DEV Lecture 4 - Neural Development

Intro to Neural Development

• Neural development examination enables physical brain growth analysis and functional network development studies.
• The study of neural development relates behavior to underlying structures and networks.

Measuring Neural Development

• Various imaging modalities are available for measuring neural development
• Each modality presents unique strengths and weaknesses
• Key considerations for selecting a modality include: temporal resolution, spatial resolution, and subject tolerance.

EEG

• EEG measures electrical activity in the brain.
• This method offers very high temporal resolution.
• EEG offers low spatial resolution.
• EEG can be used in early infancy.

fMRI

• fMRI measures changes correlated with blood flow.
• Very high spatial resolution is achieved with fMRI.
• This method requires stillness, which can be difficult to achieve.
• fMRI is not suitable for individuals with metal implants.

MEG (Magnetoencephalography)

• MEG measures magnetic fields resulting from electrical currents in the brain.
• This method provides very high temporal resolution.
• MEG requires some tolerance from the participant.

NIRS

• NIRS uses near infra-red light to measure light scattering and absorption.
• NIRS measures changes in blood flow.
• NIRS involves a trade-off between spatial and temporal resolution.
• NIRS can be used early in development.

Executive Function

• Executive function is an umbrella term for high-level cognitive processes underlying conscious, goal-directed thought, especially in novel situations.
• Components of executive function include inhibitory control, monitoring/updating working memory, planning, problem-solving, attention-switching, and forward planning.

EF: Cloth-Pulling Task

• The cloth-pulling task, developed by Willats (1999), tests means-end behavior.
• In this task, 6- to 8-month-old infants are presented with an object that can only be retrieved.
• The means entails pulling the object towards them on a supporting cloth.
• 7-month-olds sometimes retrieve the object by chance, without looking.
• 8-month-olds display intentional means-end behavior, looking at their goal while pulling the means.
• Executing a sequence of actions in the correct order is an executive function task.

EF: Towers of Hanoi Task

• The Tower of Hanoi task tests planning abilities.
• Task constraints are that only one disk can be moved at a time and larger disks cannot be placed on smaller.

EF: Towers of Hanoi Task

• Klahr & Robinson, introduced a version in 1981
• It's used to measure problem-solving and planning skills.
• Performance on the Tower of Hanoi task improves with age.
• Older children demonstrate the ability to pursue long-term goals and manage subgoals.

Neural Basis of EF

• Executive function is strongly associated with the prefrontal cortex (Robbins, 1996).

The PFC: A Central Executive?

• The brain can be conceptualized as a computer processing information.
• Cognition can be seen as the flow of information through a series of stores (Atkinson & Shiffrin 1968).
• Baddeley & Hitch (1974) proposed a central executive controls that prioritizes attention and encodes information.

The PFC in Development

• The prefrontal cortex undergoes significant changes throughout childhood and into adolescence. These include synaptic pruning, increased myelination and connectivity, and a subsequent decrease in gray matter (Giedd et al, 1999).

The PFC in Development

• A significant increase in myelination occurs during the first year of life and it develops until the frontal lobes (Deoni et al).

The A-not-B Error

• The A-not-B task is a well-known measure of a cognitive task in infancy.
• At 8-12 months, infants tend to make a perseverative error: they continue to search for an object at location A after it has been moved to B.
• Errors decrease with age, as does the delay period during which the child can search correctly.
• The A-not-B error demonstrates the development of working memory, attention and inhibition abilities.

EF and the A-not-B Error

• Diamond (1990) demonstrated A-not-B tasks are governed by the PFC in monkeys.
• Infant monkeys with lesions of the dorsolateral prefrontal cortex did not pass the task.
• Lesions of the dorsolateral prefrontal cortex resulted in a significant deficit on the A-not-B task.

How About in Humans?

• Bell & Fox, 1992, EEG differences were seen in infants in between 7-12 months on the A/not B task.
• An increased power of EEG signal at frontal electrodes (lots of change in strong group)
• Increased coherence of EEG signal between front and back electrodes
• Differences were seen in individual maturity development of prefrontal cortex depending on whether they could complete the task

EF: Shifting

• The dimension card change sort is a task for attentional shifting (Zelazo, Frye & Rupus, 1996)
• 3- and 4-year-olds are asked to sort a stack of cards by colour or shape.
• Half way through the game the rule changes.

EF: Shifting

• Although 3 years children can answer questions correctly about the game 'rules' but they typically continue sorting cards with respect to the first dimension.
• By 4-5 years, children can switch successfully.
• 3 year old lack the ability to switch attention between aspects of the scene.
• Executive function is still developing, until the age of 3-4.

Also Related

• The Wisconsin Card Sorting Task is another measure of executive function.
• This task relates to flexibility given the subject does not immediately know the rules!

EF: Shifting

• Direct evidence shows that developmental changes in PFC function correlate with changes in executive function (Moriguchi et al, 2009).
• Children do the card sorting task while brain activity is recorded via NIRS, measuring blood oxygenation.

EF: Shifting

• Nearly all 5 year olds can switch between the rules but only 75% of three year olds.
• Change in blood oxygenation is seen in the prefrontal areas between the blank/control and the study phase of the task
• This compares 3 year olds who persevere and fail to switch rules

EF: Inhibition

• The Stroop task is one famous example.
• The Day/Night task is more commonly used task to test inhibition (Gerstac).

EF: Inhibition

• The Stop-signal task (Pliszka, Lotti & Woldorff, 2000)
• Participants must press left for A, right for B.
• If S appears on screen then the participants had to stop their response

EF: Inhibition

• The Go/NoGo Task (Jonkman, Sniedt, Kemner 2007)
• 6-7, 9-10, Adult
• A button must be pressed when X appears, but only after it has been preceded by A (Go condition)
• When A is not followed by X then you must inhibit your prepared response (A-not-X, NoGo condition)

EF: Inhibition

• Across all ages: medial frontal cortex is more active during the NoGo task.
• In children only: the additional posterior source is different for 6-7 year olds.

EF: Inhibition

• Findings from Johnstone, Barry, and Clarke (2007):
• Only minor developmental changes in behavioral assessments of Go/No-Go and Stop activities between the ages of 7 and 12.
• Significant modifications in the neurological processes that went along with the performance. As an illustration, the amplitude of N2, the central and Parietal "No-Go" component, diminished with age, whereas the amplitude of N2, the Parietal "Stop" component, rose with age over this developmental period.
• Findings from Astle & Scerif (2009):
• "Using neurodevelopmental patterns offers a further level where executive control processes may be distinguished."

Last to Develop

• Studies show PFC is one of the last to develop fully until after adolescence.

Conclusions

• Executive and attentional control influences task performance significantly.
• Young children are limited in their executive abilities.
• The neural evidence aligns well with behavioral developments across tasks.