HC10 Animal Research Flashcards
What is the purpose of injecting tracers into localized brain areas?
To study transport along axons and identify neural pathways.
What are anterograde tracers?
Tracers that label pathways from the cell body to the termination site of axons.
What are retrograde tracers?
Tracers that label pathways from the termination site back to the cell body.
What is the difference between monosynaptic and polysynaptic tracers?
Monosynaptic tracers project only to the first synapse.
Polysynaptic tracers (e.g., viruses) are transmitted across multiple synapses.
Why is tracer injection not used in humans?
It is unethical, as it requires direct injection into the brain.
What brain region is primarily connected to the orbital cortex?
The amygdala.
What is the purpose of lesion techniques?
To allow causal conclusions regarding the function of a brain region or neurotransmitter system.
What are the types of permanent lesions?
- Aspiration technique: Tissue removal via suction through a glass pipette.
- Electrolytic lesion: Electric current destroys tissue, including white matter.
- Excitotoxic/neurotoxic lesion: Chemical infusion selectively destroys neurons while sparing fibers.
What are the disadvantages of aspiration lesions?
Only surface areas can be targeted, and fibers may also be destroyed.
How do excitotoxic lesions differ from electrolytic lesions?
Excitotoxic lesions use chemicals to target neurons selectively, while electrolytic lesions destroy both neurons and fibers.
Why do animals need recovery time before testing after permanent lesions?
The brain needs time to adapt and heal before behavioral assessment.
What are the types of reversible lesions?
- Pharmacological interventions (e.g., muscimol, a GABA agonist).
- Cryogenic inactivation (temporary cooling of neural tissue).
- Genetic-based approaches (optogenetics and chemogenetics).
How do pharmacological interventions create reversible lesions?
By temporarily altering neurotransmission (e.g., reuptake, synthesis, breakdown).
What is muscimol, and how does it work?
A GABA agonist that increases local inhibition in a targeted brain region.
What are the disadvantages of pharmacological reversible lesions?
The spread and effectiveness of the drug are difficult to assess, and effects are temporary.
How does cryogenic inactivation work?
Cooling prevents synaptic transmission, temporarily inactivating the targeted region.
What are the limitations of cryogenic inactivation?
It requires direct tissue access and is not well-suited for deep or subcortical structures.
What are the two main types of genetic-based lesion techniques?
Optogenetics (activated by light) and chemogenetics (activated by drugs).
What is optogenetics?
A method combining genetic and optical techniques to activate or deactivate neurons with millisecond precision.
What is chemogenetics?
A method using genetically modified receptors (DREADDs) that respond only to specific designer drugs.
Why do genetic-based approaches have high spatial resolution?
They can target individual structures, cell types, or pathways.
Why do genetic-based approaches have high temporal resolution?
They allow precise control over the timing of neuronal activation or inactivation.
Why use animals instead of humans for lesion studies?
- Lesions can be placed in a single cytoarchitectonic area.
- Grey matter can be removed without disturbing white matter.
- Identical lesions can be made in multiple animals for reliable results.
- Cognitive function can be tested both before and after the lesion.
Why use animals instead of humans for recording and inducing neuronal activity?
- Any brain area can be targeted.
- Recordings can be done in non-diseased brains.
- Neurons can be tested in a variety of conditions.
