Neuroscience Methods

Question 1

Golgi Stain

Answer 1

• neuron level
• developed many years ago to be able to identify neurons, first time we could see what a neuron looks like
• Allowed us to know there is a cell body with processes involved, some will show axon and dendrites
• Limitation: cannot differentiate between two neurons. Physically you can see that some look different from others, but doesn’t go beyond that

Question 2

Brainbow

Answer 2

• neuron level
• inject fluorescent dyes into the brain, each will be picked up by a different kind of neuron
• Each dye has a specific protein detector in it, targeting a specific population of neurons
• Allowed us to see which neurons are neurobiologically like one another(similar NTs produced, receptor makeup same, etc) due to color coding

Question 3

C-fos

Answer 3

• genetic code (transcription factor) that gets turned on when a neuron is active
• For example, if you wanted to know which particular neurons are active during stress, the neurons that have c-fos show up in them are the ones that are active when rat was experiencing stress

Question 4

Tracers

Answer 4

• neuron level
• allow us to see where neurons go
• retrograde and anterograde tracers

Question 5

Anterograde tracer

Answer 5

• Answers: Where does x project to?
• Ex. inject tracer in VTA so cell bodies take it up and then transport it to wherever they go

Question 6

Retrograde tracer

Answer 6

• Answers question: where does x receive input from?
• Ex. inject tracer in the NAc so the terminals take it up, sending it back to the cell bodies

Question 7

X-ray CT

Answer 7

• for imaging living humans
• allows you to look structurally, can see if there is anything wrong
• used routinely in clinic to identify structural differences

Question 8

Magnetic Resonance Imaging (MRI)

Answer 8

• Allows you to look at structural changes/differences
• Uses a magnetic field to identify structures
• more fine details/better image quality than MRI

Question 9

Diffusion tensor imaging (DTI)

Answer 9

• allows you to look at blood vessels and measure the CSF and blood that is flowing around
• can specifically test blood vessel damage (hemmorage, strokes, etc.)

Question 10

Positron Emission Tomography

Answer 10

• Uses radioactive material and actually allows you to detect receptor changes in the brain
• How the D2 receptor study was done

Question 11

fMRI

Answer 11

• Gives a difference image: leftover difference between control image and test image.. is the activity driven by the stimulus (can be done with any kind of task)
• BOLD signal (blood oxygen level deficiency): when neurons become active, they use up oxygen in the surrounding area (from the blood)… then using the magnetic field you can measure the amount of oxygen present in the blood in specific brain areas
• hemoglobin is magnetically charged so it can be detected by a magnetic field

Question 12

How are ex-vivo studies completed?

Answer 12

• look at the brain tissue outside of the organism’s body, but the tissue/neurons are still alive
• brain is taken out of the skull and immersed in oxygenated artifical CSF to give the same environment as if it were still attached to the animal
• Now, we can look at specific neurons

Question 13

Ex-vivo electrophysiology

Answer 13

• recording pipette goes to cell body of a neuron, pressure is applied, and the membrane breaks but forms seal w/ the pipette (called patching)
• now, the internal solution (cytoplasm) of the cell gets sucked into the pipette
• This allows you to measure electrical deflections (changes), including: single ionotropic channel changes, EPSPs and IPSPs, and action potentials

Question 14

In-vivo electrophysiology

Answer 14

• recording from an animal while behaving (alive)
• set of electrodes implanted into animal brain, so the activity of the neurons can be measured
• can measure overall activity and action potentials

Question 15

EEG

Answer 15

• measures electrical activity in humans, but less precisely than in animals
• electrodes placed over skull to measure electrical activity in specific parts of the brain to get activity of that particular region

Question 16

Ex vivo fast scan cyclic voltammetry

Answer 16

• place stimulating electrode (to stimulate NT release) next to recording electrode (picking up how much is released)
• baseline collected, then electrical stimulation that gets sent, then response, then signal goes back down
• allows you to measure changes in dopamine, serotonin, and norepinephrine (clearance from the synapse)
• works in seconds

Question 17

What does the height of the response tell you with ex-vivo FSCV? What does the slope of top 1/3 portion tell you?

Answer 17

• height of response tells you how much NT is released
• top 1/3 of slope tells you maximal rate of uptake at the transporter

Question 18

In-vivo microdialysis in freely moving rats

Answer 18

• rat walking around, perforated probe (channel in which artificial CSF w/ no NT can be sent in) embedded
• CSF flows through outlet, then NT flow in via diffusion across the membrane
• This allows the NT to be collected, processed, and then measured
• Allows you to measure changes in NTs, amino acids, and neuropeptides
• Works very slowly, within minutes

Question 19

Magnetic resonance spectroscopy

Answer 19

• new, around less than 10 years
• used w MRI to allow you to detect NT in human brain

Question 20

Behavioral testing

Wheel running

Answer 20

• exercise
• great intervention for addiction like behaviors

Question 21

Behavioral testing

Rotarod

Answer 21

• time they can stay on the rotarod is measured
• used to test motor function

Question 22

Behavioral testing

Von Frey

Answer 22

• tests pain sensitivity
• thin filaments to thick, rigid filaments brush their paw
• Measure what filament force they respond to
• if you inflame the paw, the rats can feel thinner filaments than usual

Question 23

Behavioral testing

Elevated plus maze

Answer 23

• has two closed (w/ walls) arms, and two open arms (no walls)
• rats are nocturnal and like to live in dark areas, a rat who is exhibiting anxiety will not venture out into the open arms

Question 24

Behavioral testing

Morris water maze

Answer 24

• used to test cognitive behaviors and learning/memory
• maze is placed in a center of a room with four images on each wall
• rat is placed in one location and then they measure the time it takes the rat to reach the platform
• if you place the rat in the same location each time they will immediately swim to the platform
• a rat suffering from loss of memory will take a lot longer or never learn how to find the platform

Question 25

# Behavioral testing Social interaction test

Answer 25

* Tests how addictive behaviors/anxiety/depression affect social interaction * Cage mate kept under a cover, with a non-mate kept under another cover... then measure how much time the rat spends w each mate. * A healthy rat will spend time with the non-mate because they do not fear novelty (will still spend more time with their cage-mate) * Rats in withdrawal (or having some level of stress) will spend no time with the non-mate

Question 26

Contingent vs non-contingent drug administration

Answer 26

* contingent: rat has to get it/self administerd by the rat * non-contingent: researcher gives the rat the drugs

Question 27

Drug administration: free and voluntary intake

Answer 27

* bottle hung and the rat chooses what it wants to drink (water or ethanol)

Question 28

Drug administration: operant conditioning

Answer 28

* rat is trained that when a yellow light goes off to press a lever * supposed to press the light associated w/ said lever (for oral intake) * other drugs can be given via an infusion pump after pressing lever

Question 29

Drug administration: inhalation

Answer 29

flask with a bubbler makes liquid turn to gas so the rat can inhale drugs (non-contingent)

Question 30

Optogenetics

Answer 30

* insert sodium channel in brain and then activate with blue light (473 nm), channel opens and Na+ ions flow in (Channelrhodopsin) * Halorhodopsin activated by yellow light (589 nm), Cl- ions flow in and hyperpolarize the cell * Light is shined directly where you want the neurons to be activated or inhibited * If you activate Channelrhodopsin, the mouse will move to the mouse under the cup instead of to cup w no mouse

Question 31

Transmagnetic stimulation

Answer 31

-magnetic probe is held against a human skull, providing a magnetic stimulation which affects neuron stimulation in that area of the brain -Not as accurately target in humans as it is in rats, but you can still target a specific lobe Clinically used to treat anxiety, depression, and more recently for addiction

Question 32

Deep brain stimulation

Answer 32

-probe put in brain, pulse generator pulses the brain -however, very invasive so if something goes wrong it will greatly affect someone -Used in combination w/ l-dopa to get more dopamine release in the basal ganglia area