Week 3: Research Methods Flashcards
Levels of Analysis
Different levels of looking at the brain and it’s structures and functions. Macro and micro levels
Spatial resolution
Ability to measure smaller brain structures; High SR = smaller areas
Temporal resoltion
Ability to measure change in activity in time units; high TR = fast measurement
Why measure human brain activity
Compare resting control brain and active brain to assess patterns of activation. Can be used to define and diagnose disorders
Electroencephalogram (EEG)
Picture of the brain taken using electrodes on the scalp that measure the neurons directly below them (small area). Measures the wave-like frequencies over time and correlate the patterns to a brain state.
Low spatial, high temporal
Event-related potential (ERP)
Measured in an EEG. Neural activity of brief mental processes. Averaged across many records to determine patterns of activity
Positron Emission Tomography (PET)
Develop radio tracers that act like a desired chemical, but generate gamma rays. Rays are tracked and generate colored images (blue = less activity, red = more). Theoretically can be used to diagnose disorders.
Decent spatial, low temporal
Magnetic Resonance Imaging (MRI)
Strong magnetic field aligns the spin of your brain atoms to its pull. When they realign, it send a signal to the machine and builds a picture. Not used in individual diagnoses, but results are averaged to get a basic idea of disordered brains.
High spatial resolution
Diffusion tensor imaging (DTI)
MRI but for white matter structure. Can be used to correlate white matter tracts and disorders
Functional MRI (fMRI)
Tracks change in ratio of oxygenated to deoxygenated blood. Typically only used in correlational findings
High spatial, decent temporal
Issues with fMRI (and MRI to an extent)
Reverse inference. Results can differ from natural activity due to lab environment. Expensive, inconvenient, and requires a trained professional
Reverse inference
Assuming psychological activity from brain images. This causes issues because brain areas can light up for many different processes, so assumptions can ignore possibilities or cause errors in judgement
Lesion studies
Tracking behavior changes after damage or injury to the brain. Rarely used; case studies; rarely specified to just one brain area
Micro-level measuements
Single cell recordings: measuring one cell via electrode insertion. Irreversible damage, only done when necessary
Gene/protein expression measurements: How much, what type, and epigenetic changes in protein
IHC
Immunohistochemistry (IHC)
Develop antibodies to tag cells of interest and generate an image of specific cell types in dead brain tissue
Uses of manipulating brain function
Can experimentally determine causal relationships between neurology and behavior
Transcranial magnetic stimulation (TMS)
Targets specific brain areas with magnets and exhausts the neurons to temporarily shut off function. (TCDS is the same but using electrons instead of magnets)
Deep Brain Stimulation (DBS)
Penetrate the brain with an electrode. Highly invasive, used primarily in treatment scenarios
Drug manipulation
Give drugs to temporarily change brain function.
Agonists = activate receptors
Antagonists = inhibit receptors
Allosteric modulators = tune the system
Benefits of animal brain manipulation
We can more readily do highly invasive procedures ethically and cheaper
Electrophysical animal recordings
Single cell readings, can be used to map distinct cell function
Targeted manipulation studies in animals
Surgically alter brain areas to observe behavior change. Done via lesion (irreversible, electrodes) or pharmacologically (reversible, cannulae)
Genetic studies in animals
Manipulate genes to track behavior change. Take out genomes or add modified genomes. Can restrict modification to selective (specific gene) or inducible (timed).
Not generalizable
Optogenetics
Target single cell populations and manipulate them via direct light stimulation. High spatial and temporal resolution
Chemogenetics
Target single cell populations and manipulate them via drug stimulus. High spatial, low temporal
Behavior testing in animals
4 types. Anxiety tests, Depression-like behavior tests, memory process testing, Social Interaction tests
Elevated plus maze
Knee height, cross shaped, two arms open and two arms closed. Track how long the mouse spends in each arm. More time in closed arms = more anxious
Anxiety tests in animals
Determine baseline anxiety level in animal using the elevated plus maze. Done before other test to rule out confounds in other behaviors
Depression-like tests in mice
Modelling depression symptoms and anhedonia. Swim test, tail hang test. Giving up = depressed behavior
Memory process tests in mice
Fear conditioning for LTM: Operant conditioning to fear. Measure amount of freeze response. Expression of learned fear implies memory
Object recognition for STM and LTM: Train with toys, give them a break, and then test them with old and new toys. More exploration of novel toys implies memory
Three-chamber Social Interaction Test in mice
Phase 1: mouse on its own
Phase 2: give it a friend
Phase 3: give it another friend
Measure amount of time spent with first friend (sociability) and attraction to second friend (attraction to social novelty)
Used to study social disorders
Modelling Autism in mice
Replicate poor social interaction, repeating behaviors, long slow development, etc. Use valporic acid (VPA) in mother mice to give children 9-fold chance of presenting with ASD. (VPA works in humans and mice)
