Week 1 Lecture 1 - research methods Flashcards
What kind of account does cog neuro provide?
brain-based account of cognitive processes
What does cog neuro test and not test?
- psychological theories
- however, uses local blood oxygen and RTs which are just data, this does not tell us how things happen
- only measures data –> need to combine several methods to actually understand what’s happening (1 method is not superior)
What is the method type, invasiveness and brain property used for EEG/ERP?
recording
non-invasive
electrical
What is the method type, invasiveness and brain property used for single-cell and multi-unit recordings?
recording
invasive
electrical
What is the method type, invasiveness and brain property used for TMS
stimulation
non-invasive
electromagnetic
What is the method type, invasiveness and brain property used for MEG?
recording
non-invasive
magnetic
What is the method type, invasiveness and brain property used for PET?
recording
invasive
hemodynamic
What is the method type, invasiveness and brain property used for fMRI?
recording
non-invasive
hemodynamic
Recording methods vary in terms of spatial and temporal resolution.
Which is more important?
- depends on research questions –> where vs. when
- should research question to decide primary method of investigation but ultimately multiple methods will be used
What are single-cell recordings?
- small electrode implanted into axon (intercellular) or outside of axon membrane (extracellular)
- records neural activity from population of neurons
How are recording made for single-cell recordings?
- measure the electrical potential of nearby neurons that are close to the electrode proximity
Can electrodes measure a single neuron in a single-cell recording?
no
electrodes aren’t yet precise enough for this
instead measurements come from a general population
Who are single-cell recordings used on?
animals
What is the most used neuroimaging technique in humans?
EEG
What are EEGs?
- measure electrical activity of the brain by recording from electrodes placed on the scalp
- resulting traces known as an EEG –> represent an electrical signal form a large number of neurons
What type of research is EEGs often used in?
baby research
Do EEGs require specific scalp placements?
Yes
What do EEG signals represent?
the change in the potential difference between to electrodes placed on the scalp in time
Are several trails used in an EEG?
yes
the EEG obtained on several trails can be averaged together (time locked to the stimulus) to form an event-related potential (ERP)
What are ERPs?
voltage fluctuations that are associated in time with a particular event e.g., visual, auditory etc.
Why do EEGs need to be averaged out?
to cancel out the background noise that it also measures
this means that the ERP generated in only measures signals related to the target stimulus
Are different ERP peaks associated with different aspects of face processing? Give examples
Yes
- N170 is relatively specialised for faces recorded from right posterior superior temporal sulcus (right PSTS)
- P300 peaks for famous and familiar faces
What did a comparison between the ERPs from patients with Alzheimer’s and control subjects find?
- reduced P300 is seen for the demented patients at each electrode site
What is an MEG?
- measures the magnetic fields produced by electrical activity in the brain via extremely sensitive devices known as SQUIDs.
- these measurements are commonly used in research and clinical settings
- excellent temporal and spatial resolution however is very expensive and so not as popular in research
What is an MRI?
uses differential magnetic properties of types of tissue and blood to produce images of the brain
What are the 2 types of MRI?
- structural
- functional
What is a structural MRI?
- different types of tissue have different physical properties
- these are used to create static maps of the brain
- cannot say a lot about behaviour
What is a functional MRI?
- temporary changes in brain physiology associated with cognitive processing
What are the 2 types of functional MRI?
- fMRI
-PET
What is PET?
- measures local blood flow (rCBF)
- radioactive tracer injected into blood stream
- areas of high radioactivity are associated with brain activity –> based on blood volume
How long does it take the radioactive tracer that is injected to peak (PET)
30 seconds
What does it mean when it is said that PET scans measure radioactivity based on blood volume?
- brain is constantly in need of oxygen
- oxygen brought to brain via blood
- it is thought that blood flows to the areas in the brain most in need of oxygen
- will see the radioactive tracer in these areas as it entered the blood
What is an fMRI?
- directly measures the concentration of deoxyhaemoglobin in the blood
- called the BOLD response
What is the BOLD response?
blood oxygen level dependent contrast
What are changes in the BOLD response over time called?
the hemodynamic response function
When does the hemodynamic response function peak? What does this limit?
- peaks in 6-8 seconds
- limits the temporal resolution of the fMRI
Does fMRI study correlation or causation?
studies correlation between brain activity and stimulus timings
What can fMRIs be used to produce?
activation maps showing which parts of the brain are involved in a particular mental process
In an fMRI, what is activity measured in?
voxels (volume pixels)
What are voxels?
the smallest distinguishable box-shaped part in 3D image
In order to infer functional specialisation, what do we need to compare?
- relative differences in brain activity between 2 or more conditions
- this involves selecting a baseline or comparison condition
When is a brain region active?
- if it shows a greater response in one condition relative to another
- is the experimenter chooses an inappropriate condition the regions of activity will be meaningless
How are fMRI studies designed?
consider what are the brain regions involved in specific area of interest e.g., for words you would consider brain regions involved in:
- recognizing written words
- saying the words
- retrieving the meaning of the words
What are cognitive subtractions?
activity in a control task is subtracted from the activity in an experimental task
exp - control
What is a problem for cognitive subtractions?
the difficulty of the baseline task
What did a study by Devlin et al., find when comparing two imaging methods in a semantic task?
- fMRI results activated brain areas such as cerebellum, IFG, BA8, rIFG
- PET scan results activated different areas such as the anterior temporal pole and inferior temporal gyrus (did also activate cerebellum and IFG)
What is DTI?
- an imaging method that uses a modified MRI scanner to reveal bundles of axons in the living brain
- imaging of how the brain is connected
- we can visualise connections in the brain
What does DTI measure?
white matter organisation based on limited diffusion of water molecules in axons
What is fNIRS?
- measures the same BOLD responses as fMRI but in a different way
- “light” in infrared range passes through skull and scalp but is scatter differently by oxy- v. deoxyhaemoglobin
What are some pros and cons of fNIRS over fMRI?
pros
- more tolerant of head movement
cons
- can’t image deep structures
What is iEEG / ECoG?
- intercranial recording
- gives high spatial and temporal resolution
- record directly from inside the human brain when people are undergoing neurosurgery
- they are placed to locate the seizure and map function
- recording straight from the cortical surface ~ 10 of thousands of neurons
What did a study by Mukamel et al. find using intercranial recoridngs?
neurons in supplementary motor area (SMA) and hippocampus both respond to observation and execution actions
role of hippocampus was surprising
What is TMS?
a means of disrupting normal brain activity by introducing neural noise
Who enabled to development of TMS?
Faraday and invention of Farady’s coil –> alternating currents
How does TMS work?
- TMS coil has magnetic field pulse which changes
- this induced an brief electric field on a second coil which induces a current
- continued alternating current allows TMS to work
- needs to be switched on and off at a high rate
- this interferes with the electromagnetic fields in the brain
When applying TMS to areas of the brain that support reading, what do we expect to see?
- TMS will interfere with the relevant neural signal
- efficacy of the neural signal will be degraded
- observe change in behaviour –> RT change - it will take us long to read
What are some advantages of TMS?
- interference technique
- transient and reversible
- control location of stimulation
- establishes a causal link of different brain areas and a behavioural task
What was the method and results of a TMS study on language?
- ppts left or right language dominant
- picture-word verification task
- TMS applied
Results:
- language disruption correlated with degree and side of lateralisation
- Left dominant, left TMS = slower
- Left dominant, right TMS = faster
- same pattern found for right dominant
What does the results from the TMS language study suggest support for?
Hemispheric balance theory:
- 2 hemispheres inhibit each other
- stimulation of dominant side = slower
- stimulation of other side = faster
- can be applied to all brain functions
What is TES?
- uses low level currents applied via scalp electrodes to specific brain regions
There are several different protocols for TES, what are they?
- transcranial direct current stimulation (tDCS)
- transcranial alternating current stimulation (tACS)
- transcranial random noise stimulation (tRNS)
What is the current generator in TES?
a battery delivers constant current of up to 2mA, with 2 sponge electrodes in saline solution.
Simulation is less focal and very safe
When applied in sessions of repeated stimulation, what can tDCS lead to?
changes in neuronal excitability that outlasts the stimulation itself
has promising results in therapy: migraines, dementia, depressions etc.
What are the different types of direct current that can be applied in tDCS?
- anodal –> facilitation effects
- cathodal –> inhabitation effects
- Sham (control) –> 30s stimulation
What does Anodal stimulation inhibit?
GABA –> inhibitory neurotransmitter so leads to faciliatory effects
What does Cathodal stimulation inhibit?
Glutamate –> excitatory neurotransmitter so leads to inhibitory effects
What does tACS use?
low level alternating current applied via scalp electrodes to specific brain regions
What is the rational behind tACS?
- the entrainment (synchronization) of internal brain rhythms with externally applied oscillating fields
- these fields cause phase-locking of a large pool of neurons, leading to increases of neural synchronization at the corresponding frequency
What can tACS be used to induce?
lucid dreaming
When people lucid dream, what do they show?
- overlap of waking consciousness transfer into the dream and is reflected in brain waves
- show gamma waves in the frontal cortex –> activity pattern which is linked to consciousness but absent during sleep and normal dreaming
What did a study which applied tACS to participants 2 minutes after entering REM sleep find?
- EEG data showed that the brain’s gamma activity increased during stimulations with 40Hz and to a lesser degree during stimulation with 25Hz
- insight and dissociation were induced using 40Hz
- control induced using 40Hz and 25Hz
