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Exam 2 Study Guide

by: Brittany Woody

Exam 2 Study Guide PSB4504

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Lecture and PowerPoint notes from PowerPoints 4-9. Exam is this Friday on March 18th
Developmental Psychobiology
Dr. Donald J. Stehouwer
Study Guide
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This 24 page Study Guide was uploaded by Brittany Woody on Monday March 14, 2016. The Study Guide belongs to PSB4504 at University of Florida taught by Dr. Donald J. Stehouwer in Spring 2016. Since its upload, it has received 55 views.

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Date Created: 03/14/16
Monday, March 14, 2016 Exam 2 Study Guide Epigenetics - Genetics: the study of heritability; a term coined in 1891 by biologist William Bateson; was never formally defined as a hypothetical mechanism of inheritance; as we now know, a gene is difficult to define - Mendel call genes “inheritance factors” - Current usage of “gene” is in reference to a portion of a DNA strand that codes for a particular protein - “epi”: from Greek meaning “on” or “above” - “genesis”: from Greek, meaning “origin,” “creation,” or “generation” - “Epigensis” means “above genetics,” or influences in addition to the genome; more simply, it refers to genes and environment interactions; now implies mediation via gene expression - Epigensis includes environmentally-induced changes in gene expression but also includes possible interactions between the environment and the genome that do not alter gene expression; defined by phenotype, not genes or environment - Early concepts of epigenesis implied that the fertilized egg contains building materials only, somehow assembled by an unknown directing force; this contrasted with the then prevalent notion of preformationist, which was a widely held belief prior to the 1750s - According to preformationists, a gamete (egg or sperm) contained a perfectly formed embryo that simply grew (became larger) - Current ideas of development are epigenetic in concept, but far more is now known about what directs growth and differentiation - To speak of the genome as a blueprint is simply “gene-speak” preformationism - Genes code for proteins; expression of genes (which are produced and when) is largely a result of environmental events • induction by surrounding tissues (notochord inducing neural tube) • regulation of genes by internal environment (axon guidance) 1 Monday, March 14, 2016 - There is no “hard-wired” master control panel directing development; sequence of local patterns in which one step in development is a subunit of another; each step in the developmental hierarchy is a necessary preliminary for the next - Development is four-dimensional; very early in development, most environmental events controlling gene expression are internal; later, external environments exert control over gene expression as well - Second definition used in genetics: much more restricted meaning than the first usage; alterations to the DNA, other than changes to the genes themselves (i.e. nucleotide sequence), that • are passed on with cell division • can change normal gene expression • can be caused by (early) experience - Epigenesis in this second, narrower, mechanistic sense has long been recognized as essential for tissue differentiation and organogenesis - The external environment can also activate or silence genes, leading to different phenotypes, and that these modifications can be transmitted across generations, i.e. inheritance of acquired characteristics; this is not Lamarckian in that the genome itself is unchanged - Transcriptional regulation: histone modification: chemical modification of histone proteins in the nucleosome; the nucleosome is DNA wound around histone proteins - Transcriptional regulation • DNA Methylation: methyl group (CH ) a3ded to DNA at CG dinucleotides - Reduces/prevents transcription - Tissue specific - Important in embryogenesis & tissue differentiation - zygote largely unmethylated - series of methylations leads to tissue differentiation - Possible source of trans-generational epigenetic transmission - 2 Monday, March 14, 2016 • Histone Modification: Influences “density” of DNA packaging in chromosomes - Influences transcription - Cocaine & amphetamines (and other drugs) cause histone modification • Transcription Factors - Transcription factor (regulatory protein): protein or protein complex that enhances or inhibits transcription - Alter gene expression without altering DNA itself; expression is reversibly dependent on presence or absence of transcription factors - Most well-studied epigenetic mechanism is methylation of cytosine on the DNA - If methylation occurs in an active stretch of DNA, especially a promoter region, the associated stretch of DNA (gene) will likely be silenced - Methylation of DNA, and thus gene expression, continues after birth and be influenced by the broader environment (nutrition, stress, drug use, lifestyle, etc.) - Heritability is not a calculation of, nor is it even an estimate of, the degree to which a phenotypic character is inherited - Heritability is also not a measure of the degree to which a particular character trait is genetic or environmental - Heritability is an estimate of the total population variation of a phenotypic character that is attributable to genetic variation. H = V /g t - Variance of the population (V t) is partitioned into variance due to genetic variability (V g), that due to environmental variability (V e) and their interaction (Vgxe) • V = V g + V e + V gxe - It is not possible to measure Vgxe directly, and is assumed to be negligible. Thus, Vt= Vg + Ve - It is difficult or impossible to eliminate Ve, whereas Vg is easy to eliminate through the use of inbred strains, clones, or identical twins. Thus, Ve is estimated as the residual variance in genetically homogenous populations,, in which Vg=0 So, Vt= 0 + Ve • 3 Monday, March 14, 2016 - Since we can easily measure Vt directly and have an estimate of Ve from our genetically homogenous population, it is a simple matter to calculate Vg in the random population by subtractio: Vg= Vt- Ve - Assumptions for this formulation of heritability: • genetic and environment affects on phenotypic variability are additive • that gene x environment interactions are negligible • that Ve is the same for inbred and outbred strains - Heritability quotients depend as much on environment variation as they do on presumed genetic variation - Heritability estimates are limited in that they apply only to the population represented in the sample and cannot be generalized to other populations - Twin studies: independent variables Genetic variables: monozygotic vs dizygotic vs siblings vs unrelated • Environmental variables: reared together vs reared apart • - Twin studies: dependent variables • Concordance: all-or-none; if one member of the pair has the trait, what is the probability that the other shares the trait? • Correlation: graded trait; is there a difference in the correlation of the trait in pairs in the different groups? - Monochorionic twins: share a placenta - Dichorionic twins: have different placentas - Monozygotic twins who share a placenta have a 60% concordance rate for Schizophrenia; monozygotic tons with different placentas have only an 11% concordance rate - Epigenetic transmission: • Whole Chromosome Regulation (X chromosome inactivation or Lyonization) • Regulation during Protein Synthesis - Transcriptional Regulation • methylation • histone modification 4 Monday, March 14, 2016 • transcription factors - Editing regulation • alternative RNA splicing: Different exons are spliced together to give different polypeptide blueprints; can produce variation between species; possibly why number of human genes is so small • exons are nucleotide sequences that are present in RNA products; introns are nucleotide sequences that are edited out during RNA splicing - Pre-translational regulation • “interfering” RNA: A short sequence of single-stranded interfering RNA (“iRNA”) and a complex of proteins and enzymes (“silencing stuff”) binds with mRNA and cleaves it; acts as a “dimmer switch,” reducing translation • Regulation after protein synthesis; many mechanisms - Protein activation/deactivation • Phosphorylation: add a phosphate group • Acetylation: add an acetyl group • Alkylation: add an ethyl, methyl group • Ubiquitination: adding the protein ubiquitin to an existing protein instructs cellular machinery to degrade/ destroy the protein - Epigenetic transmission: two types • Blue print transmission: sequence transmission; transmission of information via the nucleotide sequence (A,C,G,T) • Regulatory transmission: epigenetic transmission; transmission of information via gene regulation; transmission of genetics above the sequence of nucleotides (gene methylation and histone modification) - Genomic imprinting: The expression (active vs inactive) of a gene depends on which parent transmits the gene; some turned off when inherited from the father and turned on when inherited from the mother; others turned on when inherited from father and turned off when inherited from mother Mechanisms: methylation, phosphorylation of histones (examples of epigenetic • transmission) 5 Monday, March 14, 2016 - Epigenetic transmission: behavioral example: rats either handled or not handled in infancy; early handling reduces anxiety throughout life; offspring of handled rats less anxious; offspring of offspring (grandchildren) less anxious • anxiety is operationally defined as reduced activity in a open field Behavioral Embryology - Functions of embryonic and fetal behavior: necessary for normal anatomical and physiological development; serves adaptive functions as a behavior; serves as practice for future behavior; is an epiphenomenon of no particular importance - Coghill’s view of behavioral development: earliest movements are spontaneous rather than elicited; from the beginning, movements are “ mass actions”: all parts of the animal that are able to move, do move; these mass actions become individuated into more localized and discrete movements • Behavior is sculpted from undifferentiated precursor, much like a sculptor chips away all of the stone that is unwanted, leaving the final differentiated form - The behavior pattern develops as a regular, orderly sequence of movements, which is consistent with the order of development of the nervous system and its parts - In a relatively precise manner, physiological processes follow the order of their embryological development in the functions of aquatic and terrestrial locomotion and feeding - Behavior develops from the beginning through the progressive expansion of a perfectly integrated total pattern and the individualism within it of partial patterns which acquire various degrees of discreteness - Windle’s view of behavioral development: first movements are forelimb proprioceptive reflexes, other reflexes follow (oral reflex appear next); complex behaviors emerge as local responses become integrated with each other • Behavioral development is achieved by putting together small pieces, much the way a machine is assembled - Why do Coghill and kindle disagree? species differences, experimental artifacts, and types of behaviors studied - Classes of avian embryonic behavior: • Type 1 behavior: generalized behavior of the embryo; found from the onset of motility until pre-hatching; includes jerky, conditioned movements of the limbs • Type 2 behavior: startle-like behavior; found from the onset of motility thought incubation 6 Monday, March 14, 2016 Type 3: pre-hatching, hatching; highly organized, not predictable from types 1 and 2; • occurs only in the days immediately prior to hatching - Neural plate differentiates in chicks at 28 hours, rats at 7 days, humans at 19 days - Long period of motility before close of reflex arcs - First movement is lateral head movement (sideways bending), then “startle,” then generalized movements - First movements begin at about 7 weeks gestation age in humans (fetus is about 1 cm long); mothers can detect it at 16 weeks - Cryptic behavior: exists in development but not after birth - “Fetal breathing”: inhaling and exhaling amniotic fluid - Fetal hiccuping is precursor for breathing - What role does experience play? • Facilitation: experience causes accelerated development boost in terminal level achievement, and a combination of accelerated development and an elevated terminal level of achievement • Maintenance: experience must be maintained to alter sensation • Induction: sensation fails to develop if there is no experience - “Visual cliff” : cliff marked with checker board with clear glass at the end, so it appears to drop off but does not - Dark-reared animals showed delayed maturation Transition from the Womb - Birth as a “non-event”: neurobehavioral systems required by the newborn are functional prior to birth (hiccup-like, breathing-like) • “Forward reference” or “environment expectant”: by Weiss; develops anticipating needs, not in response to them; contrasts with “environment- dependent” - sucking, swallowing, “breathing”, “hiccups”, yawning” are forward reference; most occur mid-term - refinement of ocular columns is example of environment- dependent 7 Monday, March 14, 2016 - Other than constraints imposed by the intra-uterine environment (fetuses cannot cry without air, for example), there is little behavioral difference between a late-term fetus and a newborn; newborns are not doing anything new after birth - What distinguishes a newborn from a fetus is that there behaviors are necessary for survival; breathing is functional but necessary in newborn - Initiation of breathing: noxious stimuli; spanking a newborn is not necessary to initiate breathing, and birthing in warm water makes little sense from either a physiological or evolutionary perspective • temperature change is a noxious stimulus • anoxia produced by clamping the umbilical cord • fluid is expelled from lungs during delivery, the remainder quickly absorbed • changes in other sensory inputs - Infants learn the sound of a mother’s voice in utero; infants prefer sound of mother’s voice; do not have preference for father’s voice compared to other males; prefers how mother’s voice sounds in utero to how it sounds outside the womb (proof that newborns learn the sound of mother’s voice in utero) • measured preference based on how the rate of suckling changes in response to hearing different voices - Sucking and swallowing are essential to the newborn, but have been expressed by the fetus - About the only thing not apparent in the fetus that is expressed by the newborn is crying - From a neurobehavioral perspective, birth can be considered to be a “non-event,” unlike, for example, amphibian metamorphosis • better analogy for metamorphosis is weaning - Oxytocin stimulates uterine contractions, but what stimulates oxytocin release? • labor is induced medically with an injection of oxytocin - Surfactant protein A (SF-A) initiates birth: makes liquids “wetter”, reduces surface tension; essential for respiration after birth • production in lungs of fetus is signal that lungs are developed; SF-A is released into the amniotic fluid and triggers oxytocin release begins being produced in mice at 17days, birth at 19 days • begins being produced by human fetus at 32 weeks, birth at 40 weeks • 8 Monday, March 14, 2016 - Other than the capacity for independent respiration, there is little relationship between maturity and birth/ hatching - Newborn opossum continues to develop in the mother’s pouch after birth - Precocial: born in a relatively mature state (guinea pig, kittens) - Altricial: born in a relatively immature state (opossum, rats) - Humans are born with relatively mature sensory systems (precocial in that respect); motor systems are very immature at birth, can’t roll over (altricial in that respect) - Changes in total brain weight as a function of age in different animals: brain growth spurts reach a peak much after birth in altricial animals, and before birth in precocial; occurs around birth in humans - Study of survival of animals in pure nitrogen environment (no oxygen) at different ages: death of the animal is determined by survival of the brain; less mature brains can survive longer in oxygen free environments (younger animals of the same species; more altricial animals) • newborn rats survived for an hour in the oxygen free environment with no long-term brain damage • human infants can survive longer in hypoxic environment than older children (fall in pool, etc) - Most caudal parts are more mature, more rostral parts are less mature; more mature requires more oxygen consumption; throughout development, rostral begins to consume more oxygen than caudal - Maturation of myelination moves caudally to rostrally - Neonatal period in rat is first 2 weeks; weaning begins at 2 weeks - Newborn rat cannot flip himself over (“right himself”) when placed on their back in a supine position - Rats 0-4 days old can right themselves even if given a caudal transection - After 4 days old, more caudal transections in rats make it increasingly harder for them to right themselves - At four days, the caudal parts of the brain begin developing connections with rostral parts of brain; before four days, the caudal areas can act independently; after four days, the caudal parts of the brain cannot operate without connections to the rostral parts - Caudal brain organizers itself as rat ages, and the further they have organized, the more harmful transection is 9 Monday, March 14, 2016 - Brains transected at four days could develop normally, with little change based on where it was cut; after four days, the more caudally the cuts were made, the more hinderance to development there was - In an experiment where spines were cut, there was no hinderance to development if the surgery was done between 0 and 12 days; at 15 days, there was loss of control The Neonatal Niche - Neonates face problems not face by adults; unique to neonates because of their size, anatomy, and physiology - Neonates adopt their own strategies to cope with these unique problems - Coping strategies are both behavioral and physiological - Homeothermy: the physiological and behavioral maintenance of a relatively constant internal body temperature (homeotherms typically show fluctuations, e.g. circadian rhythms, in temperature); humans - Endothermy: physiological and behavioral thermoregulation, but body temperatures may fluctuate widely; - Ectothermy: use only behavioral means to regulate temperature; butterflies - Poikilothermy: the fluctuation of internal body temperature closely related to environmental temperature; most fish - Cold blooded: poikilothermy > ectothermy > endothermy > homeothermy: warm blooded - Heat gain: volume (size) of thermogenic tissue; basal metabolic rate (how active is tissue); shivering or other thermogenesis - Heat loss: surface area; insulation (fat, feathers, hair); panting, sweating, etc - Infants have small bodies for heat generation and heat loss - Peripheral thermoreceptors are found in the skin; related to behavior - Central thermoreceptors are found in the anterior hypothalamus; controls seasonal fluctuations in body temperature 10 Monday, March 14, 2016 - These thermoreceptors are important for behavioral and physiological thermoregulation both in the short term and in the long term - Short term thermoregulation is regulated predominantly by autonomic and somatic motor activity - Autonomic: • shivering when cold, sweating when hot peripheral vasodilation when hot, constriction when cold • • piloerection (fur standing up) and panting in non-human mammals • adrenal gland: release catecholamines to increase basal metabolic rate - Somatic: • seeking warm (sun) or cool (shade or water) areas • minimizing or maximizing surface area - Long term (e.g. seasonal or as adaptation to different climates) thermoregulation is predominantly regulated by hormonal regulation of metabolism - Thyrotropin releasing hormone (TRH) is secreted from the hypothalamus to stimulate release of thyroid-stimulating hormone (TSH, also thyrotropin), which stimulates release of thyroxine from the thyroid gland • tissues respond with an increase in their basal metabolic rate - Autonomic and hormonal responses to thermal challenges are mediated primarily by the medial pre optic area - Behavioral responses to thermal challenges are mediated principally by the lateral hypothalamus - Maintenance of thermal homeostasis is arguably the greatest factor influencing both energy balance (via calories spent for thermogenesis and the need for fat stores) and water and mineral balance (water lost via evaporation through the skin, metabolic processes necessary for homeothermy and panting) - Allometric growth: parts of the body grow at different rates - Problems faced by altricial neonates: 11 Monday, March 14, 2016 • sensory and motor immaturity • CNA immaturity • Physiological immaturity (autonomic control, homeostatic regulation) • morphological immaturity (small size, allometric growth) - Thermoregulatory problems of altricial mammals: • cannot shiver has precarious energy balance; do not have extra energy because all energy is • used on growth • small size • cannot vasoconstrict in response to cold no hair; humans depend on adults for clothing • • little body fat and thin skin for insulation - The problem with being small: surface area to volume ratio; if length increases linearly, surface area and volume increase exponentially; surface area increases more slowly than volume • surface area to volume ratio increases with age; more surface area per volume • at ambient room temperature, a newborn rat would have to increase its metabolic rate 6-fold to maintain its core temperature • newborn rat and dead rat lose heat at the same rate when put in cold water • hypothermia is used as anesthesia for rats; hard to overdose and less bleeding - Brown adipose tissue (BAT) is not used as long term storage for nutrients but is metabolically active; densely vascularized; dense mitochondria; increased metabolism allows newborns to raise body heat - Bears use brown fat during hibernation - Brown fat accounts for 5 to 6 percent of the body weight of the newborn rabbit. It is concentrated around the neck and between the should blades - Human infant at birth has a thin sheet of brown adipose tissue between the should blades and around the neck, and small deposits behind the breastbone and along the spine 12 Monday, March 14, 2016 - Brown fat is located near heart and spinal cord to maintain these most vital organs - Basal metabolic rate (BMR): minimum metabolic rate at thermoneutral temperature; mid 70s to mid 80s in naked adult humans - Cold stress will result in increased metabolism which will lead to increased oxygen consumption, hypoglycemia, hypoxia, and respiratory distress - Newborn rats can be cooled until their heart stops and then rewarmed to start it again; adult rats cannot start their heart back up; newborn humans can survive in water longer than adult humans - In mild cold temperatures, newborns will attempt to thermoregulate; in very cold temperatures, they will shut down their metabolism - Rats who are transected at level 3 are unable to maintain their core temperature in warm environments; have thermogenic response and heat up - Transected animals have an increased oxygen consumption in warm temperatures; intact animals show thermogenic response but then shut down to return to BMR - Blood glucose levels are initially higher in transected animals; blood glucose levels decrease in transected and intact animals, but are overall lower in intact animals - Intact animals shut down as blood glucose level drops because they are able to monitor glucose stores; transected animals maintain high metabolism in both temperatures even as glucose stores decrease - Intact animals injected with insulin do not illicit a thermogenic response; made them hypoglycemic - Lesions in hypothalamus do not affect animals; mechanisms responsible for thermoregulation is located somewhere rostral to transection but not in hypothalamus - Temperatures were taken rectally; rectal temperature is most accurate in adult rats, but not in newborns; newborns are warmest under brown fat (upper back) and rectal temperatures are coolest - Oxygen consumption (metabolic rate) compared to environmental temperature of differently aged rats: • 21 days old:steady decrease in metabolic rate as temperature decreases • 23 hours old: increase of oxygen consumption at 30 then declining as temperature decreases; have nursed so they can produce thermogenic response 13 Monday, March 14, 2016 • 4 hours: temperature does not have an affect on metabolic rate; they do not have energy to produce thermogenic response because they have not nursed yet - 5- 10 day old rats require huddling with littermates to stay warm; they have not developed thick fur or developed thermogenesis; older rats are also larger - 5 and 10 day old rats lose temperature rapidly if separated from litter; temperature decreases more slowly if with only three littermates - 15 and 20 day old rats can maintain their temperature when alone and when with three littermates - Newborn rats thermoregulate as one group when they huddle (clump) - Huddles form convection currents when moving around their clump; positive thermotaxis; if a pup is cold, they dive into the top of the huddle, pushing others out; those who were pushed out jump back to top when they get cold - In warmer temperatures, the current reverses and rats jump out of top to get to the cooler area - Rat- shaped robots programmed to move randomly resemble real rat behaviors; formed clumps; both got stuck in corners; shape of rats facilitates clumping behavior - Reptiles move to thermoneutrality: area between hot and cold - Reptiles and infant rats cannot generate a fever when injected with bacteria - Fish and reptiles spend more time in heat when injected with infectious agent - Newborn rabbits prefer higher temperatures (40.5 degrees C) when injected with pyrogen vs. saline (36.5 degrees C) Human Infants: - Heat Production • The ability to increase metabolic rate in response to cold stress begins around 28— 30 weeks postconceptional age. Postconceptionally older infants can increase heat production, but the response is weaker than in the adult. 4’16 • Limited stores of metabolic substrates (glucose, glycogen, fat, etc.) • Heat production needs met primarily through non-shivering thermogenesis; however, the amount of brown fat stores are inversely related to gestational age. 14 Monday, March 14, 2016 • Heat production obligates oxygen consumption, challenging the immature cardiovascular and pulmonary systems. • Large surface-to-mass ratio and large surface heat loss relative to heat-producing ability result in high metabolic rate. • Large evaporative loss due to status of skin maturation; evaporative loss itself may exceed heat production abilities. • Shivering response not well developed. Cannot initiate increased tone and shivering to increase heat production. - Insulation • Limited layer of subcutaneous fat, limited development of muscle and other tissues that provide insulation. • Small body diameter results in thinner layer of still air boundary layer, reducing insulation through this mechanism. - Vasomotor Response • Competent abilities to regulate skin blood flow documented in infants weighing >1 kg; however vasoconstriction abilities are outmatched by propensity for heat loss.4 - Sudomotor Response • Sweat production observed in infants of 29 weeks gestational age; maturation of response enhanced by extrauterine development. Response is slower and less efficient than in older child or adult, and occurs at a higher environmental temperature.24 - Motor Tone and Activity • Lower postconceptional aged and ill infants prone to decreased motor tone and less activity, resulting in decreased heat production. Infant with poor tone cannot use flexion posture effectively to reduce surface area and hence heat loss. - Behavioral • Limited ability to effectively communicate thermal needs or thermal comfort to caregiver. • Cues are subtle and nonspecific. 15 Monday, March 14, 2016 • Cannot use volitional actions such as altering clothing, increasing ambient temperature, using motor activity to increase heat production, drinking warm or cool beverages to modify temperature. - Brown fat is stimulated by sympathetic innervation (not blood-borne signals) - Ultrasonic Vocalizations in newborn rats: • emitted by isolated pups in first two weeks • isolation necessary and sufficient condition to elicit vocalization retrieved by dam; mom rat gets newborn if they are making vocalizations • • called “isolation distress”: distress implies that it is an emotional response; this would make a good model for separation anxiety in humans - Vocalizations as “cries” • implies emotional response • analogue of separation anxiety? - Alternative explanation? part of thermogenic response; physiological reason not psychological • • exaptation: adaptations that are selected as a consequence of another; ultrasonic vocalization may be used as part of thermogenic response, but also results in dam (mother) retrieval • not “cries,” but more like “grunts” • laryngeal braking: closing larynx; prevent passage of air - enhances gas exchange - facilitates return of blood to heart - Valsalva maneuver: tightening of abdominal muscles; like humans grunting when lifting weights or playing tennis; abdominal compression response - Thermoregulation summary: Problem: Cannot shiver to produce heat Solution: Brown adipose tissue (BAT) Problem: Precarious energy balance 16 Monday, March 14, 2016 Solution: Thermoregulate over narrow temperature range, shut down to conserve energy if temperature is out of range, tolerate lowered temperature Problem: Small size, large surface area:volume ratio Solution: Clump to reduce surface area:volume ratio Problem: Poor insulation Solution: Clump, nest insulation (mother builds nest), thermotaxis, ultrasound response to isolation, mother is source of heat while nursing, most rodents live in burrows for warmth (also to escape predators) - Thermogenesis is not a precursor to adulthood; it is specifically neonatal; it persists in adults as a machismo of hibernation - Huddling may be both for thermogenesis and as a social behavior Suckling - Source for nutrition as well as fluid - Olfactory cues are important for pups finding nipple; washed mother has much less attaching by pups than the unwashed mother; there is an odor on nipples that help them recognize it • if washed extract solution was put back on the mother, they would attach; they would also attach if pup saliva was put on nipples; also would attach if amniotic fluid was put on nipples (washed extract: the water used to wash mother’s nipples) - pups i - nhale and swallow amniotic fluid in the womb; after birth, mom licks pups and then licks nipples so that the nipples have amniotic fluid • virgin female saliva and mother’s urine on nipples did not elicit attachment • “nipple extract”: swabbed from another mother’s nipples elicited attachment; if other mother was on a different diet, there was not attachment • pups attach if washed mother is injected with oxytocin • ligated nipples: tied so milk is not released; if mother with ligated nipples is injected with oxytocin, pups still attach • if injected with atropine, there is less attachment 17 Monday, March 14, 2016 - Dimethyl disulfide is common to the effective solutions, and when a solution of dimethyl disulfide dissolved in distilled water is painted on the nipple of a washed dam, attachment is reinstated - In experiment, pups were exposed to citral (citrus smell) prenatally and/or postnatally and nipples are citral scented • if not exposed at all: no attachment • if exposed postnatally only or prenatally only: no attachment • if exposed both pre and postnatally: attachment - Nipples are not citral scented; dimethyl disulfide scented nipple • if not exposed to citral at all: attachment • if exposed to citral only post or prenatally: attachment • if exposed to citral post and prenatally: no attachment to dimethyl disulfide scented nipple - Canulas are placed in pups mouths and dam in anesthetized (cannot eject milk); anesthetized dams produce milk if injected with oxytocin - Pups form tight seal around nipple and suck in bursts; change is poster of pups once milk is released (arched back, limbs extended, stretched, tail lifted) to facilitate milk delivery; increases negative pressure (sucking); response disappears between 10 and 15 days - Pups show no preference between a non-nutritive nipple (does not give milk, fake nipple) and a nutritive nipple (real nipple) up to 12 days of age. - Pups that have gone without food for 23 hours show no more latency (time to attach to a nipple) than those who have not been deprived up to 13 days old. After 14 days old, the deprived animals will suckle quickly. - Older pups (over 13 days) have a preference for nutritive over non-nutritive nipples, so if a nipple stops producing milk, the pup will switch to a different nipple. At younger ages, the pup will stay on the nipple even if it is not producing milk. - Suggests suckling is independent of the reward of food; suckling is rewarding itself, it is not only done to get milk - Experiment measured if deprived pups would lick milk from the floor; in warm temperatures, the pups would lick the milk; in cold temperatures, they would not lick it 18 Monday, March 14, 2016 - The temperature of the pup does not affect their tendency to lap the milk, only the temperature of the environment does - More deprived animals were more likely to lap the milk - Pups will not stop suckling; they will continue to suckle until they choke on the milk (if put on a new dam each time the last dam runs out of milk) - If pups are given milk through a canula (not a nipple), they make random body movements such as curling and pelvic thrusting; compared to the coordinated stretch during suckling - Rats usually ween off the nipple between 15 and 25 days old - Rats who never suckle can still eat, showing that suckling is not a necessary precursor to eating - Feeding is seen earlier evolutionarily than suckling, supporting the idea that the two exist independently even in mammals - Suckling only ends when the dam’s ventrum (where her nipples are located) over heats and the dam leaves the nest; the pups will suckle as long as possible - Dams and pups in nature have separate “rooms” in underground burrows so that the dam can leave the pups - Methysergide: serotonin blocker • rats given the serotonin blocker will attach for longer periods of time • if given a serotonin agonist (quipazine), rats will not suckle even if they are food deprived - Beginning at 21 days of age, each rat in the experimental group was housed with a littler of 16- day- olds for five days; after five days, they were transferred to another littler of 16- day- olds until the day of testing; the older rat would continuously be put with 16- day- olds; these rats, even though they are now past adolescence, will suckle like the 16- day- olds; they were never weened - Cats can be trained to eat unusual foods: mashed potatoes and mashed bananas in this experiment; cat got rewarding brain stimulation when eating these foods; kittens would prefer the bananas even in the presence of meat pellets by modeling after the mother • human preference may be related to what the infant is first exposed to 19 Monday, March 14, 2016 - Baby animals get food safely because the mother does the hunting, so they prefer these foods later in life; prefer familiar foods; “learned safety” - Rats will take a small sample of a new food and then wait several hours to see if they get sick before eating more - Food preference begins in-utero; prefer amniotic fluid of the mother and the milk has a familiar taste; pups will prefer milk of their own mother than another dam - Human infants dislike mother’s milk if she has just worked out due to lactic acid “souring” the milk; humans are sensitive to the smell of mother’s nipple and taste of the milk (prefer their own mother) Postnatal Development of Behavior - Unique problems faced by altricial neonates • sensory immaturity: stimuli available to adults not available to neonates; human newborns have very poor vision • motor immaturity: ability to act is limited; can’t shiver, flip over, return to nest, etc • physiological immaturity: motivational systems, regulatory systems • morphological immaturity: small size, allometric growth (body parts growing at different paces); humans have early growth of the head • environmental demands are different - A difficulty in assessing behavioral development is identification of eliciting stimuli; stimuli appropriate for adult may not be appropriate for infants (cool water to elicit thermoregulatory response) - Motivations different from those of adult; suckling is an end in itself, feeding and drinking are operantly controlled - Response definition; “isolation distress” of infant rats implies cause of behavior; whether a behavior is a precursor to an adult behavior or an infant-specific behavior - Mechanisms of behavioral maturation: • CNS maturation: gaining control of various behavior such as urination • Threshold changes: a behavior develops slowly but only expresses at one specific threshold; stages of development; adult humans appear to have a sudden 20 Monday, March 14, 2016 understanding of something they are learning, but may be constantly learning until it reaches the threshold • Integration and individuation: might have the ability to do something but do not; thermoregulate vs. shutting down • Response competition: different behaviors are more important at different ages • Morphological changes • Permissive/ supportive environment: animal can perform a certain behavior under certain conditions - Is grooming behavior absent in infant rats because they are not physically able to groom or because the behavior has not developed? newborn rats cannot groom themselves because they cannot sit up to free their front hands; even at birth, animals who are sat up by humans groom themselves • permissive environment: removed postural demand • integration: postural and movement component in grooming behavior - Amputated mice still exhibit grooming behaviors: nodding down and sticking its tongue out to lick its paws; grooming behavior is not dependent on experience; fixed action pattern - In the first few weeks of human life, infants while exhibit stereotyped swimming/ crawling behaviors when held in water; at four months to a year after birth, the behavior is more random; after a year, the infant exhibits coordinated movements of the legs but not in the legs, also loss of lateral flexion of trunk; Is swimming at one year the same behavior as it is in the first few weeks? “Definite rhythmical associated flexor-extensor movements in upper and lower extremities together with a lateral flexion of the trunk corresponding to the flexor phase of the lower extremity are usually manifested.” “The quality of these movements is distinctly different from the rhythmical movements of the newborn.” - Human infants can go up stairs before they can go down; cats get stuck in trees because they can climb up but not down; human infants go down stairs backwards (back down); older adult humans put two feet on each step instead of alternating feet, reverting to more primitive motion 21 Monday, March 14, 2016 - Infants are exhibiting spinal cord/ reflexive behaviors; lose reflexive behavior with encephalization and maturation of behavior • “Doctrine of Dissolution”: loss of function • first to develop ontologically is the last to be lost in aging; last to develop ontologically is the first to be lost with age - Transections made in cat brains; sub thalamic nucleus is outflow of basal ganglia for movement • more rostral transection separated sub thalamic nucleus from forebrain which inhibited movement; cats exhibited random movement • in more caudal transection behind sub thalamic nucleus, no random movements - Behavior of week old decerebrate kittens: • Suckling was abolished • Decerebrate rigidity (release of antigravity reflexes; results in rigidity in limbs) was not observed • Reflexive eating and lapping of milk emerged at normal age of weaning; cats had posture of heads hanging toward the ground so when they ran into milk they reflexively started lapping; did not seek food; did not measure if the cats would stop on their own • Temperature regulation was only slightly impaired • All of the following developed in normal chronological order; some appeared slightly early - auditory reflexes (orienting, pawing at source of sound) - tactile placing reactions - defensive reactions (piloerecton (hair standing up), hissing, bared teeth, biting); sometimes appearing at inappropriate times - grooming - postural reflexes • Sleep-wake states (activity-inactivity states) developed normally; measured with EEG 22 Monday, March 14, 2016 • Visual recognition and social behavior were absent; transection was behind optic chasm so they were functionally blind; did not play with each other • Some behaviors, e.g. pounce, “kill” behaviors, developed precociously (early), were exaggerated in form (hypermetria) and directed toward inappropriate stimuli. • There were bouts of uncontrolled locomotion (hyperkinesis), with kittens sometimes running pell-mell (fitfull, confused) off table-tops • “Compulsive” climbing was also reported - Decerebrate humans would maintain crawling activity seen in first few weeks with torso turning - Infants will take “steps” if held up; active exercise (of behavior) increases step response; passive exercise and no exercise did not exhibit more of the behavior • Helen and Fisher suggested that biomechanical factors, rather than changes in central- neurological organization (enchephalization), account for the result; infants legs got fatter before getting stronger, so active exercise infants were strong enough but other were not; fatter infants show less stepping behavior - Allometric growth: differential rate or timing of growth of different tissues or structures; human fetus’ head is half of body length; newborn’s head is 1/4 body length; adult human head is 1/8 of length - In developing rodent walking, “punting”, pivoting around pelvis, appears first; vole, gerbil, dormouse, and jerboa locomotive differently when they are adults but all begin as punting - Similarly, the gait of kittens changes is related to allometric growth; the initial gait is one of lateral progression in which both ipsilateral limbs move in synchrony, and in alternation with contralateral limbs; left back leg with leg front leg • this unstable gait prevents the relatively “too long” limbs of the kittens from colliding • Later, the principal gait changes to one of diagonal progression, in which diagonal limbs move in synchrony; ipsilateral limbs and limbs of the same girdle move in alternation - Concentric ring analysis: put cell body in middle of target-like shape; count how many dendrites cross circles • threshold changes: increased opportunities or spatial and temporal summation 23 Monday, March 14, 2016 - Mechanisms of behavioral maturation: • CNS maturation: requisite circuitry not yet active; e.g., encephalization • 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 • Physiological Maturation: allows for new solutions to common problems • Morphological change: behaviors physically not possible; allometric growth • Permissive/supportive environment: conditions to allow for behavioral expression • New attractor states: changes in control parameters of dynamical systems 24


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