Child Development Lecture: Brain Development & Neuroplasticity

Synaptic transmission

• synapse: the gap between neurons

• electrical impulse is converted into a chemical signal

• axon vesicle releases neurotransmitter into gap

• dendrite receptor site detects neurotransmitter

Glial cells (100+ billion)

• hold neurons in place

• formation of myelin sheath

• support their biological functioning, supplying nutrients to neurons

• disposing of the brain’s biological waste matter

• recent evidence suggests that some glial cells do participate in some communicative processes

Cerebral cortex

includes frontal lobe, parietal lobe, temporal lobe, occipital lobe

Frontal lobe

cognitive control, working memory, planning

Parietal lobe

spatial processing, integrates sensory input

Temporal lobe

memory, visual recognition, processing emotion and auditory info

occipital lobe

processes visual info

Right hemisphere

• processes information from left side of the body

  • spatial awareness, imagination, facial recognition

Left hemisphere

• processes information from the right side of the body

  • language, math, logical decision-making, reasoning

Corpus callosum

large bundle of axons that connects the left and right cerebral cortices

Anterior commissure

very small bundle of axons that connects temporal lobes, amygdala, and olfactory bulbs

Lateralization

• tendency for specific cognitive processes, mental functions, and behaviors to be more specialized to either the left or the right hemisphere of the brain

• appears very early: newborns already show greater left-hemisphere activity when listening to speech

Mapping the mind

• Electrophysiological recording (EEG, ERP, Magnetoencephalography)

• functional magnetic resonance imaging (fMRI)

• Functional near-infrared spectroscopy (fNIRS)

Processes of the brain

1. neurogenesis

2. neuronal migration

3. myelination

4. synaptogenesis

5. synaptic pruning

Neurogenesis

• Proliferation of neurons through cell division

• occurs mostly prenatally but can occur with new learning

Neuronal migration

• move to their destinations where they grow and differentiation

• arborization: increase in size and complexity of dendritic “tree”

Myelination

• triples the speed of conduction along the axon

• leads to faster processing of information for infants & children

• begins 3rd trimester and continues into adolescence

Synaptogenesis

• each neuron forms synapses with thousands of other neurons→trillions of connections

  • these connections allow information to be transmitted

Synaptic pruning

• extensive generation of neurons and synapses results in an overabundance that must be eliminated

• 40% of synapses get eliminated

• not fully completed until ~30s

  • prefrontal cortex is the last to undergo synaptic pruning

Altered pruning

• Autism

  • larger brains than neurotypical

    • greater synaptic density

    • increased cortical thickness

  • reduced or delayed pruning

• Schizophrenia

  • excessive pruning during adolescence

Neural plasticity

• ability of the nervous system to change its activity in responses to intrinsic or extrinsic stimuli by reorganizing its structure, functions or connections

• experience shapes neural connections

  • brains are plastic throughout, greatest plasticity in infancy and childhood

  • experience plays a central role in determining which of the brain’s excess synapses will be pruned and which will be maintained— “use it or lose it”

Experience-dependent plasticity

• neural connections are created and reorganized as a function of an individual’s experience

• this change depends on the experience

  • ex.) riding a bike, playing an instrument, ect.

Experience-expectant plasticity

• Wiring the brain occurs as a result of experience humans are expected to have

  • ex.) visual development, language, movement (crawling, walking, ect.)

• Accompanied by vulnerability

  • if denied input during sensitive/critical period→development impaired

Sensitive period

developmental window when an individual’s brain is especially responsive and receptive to specific environmental inputs or experiences

Is there a ‘sensitive period’ for face processing?

sensitive processing→a period during which they must have experience with processing faces or else their face processing doesn’t develop correctly

Le Grand et al (2001)

• Tested individuals born with congenital cataracts that were removed 2-6 months after birth

• Tested face recognition 9 to 21 years later and compared to controls

  • tested so much later because if it were experience-dependent, researchers provide possible chance to learn and adapt

  • unknown sensitive period

  • controls were typically sighted individuals, demonstrates what “normal” face-processing looks like

• Featural information: differences in features

• Configural information: difference sin spacing of features

  • cataracts group could identify featural differences as much as controls but did worse when identifying configural differences

Conclusions from Le Grand et al (2001)

• Early visual experience is necessary for face processing

• Denying the visual input in just first 2 months can lead to permanent deficits

• There may be sensitive period for face processing

  • experience-expectant

WATCH JODIE CLIP AND MAKES NOTES HERE

Timing of brain damage and recovery

• Worst time?

  • prenatal-1st year when neurogenesis and neuronal migration occurs

• Best" time

  • Early childhood when synaptic pruning and generation is at its peak