[C] (Pt. 2) Neurology and Behaviour: NEUROSCIENCE Flashcards
3 Approaches to Brain Study
1) Clinical/ Neuropsychological Assessment
2) Stimulation Methods
3) Brain Imaging
Clinical/ Neuropsychological Assessment
- Non-invasive
- Correlates function impairment w damaged area of brain (after injury/neurological illness)
- Assesses orientation, learning, memory, language, etc
- Goals: Diagnosis, understand nature injury, monitor changes over time
Stimulation Methods
- Invasive
- Electrical current applied area brain and effect observed (patients awake and can describe experience)
- Assumes electrical stimulation mimics normal stimulation
Used:
- Identify roles speech and language areas brain
- Areas assoc. Parkinson’s, dystonia, OCD
- Deep Brain Stimulation (DBS) used treat these + depression + chronic pain
Brain Imaging
- Non-invasive
- Indicate relationship between brain structures w function
e. g. EEG (voltage fluctuations) / CT (structure) / MRI (soft tissues) / fMRI (oxygen use) / PET (glucose use)
Electroencephalography (EEG)
Mechanism:
- Electrodes on scalp detect voltage fluctuations in brain
- Provides info normal electrical activity (voltage fluctuations correlate w function of cerebral cortex/ behaviour)
- Frequency/amplitude of trace varies (e.g. sleep/age/ spike during seizure)
Uses: (function)
- Diagnosis some brain disorders e.g. epilepsy
- Sleep disorders
- Prognosis coma cases (brain death)
- Monitor depth of anaesthesia surgery
EEG: +/-
+ Non-invasive (and no intense magnetic fields)
+ Cheaper
+ Shows changes over millisecond range
- Can only detect activity in cortex (not deeper)
- Poor spatial precision (e.g. synapses where drugs act)(“when but not where”)
Computerised Tomography (CT)/ (CAT)
Mechanism:
- Combines many X ray images from diff angles to make high res cross sections (“virtual slices”)
- Can see inside body without cutting
- Bone (most dense) = white, tissue/fluids = grey, fat = black, air = more black
Uses: (anatomy)
- Can detect tumours
- Brain injuries e.g. skull fractures
- Identify whether haemorrhage/ blood clot caused stroke
CT: +/-
+ Whole body scan in seconds
+ Virtual slices show area interest only (no ghost structures)
+ Can view from different angles and high contrast
- Ionising radiation can lead cancer (pregnant women avoid)
- Rel. low resolution.
Magnetic Resonance Imaging (MRI)
Mechanism:
- Strong magnetic fields used to align protons in water molecules
- Movement of protons monitored following pulse of radio waves (return resting alignment)
- Produces detailed images soft tissue and organs
Uses: (anatomy)
- Image brain cancers/ in their surgery
- Good contrast grey vs white matter so used study abnormal brain development, demyelinating diseases (e.g. ms) and cerebrovascular disease (e.g. aneurysms which can lead stroke/dementia)
Functional MRI (fMRI)
Mechanism:
- Strong magnetic fields and radio wave pulse to construct BOLD images (Blood Oxygen Level Dependent)
- Shows flow of oxygenated blood (greater oxygen demand/ oxyhaemoglobin where active neurones)
- Brighter in area cortex responding to stimuli (second by second basis)
Uses: (function)
- Psychology
- Planning neurosurgery
Positron Emission Tomography (PET)
Mechanism:
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Positron Emission Tomography (PET)
Mechanism:
- Radioactive glucose (FDG) injected into patient and enters respiratory pathway
- Emits positron as decays which collides w electron
- -> annihilate each other and release gamma rays detected by scanner
- Active areas (use more glucose) = yellow/red
- Less active = green/blue
Uses:
- Diagnosis/ monitor cancers (identify metastasis - devel. secondary tumours)
- Neuropsychology: e.g. diagnose Alzheimer’s - decrease rate glucose metabolism/ left hemi. more active than right in linguistics
- Psychiatry: some tracers bind receptors dopamine/serotonin/opiods (schizophrenia, substance abuse, mood disorders)
- Radio-surgery (e.g. guide surgery brain tumours)
PET: +/-
+ Can detect biochemical changes before anatomical changes w brain disease occur
- High operating cost
- Must take place before isotope decays (short time of FDG radio-tracer synthesised)
Neuroplasticity
Ability of brain to modify its own structure and function (by changing neurones/ their connections) following changes changes within body/ external env
Synaptic Plasticity
Ability synapse to change in strength
e.g. amount neurotransmitter released/ response in postsynaptic neurone
Occur: When synaptic pathways used less/more due changes behaviour, emotions, env, etc
Role: Learning + memory
