Ch.7, Research Methods Flashcards
Neuropsychology
study of brain related to behavior, with emphasis on humans
3 primary modern ways of studying the brain
historically: relied on brain injuries, post-mortum data, and animal lesions
NOW
chemical lesions: through drugs/temporary neurotoxins
Genetic lesions: shutting down the target gene of interest
Noninvasive imaging: MR, EEG, FMRI, PET
Molecular genetics: genome sequencing
“Frozen addicts case”
- 1982 Santa Clara Medical centre: patients coming in that appeared to have parkinsons: couldn’t move or speak but appeared alert
- George carillo admitted he was on synthetic heroin
- Turns out Barry Kidston was trying to synthesize MPPP but instead made demerol (MTPT) since it was an opiod for pain relief: but ended up keeping the temperature wrong
- MPTP on its own: not toxic, but when it interacts with astrocytes and serotonergic neurons that have MAO, it becomes MPP+ which kills dopaminergic neurons in dopaminergic system
- Death of dominergic neurons in substantia nigra= Parkinson’s-like symptoms
GOOD THING: developed animal models of PD for study
Isomers
molecules that have the same chemical formula but different bond arrangemnent
How to conduct animal studies
exploiting species typical behavior in the design
Spanswick’s Hippocampal Rat Experiment
- control group
- Rats with ADX: adrenalectomy (adrenal glands are part of the endocrine system, secrete cortisol for stress in humans and corticosterene in rats) = 50% reduction in dentate gyrus neurons
- Rats with ADX and an enriched environment (better social interaction, diet, excercise, etc.)
Procedure - TRAINING PHASE Introduced rats to two distinct contexts to see if they would remember them for 10 minutes over two days.
TESTING PHASE
-Control group did
-ADX group couldnt tell the difference/remember it
-ADx group with enriched environment performed the same as control
RESULTS: environment can mediate affects of loss of dentate gyrus neurons, facilitate neurogenesis,
Two divisons of the hippocampus
Located in temporal lobe
Dentate gyrus: It processes spatial memories and helps you make decisions. Hippocampus proper (cornu ammonis): This region works to form memories, then organizes and stores your memories
DAPI stain
used for staining DNA nuclei: DAPI, or 4′,6-diamidino-2-phenylindole, is a fluorescent stain that binds strongly to adenine–thymine-rich regions in DNA, blue
Morris swimming task
Richard Morris
1. Place Learning Task: rats were first placed in pool, located plank, then pulled out of water. 15 min interval between trial. uses distal cues from room, tests long-term memory due to 15 min wait
2. Matching to place task: rats did the same thing, but we’re placed back in the water almost immediately, tests working memory, distal cues
3. Landmark learning task: plank in diff location every time, but marked by a landmark cue (like a picture taped to the pool wall); now uses LOCAL cues, not distal, and requires spatial navigation skills not testing any kind of memory
Probe trial: remove the plank, they will look for it in original spot (almost like a validity check?)
Skilled reaching task
-uses rats bc they are very dexterous
-animal model of stroke for study
rats had to reach in between narrow gap for food: depending on the brain area they had damaged, they may or may not be able to do this
-Movement was broken down into segments and scored seperately to see how diff neurological problems influenced it
Why modify the brain to see how behavior is altered?
- Test hypotheses about how the brain affects behavior
- Develop animal models of disorders to test pharmaceuticals
How to manipulate brain in animal modes
whole animal manipulations: food, environment, etc.
Manipulations to specific brain regions: brain lesions (chemical, genetic, surgical); stimulation/inhibition using electrical, drugs, or genetic methods
Stereotaxi apparatus
machine that is fixated on head to get very precise location of brain region
used in brain surgery
X axis: moves it lateral/medial
Y axis: moves it anterior/posterior
Z axis: moves it dorsal ventral
Phineas gage
metal rod through frontal lobe
indicated to scientists that FL is crucial in personality, since Gage had problems with impulse control, vulgarity, irrespnsibility, and being very rude afterward
Penfield and Brain stimulation
founded the MNI in 1934
worked on patients in surgery
did awake electrical stimulation
no pain receptors in cortex so easy to do
with every stimulation, recorded what patients fielt or said
Gave us detailed brain mapping
Objectives of brain stimulation
enhancing or blocking neural activity and observing the behavioral effects
Deep brain stimulation
FACILITATE/INDUCE
allows us to look at structures very deep in the brain
-used for cases of parkinsons/schizophrenia as an absolute last resort
-mobile device that provides low voltage current into specific targeted region of the brain
could be used to stimulate striatum/basal ganglia
Transcranial magnetic stimulation
-very superficial, only 3-4mm down
-can do it on clinical and non clinical samples, major benefit
Magnetic coil is placed over brain to induce magnetic field, which either induces or inhibits behavior in that area
How does manipulating brain function with drugs work
-can influence specific neurons in specific brain regions
-must either pass through indwelling cannula or bbb: a thin tube inserted into a vein or body cavity to administer medicine, drain off fluid, or insert a surgical instrument.
-drug effects wear off over time, making it possible to study their effects on learned behaviors
Difference between haloperidol and amphematines
haloperidol: reduces dopmanergic neuron function= hypokinetic (rats exhibit less movement than usual), used treat schizophrenia
Amphetamines: increases dopamine activity=hyperkinetic (rats exhibit more movement than normal
Knock out and knock in gene methods
knock out: lose function; gene deletion
knock in: gain function; gene insertion
CRISPR-Cas 9 gene deletion method
- When bacterium detects prescence of virus DNA, it produces two types of short RNA
- One short RNA contains the sequence that matches the invading virus: single guide (sgRNA)
- These two RNAS form a complex with the Cas9 protein
- When the sgRNA finds its target within the viral genome = the cas9 cuts the target DNA and the virus is disabled
- This cut activates the cell’s repair mechanism, but that is error prone and can produce mutations: KNOCKS OUT THE GENE
Electrical, pharmacological, genetic, optogenetic strageties to manipulate neural activity in vivo
In vivo: in the living organism
ELECTRICAL
Benefits: high temporal precision (time precision, responds immediately by either going on or off)
Cons: affects all the cells surrounding the electrodes; can’t study specific neurons
Pharm pros: cell specific (like TTX)
Pharm cons: low temporal precision, drugs take time to act and wear off
genetic pros: cell type specific
gene cons: no temporal precision since we’re just knocking genes in or out, irreversible
Optogenetic pros: high temporal precision
Optogenetics
transgenic technique that combines genetics and light to control targeted cells in living tissue
Transgenic: taking DNA from unrelated organism, introducing it into animal so it expresses it
Works by light sensitive ion channels (light-gated) that activate when a specific wavelength of light is expressed
Fiber optic light can be delivered to selected brain regions such that all genetically modified neurons exposed to the light respond immediately
opsins, definition and two types
opsins: Opsins are G-protein-coupled receptors (GPCRs) that are light sensitive
1. Channelrhodopsin-2, ChR2: activation of a neuron, sensitive to blue light; results in Na+ influx into cell for excitation and K+ efflux = net depolarization
2. Halorhodopsin, NpHR: inhibits neuron, chloride pump activated by green yellow light, results in Cl-influx for net hyperpolarization
Pyramidal neurons of c1 and optogenetics
amygdala
introduce haloropsin, inhibitory light = loss of normal fear response in rats, wander in center space which is abnormal for them when usually they stick to the walls of the area theyre in
Key advantage of optogenetics
high spatial and temporal resolution
electrophysiology, pros, cons, samples,
ONLY USED ON ANIMAL MODELS
measures activity with microelectrodes
MEASURES ACTION POTENTIALS AND GRADED POTENTIALS
Extracellular: poor spatial resolution, good temporal precision, non invasive, done in mobile animal, low cost, less expertise required,
Intracellular: in sitro or in vitro, must more difficult, not done on mobile animal, good spatial resolution, good temporal resolution, an get one neuron easier in invertebrates, harmful to cells
EEG, pros, cons, type
Continous direct measure
only measures graded potentials bc they are occuring in dendrites closer to the surface, can’t measure AP bc they are too short, occuring too far down
very superficial, only first bit of cortex
overview: simple, inexpensive, non-invasive,
USED FOR: sleep rythms, anaesthesia depth, brain injury detection, severity of brain injury
Current sink: drop in current, EPSP, positive inside cell but negative outside
Currrent source: rise in current, IPSP, negative inside cell, positive outside
3 EEG rules
- eeg changes as behavior changes
- an eeg recorded from the cortex displays patterns
- the liivng persons electrical activity is never silent
ERPS, pros, cons, what, sample
event related potentials
complex EEG waveforms time locked to stimulus
stimuli can be anything
low spatial resolution, high temporal precision, inexpensive, noninvasive, easy, shows related to stimulus, simple, data requires cleaning has current sink and current source, p is positive n is negative wave, they functionally image brain activity
difference between static and functional/dynamic imaging techniques
static: just picture, MRI, CT
functional/dynamic: mapping using blood flow or something else, indirect
CT, pros, cons, what
computed tomography
radiation problem is huge, gives 3D picture, inexpensive, tomo means to slice, good spatial resolution, no temporal resolution, harder areas show up white soft tissue areas show up dark/fluid, shows lesions/brain injuries well
MRI, what it does, how it works, what it is, pros and cons
process: strong magnetic field through the brain, followed by a radio wave (which is a large wavelength, low energy, type of radiation but still very safe), the measuring the radiation emitted from hydrogen atoms
-grey matter shows up darker bc it has more water and less dense tissue
-white matter shows up light bc its very dense, but not a lot of water
OVERALL FUNCTION: MAPS THE LOCATION OF HYDROGEN ATOMS/WATER AND HOW DENSE IT IS
-noninasive
have to lie completely still people with claustrophobia, children, or parkinsons would struggle
What are the pros and cons of MRI, as well as some physical body problems with it?
Some IUDs, pacemakers, and tattoos can be affected by the scanner
body weight limit
due to the strength of its magnetic field:L 60,000 times stronger than the earth , 1.5Tesla to 3Tesla
very good spatial resolution
much better with soft tissue
no temporal?
How MRI works with hydrogen atoms
hydrogen atoms behave as tiny bar mnagnbets that can be aligned by a magnetic field
once magnetic field is on,m hydrogen lines up with radio wave pulse , the radio transmitter is turned off, and then the particles re-emit radio waves
fMRI, pros, cons, what it is, what it does
functional magnetic resonance imnaging
assumes that when a brain region is active, the amount of blood, oxygen and glucose flowing to the region increases
unlike EEG, not a direct measure of electrical activity
when human brain activity increase = produces overcompensation bc the increase in oxygen produced by the increased blood flow exceeds the tissue’s need for oxygen: FMRI MEASURES THIS OVERCOMPENSATION
Difference between signal with oxygenated vs deoxygenated blood on an fmri
Oxygen-rich hemoglobin is LESS magnetic than oxygen poor hemoglobin
deoxygenated blood distorts surrounding magnetic fields, reducing signal of protons in the near vicnity= less overall MRI signal
BECAUSE
Hemoglobin is diamagnetic when oxygenated but paramagnetic when deoxygenated. This difference in magnetic properties leads to small differences in the MR signal of blood depending on the degree of oxygenation.
Diamagnetic materials are slightly repelled by a magnetic field; Paramagnetic materials are slightly attracted by a magnetic field and do nold t retain the magnetic properties when the external field is removed.
graph of fmri measure
- baseline recorded
- oxygen use, dip in signal; this lower signal = means more deoxygenated blood
- after stimulus introduction, we are now measuring overcompensation; delivery of oxygenated blood
how long does an action potential take
1 millisecond
pros and cons of fmri
good spatial resolution, but changes in blood flow take as long as 2-6 seconds, making the tempora;l resolution bad
expensive
people
PET scan, what is it how it works
used to detect changes in blood flow by measuring changes in the uptake of radiolabeled compounds such as water or glucose
^^by swapping out oxygen with something radioactive, measures unstable radioactivity
radioactive “tracers” are injected:
half life is very short: has to be done bedside
positrons emitted by nuceli and produce gamma rays
water collects in more active tissue
activity increases =inbcrease in radiation
positron’anti-matter-
anti-matter: electron with positive charge
opther uses for PET scans
could look at proteins, ph, cellular function, very good at detecting cancer cells since they tend to consume more glucose
PET pros and cons
good spatial, but both FMRI and CT ARE BETTER
poor temporal
costly
expertise
have to average participant scans to the get the “mean difference image”
ranking all methods in terms of spatial
CT= best
MRI
FMRI
PET is the worst
Best temporal resolution
EEG
