Week 4 Lecture 4 - the developing brain Flashcards
What is nature vs. nurture?
the extent to which cognition and behaviour can be attributed to genes or environment
What is nature?
genetic blueprint (things we are born with
What is nurture?
role of experience
How was Piaget the middle ground of nature vs. nurture?
- Piaget considered development as a cyclical process of interactions between the child and their environment leading to a progression through stages
- Genetic contribution = developing a brain that is ready to learn in certain ways
- Environment = assimilating evidence via experience and then developing new
mechanisms in light of the feedback obtained.
What is neuroconstructivism?
- modern approach
- Interaction between environment and genetic factors
- Cognitive system matures and transforms as the brain goes through developmental changes
True or false
Human brains are very similar, but experiences are very different
True
What is the blueprint analogy?
- each connection in the brain is pre-determined
- however there are too many neurons and synapses for this to be realistic
What did Gottlieb propose for the structural development of the brain?
- Deterministic development – structure is the same for everyone
- Probabilistic development – each stage influence each other
What are some key features of prenatal brain development?
- Cell division
- Cell specialization
- Neural tube formation
o Proliferative zones: neurons and glial cells are produced
o During early development 250,000 neurons are produced per minute
o Neurons migrate to their final location
In prenatal brain development, many structural features of the brain emerge from other constraints
Describe these
- Folded cortex emerges from having lots of neurons
- Pattern of gyri/sulci pulled into shape by tension of axon bundles (white matter tracts)
- Hebbian learning: Spontaneous electrical activity enables networks to form (e.g. electric activity from the retina helps to form the visual pathways)
When do the majority of neurons form?
prior to birth
How much does a newborns brain weigh?
450g
Postnatal, the brain increased in size.
In what ways does this happen?
- Synaptogenesis
- Myelination
- Glial cell proliferation
What is plasticity?
-experience dependent change in neural
functioning.
- experience alone can lead to small but observable structural changes (e.g. juggling, driving a taxi
What can an increase in grey matter lead to?
- new synapses, dendrites, axon
collaterals, glia cells - but doesn’t mean better cognitive ability
What is functional brain plasticity?
prenatal brain damage can lead to major
reorganisation of tracts
What is an example of functional brain plasticity?
Patient AH –> had no right hemisphere
What are some limits of functional brain plasticity?
- Spontaneous electrical activity enables networks to form intrauterine – these
connections won’t be fully lost - Opportunities for major reorganization are time-limited = critical or sensitive periods
What did Konrad Lorenz study?
studied how birds recognize their mother
What is Filial imprinting?
- the process by which young animals learn to recognize the parent
- Happens between 15h – 3 days
- Movement is crucial
What are the 2 main features of critical and sensitive periods in imprinting?
- Learning takes place within a limited window
- But opportunity can be extended in lack of experience - This learning is hard to reverse by later experiences
- But chicks imprinted to one object can generalize to similar objects (colour or shape)
- Preference can be changed after sensitive period
What are 2 possible explanations for critical and sensitive periods?
- Genetically programmed synaptogenesis (readies brain for learning), followed by reduced plasticity (learned information is then “fossilized”)
- Closure of window could be initiated by learning itself, i.e. an environmental cue
- E.g. particular gene plays a role in filial imprinting, it is switched off after exposure
What is the empiricist vs. nativist view of innate knowledge?
- Empiricism: newborn mind is a blank state
- Nativist: we are born with some knowledge
What is a more modern view of innate knowledge?
Innate = readiness to learn (e.g. imprinting)
Knowledge or behaviour that arises in the absence of appropriate experience:
- Development of cat visual cortex
- Preferences – sweet taste, visual pattern
Is viewing the structural of prenatal brains easy or hard?
easy
can use ultrasounds, MRI
What are behavioural methods for investigating brain development?
We can infer brain development from
their behaviour
- Preferential looking paradigm
- Habituation paradigm
What does preferential looking suggest about form perception?
Form perception
- 1-week-olds - 3.5-month-olds
- differential interest within pairs was
based on pattern differences.
- Infants consistently turn their gaze toward some forms more often than toward others, it must be able to perceive form.
What does preferential looking suggest about visual acuity threshold?
Visual acuity threshold
- The width of the stripes of the finest pattern that was preferred to grey would provide an index to visual acuity
- The width of the finest stripes that could be distinguished decreased with increasing age (from 0 to 6 months)
- The eye, the visual nerve pathways and the visual part of the brain are poorly developed at birth
What are modern uses of preferential looking?
- Use of video camera(s)
- Stimuli presented on screen
- Babies stay with caregiver –> Caregiver shouldn’t interfere with the study or bias the baby
What is eye-tracking in preferential looking?
- Uses infrared (non-collimated) light to measure where the participant is looking at the screen at any moment
- Fixations and saccades
- Allows more precise measurement of looking times and fixation
What are problems with preferential looking?
If infants look longer to screen 1 compared to screen 2, they must:
1. Find screen 1 more interesting than screen 2
AND
2. Discriminate 1 from 2
If the infant looks equally to screen 1 and 2:
1. Either they failed to discriminate screen 1 and 2
OR
2. The infant finds 1 and 2 equally interesting (boring)
What are modern uses of the habituation paradigm?
- make infants bored with one stimulus (A)
- then pair it with another (B)
- should the infant look more at the new
stimulus (as they are not bored of it yet),
then they have discriminated the two
stimuli from each other - overcome the problem of preferential
looking paradigm
What are functional neuroscience methods?
temporary changes in brain physiology associated with cognitive processing (e.g. fMRI
What is a problem with functional neuroscience methods for infants?
- Usually, we ask participants to perform some kind of task (categorisation, counting) or to sit/lay still and look at images
- Infants won’t perform tasks and they won’t even stay still
What are functional neuroscience methods that can be used with infants and young children?
Electrophysiological response (electromagnetic fields generated in the brain)
- EEG (Electroencephalography)/ERPs
Haemodynamic response (brain blood supply)
- fMRI (functional Magnetic Resonance Imaging)
- fNIRS (functional Near InfraRed Spectroscopy)
What is an infant EEG?
- Infant friendly EEG systems/solutions that allow quick installation
- Infant friendly stimuli
- More breaks during the study
What are infant ERPs?
- Some adult ERP peaks are present in infants, but delayed: e.g. visual ERPs
- N290 in infants = N1 or N170 in adults:
- Perceptual and/or face specific
component
We can compare visual processes in adults and infants
If processes are similar (similar ERP patterns) then what can we assume?
that the underlying brain networks and/or processing mechanisms are also similar
Some ERP components are only presents in infants and toddlers
Give an example
Nc – Negative Central peak
- Typically peaks between 300-700 ms after stimulus onset
- Reflect attention
- Larger peak reflect higher attention
What do Ncs (ERPs) suggest about whether infants recognise their mother’s face?
- Larger Nc for mother’s face compared to a stranger’s face
- Larger Nc = more attention
- Infants recognize their mother’s face
Is fMRI ideal to use with infants?
- Not ideal to use with infant participants
- Highly sensitive to motion artifacts
- Loud, restrictive environment
- But there are some attempts
Can fNRIS be an appropriate for fMRI for studying brain activity related to cognitive
tasks?
No:
- fNIRS has lower spatial resolution
- Only the surface of the cortex can be imaged
- Often only a few sensors are used above a certain brain area
Yes:
- Portable
- More tolerant of movement
