Kap 5. Methods and strategies Flashcards
Experimental ablation
is an reseach method used to investigate brain functions. It involves removing or inactivating part of the brain and evaluating an animal´s subsequent behavior
- removing brain tissue, or damaging the tissue to disrupt its functions
- it is one of the oldest methods used in neuroscience
lesion studies / method
patients with brain damage are examined to determine which brain structures are damaged and how this influences the patient’s behavior
Goal = understand what functions are perfomed by different regions in the brain and how this influences behavior
Some of the oldest and most famous studies in neuroscience are lesion studies.
Lesion
wound / injury
Brain lesion
a reaschers who destroy part of the brain, refers to the damage as a “ brain lesion”
“damage of the brain”
sham lesion
the name given to a control procedure during a lesion experiment
(placebo)
Exitotoxic lesions
lesions produces Excitotoxic lesions are permanent lesions that have been created through the injection of a neurotoxin, whichs kills neurons by stimulating them to death
Stereotaxic surgery
??
To target a specific brain region, stereotaxic surgery is used.
A stereotaxic brain atlas is used to find the coordinates required.
Use a grid system to pinpoint exact regions in a repeatable way.
Stereotaxic atlas
a book contains images that correspond to frontal sections of the brain taken at various distances rostral and caudal to bregma
Fontanelle
is a soft spot at the junction of the coronal and sagittal sutures of the head of babies
Bregma
Once the gap cloces in the fontanelle, it is called bregma “front of head”
Stereotaxic apparatus
is a device that includes a head holder, which maintains the skull in the proper orientation
- f.eks brukt på brainsurgery on rats
Autolytic
self-dissolving
Anterograde means …
moving forward
Anterograde labeling method
employ chemicals that are taken up by dendrites or cell bodies and are then transported through the axons toward the terminal buttons.
Immunocytochemical method
take advantage of an immune reaction
Antigens
proteins/peptides found on the surface of bacteria or viruses
Antibodies
proteins produced by white blood cells to destroy invading microorganisms
- either secreted by white blood cells, or located on their surface in the way neurotransmitter receptors are located on the surface of neurons
VMH
ventromedial nucleus of the hypothalamus
Retrograde means
moving backwards
Retrograde labeling methods
employ chemicals that are taken up by teminal buttons and carried backward through the axons toward the cell bodies
CT
computerized tomography
X - ray donutshaped ring tube
uses X-rays to image “slices” through the brain (or other tissues)
MRI
Magnetic resonance imaging
- uses a strong magnetic field to image the brain; better resolution than CT scans
DTI
Diffusion tensor imaging
– uses an MRI scanner to identify bundles of axons so connections between brain regions can be studied.
- takes advantage of the fact that the mocement of water molecules in budles of white matter will not be random but will tend to be in a direction parallell to the axons that make up the bundles
Retrograde tracing
Retrograde tracing involves putting a tracer where the axon terminals are which will travel backward along the axons to the cell bodies.
Histology
Histological techniques include a number of ways of examining brain tissue.
Anterograde tracing
Anterograde tracing involves putting a tracer where the cell bodies and dendrites are which will travel forward along the axons to the axon terminals.
Electrophysiology.
A technique, recording electrical activity from cells
- We can record the electrical activity from single neurons or the combined activity from multiple neurons.
This technique allowed us to understand the action potential and how neurons work at a fundamental level.
But it also lets us understand how the activity in neurons is linked to behaviour and psychology.
Calcium imaging
The electrical activity of neurons can be visualised by using an fluorescent molecule.
Calcium is generally used as a marker of electrical activity because it increases when neurons are active.
This allows us to target groups of neurons more precisely using genetic methods, for example, just the dopamine neurons.
EEG
Electroencephalogram
The electrical activity of many neurons sums together and can be recorded using macroelectrodes.
This can be easily performed in humans as the electrodes sit on the surface of the scalp.
fMRI
Functional MRI is the method of recording activity with the best spatial resolution.
It works by comparing blood flow between different conditions.
(regional activity)
Name 3. Single unit activity methods
“a unit refers to an individual neuron”
n vivo electrophysiology
In vitro electrophysiology
Calcium imaging
Name 2. multi unit activity methods
EEG
fMRI
TMS
Transcranial magnetic stimulation
can be used to control the brain in humans.
Applying a magnetic field can induce electrical activity in neurons.
Ongoing work is attempting to use TMS as a therapeutic option, for example, for neurological and mental disorders.
Optogenetics
Optogenetics is a modern technique (~15 years old) that allows neurons to be controlled by light.
A main advantage over traditional techniques is that it can targeted very precisely to just one type of neuron.
Light can also be controlled very precisely and has no effect on neurons normally.
Chemogenetics
is another modern technique that involves adding a designer receptor to neurons.
These are known as DREADDs*. They are completely artificial and respond to a drug called CNO that has no effect on normal neurons.
As with optogenetics, these DREADDS can be targeted very precisely to one type of cell.
This means when you inject the CNO it will only affect the neurons that you have targeted and not the others near it.
In voltammetry experiments, ……
In voltammetry experiments, neurochemicals can be detected by oxidation/reduction with higher time resolution (sub-second).
In microdialysis experiments…..
In microdialysis experiments, tiny amounts of fluid can be extracted from a region of the brain and chemically analysed.
MRS
(magnetic resonance spectroscopy)
uses the same technology as MRI but analyses the signal to detect different chemicals based on how they react to the magnetic field.
PET
(positron emission tomography)
indirectly can measure a neurochemical by observing how concentration of a radioactive drug changes.
Twin studies
– examine heritability of a trait by comparing monozygotic and dizygotic twins.
Adoption studies
– examine effect of environment and interaction by looking at different upbringings.
Genomic studies
include linkage studies and genome wide association studies (GWAS), examine how a particular gene is linked to a behavior.
We can study the effects of a particular gene on behavior in a few different ways:
Name two
Targeted mutations – e.g. “knockout” mouse studies allow us to answer more focused questions.
Antisense oligonucleotides – can turn genes off buy stopping them being translated into protein.
