Week 13 - Brain Development

  • Cortical folding begins end of 1st trimester → 80% adult volume by 2 years

    • Neural tube → telencephalon → cortex (CNS)

    • 70 days - major sulci form (central, calcarine, sylvian fissure) then smaller sulci (superior temporal sulci) → finer folding, more surface area

  • Experience-dependent plasticity begins in utero

    • Heschl’s gyrus larger in infants who received maternal sounds vs no noise

    • Playing auditory sounds → voice-selective areas can be localized

  • Less myelination → hard to distinguish grey and white matter

    • Increasing myelination → increase transduction speed

Could not measure more distal dendrites - potential biasLess pruning in higher cortical areas

  • Measuring cortical tissue development

    • QMRI - tip proton in different angles & measure the exact relaxation time

    • Units: millimeters of water to macromolecular tissue (neurons)

      • T1 relaxivity (R1) = 1/(T1)

      • Dense tissue - quicker relaxation (more things to bump into vs uninterrupted) → tissue growth predicts T1 decreases, R1 increases (pruning opposite) → higher R1 → denser tissue → warmer color

        • Primary sensory regions become redder first

R1 higher in primary regions, slope higher in higher level regions

  • Hierarchical development - V1 has head start, other regions more protracted development trying to catch up

  • Follow-up study on category selective regions (instead of visual field maps)

    • Face-selective on posterior fusiform (pFus) and place-selective on collateral sulcus (CoS) → high-level, tissue growth or differences?

  • Cortical tissue predominantly growing than pruning; different regions, different trajectories

  • Behavior analysis - microstructural proliferation, function, and behavior are linked

More tissue -> better recognition; no change -> stable behavior

  • Function/behavioral necessitates brain tissue growth → no behavioral change, no growth

VWFA grows significantly

  • VFWA (OTS) emerges over first year of preschooling, becoming robust after learning to read

    • VWFA starts to prefer visual image of word over other categories

    • Continuing to grow as reading gets better (more words per minute)

  • Does becoming proficient with words or faces “recycle” a lesser used one (bodies in OTS)?

Limb area pruned, less selective - less needed

  • Migration happens to make more room, when there is competition (fusiform more medial to make space for the more lateral )

  • Cat experiment - cortical development depends on sensory input

    • Kittens see only vertical lines → pruned so only vertical orientation tuned neurons