Psych
311 - Psychophysical Development
OUTLINES
Chapter 1
Origin and Function of Embryonic Behavior
Rev.
Return to Syllabus
I. Introduction
A. Embryonic Behavior is a Critical Element in Ontogenesis
B. Contributing Factors
1. Development of noninvasive ultrasonic imaging techniques
2. New techniques in subfields of neuroscience
3. Consequences of embryonic exposure to drugs
II. Embryonic Motility and Spontaneous Neuronal Discharge
A. Preyer
1. Chick embryo
2. Movement displayed days prior to time a reaction can be evoked by tactile stimulus
B. Tracy (1926)
1. Toadfish
2. Bending the trunk in the anterior region before movement could be evoked by tactile stimulation (“spontaneous behavior”)
3. Suggested spontaneous behavior caused by changes in blood chemistry (accumulation of carbon dioxide) & response to sensory stimulation occurs later.
C. Gottlieb, Bradley, and Mistretta
1. Species differences on when sensory systems kick in.
1. Receptor complexes become more mature in embryos with long gestation periods
2. The more mature the motor system at birth or hatching the more likely particular sensory systems (vision) will possess the capacity to function during the embryonic period
D. Preyer and Tracy
2. The longer the gestation period, the more mature the motor system at birth the more likely sensory systems will function during embryonic period.
3. Early movement is a result of the neural motor system and the development of that system - suggested behavior was predetermined.
4. Spontaneous discharge theory received support from neuroanatomical experimentation.
E. Hamburger and Associates
1. Embryonic movement can be initiated and maintained by the spinal cord without stimulation.
a. Movements are not related to each other.
b. Length of activity increases with embryos age increasing.
2. Can movement be elicited by spinal cord itself?
a. Two-day-old embryos had section of spinal cord removed severing the spinal cord from brain.
b. Therefore movement is produced by motor neurons exiting the cord.
c. Cutting reduced activity by twenty percent.
F. Provine
1. Recorded electrical
activity directly from spinal cord.
2. On day five bursts of electrical activity were seen which coincided with body movement.
G. O’Donovan and Landmeisser
1. Recorded electrical
activity in the ventral root of the isolated cord.
2. It appears that is it the initial portion of the electrical burst that actually triggers muscle activity.
H. Combined Theories
1. Motility is the result of spinal reflexes that trigger output of muscle fibers.
2. Thoracic portions of spinal cord of two-day old embryos were removed so sensory input originating from the legs could be eliminated.
I. Conclusions
1. Sensory input not
required for embryonic motility.
2. The studies showed that under normal circumstances that embryos do respond to exteroceptive stimulation.
a. Embryos possess capacity
to respond spontaneously, they might not normally do so.
III. Embryonic Motility and Sensory Stimulation
A. Stimulation and assessment of nervous system development
1. Embryos were initially used for research of nervous system
2. Stimulation was thought to have no effect on development
3. Discovered motility of embryo without stimulation
4. 1902 – G.E. Coghill, Neuroanatomist
a. Researched the development of embryonic motility
b. Used salamander embryos with a human hair as stimulus
c. Correlations found between stimulation and motility
5. Coghill: Individuation
6. Mammalian embryos - methodological problems
a. Removed from uterus with care
b. An embryo is stimulated by a hair, needle or acid.
7. Angulo Y. Gonzalez
a. The responses of 643 rat embryo’s aged 14 to 21 days to stimulation were observed and recorded.
b. The earliest movement was seen at 15.7 days after insemination, which was movement of the head in response to stimulation.
c. Between 16.0 and 16.9 days movement spread in a caudal direction, first from the forelimbs, the rump and the finally the hindlimbs.
d. He concluded that tactile stimulation began as a total pattern of motility and over time became specialized to certain area’s of the body.
2. Hooker (see Table 1.1)
a. Performed experiments on aborted human embryo’s.
b. Hooker concluded that tactile stimulation is accompanied first by a total pattern response and later becomes individualized or discrete responses.
3. Windle
a. Studied the cat embryo
b. He found that asphyxia may abolish the individual behaviors before they are elicited by stimulation because of the impaired respiration that occurs when the embryo is removed from the uterus.
4. Carmichael
a. Experimented with the guinea pig embryo
b. He argued for the abandonment of mass action and individuation concepts because his data supported both concepts.
c. Carmichael suggested that we must collect data from a wider range of species before generalization about behavioral ontogeny could be conceived.
B. Motility and the interaction between embryo and environment
1. E.B. Holt
a. Environmentalistic View
1) embryonic behavior is not merely the result of nervous system development but rather the interaction between embryo and environment
2). development of nervous system is not predetermined
3) early movements are random
a. Dynamic Interaction
1) environment and behavior act continually on each other
2) behavioral potentials
3) wide range of possible outcomes of behavioral development
4) book - The Dynamics of Behavioral Development
b. Rejected the concept of reflex
c. Replaced with ‘behavioral gradients”
d. said
that entire embryo, all body parts and organs are involved in every response.
3. Ways light exposure affects embryos (Peters, Vanderahe, & Powers):
a. Exposure to light stimulus 2 to 3 days prior to hatching advanced the development of electrical responsivity of both the eye and optic lobe. The stimulus appeared to hasten maturation of the visual system.
b. Time of hatching: Intact chicken eggs exposed continuously to incandescent light from the first day of incubation hatched approximately 16 hours earlier the controls.
c. Brain lateralization: Chickens normally exhibit asymmetry in forebrain function. However, lateralization of attack and copulation is not reliably observed if incubated in darkness.
d. Light affects mammalian fetus: If the maternal suprachiasmatic nucleus (SCN) is destroyed, the rhythm in the embryo brain no longer is synchronized with the external lighting condition. Light therefore stimulates the maternal SCN, which, in turn, activates the embryonic SCN.
4. Sound as well as light plays a significant role in the development of the avian embryo
a. Vince and colleagues discovered that a particular sound regulates timing of hatching, speeding up development in more slowly developing embryos.
1) Quail embryos emit a clicking sound coincident with the onset of breathing. That hatching is regulated by clicking sound is supported by
a) When the eggs are in physical contact, hatching is virtually synchronous
b) When eggs are kept physically apart, the range of hatching times for a given clutch is markedly increased among the eggs
c) Playing the appropriate clicking sounds to eggs not in physical contact leads to synchronized hatching
2) A determiner of the efficacy of the click stimulus is its rate of presentation
5. Hypothesis that sensory receptors located in the neck are activated by the bending of the head, and it is this signal that initiates hatching
a. Bekoff and Sabichi used 0 and 1 day old chicks to test this idea
1) Two groups injected with anesthetic lidocaine, one group in the neck and the other in the thigh, the third group injected with saline in the neck
2) Group of subjects receiving anesthetic in the neck exhibited hatching activity much later than did the other groups
b. Supports
idea that interoceptive stimulation from the neck
initiates hatching behavior
7. Embryo is capable of responding to Stimulation as a matter of course
a. Arises from sources internal to the embryo, external to the embryo but internal to the amnion, external to the amnion but internal to the membranes or uterus, or external to the shell or the adult female
III. Functions of Embryonic Behavior
A. One approach to assessing function is to determine the effects of its absence.
1. Drachman and Coulombre (1962)
a. Infused paralytic agent curare into 15-day-old chick embryos for periods of 24 and 48 hours
b. Toes were hyper-extended, clawed, and crossed; ankle joints rigid
1) referred to as “clubfoot”
c. found that articular cavity formation and fine sculpting of the cartilaginous surfaces require the mechanical action normally provided by the embryo’s own skeletal muscle
2. Moessiger rat embryos
a. Discovered symptoms in rat that are similar to those of the Pena-Shokeir syndrome, a genetic disorder afflicting humans.
1) Been suggested that the defects are caused by fetal immobilization
3. Kuo (1976)
a. Embryonic behavior may be preparatory and therefore necessary for development of normal postembryonic behavior
B. Other studies of prenatal - postnatal relationship
1. Hamburger and Oppenheim (1967)
a. Chick embryo at day 17 shows coordinated movement
b. Suggests that coordinated movements may be guided by sensory information
2. Robinson and Smotherman (1987)
a. Rat embryo showed synchronous activity at day 17 of gestation
1) This was defined as a “true” behavior
3. Electromyographic Recordings (EMG’s) & Joint Angle Analysis
a. Provides a direct assessment of the pattern of muscle contractions assessment of the motor output pattern of the central nervous system (CNS)
b. Readings are obtained by inserting wire electrodes into muscle tissue and recording the electrical potentials
c. Measure angles of joints to determine movement of joints.
4. Bekoff and Lau (1980)
a. Observed similarities between prenatal and postnatal rats
b. Embryonic behavior preparatory for later activity
5. Smotherman & Robinson’s (1987) study on 19-21 day old embryos.
a. Rat embryos respond similarly to neonates when given milk, lemon juice in response to stimulation of the anogential region.
6. Number of embryos in a uterus may govern rate of development.
a. Gandelman & Graham created singleton mouse fetuses by surgically removing all but one embryo from the uterus.
1) Enhanced nutrition leads to more overall activity
2) Exhibited walking and eye opening earlier after birth.
C. Embryonic behavior serves important development functions and facilitates the survival of the embryo
1. Developmental functions
a. Embryonic motility may function to maintain the embryo in an optimal position within the amnion to benefit maximally from the buffering property of the fluid.
b. Hatching posture of chick embryo may be viewed as a precursor to escaping from its cramped environment
2. Survival of the embryo
a. If prenatal behavior is for survival of the fetus pre and postnatal behaviors should differ because of the differences in their environments.
b. Study by Smotherman & Robinson concerning the behavior of the rat fetuses in response to hypoxia induced by clamping umbilical cord compared to neonatal rats deprived of oxygen proved very different.
3. Smotherman & Robinson (1988b) - rat fetus response to hypoxia
a. 3 phases
1) suppression of activity
2) hyperactivity - body flexions
3) suppressed activity with rostral extensions of the head.
b. Virtually opposite to response of neonatal rats under conditions of hypoxia.
IV. Concluding Comments
A. Early embryonic behavior likely results from spontaneous discharge of spinal motor neurons.
B. Later the embryo is responsive to stimulation with more complex behavior.
C. Two functions of prenatal and post hatching behavior:
1. development of structure.
2. Precursor for later behavioral development.
D. Behavior constitutes adjustments to a changing environment which enhance survival.