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Intro to Neuro 6: Neuroscience Techniques
neuroscience techniques
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Undergraduate 3
03/30/2022

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Cards

Term
Name 4 in vitro models
Definition

- Bacteria / yeast cells

- Cell culture

- Tissue slice

- Invertebrates

 

(In vitro = in glass, isolated parts of organisms)

Term
Name 2 in vivo models
Definition

- More complex animals

- Humans

 

(In vivo = in living, alive cells or organisms)

Term
What is in silico?
Definition
Using computers for neuroscience modelling.
Term
Why are rats so popular in neuroscience?
Definition

- Cheap housing / maintenance / breading

- Easy to handle (very friendly!)

- Quite intelligent and agile

- Resistant to infection

 

- Many inbred strains availible

- A lot of background data

Term
Name 3 kinds of lesion techniques
Definition

- Mechanical lesions: actually cutting the brain

 

- Electrolysis: using electrical pulses to locally destroy small regions of tissue

 

- Chemical lesions: using chemicals (like ibotenic acid) to destroy cells, fibers of passage are spared

Term
Describe the difference between systemic, intracerebroventricular, and local intracerebral injections, and mention how the chemical spread throughout the brain for each
Definition

- Systemic: inject into bloodstream or muscles (chemical will go everywhere)

 

- Intracerebroventicular: surgery, release substance into cerebrospinal fluid (chemical will spread throughout CSF and across brain)

 

- Local intracerebral: injection straight into the target area (chemical will affect target area)

 

 

Term
Where are osmotic pumps placed and how do they release chemicals?
Definition

- Under the skin

- Slow and controlled release of chemicals

Term
What are 3 in vivo monitoring techniques?
Definition

- Electrophysiology (electrical)

- Microdialysis (chemical)

- Behavioural evaluation (tasks)

Term
What are 3 ex vivo monitoring techniques?
Definition

- Histology: assessing quantity of cellular components (like NMDA receptors) in slices of tissue using staining techniques

 

- Immunohistochemistry: specific kind of histology to detect chemical components (like serotonin)

 

- In situ hybridisation for mRNA or DNA: specific kind of histology to visualise genetic material (like mRNA)

 

Term
What is stereotaxic surgery and what can this be used for?
Definition

- Using a device that allows you to keep the head still and perform surgery at a precise location

 

- Lesions

- Microinjections

- Cannula placements (cannula = small tube)

- Microdialysis

- Electrodes

- Headset (made of electrodes)

Term
What technique can be used to chemically lesion a brain area using ibotenic acid?
Definition
- Stereotaxic microinjections
Term
What is the main principle of microdialysis?
Definition

You insert a small catheter (tube) that contains a physiological salt solution and has a semi-permeable (allows gas/liquids to pass through) outer membrane.

 

Extracellular substances can flow into the tube, substances in the tube can flow out. The dialysate (outflow)/perfusate (inflow) is collected for later analysis.

Term

 [image]

Fill in the red boxes.

Definition

 1) Perfusate, inflow, physiological salt solution (contains as many salt molecules as intracellular fluid)

 

2) Dialysate, outflow, contains analyte (substance being analysed) 

Term
What are 3 applications of microdialysis?
Definition

- Continuous monitoring of chemical events in living tissue

 

- Continuous drug delivery

 

- Simultaneous drug delivery and monitoring of drug effects

Term
What are the 4 levels of electrophysiological measurement?
Definition

- Single ion channel

 

- Single unit (one cell)

 

- Multi unit

 

- Field potentials (synchronous activity of many cells)

Term
How do you record signals from a single ion channel?
Definition

- Patch-clamp technique

 

Cell-attatched mode: A micropipette is attached to the cell membrane. Suction is applied through the pipette to draw a piece of the membrane into the microelectrode tip.

 

Whole-cell mode: With more suction, the patch of membrane can be displaced. Allows for stable intracellular recording.

 

Perforated-patch technique: Tries to prevent intracellular fluid of the cell mixing with the solution inside the electrode. This is done by withdrawing the membrane from the rest of the cell. Allows for pharmacological analysis of membrane patch. 

 

 

Term
How do you record signals from a single ion channel? What are the 3 modes of this technique?
Definition

- Patch-clamp technique

 

Cell-attatched mode: A micropipette is attached to the cell membrane. Suction is applied through the pipette to draw a piece of the membrane into the microelectrode tip.

 

Whole-cell mode: With more suction, the patch of membrane can be displaced. Allows for stable intracellular recording.

 

Perforated-patch technique: Tries to prevent intracellular fluid of the cell mixing with the solution inside the electrode. This is done by withdrawing the membrane from the rest of the cell. Allows for pharmacological analysis of membrane patch. 

 

[image]

 

 

Term
How do you record signals from a single unit/cell? (Intracellular recording)
Definition

- Use a sharp electrode that penetrates the cell membrane

 

- Records voltage/current over cell membrane

 

- Like single ion channel recording, here too you use a pipette that applies suction to the cell membrane, but the pore is much smaller.

Term
How do you record extracellular single/multi-unit signals?
Definition

- Place an electrode close to the cell

- Will record activity from one neuron 

- Reference electrode is grounded

- This is how all recordings of single neurons in conscious animals is done (think Hubel and Wiesel's cat measurements)

 

- If the tip is slightly larger --> multi-unit signals

- Records changes in activity of brain areas

Term
What is a field potential and how is it recorded?
Definition

- Field potential: activity generated by simultaneous activation of many neurons 

 

- Recorded using multiple electrodes with larger tips

 

- Synapse releases neurotransmitter onto postsynaptic cell

- Current sink is generated (net flow of current inward and outward gets more negative)

- Extracellular electrode detects this as negativity with respect to ground (2)

- Intracellular electrode records change in membrane potential, inside of cell becomes more positive (1)

 

[image]

Term
How can long-term field potentials be recorded in freely moving animals?
Definition
- Using stereotaxic surgery to implant a headset that contains the electrodes which stick out
Term
What does EEG measure? What is the source of the signal?
Definition

- Postsynaptic potentials of cortical neurons

(Not ionic currents that generate fast action potentials)

 

Source:

- Extracellular ionic currents caused by dendritic electrical activity

Always reflects summation of syncronous activity of thousands/millions of neurons with similar spatial orientation

- Measures oscillating potentials

 

 

Term
What are the BOLD signals measured using fMRI? What is BOLD-imaging sensitive to?
Definition

- Blood-oxygen-level-dependent imaging

- Measures flow of oxyhemoglobin-rich arterial blood towards 'active' brain areas

 

- Sensitive to differences between two brain states / regions

- So not 'absolute'

Term
What do BOLD signals correlate with?
Definition

- Modulatory activity

- Brain states

Term
What are transgenes and transgenetic organisms?
Definition

- Transgene: foreign DNA inserted into host organism

- Transgenetic organism: organism transformed with transgene

Term
How does genetic engineering work?
Definition
- Proteins occurring in an organism are altered by changing the DNA that codes for the given protein
Term
What are two ways of inserting foreign DNA (genetic engineering)?
Definition

- Foreign DNA exists in the cell in the form of a plasmid

(Common in prokaryote hosts, unicellular organisms with simple cell structure, like bacteria)

 

- Foreign DNA is integrated into the host genome

(Always the case in mammals)

Term
What are the 5 main steps of genetic engineering? (Recombinant DNA technology)
Definition

1. Isolation of gene of interest (this creates a PCR fragment)

2. Modification of the gene

3. Insertion of the gene into a vector

4. Insertion of the vector into organism's cells 

5. Test to isolate genetically modified organisms

Term
What are 3 applications of recombinant DNA technology in neuroscience?
Definition

1) Loss of function experiments:

Alter genes to cripple a function

 

2) Gain of function experiments:

Increase function of gene (via extra copies of increased synthesis)

 

3) Tracking experiments/expression studies:

- When and where is a protein produced?

- Fuse a gene with a reporting element (green fluorescent protein)

- Reintroduce this gene into organism, the GFP catalyses the production of a dye, allows us to see when and where proteins are produced

Term
What are the 2 ways to produce a transgenic animal?
Definition

- Old-school: inject DNA and hope it integrates into their genome

- Not very effective, transgene may disrupt function of some gene critical to survival/development

 

- New-school: transfer new DNA into embryonic stem cells

- Allows for precise genetic modification

- Works for only one particular mouse strain 

- When DNA strands split, one DNA strand can pair with the 'guest' strand

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