Psychology 216 Quiz and Brain Development

• Quiz #1 will be on Thursday, January 30, 2025.
• Review the Sugita, 2008 article available on Canvas
• Study the provided study guide to prepare for the quiz.
• The quiz will include True/False questions and is open book/note.

Brain Development Principles

• Brain development follows systematic principles.
• The type, timing, and extent of experience influence brain development.

Prenatal Development Stages

• Germinal Stage: Conception to 2nd week
• Embryonic Stage: 3rd to 8th week
• Fetal Stage: 9th week to birth

Germinal Stage (Conception to 2nd week)

• Rapid cell division and physical size increase occur
• The organism is called a zygote.
• The neural plate, a bundle of cells, develops and folds into the neural tube.

Embryonic Stage (3rd-8th week)

• Stem cells differentiate into specialized cells.
• Cells migrate to appropriate locations.
• Major organs develop.
• The organism is called an embryo.
• The neural tube develops into major brain structures.
• Differentiation of the brain and nervous system happens then.
• Hemispheres emerge.

Neuronal Migration

• Neurons move from central to peripheral regions.
• It starts prenatally and mostly finishes before birth.

Fetal Stage (9th week to birth)

• This is the longest stage of prenatal development
• The organism is called a fetus.
• Significant brain expansion, proliferation, and growth, including neuro- and synaptogenesis occur.
• Further structural organization and folding (gyrification) happens too.

Brain Matter

• Gray matter consists mostly of cell bodies/neurons and forms the surface of the brain/top layers in the cerebral cortex.
• White matter consists mostly of connective and supportive tissue, forming the lower layers.

Neuroanatomical Distinctions

• A neuron is a brain cell that transmits information, consisting of an axon, dendrite, and synapse.
• Gray Matter: made up of many neurons

Glial Cells

• Glial cells form white matter fibers.
• They provide critical supportive functions.
• Glial cells make up approximately half of the human brain.

Principles of Neuronal Development

• Proliferation
• Organization
• Consolidation

Proliferation: Neurogenesis

• Neurogenesis is the growth of new neurons.
• Approximately 250,000 neurons grow per minute until about 100 billion are reached.
• Neurogenesis starts during the prenatal period, mostly during the fetal stage.
• It mostly stops around birth.
• New neurons continue to form on a smaller scale in some brain regions throughout life, such as the hippocampus.

Proliferation: Synaptogenesis

• Synaptogenesis is the exuberant growth of connections between neurons during prenatal development.
• Trillions of connections are formed.
• There are many more connections in the infant brain than in the adult brain.
• Peaks around 1 year of age.
• Synaptogenesis happens at different times in different regions of the brain; for example, it happens earlier in the visual cortex than in the frontal cortex.

Proliferation: Gyrification

• Neurogenesis leads to rapid increase in brain mass/size.
• Gyrification results in the formation of sulci (depressions) and gyri (ridges).
• The brain folds in on itself to fit within the skull.
• Gyrification starts prenatally.
• Gyrification is fully present around 1 year after birth (~37-42 weeks, full term).

Brain Organization

• Lobular
• Hemispheric
• Contralateral
• Retinotopic
• Somatotopic

Lobular Organization

• The cerebral cortex has 4 lobes.
• Frontal lobe: planning, information integration, inhibition, decision making, movement
• Temporal lobe: auditory processing, memory, sensory integration
• Occipital lobe: visual signal processing and representation
• Parietal lobe: somatosensory processing (touch), attention, short-term memory, sensory integration, spatial representation

Hemispheric Organization

• The brain is organized into two halves (left and right).
• The structures are strikingly symmetrical globally.
• There are some notable asymmetries in function.

Contralateral Organization

• Sensory information entering one side of the brain is initially routed to the other side.
• Visual processing of the left visual field is routed to the right hemisphere, and vice versa.
• The motor and somatosensory cortex also have contralateral organization.

Retinotopic Organization

• Much of the visual system is arranged spatially as the information falls on the retina/eye.

Somatotopic Organization

• The motor and somatosensory areas of the brain are arranged like a spatial map of the body.

Proliferation: Myelination

• Myelination is the growth of fatty tissue around axons.
• It acts as an insulation sheath.
• Myelination speeds up the transmission of signals/communication between neurons, making the process up to 100 times faster.
• It begins prenatally but is mostly a postnatal developmental process.
• Myelination happens earlier in more basic (e.g., brain stem) compared to higher (e.g., frontal lobe) functional brain structures.

Environmental Influence

• The prenatal development environment includes:
  • Drugs
  • Pollutants
  • Plasticizers (e.g., BPA, DEHP)
  • Occupational Hazards: Toll booth collectors-exhaust from car

Socioeconomic Status (SES)

• SES is the level of access to resources.
• Multiple risks are associated with low SES.
• The outcome is generally less positive for infants of lower SES parents.
• Low SES correlates with a variety of risk factors.

Dose-Response Relation

• The amount of exposure influences the outcome.

Sensitive Periods

• The timing of exposure is important to the outcome.

Prenatal Brain Vulnerability

• The greatest vulnerability to harmful environmental impact is in the embryonic period.

Developmental Periods

• Neonatal: birth to ~1st month after birth
• Postnatal: (anytime) after birth
• Infancy: birth to ~2 years (24 months)

Consolidation: Synaptic Pruning and Plasticity

• Synaptogenesis creates a huge surplus of connections.
• Cells that fire together, wire together.
• Inactive/less active connections may disappear or be “pruned away” and accounts for approximately 40% of connections.
• Synaptic pruning is the systematic loss of connections between neurons.
• It starts during prenatal development but continues into early adulthood and is mostly postnatal.
• Different brain regions “prune” at different times.

Initial Production of Excess Connections

• Production is largely controlled by genes but can be influenced by the environment (stress, pollution, etc.).
• Which connections are pruned is largely controlled by experience.
• This possibly allows for more plasticity or flexibility in the final wiring of the brain.
• Less information is needed to be coded by genes.
• The brain can recover from early injury, the earlier, the better.
• It may be needed to better adapt to the environment.

Role of Experience: Two Kinds of Developmental Processes

• Experience-Expectant Process (E-E)
• Experience-Dependent Process (E-D)
• They both describe processes related to the role of experience

Experience-Expectant Process (E-E)

• Development resulting from the kinds of general experiences every member of the species is likely to have.
• Reliable experiences the brain can “expect”.
• EX: Patterned visual stimulation, faces, voices, other sounds, movement, etc.
• Lack of those types of experiences often has severe developmental consequences.

Limitations to E-E processes

• The brain is vulnerable if adequate stimulation is not present (deprivation).
• Ex: Born with cataracts causes disturbance in basic visual input.
• The longer the cataract remains, the worse the damage.
• Dramatic improvement is possible following early extraction of cataracts.
• Permanent damage is possible with longer deprivation, where synapses that would have been activated by visual stimulation (but were not) get pruned.

Brain Without Expected Input

• If a region is not used for its typical purpose, in some cases, it may be co-opted for other purposes.
• EX: Neville et al. (1998) study of congenitally deaf individuals: auditory cortex used for vision in deaf individuals that learned ASL (visual-motor language system).
• Activity related to visual stimulation is greater in deaf individuals.
• Activity related to auditory stimulation is less deaf individuals.

Sensitive/Critical Periods

• These periods are windows of vulnerability and opportunity in development
• Different developmental processes are more or less sensitive to the timing of experience.
• Processes differ in the strictness of temporal boundaries and consequences of timing/deprivation.

Critical Period

• Experience/development MUST occur during a defined period.
• The period begins and ends abruptly.
• Consequences are often irreversible/cannot be established later.

Imprinting

• Geese attach themselves to the first individual they see shortly after hatching.
• Results in maintaining physical closeness/following.
• Must happen between about 0-36 hours after hatching.
• No imprinting occurs if no exposure for 36 hours.

Critical Period for Vision?

• Controlled rearing experiment with kittens
• Surgically closing one eye of kittens to deprive that eye of normal visual input.
• Varied duration of deprivation
• Measured from cells in the visual cortex after the eye was opened
• The timing of the deprivation mattered.
• Newborn cats deprived of input for 6 months had little activity in visual regions of the brain associated with the deprived eye.
• Mature cats experiencing 1 year of deprivation caused no measurable change in the brain response/impairment.
• Further experiments systematically manipulating the deprivation period and age found that the first 3 months of experience are critical to visual development.

Critical Period for Depth Perception?

• Kittens reared in dark
• Only visual experience they were given was in the carousel
• Pairs of kittens received the same visual experience
• One moved itself
• The other was moved by the carousel
• Only kittens that moved themselves developed normal depth perception.
• Must experience this within ~3 months

Controlled-Rearing Studies

• Basic visual function develops in an experience-expectant way.
• Self-propelled movement and visual input are necessary for the development of typical depth perception.
• If experience is not received, vision does not develop normally.
• There is a strict critical period for visual function to develop normally.
• Experience needs to happen within the first few months (~3).

Sensitive Period

• Optimal timeframe to receive necessary input/development to occur.
• Begins and ends more gradually.

Sensitive Period for Language

• Flexibility in Language Organization in the Brain
• Language activates the visual cortex in blind participants.
• It depends on the age of blindness onset.
• To the greatest extent in congenitally blind (born blind).
• To a lesser extent in late blind (after 9 years).
• Not at all in sighted individuals.

Sensitive Period for Music

• Increased cortical area for fingers of the left hand in string instrument players.
• Was related to age at which a person began playing.
• Younger = larger cortical representation.

Critical/Sensitive Periods in Education

• The concept of a “window of opportunity” contributed to the modern educational emphasis on early experience.
• Examples include Head Start/preschool programs
• Montessori-based programs ("optimal periods”)
• Modern early intervention approach for developmental disorders (e.g., autism)

Modern Thought on Critical Periods

• Sensitive vs. critical periods are debated for many skills.
• Critical periods are widely viewed as the exception rather than the rule.
• Most developments are thought of in terms of sensitive periods.

Experience-Dependent Process (E-D)

• Development resulting from the idiosyncratic (individual) experiences of the organism.
• Plasticity (flexibility) in brain development to accommodate for individual experiences.
• Examples include the type of language you learn (phoneme/sound discrimination).
• Type of sounds you hear: Music perception.

Perceptual Narrowing

• Phenomenon associated with Experience-Dependent processes.
• The ability to perceive certain distinctions in environmental stimuli becomes specialized or tuned to that which is commonly present/experienced.
• Accompanied by the “loss” of distinctions outside the range of those commonly encountered/experienced.
• Likely the behavioral consequences of synaptic pruning.

Language Acquisition Example:

• Infants start life able to distinguish between all sounds (phonemes) in all human languages (~0-8 months).
• Become experts in their own language.
• Lose the ability to discriminate between sounds in foreign languages (~8-12 months).

Music Perception

• The structure (meter) of music differs by culture and region.
• The ability to perceive the structure of music narrows over the first year of life.
• 6-month-olds perceive changes in a variety of musical structures (e.g., foreign and non-foreign structured music).
• By 12 months, they lose the ability to perceive differences outside of their musical experience.
• Western infants can only detect changes in the musical structure of Western music (Western-like meter).

Conclusions

• Early brain development unfolds systematically, including some prenatal and postnatal processes and proliferation and consolidation processes.
• The outcome is dependent on experience/environmental influence.
• Certain experiences are REQUIRED for typical development.
• Other experiences TUNE or shape development.
• The extent and timing of experience matters.

This lesson covers the format and focus of Psychology 216 Quiz #1, preparation strategies, and effective approaches. It explores brain development concepts such as perceptual narrowing, language acquisition, and the shift from critical to sensitive periods. It also touches on experience-dependent processes and the influence of early musical exposure.