L08 Flashcards
What is experimental ablation (lesion study)?
Experimental ablation involves the removal or destruction of a portion of the brain. Presumably, the functions that can no longer be performed following the surgery are the ones the brain region normally controls.
What is an excitotoxic lesion?
Brain lesion produced by intracerebral injection of a glutamate receptor agonist, such as kainic acid. These drugs cause so much excitation (and calcium influx) that the affected neurons often undergo apoptosis, while axons passing through (fibers of passage) are usually spread.
What is a sham lesion?
“Placebo” procedure that duplicates all steps of producing brain lesion except for one that actually causes extensive brain damage.
What is a reversible lesion?
“Placebo” procedure that duplicates all steps of producing brain lesion except for one that actually causes extensive brain damage.
What is reversible lesion?
A temporary brain “lesion” can be achieved by injecting drugs that block or reduce neural activity in a given region. Common drugs include…
-Voltage-gated sodium channel blockers (stops all action potentials)
-GABA receptor agonists (which hyperpolarize cell bodies)
What are microelectrodes?
Thin metal wires with a fine tip that can record the electrical activity of individual neurons (known as single-unit recordings).
What does electric stimulation?
Electric stimulation involves passing an electrical current through a wire inserted into the brain. This will affect everything in the area (cell bodies and fibers of passage). Some electrical stimulation patterns (often very high frequencies), counterintuitively, tend to produce the same behavioral effects as lesioning the brain area.
What is chemical stimulation?
Chemical stimulation is achieved with drugs. In rodents, drugs are often administered through a guide cannula (hollow tube) implanted in a particular brain region. Anesthetics can be injected to shut down all neural activity. Alternatively, receptor agonist/antagonist can be used, which should not affect fibers of passage (i.e., axons just passing through the area), since there are no neurotransmitter receptors on the membrane in the middle of an axon.
What are optogenetics?
The use of light to control neurons which have been made sensitive to light through the introduction of foreign DNA. This foreign DNA encodes light-sensitive proteins known as opsins. Opsins are proteins that are sensitive to light.
The opsins we have in our eye are metabotropic receptors that operate with a 30-millisecond delay. The opsins we use for optogenetics are often ion channels that open and close instantly in response to light. The original ones were discovered in bacteria in different parts of the world. Recently people have started to intelligently design and modify opsins for research purposes.
What does retrograde labeling trace?
Afferent neurons.
What brain areas send their axons here? Retrograde labeling is used to label the cells that innervate (project to) a given region.
What does anterograde labeling trace?
Efferent neurons.
Where do the axons from these cells go? Anterograde labeling is used to label where axons from a particular location go to.
What is an example of a chemical used for retrograde labeling?
Fluorogold.
Fluorogold molecules are taken up by axon terminals and transported back to the cell body
What is an example of a chemical used for anterograde labeling?
PHA-L
PHA-L molecules are taken up by cell bodies and transported down to axon terminals.
What is stereotaxic surgery?
A surgical intervention that uses a stereotaxic apparatus. This is a device that permits a surgeon to put something into a very specific part of the brain.
It is used to inject things into the brain, such as drugs, viruses, or tracer molecules (dyes).
It is also used to permanently implant things, like cannula, electrodes, or fiber optic cable.
What is the bregma?
The junction where pieces of skull fuse together. Bregma is often used as a reference point for stereotaxic brain surgery.
