Lecture 3: Neuroimaging Flashcards
What components use energy in the brain over different timescales?
(1) Ion channel proteins, synaptic receptors, signal transduction pathways, synapses: Minutes, hours, days (frequent turnover).
(2) Neurons: Decades.
Why does brain development require a lot of energy?
To protect it from losing important functions later in life.
At what age does the brain have the highest number of synapses? What happens after?
- Age 3: highest number of synapses.
- Afterward: Synaptic pruning removes unnecessary connections.
What happens to brain growth during early childhood and adolescence?
- quick growth in early childhood.
- refining and fine-tuning during adolescence to early adulthood.
At what age do brain activity peaks occur, and what happens afterward?
- peaks around age 8.
- rapid decline in synaptic density afterward.
What does brain plasticity refer to, and why is it important?
- Brain plasticity: Ability to change and adapt
- Helps understand normal and psychiatric brain development
What is a caveat of structural MRI?
Temporal Resolution
How long a human stays in the scanner.
How does MRI work?
MRI focuses on nuclear spin systems, specifically 1H (hydrogen) nuclei, which are abundant in the body due to water. Around 57% of the human body and 75–78% of the brain is water, making it an ideal imaging target. Each hydrogen atom contains a proton, which has mass, spin, and a positive charge. These protons give the MRI signal.
Protons in hydrogen atoms rotate and carry a tiny positive charge, creating a magnetic moment vector—a small magnetic field. When placed in an external magnetic field during MRI, the protons align with the field and rotate like tiny tops (nuclear magnetism). The rotation speed of these protons depends on the strength of the external magnetic field.
When a radio frequency (RF) field is applied, the protons absorb energy, shifting their magnetization to the transverse plane. When the RF field is removed, the protons return to their original alignment, releasing energy in the process. This released energy generates the MRI signal.
The primary source of the MRI signal is the hydrogen protons in water, which are abundant in tissues like the brain. This process allows MRI to create detailed images by manipulating the protons’ magnetization and measuring their response.
Why is structural MRI valuable?
It provides detailed, reliable, and reproducible imaging of the brain.
What impacts structural MRI acquisition results?
The choice of the acquisition protocol.
Why is structural MRI analysis flexible and multi-featured?
It supports population neuroscience, detects subtle changes in brain morphology in vivo, and integrates early AI applications in brain imaging.
Where is grey matter located, and how does it change with age?
Grey matter is found in the brain’s cortex and structures like the basal ganglia and thalamus; its volume decreases with age.
What is white matter, and where is it located?
White matter lies beneath grey matter and consists of axons connecting brain regions.
What are quantitative metrics used for in structural MRI?
Comparing groups, performing regression, and creating statistical images like thresholded T-stat images.
How are changes in cortical thickness detected?
Algorithms classify grey and white matter and use deformable ellipsoids to capture cortical anatomy.
What is cortical surface modeling, and how does it measure cortical thickness?
- Two distinct surfaces are created, representing cortical boundaries.
- A “digital ruler” measures the distance between these surfaces to determine cortical thickness.
- The process smooths measurements and grows points from one surface to the next, capturing the grey-white matter boundary.
Is brain biology static of dynamic?
Dynamic.
How does normal brain development progress?
- Brain grows rapidly early in life, with significant pruning peaking at age 3 and refining through adolescence.
- Brain volume increases until age 8, then starts declining, with individual variation in speed.
What does brain morphology and imaging reveal?
- Imaging (e.g., MRI) shows brain changes and development but doesn’t provide details on cell type or neural specificity.
- Interpreting MRI requires knowledge of underlying brain processes.
How does the environment affect the brain?
Rat studies show exposure to complex environments increases brain volume by 50%, a difference not detectable by MRI alone.
How does experience shape the brain (V5 & Juggling)
- A 6-week juggling study showed changes in sensory-motor integration areas.
- Lifelong skills like juggling or tennis create lasting changes in relevant brain areas, even after training stops.
How does musicianship affect the brain?
- Alters regions like the middle frontal gyrus (memory) and auditory cortex (planum temporale).
- Different regions show altered connectivity depending on training and specialization.
How do genetics, environment, and imaging integrate in brain studies?
- Genetics and twin studies (MZ/DZ) reveal heritability of brain features and mental health conditions.
- Twin correlations help identify heritable traits.
How do psychiatric disorders relate to brain development?
- Most psychiatric disorders emerge before age 30-35, often during rapid brain growth or pruning.
- ADHD shows delays in brain maturation, particularly in the frontal lobe.
- Childhood-onset schizophrenia involves cortical thickness reduction, with 40% heritability.
