Neural Development

Question 1

Plasticity in the early brain

Answer 1

• Plasticity = brains ability to change its structure, function or connections in response to stimlui
• Brain CT scans of hydrocephalus (water on brain) as a baby + neural plasticity allowed him to survive
• Feuillet, Dufour + Pelletier (2007)

Question 2

The Zika virus

Answer 2

• Microcephaly = below average head size
• Caused by failure if brain to grow at normal rate
• 25,000 children in US every year

Question 3

Evolutionary perspective

Answer 3

• Humans have largest brains + longest period of brain dev
• Huge head being 25% of indants total body length: to accomodate the brain
• From birth to teenagers there is increase in volume of human brain
• Adult brain = 2% of body weight but 20% of o2 consumption

Question 4

3 main prenatal stages - 1= Germinal phase

Answer 4

• The Zygote
• First 2 weeks
• Sperm ferilises ovum which is reffered to as zygote (fertilised egg)
• Proceeds down fallopian tube undergoing rapid cell division + implants in uterus wall
• Placenta formation to provide o2 + remove waste

Question 5

3 main prenatal stages - 2 = Embryonic Stage

Answer 5

• Embryo
• Weeks 3-8
• Amnionic sac, placenta + umbilical cord dev
• Cephalocaudal dev, proximal to distal
• Inner layer mass differentiates into 3 layers:
  1) Endoderm - vital organs
  2) Mesoderm - muscles, skeleton, innter skin, circulatory
  3) Ectoderm - Sensory cells + nervous system
• Neurulation = formation of neural tuve + crest from neuroectoderm - foundation of brain

Question 6

3 main prenatal stages - 3 = Foetal stage

Answer 6

• Weeks 9-38
• Rapid dev of muscles + nervous system
• End of 3rd month have all body parts
• 5 month = reflexes
• 6 months = eyes open + close
• 22-26 weeks = age of viability - fetus physical systems advance enough so has chance of survival if born prematurely

Question 7

Birth of neurons

Answer 7

• Need mass neural proliferation: 250,000 neurons added every minute
• Neurogenesis = birth of brain ceels
• Neurons dev from neural cells + progenitor cells
• AT birth babys brain has most of its neurons

Question 8

Cellular dev

Answer 8

• Proliferation of glial cells - surround + protect neurons
• Neural migration - migrate to various parts of brain + specialise
• Myelination - cells insulated in myelin sheath (improved synoptogenesis - cell communication)
• Synaptogenesis = formation of synapses

Question 9

Lissencephaly

Answer 9

• Smooth brain
• Caused by defective neural migration at 12-24 weeks
• Lack folds (gyri) + groves (sulci)
• Severe dev problems, seizures, muscle spasms
• Caused: viral infections, genetic anomalies or insufficient blood supply

Question 10

Step in utero

Answer 10

• 7 months spends most of its time sleeping
• Cycle every 20-40 mins between rapid eye movement (REM) sleep + non-REM
• Yawning (Reissland, 2012)

Question 11

Neural plates

Answer 11

• Form + fold to form neural groove + curls to form tube which differentiates into forebrain, midbrain, hindbrain + spinal cord
• Forebrain dev into cerebral cortex = sensory stimulation, memory
• Midbrain = neural relay station
• Hindbrain = Basic physiological process
• Spinal cord = pathway to convey info from brain to rest of body
• 8-26 weeks cerebral cortex growd to cover midbrain

Question 12

Fine tuning

Answer 12

• 2 processes reduce number of neurons:
  1) Synaptic pruning - axons + dendrites disposed if neuron nor receiving much stimulation
  2) Programmed cell death (apotosis) = new synapses formed, surrounding neurons die to provide more space
• Helps achieve more efficient functioning

Question 13

Brain maturation in infancy

Answer 13

• As cerebral hemispheres mature early motor reflexes disappear + replaced by voluntary motor beh (reaching, crawling)
• 6 months hearing + vision are mature
• Cerebellum dev in Y1 to tone muscles + balance
• Prefrontal areas (planning) are last to dev

Question 14

Reflexes

Answer 14

• Involuntary reactions to external stimuli
• First forms of human movement
• Serve as protection or nourishment
• Dev of future movement
• Diagnostic tool

Question 15

Reflexes correlating with brain dev

Answer 15

• Moro (3+ months) - Dropped/loud noise = extend limbs + draws back head
• Grasping (4+ month) - palm stroked = strong fist
• Stepping (1-4 months) - held under arms + hover above floor = step like motions
• Rooting (4+ months) - Turn face to cheek when touched = breastfeeding aid

Question 16

Teratogens

Answer 16

• An env agent that cause dev deviations
• Impact depends on many factors
• Most threatening in embryonic stage
• Each organ system has critical periof
• Exposure length + intensity important factors
• Maternal or foetal genotypes may counteract effect

Question 17

Teratogens examples

Answer 17

• Drugs: Thalidomide, heroin, nicotine
• High caffeine: miscarriage, low birth weight, prematurity
• Paternal factors: age, diet, emotional state
• Disease: rubella, herpes, chicken pox
• Metals: lead, mercury
• Radiation: cell death, chromosome injury

Question 18

Foetal alcohol syndrome

Answer 18

• Physical defects: flattened midface, thin upper lip, short eye slits
• Growth suppression: low birth weight, height/weight low
• CNS: Impact fine motor skills, learning disabilities + beh disorders

Question 19

Postnatal env + brain plasticity

Answer 19

• Brain plasticity changes in brain due to experience
• Diamond: cortical structures of brains o frats raised in enriched or impoverished env
• Cortical thickness differed due to env
• Impoverished reduced

Question 20

Neurological impact of neglect

Answer 20

• Much brain structure is genetically determined
• Brains plasticity means = amount + type of stimulation received is also crucial
• Bruce + Perry (1997) extreme neglect scan showed sig decrease of brain size

Question 21

Recovery from neglect

Answer 21

• Perry + Pollard (1998) examined brains of neglected children, some also had pre-natal drug exposure
• Frontal occipital circumference: brain growth + organisation were all worse compared to non-neglected children