newborn-2 months: reflexive grasp, hand is open during reaching (extensor synergy)
2 months- hand is fisted during reaching
3 months- open hand when infant is visually fixated on target
What infant grasp from 4-6 months look like?
4-5 months: begin to use vision to correct hand trajectory, palmar grasp emerges
5-6 months: expect to see hand and performance is disturbed if vision of hand is blocked, visual info is used to adjust grip configuration, radial palmar grasp
From 8-13 months what does grasp look like?
8-9 months: opening of hand during reaching is related to size of object, pincer grasp emerges
12-13 months: grasp is initiated earlier in reach, timing is similar to adults, pincer grasp is well-developed
What does grasping look like in childhood?
2 years: grip and load force are negatively correlated, tendency to over shoot targets
4 years: children use anticipatory control strategy for grasp (grip and load force become positively correlated, less overshooting)
adults: grip and load forces are programmed in parallel to prevent slips and avoid squeezing too hard, integration of feedback and feedforward strategies
