PSY290 - Research Methods

Electroencephalography (EEG)

measures electrical activity in specific brain regions

• studies: arousal, consciousness and epilepsy

what is the main advantage of EEG?

Great temporal resolution

• ability to measure changes in arousal/consciousness

Temporal Resolution

ability to resolve neural activity in the brain

Spatial resolution

ability of specific brain structures to identify specific parts of the brain

What is the main disadvantage of the EEG?

poor spatial resolution so deeper brain areas cant be measured

Event Related Potential (ERP)

neural activity related to a brief mental process

• measured using EEG equipment, good for rapid mental processes

Positron Emission Tomography (PET)

measures metabolic activity and characterizing distribution of specific substances

what is the main advantage of PET?

it has better spatial resolution than EEG but worse than MRI

what is the main disadvantage of PET?

it has terrible temporal resolution so it is difficult to resolve rapid changes in neural activity

• mainly used for characterizing substances (receptors or proteins) but no longer used for diagnosis because of its resolution issues

how do EEGs work?

• electrodes are placed on a small amount of neurons

• the basis of the signal is the activation of the synapse

• the variation in voltage as the signal passes is what gives us the frequency

how does PET work?

• synthetic radiotracer is injected into the subject

• reacts with tissue in the brain + reaction produces signal that is measured with the equipment

how do we read PET scans?

• if there is similarity to glucose in the radiotracer, it is distributed in the same way

• the signal differences between the different regions of the brain are what reflect differences in glucose demands/ neuronal activity

how do we measure substances with PET?

• if similar to opiate transmitters, it distributes in the same way binding to the same receptors

• signal differences between the various brain regions will reflect opiate receptor occupancy

Major Depressive Disorder diagnosis by MRI

the orbitofrontal cortex and hippocampus are smaller while the lateral ventricles are larger

Diffusion Tensor Imaging

adapted form of MRI used to study white matter

Magnetic Resonance Imaging

• good for studying grey matter

• assesses structure

Functional Magnetic Resonance Imaging (fMRI)

used to study function

how does the fMRI work?

the magnetic properties of oxygenated and deoxygenated blood is measured

• the ratio in a given area will provide us with the correlate of neuronal activity in that area

what is the main advantage of fMRI?

• great spatial resolution (best out of all techniques discussed)

what is the main disadvantage of fMRI?

doesn’t have a big disadvantage since temporal resolution is still considered pretty good

• not as good as EEG or MEG

why should we be weary of fMRI diagnosis?

due to reverse inference errors

• by inferring the involvement of a specific cognitive process to observed brain activity when that activity could mean the activation of several other cognitive processes

why are fMRIs not used as often?

• costly and expertise required

• test-rest reliability is poor so conclusions are not very reliable and in turn so are diagnosis that are solely reliant on it

• cant be used to measure some behaviors cause it disrupts them

Lesion studies

if damage to a specific brain region impairs a particular behavior, plausible that region controls behavior impairment

Patient HM

removal of hippocampus + adjoining areas

• impaired memory

Phineas Gage

lesion of frontal lobe

• impulsivity + impaired social behavior

Patient SM406

Lesion of the amygdala

• reduced fear

What are the limitations of case studies?

• lesions are not specific as behavioral impairments could be due to damage in any of these areas

• effects could be more extensive than what is being measured

• very rare cases so conclusive arguments cant be made, not generalizable

• no control variables

single cell recording

records activity of individual neurons

• very invasive

Jennifer Aniston Neurons

found neurons that fire specifically to different pictures of the same person

gene inferences on Jen Ann study

• they encode for proteins

• since they determine structure of the nervous system they determine functional output too

what are genetic testing methods?

• PCRs (polymerase chain reaction)

• microarrays

what does genetic testing do?

• identifies genetic variants associated with conditions

• changes in gene expression with experience

• uses variations to predict behavior

why do we tend to measure transmitter precursors/metabolites?

because they are more readily available compared to regular neurotransmitters

5-HIAA urine test

• tests for serotonin

• shows higher levels of transmitter in autism

Immunohistochemistry

localizes substances and cell groups defined by them with specialized stains and antibodies

• requires post-mortem brain tissue

• used for animals and humans

what are the 3 main strategies for identifying causal relationships?

• TMS

• EBS

• Drugs

Transcranial Magnetic Stimulation

neuronal activity in specific brain areas is manipulated by magnetic fields

• if behavior is changes then the target brain area is involved in that behavior

• good treatment for depression

TMS imagery study

• subjects asked to answer questions about a panel of objects

• subjects did perception trails (w/objects) and imagery trials (no objects + had to be visualized)

what was the real treatment of the TMS study?

TMS application to the primary visual cortex

what is the control treatment of the TMS study?

TMS application to the non visual area

what were the results of the TMS study

• when inactive, judgements during perception and imagery trials took longer, increased response time

• suggested that visual cortex activation is crucial for imagery + perception

• allows us to make causal inferences

TMS therapeutic applications

may help treat depression when applied to the frontal lobe

what are the main advantages of TMS?

• non invasive

• can be used multiple times in one subject

• pretty fast

what are the main disadvantages of TMS?

• unclear what stimulation parameters should be used

• difficulty targeting deep brain areas

• newer method

who developed electrical brain stimulation?

Penfield

what is the purpose of electrical brain stimulation?

• informative of causal relationships

what are the disadvantages of electrical brain stimulation?

• highly invasive

• only used when there is already another pathology present (potential confound

• small sample size available

• findings may not be generalizable

Deep Brain Stimulation

trailed for potential treatment for Parkinson’s Disease and depression

• neural implants to treat epilepsy are currently being researched

what are other methods of measuring brain activity?

• drugs (haloperidol affects learning)

• neurotransmitter alteration through diet (Tryp loading for serotonin)

electrophysiological recordings

study of electrical + physiological properties of neurons

• individually or large groups of cells at once

Targeting Manipulation Studies

• rodent brain mapped using stereotaxic guide

• guide locates brain regions we can target

what are the techniques available for stereotaxic surgery?

• lesion the region

• pharmacological treatment

• electrical stimulation

• implant electrodes (stimulus) cannulae (delivers drugs) to specific brain regions

• inhibit or excite specific brain areas

what is an example of cannulation?

• cannula implanted into the hippocampus

• GABA (muscimol inhibits the hippocampus)

causes memories of objects to not be stored in a sleeping state

transgenic animals

has a genome that has been genetically modified to include a gene from another source

• express different protein fluorescence

why are mice the preferred species for transgenic modification?

• they breed very quickly and in large quantity

• genes in humans also cause dysfunction in mice

knock in

adding a gene

• reporter proteins

• drug responsive and light responsive receptors (chemo and optogenetics

knock out

removing a gene

what are some applications of transgenic models?

• limit your gene modification to specific cells

• add modification at a specific time

conditional transgenic knockout

one gene specifically removed from dentate gyrus cells

• mice showed stronger resilience to fear conditioning over time

what is the process of chemo and optogenetics?

• target a single cell population in a single area

• manipulate activity of population

• determine role of cells in behavior

anxiety

feeling of worry, nervousness or unease about something

• adaptive ( avoiding danger)

• problematic when unregulated

Elevated Plus Maze

open arm avoidance is an anxiety indicator

• closed arms: unexposed (safe)

• open arms: exposed (light)

EPM results

• closed arm time high in both groups but significantly higher in transgenics

Forced Swim test

animal is placed in an aversive environment (water flask)

• measures escape response

• short escape response indicates depressive like behavior

• deletion of delta GABAa receptor associate with depression

sucrose preference test

animal is given the choice of sucrose and water solutions

• loss of sucrose preference is indicative of anhedonia

why do we use fear to test memory?

fear is mostly learned so exposure to an aversive stimulus means they will remember that experience

• re exposure will show fear which indicates expression of learned fear indicates memory

associative learning task

• shock paired with blue box and tone (shock signals)

• when re exposed, animal freezes due to expectancy of another shock

fear conditioning

acquiring memories about aversive events

object recognition

non aversive memory test animal is exposed to a set of identical objects

• break where removed from chamber

• returns to it and old object replaced with a new one

• recall will show exploration of novel object

• deletion of delta GABAa receptor = poor performance in task

Three-chambered social interaction test (SIT)

• habituation of the apparatus

• mouse 1 in one chamber

• mouse 1 and 2 in new chamber

What are the key features of a disorder model?

• behavioral impairments similar to real disorder

• biological changes similar to the real disorder

• both are at least partially reversed by drugs which treat the real disorder

VPA model of autism

used to treat bipolar disorder, epilepsy and migraine headaches

• effects epigenetic processes

• linked to birth defects, lower IQ scores and increased autism in children