Postnatal Development
of
Behavior
Unique Problems Faced
by Altricial Neonates
1. Sensory immaturity
stimuli available to adults not available to
neonate
2. Motor immaturity
ability to act on motivations is limited
3. Physiological immaturity
motivational systems, regulatory systems
4. Morphological immaturity
small size
Difficulties in Assessing
Behavioral Development
Identification of eliciting stimuli
Motivations different from those of adults
Response definition
(recall “isolation distress” of infant rats)
Mechanisms of
Behavioral Maturation
CNS maturation
Threshold changes
Integration and individuation
Response competition
Morphological change
Permissive/supportive environment
Permissive
Environment
CNS maturation (also in
development of locomotion
in the frog)
How do we know if hiccuping and breathing are the same
behavior that differ only quantitatively, or whether they are
qualitatively different behaviors? Should function matter?
Should neural substrates matter? (Recall suckling and
feeding, non-shivering thermgenesis; Response Definition)
First few weeks
Four months to one year
After approximately one year
McGraw, M. (1939) Swimming behavior of the human infant.
J. Pediatrics, 15, 485-490.
Is swimming at one year the same behavior as it is in the first
few weeks?
Mechanisms of
Behavioral Maturation
CNS maturation
Threshold changes
Integration and individuation
Response competition
Morphological change
Permissive/supportive environment
First few weeks
Four months to one year
After approximately one year
McGraw, M. (1939) Swimming behavior of the human infant.
J. Pediatrics, 15, 485-490.
Encephalization and the maturation of behavior
British neurologist John Hughlings Jackson
“Doctrine of dissolution”
Histology
a. Nissl stain
(cell bodies)
Prosencephalon
Mesencephalon
Thalamus
Rhombencephalon
Hypothalamus
Subthalamic nucleus
FIG. 1. Parasagittal section through the brain of kitten K-l,
showing the level and extent of transection. The rostra1 tilt
of the cut is the result of growth of the brain in that direction
in the weeks after the transection. Weil stain.
b. Weil stain
(myelin)
Histology
Kitten #1
Kitten #3
Kitten #2
Behavior of Decerebrate Kittens
Suckling abolished
Decerebrate rigidity not observed
Reflexive eating and lapping of milk emerged at normal age of weaning
Temperature regulation was only slightly impaired
All of the following developed in normal chronological order
auditory reflexes (orienting, pawing at source of sound)
tactile placing reactions
defensive reactions (piloerecton, hissing, bared teeth, biting)
grooming
postural reflexes
Sleep-wake states developed normally
Visual recognition and social behavior were absent
Some behaviors, e.g. pounce, “kill” behaviors, developed precociously, were
exaggerated in form (hypermetria) and directed toward inappropriate stimuli
There were bouts of uncontrolled locomotion (hyperkinesis), with kittens sometimes
running pell-mell off table-tops
Also, “compulsive” climbing was observed.
First few weeks
Four months to one year
After approximately one year
McGraw, M. (1939) Swimming behavior of the human infant.
J. Pediatrics, 15, 485-490.
Zelazo, P.R.,
Zelazo, N.A. &
Kolb, S. (1972)
“Walking in the
newborn infant.
Science, 176,
314-315.
The first supporting evidence is the likelihood that newborn stepping does not
‘disappear”, but that stepping in the upright posture is masked by other
developmental changes in the infant. First, in infants who no longer step, a
simple alteration of posture -- that of placing infants supine — releases
pattern generation identical to that of steps. Thelen and Fisher have
suggested that biomechanical factors, rather than changes in centralneurological organization, account for this paradoxical result. Specifically,
they suggested that the rapid acquisition of s.c. fat in the first 2 or 3 months of
life taxed the available muscle strength when infants were in the demanding
upright posture. When infants were placed supine, movements were
facilitated. Indeed, infants who gained weight most rapidly between 2 and 6
weeks showed the most rapid decline in step rate. When growth changes
were simulated by adding small weights to the legs of 1-month-old infants,
their step rate and amplitude declined. Likewise, placing infants in torso-high
water restored high levels of stepping, even in 3-month-old infants. These
results suggest that when the context was appropriate, the underlying
coordination traditionally believed to be cortically inhibited would become
manifest.
Thelen, E. & Bradley, N. (1988) Motor development: Posture and locomotion.
In E. Meisami and P. S. Timiras (Eds.) Handbook of human growth and
developmental biology. Volume I: Part B. CRC Press, Boca Raton, FL.
Rat Somatosensory Cortex
From Wise, Fleshman & Jones (1979) Neuroscience, 4, 1275-1297
Increased opportunities for spatial and temporal
summation.
Stehouwer, D.J., McCrea, A.E. & Van Hartesveldt, C. (1994)
L-DOPA-induced air-stepping in preweanling rats: II. Kinematic
analyses. Dev. Brain Res., 82, 143-151.
Stehouwer, D.J., McCrea, A.E. & Van Hartesveldt, C. (1994)
L-DOPA-induced air-stepping in preweanling rats: II. Kinematic
analyses. Dev. Brain Res., 82, 143-151.
Stehouwer, D.J., McCrea, A.E. & Van Hartesveldt, C. (1994)
L-DOPA-induced air-stepping in preweanling rats: II. Kinematic
analyses. Dev. Brain Res., 82, 143-151.
Stehouwer, D.J., McCrea, A.E. & Van Hartesveldt, C. (1994)
L-DOPA-induced air-stepping in preweanling rats: II. Kinematic
analyses. Dev. Brain Res., 82, 143-151.
Stehouwer, D.J., McCrea, A.E. & Van Hartesveldt, C. (1994)
L-DOPA-induced air-stepping in preweanling rats: II. Kinematic
analyses. Dev. Brain Res., 82, 143-151.
Stehouwer, D.J., McCrea, A.E. & Van Hartesveldt, C. (1994)
L-DOPA-induced air-stepping in preweanling rats: II. Kinematic
analyses. Dev. Brain Res., 82, 143-151.
Soiled
nest
shavings
Start Box
Soiled
nest
shavings
Clean
nest
shavings
Clean
nest
shavings
Mechanisms of
Behavioral Maturation
CNS maturation
requisite circuitry not yet active
Activation of existing circuitry
circuitry present, not active under normal circumstances
Integration and individuation
complex behaviors emerge when all component parts
become functional, differentiation of gross behaviors
Response competition
behavioral dominance changes with age
Mechanisms of
Behavioral Maturation
Physiological Maturation
physiological development allows for new solutions to problems
Morphological change
behaviors physically not possible
Permissive/supportive environment
special conditions necessary to allow for behavioral expression
New attractor states
Changing value of control parameters in dynamical systems
What can we infer
about CNS development
from studies of behavior?
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Postnatal Development of Behavior