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The Reflexive Phase

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Kim Siekerman

on 28 November 2013

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Transcript of The Reflexive Phase

The 'reflexive phase'
How do we get from here...
... to here???
Lecture 3
Monday 11 Feb
Kim Siekerman
Why study infants
PE
SES
Do we really need to start THAT young...
...in order to get the bigger picture?
Lecture contents
Infant motor development as a
process
-What can we see?
-How does it change?

Infant motor development as a
field of study
-What have they found?
-What does it mean?
Role of infant reflexes in the development process
Cerebral cortex
-Voluntary movement
-Decision making
Brain Stem
-Breathing
-Blood pressure
Spinal Cord
-Tract for connections to muscle and some sensory organs
Cortical
Sub-cortical
During development:
-Hyperplasia (250.000/min)
-Hypertrophy
-Specialisation
-Migration
-Connection
At Birth...
-The
brainstem
is relatively well-developed
-
But the rest of the brain is
not finished!
-
Connections
-
Myelinisation
-Too many
generic pathways
RESULT:
slow
and
inefficient
movements
We are pretty unprepared for the world
Fortunately
Nature gave us some basic movements that were

Pre-wired
Regulated by the
brainstem

These are the
INFANTILE REFLEXE
S
DEFINITION

Involuntary
,
sub-cortically
controlled movements’ (Gallahue and Ozmun 2002, p. 47)

Response to
external stimuli

Specific, localised and repeatable
(Haywood and Getchell (2009)
Primitive reflex: rooting
Postural reflex: Landau
Locomotor reflex: swimming
Is this all they do?
Spontaneous movement:
rhythmical stereotypies
Purpose of infantile reflexes
Some different opinions:

By-product of
hard-wiring

Survival
(nourishment and protection)

To provide infants with movement
experience
What happens to these reflexes?
They
disappear
, and after a ‘quiet’ period
voluntary

movement
appears

If infantile reflexes don’t disappear: indicative of
pathology

Role of infant reflexes in research
Major point of discussion!
Neuromaturation
Dynamical Systems
Motor skills develop as the
brain
matures

Different brain centres
are responsible for reflexes and voluntary control

Infants cannot move voluntarily until reflexes are
inhibited
Motor skills develop under the influence of a
lot of factors,
including brain development

Focus not on reflexes as part of brain structures: development is a
bigger picture

Movement
experience
develops the brain
Bernstein
Newell
Kelso
Thelen
McGraw
Eckert
How?
Self-organising processes:

Pruning
of redundant neurons
Myelin
development

…occur more strongly in brain areas that are
used extensively
.
So what role do infant reflexes have
according to DST?
They may be
precursors
to the voluntary movement (e.g. the stepping reflex)

They might provide movement
experience

Can we test this?
Step reflex training
(Zelazo 1972)
Conclusion:voluntary walking happens earlier!

BUT: stepping reflex disappears
It didn’t really disappear…
(Thelen & Fisher 1982; Thelen et al 1984)
Different factors
determined development
What is so important about the difference?
It means that:
Nature vs. nurture: we can influence the outcome by providing the right
experience
(i.e. in pathology, developmental delay)

Opposite
also true!!!

There is a
critical window
(approx birth-2 years)
Yes, because...
1) We can
apply the same principles
to

Children and adolescents (background?)
Athletes (talent?)
Rehabilitation (plasticity?)
...


2) Much of this knowledge was
supplied by
people studying babies!
My research, briefly:
Relationship vision and locomotion

Vision centres reside in
cerebral
cortex

Newborns step more vigorously when exposed to
visual flow

Newborns step more vigorously when exposed to
faster treadmill
speed
Can treadmill training be used
from birth

Is there a
speed effect
?
Does
vision
affect stepping?

Control of infant movement may be
more complex
than just ‘subcortical’
Reading:
Simple
:











Essential
:
Gallahue (2006), Chapter 7
Haywood (2005), Chapter 5

Challenging
: http://www.udel.edu/PT/galloway/motordevelopment.pdf
References
Haywood, K. M. and Getchell, N. (2009) Life Span Motor Development, ed. 5, Champaign, IL: Human Kinetics
Gallahue, D. L. and Ozmun, J. C. (2002) Understanding Motor Development: Infants, Children, Adolescents, Adults, ed. 5, New York, NY: McGraw-Hill
Thelen, E. & D. M. Fisher (1982) ‘Newborn stepping: An explanation for a "disappearing" reflex’, Developmental Psychology, 18, 760-775.
Thelen, E., Fisher, D. M, and Ridley-Johnson, R. (1984) ‘The relationship between physical growth and a newborn reflex’, Infant Behavior and Development, 7, 479-493.
Zelazo, P. R., Zelazo, N. A. and Kolb, S. (1972) ‘"Walking" in the newborn’, Science, 176, 314-315.
3 Categories
Primitive

Postural

Locomotor
Full transcript