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Postnatal Development of Behavior

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  1. Postnatal Development of Behavior

  2. 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

  3. Difficulties in Assessing Behavioral Development Identification of eliciting stimuli Motivations different from those of adults Response definition (recall “isolation distress” of infant rats)

  4. Mechanisms of Behavioral Maturation CNS maturation Threshold changes Integration and individuation Response competition Morphological change Permissive/supportive environment

  5. Permissive Environment

  6. CNS maturation (also in development of locomotion in the frog)

  7. 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)

  8. 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?

  9. Mechanisms of Behavioral Maturation CNS maturation Threshold changes Integration and individuation Response competition Morphological change Permissive/supportive environment

  10. 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.

  11. Encephalization and the maturation of behavior British neurologist John Hughlings Jackson “Doctrine of dissolution”

  12. Histology Mesencephalon Thalamus a. Nissl stain (cell bodies) Rhombencephalon Prosencephalon 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)

  13. Histology Kitten #2 Kitten #1 Kitten #3

  14. 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.

  15. 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.

  16. Zelazo, P.R., Zelazo, N.A. & Kolb, S. (1972) “Walking in the newborn infant. Science, 176, 314-315.

  17. 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 central-neurological 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.

  18. Increased opportunities for spatial and temporal summation.

  19. 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.

  20. 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.

  21. 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.

  22. 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.

  23. 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.

  24. 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.

  25. Start Box Clean nest shavings Soiled nest shavings Soiled nest shavings Clean nest shavings

  26. 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

  27. 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

  28. What can we infer about CNS development from studies of behavior?