Week 11 - Methods For Studying Brain Structure And Function Flashcards
Explain Phrenology
- Bulges and depressions on the skull correspond to specific brain areas therefore specific behaviours
- Usually based on unusual individuals
- Skull shape has little relationship to brain anatomy
Historical Perspectives of methods to study the brain structure / function
[Franz Gall]
- Observed people with excellent verbal memories & bulging eyes
- Good verbal memory = large brain pushes eyes forward
Neuroanatomical techniques
- Histological Procedures : study cells , brain slices are stained and viewed under microscope
How are cell body stains used to identify anatomical structures?
- Commonly
- Selectively target cell bodies through identify specific areas
2. MYELIN STAINS : Selectively colour myelin sheath allowing for observation of bundles of myelinated nerve fibres
3. MEMBRANE STAINS :
How are histochemical techniques used to identify anatomical structures?
- IMMUNOCYTOCHEMICAL TECHNIQUES
- Specific binding of antibodies and antigen
- Selective binding ; if protein present = binds with antibody
Issues with brain techniques?
- Brain tissue needs to be removed
Features of CAT Scans
- Computerised (Axial) Tomography
- X-rays passed through brain , 2D image produces
- Whiter image = more dense tissue
- Commonly used for diagnosis of tumours / strokes / blood clots / neural degeneration
Features of MRI scans
- MAGNETIC RESONANCE IMAGING
- Powerful magnet used to observe magnetic radiation from hydrogen atom
- Can produce 3 anatomical planes (horizontal , sagittal , coronal)
- Only looks at structure
Features of fMRI scans
- FUNCTIONAL MAGNETIC REASONING
- Structure and function
- Measures heamodynamic responses (metabolic activity)
- Brain active = oxygen consumption = activity
- Colder colours = less activity
- Warmer / Hotter colours = greater activity
Features of PET scans
- POSITRON EMISSION TOMOGRAPHY
- Radioactive glucose tracer injected into patient
- Glucose taken up by active / metabolising cells
- During rest and activity to see which brain areas are involved in specific metal operations
- Between healthy and diseased brains to observe areas in decline and relate areas to behaviour
Advantages of brain imaging
+ Relatively non invasive (CAT/MRI/fMRI)
+ Good spatial resolution
+ See structure (CAT/MRI)
+ See function (fMRI/PET)
+ Can compare healthy / diseased brains , and activity during tasks (PET/fMI)
Disadvantages of brain imaging
- Risks from X-rays (CAT) and radiation (PET)
- Poor temporal resolution = can’t link events to changes
- Noisy (MRI/fMRI)
- Expensive (fMRI) , lots of equipment
How can we measure electrical activity to tell us which structures are used in particular functions? [Micto-Electrodes]
- Look at action potentials / post synaptic potentials
- Micro-electrodes implanted into brain to record neural activity and monitor individual neurones
- But invasive and can neglect neural integration
How can we measure electrical activity using macro-electrodes?
- EEG (Electroencephalogram)
- Active electrodes attach to scalp in areas of expected neural activity
- Indifferent electrodes attached to neural areas
- Differences in active and neutral electrodes measured
- Pick up on EEG waves
What are the different distinct patterns of EEG waves?
- BETA : show person is actively attending and aware of surroundings
- ALPHA: awake but not actively processing info , observed in relaxation
- THETA : light sleep
- DELTA: often related to deep sleep
Advantages and disadvantages of macro electrodes
+ Non invasive
+ Can differentiate from different neurological conditions
- Time consuming
- Interpretation requires considerable experience
- Crude measure
Brain damage studies
- EXPERIMENTAL : controlled and localised damage to specific areas associated with behaviours
- Brain is interconnected so one lesion may affect another
- Generalising from artificial damage to natural damage - HUMAN STUDIES: natural damage , unintentional damage , some may willingly take neurotoxins to see change in function and behaviour
- rarely know what function / behaviour was before damage
How can the nervous system be used to measure activity?
- Sympathetic NS = HR and BP increase with sympathetic activation
- Galvanic Skin Response = measures amount of sweating
How can the endocrine system be used to measure brain activity?
- Endocrine markers (hormones)
- Samples in saliva and blood
How can Alzheimer’s disease be measured through brain activity and structure ?
- MRI and PET scans
- Cortex shrivels up and ventricles get larger
- Looking at neurofibrillary tangles (protein twisted strands to form microtubules) and amyloid plaques (accumulation of protein fragments) through immunostaning
