W3 Introduction to Imaging in Neuroscience Flashcards
medical imaging structural
- X-rays
- Computed Tomography (CT)
- Magnetic Resonance Imaging (MRI)
- Diffusion Tensor Imaging (DTI)
- Cerebral angiography
medical imaging for functional
- Functional Magnetic Resonance Imaging
(fMRI) - Positron Emission Tomography (PET)
- Electroencephalography (EEG)
- Magnetoencephalography (MEG)
- X-rays
- X-rays penetrate the body to create a 2D image
- Bone fractures; infections
- Computed Tomography
- Multiple X-rays rotated around the patient measuring relative tissue density.
- A computer reconstructs the data to create detailed 3D images.
- Preferred choice in emergencies for a quick image
- Depicts fractures and bone abnormalities; acute
intracranial hemorrhages - However, not good for fine tissue detail
- Magnetic Resonance Imaging
- Magnetic fields cause hydrogen protons in tissue to align
- Radiofrequency wave then pulsed to tissue, changing proton alignment
- Protons return to original position, generating an electrical signal
- The speed the proton returns to position depends on the density and mobility of the tissue, creating contrast between various tissues in the MRI
- This creates an extremely detailed image that is presented in slices
why would you use an mri
- Soft tissue disease (including the nervous system) – tumors, MS, inflammation
3a. Diffusion Tensor Imaging
- Measures how water diffuses around axon bundles
- Useful for assessment of white matter/ tracts/pathways.
- E.g. corticospinal tract (CST) – for
movement.
- Cerebral Angiography
- 3D reconstruction of blood vessels
- Radio-opaque contrast agent injected into
an artery and imaged using sequential Xrays, CT or MRI scans - Useful for screening for narrowing
(stenosis), dilation (aneurysm) and
abnormal connections (malformations)
Functional Imaging tests for
- How the typical & atypical brain is working to assist in neuro rehabilitation
- Shows brain regions used during thought, speech, movement and sensation.
- Help assess effects of stroke & degenerative disease (e.g. Alzheimer’s) on brain function.
- Monitor the growth of brain tumours.
- A task is performed during the imaging process; determines brain activity before & during task
- Functional Magnetic Resonance Imaging (fMRI)
- The fMRI detects changes in blood flow and oxygenation that occur in response to neural activity while performing a task
- Safe and non-invasive
- Positron Emission Tomography (PET)
- Injection of radioactive isotopes
- Detectors measure gamma rays as travel in cerebral blood vessels
- Highlights metabolically active cellular regions
- Not used frequently (invasive)
- $$$ and radiation
- Electroencephalography (EEG)
- Detects and records electrical activity in the brain
- Non-invasive electrodes (sensors) placed on scalp, while an electronic device (electroencephalogram) records activity.
- Can help diagnose abnormal brain electrical activity e.g. epilepsy, sleep disorders.
- Magnetoencephalography (MEG)
- non-invasive imaging test that measures magnetic fields produced by electrical currents in the brain
- Identifies functional areas of the brain AND the precise location of abnormal activities
Neuroplasticity
“the ability of neurons to change
their function, chemical profile (quantities and types of neurotransmitters produced), and /or structure”
Mechanisms underpinning neuroplasticity
- Habituation
- Long-term potentiation, long-term depression
- Cortical reorganisation
Habituation
A decrease in response to a repeated, benign
stimulus
* One of the simplest forms of neuroplasticity
Long term potentiation
Neurons that fire together, wire
together
Long term depression
Neurons that fire out of sync, fail to
link
Cortical remapping
Plasticity of the sensorimotor cortex
representation of the reading finger in Braille readers.
Motor learning
The acquisition of motor skills.
The reacquisition of skills following injury, disease, and the like.
Performance
- Observable behavior
- Execution of a skill at a specific
time and in a specific location - May not be due to practice
- May be influenced by
performance variables
Learning characteristcs and inferred from what
Inferred from performance
* Relatively permanent
* Due to practice
* Not influenced by
performance variables
Stages of learning
cognitive, associative,
autonomous,
Principles of experience-dependent neuroplasticity
Use it or lost it
Use it and improve it
Specificity
Repetition matters
Intensity Matters
Time matters
Salience matters
Age matters
Transference
Interference
The following is a list where neuroplastic changes are regarded are adaptive:
rehabilitation after neurological injury
learning a new language
learning a new skill
changing habits for the better
learning to play a musical instrument
The following is a list where neuroplastic changes are regarded as maladaptive
drug addiction
continuing to walk with a limp even after the original injury has resolved
phantom limb pain
gambling addiction
musculoskeletal pain due to over-activating particular muscles
why wouldnt you use an MRI
- However, not ideal for:
- bone or acute hemorrhage imaging
- Metal implants
- People who experience claustrophobia
- Narrow, takes longer and loud
- Expensive
Use it or Lose it principle is defined as
Failure to use and practice specific brain functions can lead to the degradation of that pathway and therefore loss of abilities
Use it and improve it principle is defined as
Practicing a specific brain function leads to strengthening of those pathways and improved performance
Specificity Matters principle is defined as
The nature of the training task dictates the nature of the change in the brain. Ie. You will get better at doing exactly what you practice doing
Repetition Matters principle is defined as
Induction of plasticity requires sufficient repetition. Thousands to tens of thousands to see changes in the brain
Intensity Matters principles is defined as
Induction of plasticity requires intensive training
Timing Matters principles is defined as
Different forms of plasticity happen at different stages of rehabilitation/recovery. Training prior to maladaptive behaviours emerge is important
Transference principle is defined as
Plasticity induced by one training activity may improve the performance of similar activity
Salience Matter principle is defined as
The training needs to be based on something that is deemed as being important to the patient
Interference principle is defined as
Plasticity induced by one training activity may impair the performance of similar activity
Age Matters principle is defined as
Dependent based neuroplasticity occurs more readily in younger brains.
on a CT more dense tissue appears what colour
More dense tissue appears WHITE
o Metal, bone
on a CT Less dense tissue appears
- Less dense tissue appears BLACK
o CSF, air
On a CT Tissue with high water content appears
DARK GRAY
o Fat, white matter
On a CT Tissue with high protein content appears
LIGHT GRAY
