5. Research Methods Flashcards
golgi stain
golgi stain is taken up by few neurons
Shows outside neuronal structure in great detail
Nissl stain
provides gross indication of brain structure by selectively staining groups of neural cell (low magnification)
individual neural cell bodies can be distinguished a high resolution
what are the comparisons between the nissl and golgi stain?
- Golgi stain shows shape and reach of neurons.
* Nissle stain shows number of neurons in each layer.
what different layers of the neicortex do nissl and golgi stains reveal?
- molecular layer
- External granular layer
- external pyramidal layer
- internal granular layer
- internal pyramid layer
- multiform layer
electron microscope
- Preparation of tissue slices with electron-absorbing substance
- Neuronal structure captured in great detail.
what are contrast x eays?
used for visualising the living brain. they are an adaptation of standard X-ray technique
how do contrast x-rays work?
- Inject radiopaque substance into structure of interest
- Radiopaque substance absorbs X-rays
- Result: increased contrast with neighbouring tissue
- Specific technique: Angiography
what do Computed (axial) Tomography do?
- CT scan provides 3D view of brain structure
* Image not sharp
how do CAT work?
- X-ray gun & X-ray detector rotate appositionally at about 8 different levels of the brain
- Image constructed from combined scans
- Figure shows CT scan of one level
- Each pixel (picture element) results from complex mathematical computation of associated brain region viewed from different angles
- Spatial resolution high enough to observe even small changes (e.g., shrinkage of a gyrus)
Where are CATs used?
Used in a number of disorders (e.g. Alzheimer’s, dyslexia)
Magnetic Resonance Imaging
MRI has greater contrast resolution than CT; no exposure to X-rays
• Provides 2D and 3D images
• Resolution superior: neural structures vary in hydrogen atom density
• Reveals very small changes, such as loss of myelin around groups of axons
How do MIRs work?
Measures waves emitted by hydrogen atoms when placed in magnetic field
Provides 2D and 3D images
What do Positron Emission tomographys do?
Highlights active brain regions (rather than showing all)
• Brain can be mapped during different states (attention, movement, tasks)
• Can identify also abnormally functioning regions
how do the Positron Emission tomographys work?
- Injection of radioisotopes (e.g. , 2-deoxyglucose): differential uptake
- 2-DG (type of radioactive glucose) taken up but cannot be metabolised
- Increased metabolic activity revealed through accumulated radio-activity
What do Functional MRI (fMRI) do?
Can detect oxygen consumption in active brain regions
• BOLD signal (blood-oxygen-level-dependent signal)
how do fMRIs work?
- Improvement on MRI in terms of speed (temporal resolution)
* Uses rapidly oscillating magnetic field gradients & more powerful computational techniques
What is the benefits between fMRI and PET?
- No substances injected
- One image provides structural and functional information
- Better spatial resolution
- Real time measurements; can measure many times from same person
what are the difficulties with the fMRI and PET
- Noise
* Disentangling various cognitive processes
What does Transcranial Magnetic Stimulation do?
Stimulates the living brain
• NOT a measure of neural activity
• Provides an experimental probe to alter neural activity
how do Transcranial Magnetic Stimulations work?
TMS applies a brief, strong magnetic field that alters neural activity
• Can either activate or “deactivate” brain structures
• Observe changes in behavior in consequence to manipulation
what does Electroencephalography do?
records physiological signals.
• EEG represents sum of all electrical activity: does not reveal underlying
neural activity
• EEG wave forms associated with different states of consciousness
EEG signal
difference as a function of time in electrical potential between two scalp electrodes
what is seen in epileptic seizures according to the EEG?
synchronised depolarisation of neurons.
What does Event-related potentials (EPRs) record?
physiological signals.
They reveal characteristic peaks (with differing latencies and amplitudes)
How do Event-related potentials work?
Filtered electrical activity (obtained from scalp EEG) associated with specific cognitive processes. The ERP signal is obtained through signal averaging. The resulting ERP reveals characteristic peaks (with differing latencies and amplitudes)
what is the advantage of Event-related potentials?
real time measurement
what does stereotaxic atlas show?
the position of the target location e.g. the atlas indicates that the amygdala target site is 2.5mm posterior to bregma. 4.5mm laterla and 8.5mm vertical
Bregma
where the skill fuses is reference point
stereotaxic unstruments
head holder and electrode holder
what is the process of stereptaxic surgery performed on mice?
- the atlas indicates that the amygdala target site is 2.8mm posterior to bregma. 4.5mm lateral and 8.5mm vertical
- A hole is drilled 2.8mm posterior to bregma and 4.5mm lateral to it. Then, the electrode holder is positioned over the hold and the electrode is lowered 8.5mm through the hole
- The electrode is anchored to the skill with several stainless steel screws and dental acrylic that is allowed to harden around the electrode connector
what are the kinds of lesion methods?
aspiration method
radio-freqency lesions
sectioning
cryogenic blockade
aspiration method
visible part of cortical regions; tissue drawn off by suction
radio-frequency lesions
currents of radiofrequency through stereotaxic isntrument -> heat destroys target region
sectioning
(Subcortical knife cuts)
Eliminates nerve or tact conduction
crygenic blockade
reversible lesion. Temporarily eliminates activity in target area. Same subject an be case and control
Electrical stimulation
effect usually opposite to that of lesion. Done prior to lesioning
What are recording methods?
intracellular recording
extracellular unit recording
multiple unit recording
invasive EEG recording
what is the process of intracellular recording?
Electrode enters neuron through amplifier.
Intracellular unit recording
an intracellular microelectrode records the membrane potential from one neuron as it fires
An extracellular unit recording
An extracellular micro-electrode records the electrical disturbance that is created each time an adjacent neuron fires
A multiple-unit recording
A small electrode records the action potentials of many nearby neurons. These are added up and plotted.
An invasive EEG recording
A large implanted electrode picks up general changes in electrical brain activity. The EEF signal is not related to neural firing in any obvious way
what are the pharmalogical methods?
drug administration
selective chemical lesions
measuging chemical activity in behavioural studies
Locating neurotransmitters and receptors in the brain
drug administration focuses on…
the effect of neurotransmitters
what are the common methods of drug administration?
intragastric, intraperitoneal, intramuscular, suhcutaneous –> difficulty of traversing blood-brain barrier
intraventricular cannula
drug administration method where a small tube is implanted in the brain
selective chemical lesions
injection of neurotoxins
What are the techniwues chemical activity in behavioural studies?
- 2-deoxyglucose technique
* In vivo cerebral microdialysis
What is involved in locating neurotransmitters and receptors in the brain?
immunocytochemistry
In-situ hybridisation
immunocytochemistry
antobody generation for neuropeptides
In-situ hybridisation
Acts on messenger RNA
What are the techniques involved in genetic engineering?
Gene knock-out techniques
Gene replacement techniwues
gene knock-out technique
lack of specific gene
Gene replacement technique
replace one gene with another
what is an example of the gene replacement techniques?
- transgenic mice (receive genetic information from different species
- modified genes inserted to switch on/off gene at different developmental periods
neuropsychological testing
- Information obtained assist in diagnosis of specific disorder
- Evaluation of treatments (before & after)
- Rehabilitation
- Insight into cognitive functioning
- Behavioural effects of lesions
what are the common neurpsychological tests?
Single-test vs batter approaches • Intelligence (e.g. WAIS) • Memory • Language • Language lateralisation • Frontal lobe function
what is an example of a language lateralisation test?
Sodium amytal, dichotic listening
what is an example of frontal lobe functioning test?
Wisconsin Card Sorting Test
what are some behavioural paradigms in the lab?
- Species common behaviours
- Traditional conditioning paradigms
- Learning paradigms
what are the traditional conditioning paradigms?
- Pavlovian paradigm
* Operant conditioning
what are some learning paradigms?
- Taste aversion
- Radial arm maze
- Morris water maze
- Defensive burying
