week 3 - neurimaging and motor learning

what is the purpose of medical imaging in neuroscience?

visualise brain structure and brain function to answer clinical or research questions.

what is the difference between structural and functional imaging?

structural imaging shows brain anatomy, functional imaging shows brain activity during tasks.

what planes are brain images viewed in?

sagittal (left/right), coronal (front/back), horizontal or axial (top/bottom).

compare x-ray, ct, and mri (main differences).

x-ray → 2d image, good for bone
ct → cross-sectional images, fast emergency imaging
mri → high-resolution soft tissue imaging.

how do x-rays work and what are they used for?

ionising radiation passes through tissue; dense structures appear white. used for fractures and joint problems; quick and inexpensive but poor soft tissue detail and involves radiation

how does ct imaging work and when is it used? + what tissues appear

multiple rotating x-rays create cross-sectional images. used in emergencies like head trauma and haemorrhage; fast but involves radiation and has lower soft tissue detail than mri.

white = bone/metal
black = air/csf
grey = brain tissue.

how does mri work?

magnetic fields and radio waves detect hydrogen protons to create detailed soft tissue images.

contrast: difference in proton relaxation times

advantages and limitations of mri?

excellent soft tissue resolution; used for tumours and neurological disease. expensive, slower, unsafe with metal implants, may cause claustrophobia.

what is dti and what does it measure?

a specialised mri technique measuring water diffusion along axons to map white matter pathways.

important because: reveals connectivity and microstructural damage (e.g. diffuse axonal injury) even when ct/mri look normal.

what is cerebral angiography used for?

visualising brain blood vessels using contrast dye with ct/mri/x-ray to detect stenosis, aneurysms, and vascular malformations.

what does functional imaging measure?

brain activity based on metabolism, blood flow, or electrical activity.

how does fmri measure brain activity?

detects changes in oxygenated blood flow (bold signal) when neurons are active.

• research, brain mapping before surgery; non-invasive and safe.

how does pet scanning work?

radioactive glucose tracer measures cellular metabolism and blood flow.

• used for tumours, epilepsy, dementia; expensive, invasive, involves radiation.

how does eeg work and what is it used for?

scalp electrodes record electrical brain activity; used for epilepsy and sleep studies; poor spatial localisation.

how does meg differ from eeg?

meg measures magnetic fields from neural activity and better identifies functional brain areas.

match imaging type to information provided.

x-ray/ct → bone and acute structural damage
mri → soft tissue structure
dti → white matter connectivity
angiography → blood vessels
fmri/pet/eeg/meg → brain function.

what is neuroplasticity?

the nervous system’s ability to change structure, function, and chemistry due to experience, learning, or injury.

• supports learning, memory, rehabilitation, and recovery after injury.

• adults brain can. change within stability limits

what is habituation?

reduced response to repeated harmless stimulus.

what is long-term potentiation (ltp)?

repeated co-activation strengthens synapses (“neurons that fire together wire together”).

• stronger synapses, more receptors, new dendritic spines.

what is long-term depression (ltd)?

weakening or loss of unused synapses (“use it or lose it”).

• receptors withdraw and synaptic connections weaken.

what is cortical remapping?

brain areas reorganise based on use or injury; can be adaptive or maladaptive (phantom limb pain).

what is motor learning?

acquisition or reacquisition of motor skills through practice.

difference between performance and learning?

performance = temporary observable behaviour
learning = permanent change from practice.

stages of learning

cognitive stage
understanding task; high effort and attention.

associative stage
movement refinement and fewer errors.

autonomous stage
automatic performance with low cognitive demand.

principles of motor learning

practice specificity
training should match real performance conditions.

intensity and repetition
high effort and many repetitions drive neural change.

distributed vs massed practice
spaced practice improves long-term retention and reduces fatigue.

practice variability
random practice worsens short-term performance but improves long-term learning.

motor imagery
mental rehearsal improves learning, but physical practice is strongest.

compare cns and pns recovery after injury.

cns → limited regeneration
pns → axons regenerate if cell body intact.

what is wallerian degeneration?

degeneration of the distal axon after injury.

role of schwann cells in recovery?

clear debris and guide axon regrowth (~1 mm/day).

key principles of experience-dependent plasticity

use it or lose it
unused skills weaken → disuse, decay

use it and improve it
practice strengthens function → practice, strengthening

specificity
train exact skill → task-specific training

repetition matters
many repetitions needed → high reps, consolidation

intensity matters
practice must be challenging → effort, challenge

time matters (early rehab window)
early training improves recovery → early intervention

salience matters
learning must be meaningful → motivation, relevance

age matters
younger brains adapt more → developmental plasticity

transference
learning transfers to related skills → skill carryover

interference
multiple skills disrupt short-term performance → contextual interference