Neuroscience

Question 1

The blood-oxygen-level-dependence (BOLD) signal

Answer 1

The blood-oxygen-level-dependence (BOLD) signal detected in fMRI reflects changes in deoxyhemoglobin driven by localized changes in brain blood flow and blood oxygenation, which are coupled to underlying neuronal activity by a process termed neurovascular coupling.

Question 2

Features of fMRI (6)

Answer 2

Functional Magnetic Resonance Imaging (fMRI)

1. A neuroimaging technique that detects oxygen changes in the blood in the brain.
2. The technique uses a strong magnetic coil to measure the BOLD contrast (blood oxygen level dependent).
3. The magnet is very noisy, so ear protection must be worn, and the participant must remain motionless to prevent artefacts in the data.
4. Therefore, using this technique with babies is challenging, as we do it while they are asleep.
5. It has very good spatial resolution, providing an image of the whole brain but low temporal resolution.

Question 3

Adjustments to fMRI for infants (5)

Answer 3

Controlling for Anatomical Differences:

• Smaller head sizes and shorter neck lengths require the specific use of paediatric head coils or careful placement of the infant’s head inside the coil.
• Normalisation of images into stereotactic space and localising brain regions may be problematic due to anatomical differences between children and adults.

Controlling for Physiological Differences:

• Various features of the BOLD response differ between adults and young infants, including the peak amplitude, response onset, duration, and morphology of after-shoot.
• As a result, standard adult analysis of fMRI data with a pre-defined HRF may not be accurate for infant data.
• This can be overcome by adopting more general analysis strategies.

Question 4

Infant fMRI Safety Considerations/Measures (3)

Answer 4

• Thermoregulation: premature babies have very immature temperature regulation systems.
• Respiration: many premature babies present respiratory problems due to their immature lungs, so additional oxygen may be required.
• Incubators: MRI-compatible, compact units that provide a warm environment, an optional additional oxygen supply, continuous monitoring of vital signs and an incorporated paediatric head coil.

Question 5

Define The perinatal period

Answer 5

The perinatal period encompasses the time frame beginning one year before birth until 18 to 24 months after birth.

Question 6

Define ERP

Answer 6

An event-related potential (ERP) is an electrophysiological response to a specific sensory, cognitive or motorevent, as measured using EEG.

Question 7

Key Features of EEG (5)

Answer 7

Electroencephalogram (EEG)

A neuroimaging method which detects electrical activity from the neurons in the brain.

A sensor net is placed on the head, and wet sponges or gel pads are used to help the activity pick up.

These sensors register naturally occurring electrical activity on your scalp.

• High Temporal: EEG has a good temporal resolution (milliseconds - ms), allowing for precise timing of the time course of brain activation.
• Low Spatial: However, it has low spatial resolution, meaning it cannot easily identify the specific anatomical location from which the electrical activity originated in the brain.

EEG takes advantage of the interdependent relationship between physiological changes and neural and vascular responses.

Question 8

Define ERP components

Answer 8

ERP components are peaks or troughs in an ERP waveform characterized by consistent timing, scalp distribution, polarity, and relationship with a particular experimental context.

Question 9

Key Features of FNIRS (7)

Answer 9

Near-infrared spectrum light takes advantage of the optical window in which skin, tissue, and bone are mostly transparent to NIR light in the spectrum of 700-900 nm, while oxygenated haemoglobin (HbO2) and deoxygenated haemoglobin (HHb) are stronger absorbers of light.

• Light is reflected, scattered, absorbed, or transmitted within the tissue.
• Measuring the amount of light absorbed will tell us the colour of the blood and, therefore, the amount of oxygen it contains.
• Deoxygenated blood will flow away from an area of activation and oxygenated toward an activation area.

How it works:

• Measures changes in oxygen in the blood in the brain.
• It uses small near-infrared lights and detectors on a sensor pad
• The light travels a little way into the head, through the skin, skull and tissue to the cortex.
• The detectors measure the light that reflects back.
• The reflected light tells us how red the blood is and how much oxygen is in the cortex.