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Flashcards in chapter 8 Deck (122):
1

development of brain and behavior

brain and behavior appear to develop at similar rates

2

Does the visual system develop slowly?

no, it develops quickly

3

What part of the brain is the last to develop?

frontal lobes (ability to plan efficiently, organizing daily activities)

4

Preformation

the idea that a human embryo is an adult miniature

5

What do early vertebrate species look like?

similar looking primitive head, a region with bumps or folds and a tail

6

Zygote

consists of a single cell; when a sperm fertilizes an egg

7

What happens after a zygote forms?

by the 15th day the cell begins to divide forming an embryonic disc

8

Embryonic disc

formed by several sheets of cells with a raised area in the middle

9

Neural Plate

primitive neural tissue formed by day 21; occupies part of the outermost layer of the embryonic cells.

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Neural Groove

neural plate folds to form this

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Neural tube

neural groove curls to form this;

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What forms the brain's ventricles

the open region in the center of the neural tube remains open and matures into the brain's ventricles and the spinal canal

13

7 weeks into development

embryo begins to resemble a miniature person

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when do gyri and sulci begin to form?

7 months

15

When do the genitals begin to form?

7th week after conception; they appear identical (indifferent) in the two sexes at this early stage

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sexual dimorphism

structural difference between the sexes

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60 days after conception

male and female genitals start to become distinguishable

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testosterone

stimulates sexual differentiation in male embryos

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gonadal (sex) hormones

prenatal exposure acts to shape male and female brains differently because these hormones activate different genes in the neurons of the two sexes

20

Neural stem cells

lining the neural tube have an extensive capacity for self-renewal. When a stem cell divides it produces two stem cells; one dies and the other lives to again divide

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where do neural stem cells live?

line the ventricles forming the subventricular zone

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Progenitor cells

precursor cells; develop from stem cells; it migrates and also can divide and produce neuroblasts and glioblasts

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neuroblasts

formed from progenitor cells; form neurons

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glioblasts

formed from progenitor cells; form glia

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subventricular zone

lining of neural stem cells surrounding the ventricles in adults

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When do stem cells work?

well into the aging brain

27

prolactin

neuropeptide that increases in pregnant rats; stimulates the brain to produce more neurons

28

Gene expression

a formerly dormant gene becomes activated, resulting in the cell making a specific protein.

29

gene methylaiton

common epigenetic mechanism; a methyl group (CH3) attaches to the nucleotide base cytosine lying next to guanine on the DNA sequence; resulting in the suppression of gene expressoin

30

does methylation alter gene expression?

yes, it can do so dramatically during development.

31

what impacts methylation?

prenatal stress can reduce gene methylation by 10 percent

32

what impacts cellular differentiation?

neighboring cells, chemicals, hormones

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stem cell differentiation

a chemical signal must induce stem cells to produce progenitor cells; another chemical signal induces the progenitor cells to produce either neuroblasts or glioblasts and then a last chemical signal induce the genes to make a specific type of neuron/glia

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neurotrophic factors

class of compounds that acts to support growth and differentiation in developing neurons and may act to keep certain neurons alive into adulthood

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epidermal growth factor (EGF)

stimulates cells to produce progenitor cells

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basic fibroblast growth factor (bFGF or FGF-2)

stimulates progenitor cells to produce neuroblasts

37

Stages of brain development

1. cell birth (neurogenesis; gliogenesis)
2. cell migration
3. cell differentiation
4. cell maturation (dendrite and axon growth)
5. synaptogenesis (formation of synapses)
6. cell death and synaptic pruning
7. myelogenesis (formation of myelin)

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neurogenesis

rapid formation of neurons

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gliogenesis

rapid formation of glia

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migration

when cells travel to their correct locations

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when is neurogenesis about finished?

after about 5 months of gestation

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what is the exception to when neurogenesis is finished?

the hippocampus--> continues to develop new neurons throughout life

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teratogens

chemicals that cause malformations

44

When can the human brain best cope with injury?

early during development; during neurogenesis. More neurons can be made to replace injured ones or perhaps existing neurons can be allocated differently

45

when does cell migration begin?

shortly after the first neurons are generated and continues for about 6 weeks in the cerebral cortex and longer the hippocampus

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how to neurons migrate?

subventricular zone contains a primitive map of the cortex that predisposes cells formed in a certain ventricular region to migrate to a certain cortical location

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how do cells know where the different parts of the cortex were located?

radial glial cells; some follow a chemical signal

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radial glial cells

path-making cell that a migrating neuron follows to its appropriate destination

49

how do cortical layers develop?

from the inside out

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Maturing neurons

1. grow dendrites to provide surface area for synapses with other cells
2. extend their axons to appropriate targets to initiate synapse formation

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Dendrite development

dendritic arborization (branching) and the growth of dendritic spines

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do dendrites grow fast or slow?

slow

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do axons develop fast or slow?

fast; about 1000x as fast

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why is it good that axons develop faster than dendrites?

axons can contact its target cell before the cell's dendrites are completely formed --> may play a role in dendritic differentiation and neuronal function

55

Autism spectrum disorder

range of cognitive symptoms, from mild to severe, that characterize autism; severe symptoms include greatly impaired social interaction, a bizarre and narrow range of interests, marked abnormalities in language and communication and fixed, repetitive movements

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growth cone

growing tip of an axon

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filopod (filopodia)

process at the end of a developing axon that reaches out to search for a potential target or to sample the intercellular environment

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what are the two cues that growth cones are responsive to?

cell-adhesion molecules and tropic molecules

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cell-adhesion molecule (CAM)

a chemical molecule to which specific cells can adhere, thus aiding in migration; can attract or repel growth cones

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tropic molecules

signaling molecule that attracts or repels growth cones

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netrin

member of the only class of tropic molecules yet isolated

62

thickness of the cortex

becomes thinner in a caudal-rostral (back to front) gradient; probably due to synaptic pruning

63

how much is typically eliminated during synaptic pruning?

42% of all synapses in the human cortex

64

neural Darwinism

hypothesis that the processes of cell death and synaptic pruning are, like natural selection in species, the outcome of competition among neurons for connections and metabolic resources in a neural environment

65

why do neurons die?

because target cells produce neurotrophic factors that are absorbed by axon terminals--> function to regulate neuronal survival. (ex. nerve growth factor). If many neurons are competing for a limited amount of a neurotrophic factor only some can survive

66

apoptosis

when neurons are deprived of a neurotrophic factor certain genes seem to be expressed--> resulting in a message for the cell to die

67

does apoptosis account for synaptic pruning from cells that survive?

no

68

synaptic pruning and language

young infants can discriminate speech sounds of different languages without previous experience, but this ability declines after year 1. synapses encoding speech sounds not normally encountered in an infant's daily environment are not active simultaneously with other speech-related synapses and thus are eliminated

69

when does cortex thinning take place?

age 5-20

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does the entire brain thin?

NO! major language regions show an increase in gray matter

71

frontal lobe development

it is especially sensitive to epigenetic influences; the trajectory of frontal lobe development correlates with adult IQ

72

IQ and plasticity

children who score highest in intelligence show the greatest plastic changes in the frontal lobe over time

73

when does myelination occur?

begins just after birth and continues until at least 20 years of age

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Flechsig myelination hypothesis

earliest myelinating areas control simple movements or sensory analyses, whereas the latest myelinating areas control the highest mental functions

75

infant movement: after birth

flexing joins of an arm (scooping)

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infant movement: 1-3 months

make spontaneous hand and digit movements that consist of almost all the skilled finger movements of an adult; motor babbling; movement toward objects

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infant movement: 8-11 months

grasping becomes more sophisticated as in the pincer grasp

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meylination and motor movements

a group of axons from motor-cortex neurons myelinate at about the same time that reaching and grasping with the whole hand develop. Same thing with neurons that control finger movements and the pincer grasp

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Language development

1. 12 months: start to form vocab (5-10 words; doubles over next 6 months)
2. 2 years: vocab ranges from 200-300 words
3. 3 years: 1000 words and simple sentences
4. 6 years: 2500 words and can understand 20,000-50,000 words

80

thickening of broca's area

the left inferior frontal cortex--is associated with enhanced phonological processing (understanding speech sounds)

81

Jean Piaget

stages of development

82

object permanence

understanding that objects continue to exist even when out of sight

83

conservation of liquid volume

develops by age 7; the understanding that the amount of liquid remains constant despite the difference in appearance

84

Piaget's stages of cognitive developemtn

1. sensorimotor
2. preoperational
3. concrete operational
4. formal operational

85

stage 1: sensorimotor

birth to 18-24 months; experiences the world through senses and actions (looking, touching, mouthing); object permanence and stranger anxiety

86

stage 2: preoperational

2-6 years; represents things with words and images but lacks logical reasoning; pretend play, egocentrism, mathematical transformations

87

stage 3: concrete operational

7-11 years; thinks logically about concrete events, grasps concrete analogies and performs arithmetical operations; conservation, mathematical transformations

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stage 4: formal operational

12+ years; reasons abstractly; abstract logic, potential for mature moral reasoning

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growth spurts

sporadic period of sudden growth that lasts for a finite time

90

when do growth spurts occur?

between 3-10 months (30% increase in brain weight); age 2-4; 6-8; 10-12; 14-16+

91

what leads to increase in brain weight?

brain growth takes place without a concurrent increase in the number of neurons SO probably due to glial cells, blood vessels, myelin and synapses

92

connection between brain and behavior development

don't confuse correlation with causation

93

brain plasticity

brain is plastic in response to external events in addition to internal events (hormones, injury, genetic mutations)

94

stimulating environments

Hebb-- reasoned that people reared in stimulating environments will maximize their intellectual development whereas people raised in impoverished environments will not reach their intellectual potential

95

Tactile stimulation

important for bonding with caregivers & stimulates brain development

96

brains of animals from complex environments

larger, have more synapses, have more and larger astrocytes,

97

Exposure to music

early exposure alters the brain--> perfect pitch

98

chemoaffinity hypothesis

proposal that neurons of their axons and dendrites are drawn toward a signaling chemical that indicates the correct pathway; each cell has an identifiable biochemical label

99

neuronal placement

is activity dependent

100

amblyopia

condition in which vision in one eye is reduced as a result of disuse; usually caused by a failure of the two eyes to point in the same direction

101

critical period

developmental "window" during which some event has a long-lasting influence on the brain; often referred to as a sensitive period

102

imprinting

process that predisposes an animal to form an attachment to objects or animals at a critical period in development

103

deprivation and brain development

depriving young animals specifically of visual input or of maternal contact has devastating consequences for their behavioral development and presumably for their brain development

104

Harlow & monkeys

separated baby monkeys from their mothers shortly after birth and raised them in individual cages. They were unable to establish normal relations with other animals in adulthood

105

Androgen

class of hormones that stimulates or controls masculine characteristics; released during a brief period in the course of prenatal brain development for masculinization

106

masculinization

process by which exposure to androgens (male sex hormones) alters the brain, rendering it identifiably male

107

estrogens

variety of sex hormones responsible for the distinguishing characteristics of the female

108

testosterone

changes the structure of cells in many regions of the cortex, with diverse behavioral consequences that include influences on cognitive consequences

109

experiences for males and females

can impact the brain differently due to the mediating influences of gonadal hormones

110

gonadal hormones and brain developemtn

gonadal hormones alter the basic development of neurons, shape the nature of experience-dependent changes in the brain, and influence the structure of neurons throughout our lifetimes.

111

mental disorder onset

peak age 14

112

why do many mental disorders occur during adolescents?

neurobiological and associated behavioral changes linked with the period of adolescence are designed to optimize the brain for challenges that lie in adulthood but the brain's plasticity can also make it vulnerable to psychopathologies that can last for the rest of their life

113

drugs and brain development

prenatal exposure to drugs (of all sorts) likely impact brain development; increase in later drug use

114

spina bifida

condition in which the genetic blueprint goes awry and the neural tube does not close completely--leads to incompletely formed spinal cord. serious motor problems

115

anencephaly

failure of the forebrain to develop; front end of the neural tube (forms brain) does not close properly

116

brains of children with ID

stunted dendrite growth, sparse spines

117

genetic abormality

error of metabolism chromosomal abnormality; phenylketonuria (PKU), down syndrome

118

abnormal embryonic development

exposure to a toxin; fetal alcohol syndrome (FAS)

119

prenatal disease

infection; rubella, retardation

120

birth trauma

anoxia (oxygen deprivation); cerebral palsy

121

malnutrition

abnormal brain development; kwashiorkor

122

environmental abnormality

sensory deprivation; children in Romanian orphaneges