Lecture 8 Flashcards

(24 cards)

1
Q

Overview of the adult brain?

A
  • Composed of billions of neurons
  • Neurons are information-processing cells
  • Make connections with other neurons to create networks
  • Each neuron can connect with 1000 other neurons = 60 trillion neuronal connections in adult brain
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2
Q

What are the composition of neurons?

A
  • Dendrites are the where neuron receives incoming signals
  • Cell body and axon at the end = signal is propagated to axon terminal where it connects with other neurones or effector cells
  • Synapse: chemical in brain not electrical = usage of neurotransmitters in vesicles into synaptic cleft to bind to post-synaptic membrane
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3
Q

What are terms for the brain?

A
  • Grey matter - cell bodies (neuron)
  • White matter - nerve fibres (axons) - myelinated = insulated layer
  • Gyri - ridges
  • Sulci - depressions/folds
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4
Q

What is fetal and post-natal brain development size?

A
  • Biggest growth spurt is from around 7mo prenatally to 2yo postnatally
  • Basic structure of brain is formed from week 8 from conception
  • Adult neurons present in utero
  • Brain grows so much postnatally because of connections made between neurones and links between dendritic trees
  • Neurones appear at birth and then migrate and specialise
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5
Q

What is the timecourse of maturation of different regions?

A

Development is so sensorimotor cortex develops first, then parietal and temporal association cortex, and then prefrontal cortex

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6
Q

What is the study looking at grey matter?

A
  • Looked at children every 2 years from 5-20
  • By age 5, regions are mature (developed and pruned) = visual cortex and motor
  • By age it spreads into parietal and temporal
  • Dorsolateral pre-frontal cortex is last
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7
Q

What happens in the first 1-2 years?

A
  • Brain doubles in volume
  • Cortical thickness and SA increase
  • Complexity of neurons and no. of synapses
  • Myelination begins before birth but continues beyond adolescence
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8
Q

How does face perception develop?

A
  • Genetic: have genetic program and will have face processing system
  • Innate: present at birth = do we have a precursor system and we develop and finetune it
  • Experience-dependent: experience needed to develop
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9
Q

What are the genetic contributions to face perception?

A
  • Twin study of face-specific recognition ability, face inversion effect, and composite face effect
  • All more highly correlated in monozygotic than dizygotic twins = suggests something heritable about face perception
  • Developmental prosopagnosia is a lifetime inability in recognising faces = runs in families
  • No heritability for inverted faces or houses
  • Face heritability seems to be independent of general cognitive abilities
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10
Q

What perceptual abilities are present in newborns?

A
  • Face detection: face vs non-face
  • Preference for faces
  • Face recognition - discriminate between identities
  • Face recognition across viewpoint changes
  • Special face-processing related effects e.g inversion effect
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11
Q

What was a study about face detection and attention in newborns?

A
  • Tested newborns within hour of birth
  • Babies lying over caregivers lap and paddles either had schematic of face, features/scrambled face, and nothing
  • Measured the head and eye turning for each paddle
  • Face had the most response, then scrambled, and then low levels to the blank paddles = idea of innate system
  • Could just be the template = more structure on top than bottom = sufficient for a face
  • Newborns can detect faces and preference to faces within an hour
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12
Q

What was a study looking at recognition in newborns?

A
  • 1-3 day old infants recognise the identity of non-familiar faces = babies like looking at new things, habituate quickly and new things grab their attention
  • Present babies with identity during habituation phase, and then 2 other images, one of which has a different identity. If baby looks more at new identity = recognise its different as its new
  • When presented babies with a 45 degree viewpoint change = still preferred to look at new face vs one they had seen, but could not differentiate with a full 90 degree change
  • Face recognition abilities early on
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13
Q

What was a study looking at specific facial recognition (inner/outer features of face) in newborns?

A
  • Had a full features condition, inner features and outer features
  • Each condition provides sufficient cues for face recognition
  • Inversion disrupted recognition of inner features condition = suggests that infants have a lot of signatures associated with face perception
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14
Q

What is an overview of face perception in development?

A
  • By age 4, children have adult-like signatures of face perception
  • Lots of tasks have no evidence of children under 3yo as not performed
  • Lots of evidence of presence in birth and not much development across age
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15
Q

What are critical periods for face perception?

A

1) Cases of early visual deprivation due to congenital cataracts: typically show normal recognition of same-image faces later in life BUT impaired recognition across viewpoint changes
- No composite face effect = indicates some critical periods for viewpoint changes etc. and others do not need input.
2) Patient MM, blind 3-46 and some experience of brightness, got corneal transplant and monocular vision restored at 46, tested following surgery and 10y later
- No evidence for experience-depending recovery of function, neither behaviourally nor neurally = function cannot be recovered = aspects of face perception need to occur early in life = need external input for perceptual system to develop

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16
Q

What is perceptual narrowing in face perception?

A
  • Infants are better discriminating at their native language than foreign ones after 6mo
  • After 6 mo they hone in on faces they know, and lose this ability (can discriminate between monkey faces also) = experience seems to be eliminating ability to discriminating monkeys
17
Q

What was controlled rearing in monkeys? (study)

A
  • Monkeys were reared about exposure for faces for 6,12 or 24 months (neither monkey or human faces)
  • A week before deprivation ended, monkeys showed preferential looking to faces vs other ovjects and could discriminate monkey and human faces equally well
  • Face discrimination with adult-like accuracy
  • After deprivation happened, monkeys either exposed to monkey faces only or human faces only for a month
  • There was selective discrimination of exposed species, difficulty discriminating non-exposed species = suggests experience need for perceptual narrowing = but also had an innate way of discriminating
18
Q

What is the development of face perception in the brain?

A
  • By age 5, most of face specific regions are evident
  • Put 4-6mo infants in a mri scanner looking at faces and houses
  • Orange regions respond to faces more than houses and blue is vice versa: identifies FFA etc. BUT these regions are less selective than adult FFAs = spatial layout of face-specific regions apparent
19
Q

What was a longitudinal study of monkeys?

A
  • From birth to first year of life: scanned them every month and showed them with faces and scrambled faces and object to see how brain regions develop
  • Some functional organisation of IT apparent at 30 days
  • Prior to 170 days (6mo), no evidence for face-specific patches (face vs object)
  • From day 200, face-selective response is stable
  • Is it due to experience - no because of prior study with monkeys - could be innate/pre-programmed
20
Q

Is seeing faces necessary for development of face-domain?

A
  • Monkeys reared without ever seeing a face (controlled rearing)
  • Monkeys could hear and smell other monkeys had social contact and visual experience but not faces
  • At 90 days old, during MRI scans they saw faces = by 252 days in control there are face patches, but in exp there is no face patches = no exposure = no face patches = experience is necessary = cannot be preprogrammed and requires input
21
Q

What was the link between connectivity and function of a region?

A
  • Surgically removed connections in ferrets and rewired them so the auditory cortex receives input from retina
  • When presented with visual stimuli there is an auditory cortex response - developed to process visual input = long-range connections that are in place when the system begins to take in information determines what function that region will have
  • Even orientation columns develop in auditory cortex = looks like a visual cortex
  • Ferrets do not hear things but see things = clear link between connections and functions of a region BEFORE function is exposed to stimuli
22
Q

What is the link between connectivity and selectivity of faces?

A
  • Looked at FFA and connectivity fingerprints from that region = tracking nerves to other areas of the brain from FFA to create probability maps of where things connect to = linked to individual differences of activity of each regions
  • Could predict on connections = how strongly area could respond to faces
23
Q

What is evidence from early brain damage?

A
  • Adam had a stroke when he was 1 day old and had damage to occipital lobe
  • Tested at 16, visual acuity was not great and object recognition was not good
  • Profound prosopagnosia
  • Stroke destroyed his long range connections to FFA
24
Q

What is further development through adolescence?

A
  • Hard to assess children as tasks are not designed for them = most abilities are present and adult like at ages 4-5
  • Ffa grows in size and selectivity due to myelination affecting cortex, and those that were limb selective have been taken over by face selectivity
  • Facial expression perception is not seen properly before 7mo = emotion recognition develops well into adolescence