Lecture 13: Brain Development

macro neuroanatomy (also learning goals)

Recognize basic neuroanatomy, and patterns of anatomical and functional brain development

Explain the difference between “forward inference” and “reverse inference”

Explain how both behavioral and neural data inform the puzzle of face processing in infancy

Explain how both behavioral and neural data inform the puzzle of infant memory, and infantile amnesia

micro neuroanatomy

Anatomical development

Grey matter grows most ~1 yr, white ~2yr

maxima see image

• maximum white matter around our age, 18! according to prof, but clearly its greater than that according to the graph lol, but close enough ig

idk not important

more anatomical development

many changes in gray and white matter volume continuing into childhood and even young adulthood

specifics not important

random image

organization of brain networks

adult brains organized into functional networks - regions of brain whose activity rises and falls together (even at rest)

much of this functional structure is present from birth

• measured while infants were asleep

but this is not measuring neural responses in awake people

• want to see how brains support cognition and behavior of ppl who are awake and doing things

How can we think about (1) the anatomical immaturity of the infant brain, and yet (2) the early emergence of cognitive functions?

Presence of change does not imply starting from 0

• nonzero starting point

wow revolutionary

what does brain data add to learning about the developing mind????

• hard to learn about mind by measuring brain

• all cognitive functions have neural origins (so finding capacity through behavior implies neural mechanisms that support it)

  • um she’s saying idk… everything is brain, so duh you don’t learn anything? so by itself it’s not satisfying

  • u have to think about why this specific brain area (shocker)

• brain responses don’t always support behavior

  • causation correlation

forward vs reverse inference

forward:

• manipulating stimulus or task, then measuring the brain

• Q: What is neural basis for [mental function]?

• A: Brain areas, X, Y, and Z

Reverse:

• measuring brain and making inference about underlying mental function

• Q: What [mental process] involved in [task]?

• A: Cognitive processes X, Y, and Z

Forward inference: which brain regions respond more to personal v impersonal moral scenarios?

“Impersonal scenarios evoke calculated thinking, more so than personal scenarios”

“Personal scenarios evoke emotional reasoning, more so than impersonal scenarios”

reverese: given neural activation, what cognitive processes are likely involved in processing moral vs impersonal moral scenarios?

controversial??!

Using brain to learn about mind requires making reverse inferences.

• controversial because the same region can be active during many different mental processes

what do brain data add to learning about developing mind? (again)

um ig can tell us about “Common mechanisms” vs “Distinct mechanisms”
- in adults v infants, is same mental process/behavior supported by same or distinct neural mechanism

face processing

what is neural basis for face perception early in life

adult face processing

Multiple face-selective regions, including the fusiform face area (FFA), superior temporal sulcus (STS), and medial prefrontal cortex (MPFC)

• ‘face selective’: responds more to faces than other stuff

  • like houses, objects, bodies, scenes

FFA in adults

In adults, FFA does not merely respond to faces, but is causally involved in face perception

N=1 case study in patient with electrodes implanted over FFA

• electrode stimulate FFA, japanese guy sees face on random stuff like box/soccer ball

• looks at doctor, and his face like changes

  • eyes nose change. dude becomes anime character

  • hair stays same

FFA STS MPFC

these brain areas hypothesized to have increasingly abstract functions  as we move from back to front of brain

• FFA: processing faces

• STS: processing social interactions

• MPFC: processing self relevance and social value

Serial hypothesis

face processing proceeds from concrete to absract over development, with brain areas developing face-selective response in a particular order

• first infants learn to identify face (FFA)

• Next, learn to sense other ppl’s interactions (STS)

• Finally, connect what they see to themselves and attribute social value (MPFC)

case study 1: face processing

n=47 infants (2-10 months)

• dynamic videos of different visual categories, plus a baseline (reference point)

  • basically see if response was more positive compared to baseline

• selective responses: greater response to category X than any other

case study 1 continued

• infant FFA responds to faces as early as we can measure

• Ditto for areas in adults have more abstract functions like STS (social perception) and MFPC (social value)

Forward inference: infant FFA, STS, and MPFC, show a face-selective response, as early as we can measure

Reverse inference: Infants appreciate that faces are potentially valuable social partners, as early as they can perceive faces

the previous reverse inference is controversial

but there is supporting data: (past lectures)

face processing more support

In infants: STS and MPFC don’t merely respond to faces, but are also sensitive to social interaction and self relevance

in 4 mo: more response to mutual vs averged gaze in STS and MPFC

in 6 mo: greater response to MPFC to hearing own name vs familiar name

serial hypothesis conclusion?

No support for this proposal

• instead face-selective responses emerge in parallel in these regions (forward inference).

• Plausibly, perceiving faces, social partners, and making social evaluations emerge in parallel (reverse inference + behavioral evidence).

memory demo

shows a bunch of squares and one of em changes color.

i guess its harder if theres more total squares

short term memory

information that is briefly stored so that it can be actively processed

• limited to just a handful of items

• capacity limit of about 3 items

• temporal scale: ~seconds

can measure this with a change detection array (the squares thing)

• excellent performance when 1-3 items to track, lower 4+

demo 2

series of images of like houses and stuff

• asking u what changed

• everything changed but there were too many things to track and it happened “slowly” (ig one or couple changes at a time)

demo 3 science lab

stuff disappearing and moving

• can’t keep track of everything all at once

long term memory

Stored information that constitutes our general knowledge base

• higher capcity

• temporal scale: minutes to lifetimes

e.g. what ur mom looks like, that JHU is in baltimore (declarative); how to cook ur fave recipe (procedural), something that happened in 8th grade (episodic)

evidence for shrotish-term memory in infancy

longish term memory

3mo infants learned that kicking makes mobile move

after a few days delay:

• infants kicked when set up with same mobile as before

• but not a different mobile

also “every single aspect of language development"

• u need memory to learn language lol

infantile amnesia

infants clearly can remember things

but! how come older children or adults can’t recall memories from early childhood, up to age 3-4

hypothesis: developmental change in neural mechanisms for memory formation explains infant amnesia

if true: neural mechanisms for memory should differ between adults + infants

In adult humans and other animals: hippocampus is critical role, which matures into adolescence

• perhaps in infants, memory operates via diff mechanisms, that do not involve hippocampus

methods to test adults memory

show particpants pictures in lab, and test them later to see what they remember

Finding: in adults, greater responses in hippocampus to items that will be remembered than those that will be forgotten

adapted method for infants

4-24 mo infants scanned using fMRI, in similar task of sequences of images

evidence of whether infants remembered:

• preferential looking for the familiar item, after a delay

infants also showed greater responses in hippocampus for items that will subsequently be remembered vs forgotten, just like adults

• common mechanisms

infantile amnesia hypothesis

• no evidence that infants can’t remember stuff

• both infants and adults use hippocampus

  • no support for distinct mechanisms

remaining hypo: Issues storing or retrieving memories from early childhood?

closing/summary

• Brains develop. Yet, many of the brain systems present in adults are wired up at birth and functional soon after.

• Itʼs hard to learn about the mind by measuring the brain (reverse inference). But itʼs possible! For example, neural data has provided evidence for common mechanisms of face perception and memory in infants and adults

• Developmental cognitive neuroscience works best with a multidisciplinary toolkit, including both behavioral and neural studies