Brain Methods

Methods of Measuring

Interviewing

Naturalistic Observation

Clinical interviewing: Researcher begins with a set of prepared questions, but will have an emphasis on the child's way of conversation


  • Advantage: It can lead to better conclusion, because it is tailored to the individual

Structured Observation (takes place in laboratory with prearranged tasks)

Study Designs

Correlational Designs


  • Determine whether children who differ on the one variable, also differ on the other

Experimental Designs


  • Conducted in laboratory setting

Cross-Sectional Designs


  • Compares children of different ages on a given behavior at one time

Longitudinal Designs


  • Following the same group of children over a substantial period of time

Microgenetic designs


  • Recruiting of children, who are in the verge of an important developmental change


  • Difference to Longitudinal Designs: They include a greater number of sessions presented over a shorter period of time

Development of Nervous System

Embryo: The earliest stage in the developing animal (first 10 weeks of development)


Fetus: A developing individual after the embryo stage

Sequential Desing


  • Combination of cross-sectional and longitudinal design

Basic concepts about human brain

Grey matter: Neuronal cell bodies and synapses

White Matter: Axons (myelin)

Gray matter loss over time, because of cell death + Myelin Increases and processing becomes faster

Postnatal growth/ Functional&cognitive development

Prenatal brian tissue growth/ Structural growth

1. Neurulation

2. Cell proliferation/Neurogenesis

3. Migration/
Aggregation

CNS arises from neural plate

Neural plate --> Neural grove --> Neural tube

Within 3 weeks from conception the first brain tissue is starting to form

  • Differentiation of the neural tube


  • Production of new nerve cells

  • Supported by glia cells


  • Inside/out pattern of cortical development


  • External influences (e.g. alcohol) --> fetal alcohol syndrome


FAS affected baby: Small eye opening, thin upper lip, smooth philtrum

4a. Dendritic/
axonal grwoth

4. Synapse production (Synaptogenesis)

5. Synaptic Pruning/ Neuronal cell death

6. Myelination (during adulthood)

  • Axons and dendrites are formed
    -At tips of both axons & dendrites are growth cones
  • Some axons have to bridge long distances of up to 1 m (motor neurons)

Dendritic and axonal overproduction

Loss of synapses (20-80% of cells die during development)

Conncetions that are not used are eliminated

Increases the speed at which impulses travel along the myelinated fibers

The establishment of synaptic connections as sons and dendrites grow

Changes in behavior and brain during Adolescence

Risk perception,Reward(incentive), Self regulation

Changes traditionally explained by protected development of the prefrontal cortex

Neural tube: Differentates into forebrain, midbrain, hindbrain, and spinal cord

The movement of cells from site of origin to final location

Timeline of Development

  • 4 weeks after conception: Facial features have their origin in the set of the four folds
  • 5 1/2 weeks: Nose, mouth and palate begin to differentiate into separate structures
  • 9 weeks: Head constitutes roughly half the length of the fetus, rudimental eyes and ears are forming, sexual differentiation has started, nails are growing, ribs are visible
  • 11 weeks: Heart is achieved its basic adult structure, major divisions of the brain can be seen
  • 16 weeks: Growth of the lower part of the body accelerates
  • 18 weeks: Covered with fine hair and sucking its thumb
  • 20 weeks: Spends more time in head down position; can move its mouth
  • 28 weeks: Lungs are sufficiently developed, auditory system is functioning, brain waves are similar to that of a new born
  • During the last three months: Grows dramatically in size, tripling its weight

Timeline of Cortex Development

1st month until 2nd Year: Sensory motor cortex

1st month until 8 year: Parietal-temporal cortex

1 month until adolescence (and even longer) : Prefrontal cortex

Meta-anayltic studies

After Gray matter development follows functional maturation sequence

  1. Regions related to primary function= Motor/Sensory systems
  1. Regions associated with spatial attention/basic language skills develop next: Temporal/Parietal areas
  1. Regions related to higher-order functions mature last: Prefrontal cortex
  1. Structural changes correlate directly with onset of cognitive functions

Stages of prenatal development

1. Zygote (0-14 days) From conception to implantation on uterine wall; cell division

2. Embryo (Week 2-8) Differentiation of most organs and body systems, a sensitive period of development (Highest risk of brain abnormalities around 2-6 weeks post conception)

3. Foetus (Week 8-birth) Growth in size and genesis of processes to help organs and systems function

Development of cerebral cortex relatively late as compared to midbrain/brainstem

Mechanisms

Competition, stabilization, elimination

Changes during adolescence

Risk perception

Changes traditionally explained by protracted development of the prefrontal cortex and hormone changes

Development during 12-18 years --> They are often bad in decision making (Are just about to learn to think abstractly, analyze, realistically, hypothetical

Reward/incentive

Self regulation

Takes place in the Nucleus Accumbens

"affective pathway" develops relatively early in children

"Cognitive pathway" develops relatively late in adolescence / linked to changes in the prefrontal cortex (which is linked to inhibition and decision making)

Activity in Amygdala when processing negative information --> Teens are less efficient in surprising emotional reactivity

When limbic system dominated prefrontal cortical function: Decreased in reasoned thinking; Increase in impulsive behavior

Gray matter loss occurred earliest in primary areas and then in PFC

Casey (article) describes: Development of different brain areas seems related to cognitive development (like Piaget said,too)

Dual System Model (Smith)


a) an affective (reward sensitivity) pathway

  • Is associated with network of limbic & para-limbic areas
    --> Involved in emotion-and reward-relation
    --> Matures earlier than the cognitive control pathway

b) a cognitive (cognitive control) pathway

  • Matures later and thus brain creates a period of vulnerability , in which young adolescence are hypersensitive for risky behavior

Risk-taking behavior is prevalent in "hot situations", in which subjects are aroused

Limbic functions (affective pathway) show earlier onset than pathway of prefrontal cortex

Cohort effect (Generational effect) are limitations to these studies, Reason:
e.g. every group has unique experiences (play with tablet vs. play with playmobil )

Imaging Methdos

3. EEG/ERG recordings

Direct and continuous measures of electrical brain activity

2. Functional MRI: Activation patterns within structures

Activation patterns in the brain during different activities: Speech, fingertip and listening

Results

  • More diffuse brain activity in infants and young children
    -More regional activity in children and adolescents
  • Shift from diffuse to focal cortical regions

1. Structural MRI: Anatomical Studies

Grey and white matter densities can be computed for different regions and be compared across subjects/time