Lecture 8: Research Methods

Question 1

how does a CT Scan work?

Answer 1

High-energy electromagnetic radiation is delivered to the head from all angles. A computer translates the information received from the X-ray detector into a series of pictures of the skull of the brain

Question 2

advantages & disadvantages of a CT scan

Answer 2

advantages: cheap and fast
disadvantages: the resolution is not great for soft tissue like the brain

Question 3

how do MRIs work?

Answer 3

• A strong magnetic field is applied to the body,
• the spin of every hydrogen atom (proton) assumes a particular direction in line with the magnetic field
• Radiofrequency waves are administered to the body
• The energy is absorbed by protons, changing the direction of their spin
• Protons then emit their radio waves when their spin flips back to that determined magnet

Question 4

the MRI can estimate ____

Answer 4

the relative density of protons in each area of the body

Question 5

there are more protons in

Answer 5

fat and water

Question 6

MRIS can be optimized to detect

Answer 6

the hydrogen atoms in water molecules

Question 7

how does diffusion tensor imaging (DTI) work?

Answer 7

measures the direction and speed of the diffusion of water molecules by taking several pictures in rapid succession

Question 8

DTI is used to identify ___

Answer 8

axon tracts

Question 9

how does Functional Magnetic Resonance Imaging (fMRI) work?

Answer 9

infers the movement of oxygenated blood around the brain by collecting a rapid series of MRI scans and measuring the movement of these magnetic field distortions over time. goal = measure brain activity during behaviour

Question 10

how does Positron Emissions Tomography (PET) work?

Answer 10

injects a person with a radioactive compound (ex. 2-DG) to detect changes in energy use in the brain. identifies where radioactive molecules are located over time & measures the changes in expression levels of neurotransmitter receptors.

Question 11

disadvantage of PET scans

Answer 11

operating costs (2-DG has to be made on-site the morning fo the experiment because it decays so quickly)

Question 12

what are macroelectrodes?

Answer 12

metal discs attached to the scalp to record the summed population-level activity of millions of neurons on cortical surfaces

Question 13

diagnosis & EEGs

Answer 13

macroelectrodes and EEGs can be used as diagnostic tools since specific patterns of EEG activity are associated with different states of consciousness, sleep, and type of cerebral atrophy

Question 14

experimental ablation

Answer 14

Involves the removal or destruction of a portion of the brain

Question 15

radiofrequency lesions

Answer 15

destruction of a brain region. burning a part of the brain with low-energy radiation.

Small lesions made by passing a radiofrequency current through a metal wire that is insulated everywhere but the tip.This electric current produces heat that burns cells around the tip of the wire

Question 16

how are the size and shape of radiofrequency lesions determined?

Answer 16

the duration and intensity of the current

Question 17

the downside of radiofrequency lesions

Answer 17

axons & cell bodies just passing through will also be burned

Question 18

excitotoxic lesions

Answer 18

destruction of a brain region. lesions produced by intracerebral injection of a glutamate receptor agonist, such as kainic acid. causes cause so much calcium influx that the affected neurons undergo apoptosis

Question 19

advantage of excitotoxic lesions

Answer 19

axons passing through are usually spared

Question 20

sham lesion

Answer 20

Placebo procedure that duplicates all steps of producing brain lesions except for one that causes extensive brain damage

Question 21

reversible lesions

Answer 21

Temporary brain lesions achieved by injecting drugs that block or reduce neural activity in a given region

Question 22

common drugs for reversible lesions include

Answer 22

voltage-gated sodium channel blockers and GABA receptor agonists

Question 23

voltage-gated sodium channel blockers

Answer 23

stop all action potentials

Question 24

GABA receptor agonists

Answer 24

hyperpolarize cell bodies

Question 25

microelectrodes

Answer 25

Thin metal wires with a fine tip that can record the electrical activity of individual neurons (called a single-unit recording)

Question 26

new microelectrodes can

Answer 26

record the activity of hundreds of neurons simultaneously

Question 27

chronic electrical recordings

Answer 27

electrical recordings made over an extended period of time

Question 28

acute recordings

Answer 28

made over a relatively short period (often after surgery)

Question 29

electrical stimulation

Answer 29

involves passing an electrical current through a wire inserted into the brain

Question 30

high-frequency electrical stimulation patterns ___

Answer 30

tend to produce the same behavioural effects as lesioning the brain area

Question 31

chemical stimulation

Answer 31

Drugs are administered through a guide cannula (hollow tube) implanted in a particular brain region

Question 32

optogenetics

Answer 32

The use of light to control neurons which have been made sensitive to light through the instruction of foreign DNA

Question 33

opsins

Answer 33

light-sensitive ion channels

Question 34

excitatory opsins

Answer 34

you can either pulse light or leave it on to drive action potential activity

Question 35

inhibitory opsins

Answer 35

continuous light pulses can be used to inhibit action potential activity

Question 36

excitatory opsin example

Answer 36

ChR2

Question 37

inhibitory opsin example

Answer 37

halorhodopsin

Question 38

virus

Answer 38

A small infectious agent that replicates inside the cells of other organisms The DNA of a virus encodes instructions on how to make more virus

Question 39

virus-mediated gene delivery

Answer 39

adding foreign DNA to the virus that encodes things like optogenetic proteins. when a modified virus is injected into an animal's brain, it infects the cells it comes into contact with. Once the virus gets its DNA into the infected cell's nucleus, that cell will start to transcribe it and make the foreign protein

Question 40

we can target opsin expression to specific neurons according to

Answer 40

1. where their soma is located 2. where their axons are located 3. the proteins they express 4. whether they recently had more action potentials than normal

Question 41

fluorescent calcium imagining

Answer 41

records neural activity from specific genetically-defined neurons. Green fluorescent protein (GFP) is modified into GCaMP, allowing it to bind to calcium and fluoresce much brighter when it does. Since a calcium influx occurs during action potentials, monitoring GCaMP fluorescence is a good way to measure neural activity

Question 42

retrograde labelling

Answer 42

tracing afferent axons

Question 43

anterograde labelling

Answer 43

tracing efferent axons

Question 44

retrograde tracers example

Answer 44

flurogold

Question 45

anterograde tracers example

Answer 45

PHA-L

Question 46

stereotaxic surgery

Answer 46

uses a stereotaxic apparatus to inject and permanently implant things into the brain

Question 47

bregma

Answer 47

the junction where pieces of the skull fuse together. often used as a reference point for stereotaxic surgery

Question 48

reasons for sterotaxic surgery

Answer 48

- lesion a brain area - lesion a specific type of cell - change gene expression - implant guide cannula - implant microelectrodes - implant fibre optic cables

Question 49

guide cannula

Answer 49

hollow tube

Question 50

microdialysis

Answer 50

the use of a semipermeable membrane to either deliver molecules or measure the number of molecules in some solution or brain area

Question 51

microdialysis probe

Answer 51

small metal tube that holds dialysis tubing. these can be placed in the animal's head

Question 52

fastest sampling rate for molecules to equilibrate across a dialysis membrane

Answer 52

once per minute

Question 53

typical sampling rate for molecules to equilibrate across a dialysis membrane

Answer 53

once per 10 mins

Question 54

only serotonin neurons express ___

Answer 54

serotonin reuptake proteins

Question 55

only glutamate neurons express ___

Answer 55

vesicular gluatamate transporter proteins

Question 56

immunohistochemistry

Answer 56

a histological method that is used to label proteins and peptides of biological tissue. when fluorescent antibodies that selectively bind to different types of proteins are washed over a brain slice, the brain slice of interest becomes fluorescently labelled

Question 57

t or f: it is easy to make an antibody that selectively binds to a small molecule such as a classic neurotransmitter

Answer 57

false; it is impossible

Question 58

t or f: it is easy to make an antibody that binds to a specific protein

Answer 58

true

Question 59

antibodies

Answer 59

proteins made by the immune system of mammals.

Question 60

advantages of fMRIs

Answer 60

they are not invasive & provide structural and functional information with decent spatial & temporal resolution

Question 61

do recpetor agonists & antagonists affect axons passing through the area

Answer 61

no

Question 62

what do anesthetics do to neural activity?

Answer 62

shut it down

Question 63

how do researchers identify cells that make and release classical neurotransmitters?

Answer 63

using antibodies against the enzymes that make these neurotransmitters

Question 64

the downside of excitotoxic lesions

Answer 64

animals can't serve as their own controls; sham lesions are needed

Question 65

advantage of chemical stimulation

Answer 65

animals can serve as their own controls

Question 66

neuronal projection

Answer 66

Function: map axonal projections in the brain Method: inject fluorescent molecules

Question 67

2 types of neuronal projection

Answer 67

retrograde & anterograde labelling

Question 68

immunohistochemistry disadvantage

Answer 68

can't localize small molecules like classical neurotransmitters