week 2 - methods to study cognition Flashcards
three different approaches
experimental cognitive psychology
cognitive neuropsychology
cognitive neuroscience
experimental cognitive psychology - what
studying behaviour in controlled lab conditions
shed light onto cognitive processes by using clever experimental manipulations
uses behavioural measures (instead of brain measures)
- reaction time
- accuracy
(indirect measures)
experimental cognitive psychology - an experiment
stroop test
tests whether word reading is automatic
if it interferes with colour naming
experimental cognitive psychology - strengths
successful at generating theories about cognition that can be tested in neuroscience (only when cognitive psychologists had developed reasonable accounts of healthy human cognition that the performance of brain-damaged patients could be understood fully.)
has made a huge contribution to making psychology a more empirical science (quantitative)
first systematic approach to understanding cognition
the source of most theories and tasks used by the other appoaches
flexible and can be applied to any aspect of cognition
has produced numerous replicated findings
has strongly influences social, clinical and developmental psyc
experimental cognitive psychology - weaknesses
ecological validity - can we generalise findings outside the lab (behavioural differences)
face validity - only provides indirect measures of cognitive processes, so how do we know what we are measuring is correct as the mind is very complicated
do psychological concepts even exist? - cant assume something exists because we have given it a name
difficulty in falsifying
paradigm specificity - sometimes findings do not generalise
lack of an overarching theoretical framework
most cognitive tasks are complex and involve many different processes
theories vague and hard to test empirically
cognitive neuropsychology - what
Studying cognition in patients with brain injury
(lesions)
this tells us about cognition in healthy individuals
cognitive neuropsychology - goal
to find which cognitive functions are impaired and which ones are preserved when a given brain region is damaged
tells us which area affects what
cognitive neuropsychology - research
search of dissociations
which occur when a patient has normal performance on one task (task X) but is impaired on a second one (task Y).
must avoiding sweeping conclusions!!
- differences in complexity
- opposite patterns
cognitive neuropsychology - single case studies vs case series
single case
- only access to one patient with pattern of cognitive impairment
- assume certain uniqueness to each case
in recent years move towards case series
- several patients with similar cognitive impairment are tested
- then data is compared and variation across patients is assessed
- provides richer data
- able to identify and de-emphasise outliers
cognitive neuropsychology - strengths
allows us to draw causal inferences about the relationship
between brain areas and cognitive processes and behaviour.
ability to provide evidence falsifying plausible cognitive theories.
“produces large-magnitude phenomena which can be initially theoretically highly counterintuitive”
combined fruitfully with cognitive neuroscience
Discovering the true extent of the brain areas adversely affected by a lesion facilitates the task of relating brain functioning to cognitive processing and task performance.
double dissociations have provided strong evidence for various processing modules
causal links can be shown between brain damage and cognitive performance
straddles the divide between cognitive psychology and cognitive neuroscience
cognitive neuropsychology - limitations
no baseline - we don’t know exactly what the patient could do before their injury, therefore have to make assumptions
theoretical assumptions seem too extreme
generalisation - lesions in some areas of the brain are relatively common while others are rare. same deficits in different people?
modularity - cognitive process X is likely distributed across multiple areas not just one - detailed cognitive processes and their interconnectedness are often not specified
lesions can alter the organisation of the brain
- compensatory major strategies not found in healthy individuals
brain plasticity complicated interpreting findings
cognitive neuroscience - what
relates brain structure and brain function to cognitive processes
cognitive neuroscience - how
typically done by recording brain activity while participants perform cognitive tasks
cognitive neuroscience - the brain
very complicated
highly connected
cognitive neuroscience - strengths
great variety of techniques offering excellent temporal or spatial resolution
functional specialisation and brain integration can be studied
TMS is flexible and permits causal inferences
rich data permit assessment of integrated brain processing as well as specialised functioning
resolution of complex theoretical issues
cognitive neuroscience - limitations
functional neuroimaging techniques provide essentially correlational data
does it help us understand cognition? - need to q whether the info that we are gaining actually helps us understand cognition
much over-interpretation of data involving reverse inferences
there are many false positives and replication failures
it has generated very few new theories
/ is a theory being tested? or just saying it exists
difficulty in relation brain activity to psychological processes
expensive / invasive - often mean sample sizes small (generalisable?)
cognitive neuroscience - tools to study the brain
electrophysiology - single cell and EEG
structural imaging (MRI)
functional imaging (fMRI)
brain stimulation (TMS)
cognitive neuroscience
- electrophysiology
- single cell recordings
○ Very small electrodes that you can implant in the brains of people and animals that record from one neuron
can record neural activity from within axon (intracellular) or from other axon membrane (extracellular)
usually, only obtained from animals? - when is this justified
- sometimes can record patients with epilepsy (during surgery)
Patients have to sit in the hospital waiting to have a seizure in order to identify the cause
- So these patients get involved in research where cognitive scientists come along and ask if they want to do cognitive tests
Rare opportunity
cognitive neuroscience
- electrophysiology
- electroencephalography (EEG)
electrical activity of a large no. of neurons all firing together
recorded via electroded on the scalp
allows us to measure neural activity in esssentially real time (ms scale)
non invasive
cognitive neuroscience
- electrophysiology
- electroencephalography (EEG)
what does it record?
event-related potentials (ERPs)
measure EEG response to same stimulus task over and over
average waveform to generate an ERP
we can compare the ERPs between differnet psychological conditions
eg Paying attention vs not paying attention
cognitive neuroscience
- electrophysiology
advantages of EEG/ERP
very good temporal resolution (ms)
portable and relatively cheap
cognitive neuroscience
- electrophysiology
limitations of EEG/ERP
poor spatial resolution (cm) (where in brain)
- infinite possible origins for any signal recorded on scalp
- The electrical activity doesnt necessarily come from underneath the electrode it was detected
- Not a lot of info of which part of brain is responsible
cognitive neuroscience
- magnetic resonance imaging (MRI)
Works by putting someone in an extremely strong magnet
- An enormously powerful magnetic field
- Very dangerous –> lots of safety screening to be allowed near it
cognitive neuroscience
- magnetic resonance imaging (MRI)
basic principle
The reason for the extremely powerful magnet is because basically in your brain and entire body you have protons in water molecules and these protons are spinning
When you put them in a very powerful magnet these protons start sponning and lining up with the direction of the magnetic field
In an MRI scanner the magnetic field goes through the hole in the middle and all of the protons in the water molecules in your brain start lining up with that magnetic field
The way MRI works is that it then distrupts the spin of these protons by firing short radio frequency pulses at your head (these aren’t dangerous)
This makes the proton wobble
The amount that it wobbles will change the magnetic field that is being generated by your protons in the water molecules
We can measure how long it takes for those protons to stop wobbling
Because we know protons in different types of tissues stop wobbling at different rates
- They take different amounts of time to go back to point in the direction of the magnetic field of the magnetic
○ “to relax”
If we do this in a clever way using gradients ect.
We can create images of what tissue we think exists at each point inside this persons head
- Based on how much time it takes for the protons in that part of the head to return to facing in line with the magnetic field of the scanner after we’ve turned off the radio frequency pulse
cognitive neuroscience
- structural MRI
Can look at the outside and inside of brain
Extremely powerful in terms of its spatial resolution
- What we can vabout where things are in the brain
cognitive neuroscience
- structural MRI: diffusion tensor imaging (DTI)
can image white matter fibres (bundles of axons) by measuring the direction of water diffusion
allows us to study how cognition/perception is supported by connections between brain regions
cognitive neuroscience
- functional MRI
does not measure neurons directly
measure the blood oxygenation level-dependent signal (BOLD)
- active neurons need O2
- the brain starts supplying O2 to acyive areas producing an overshoot is oxygenated blood
- oxygenated blood causes less magnetic field disturbance than deoxygenated blood so active brain regions will have higher signal
cognitive neuroscience
- functional MRI
advantages
very good spatial resolution (mm)
where
cognitive neuroscience
- functional MRI
limitations
poor temporal resolution (seconds)
when
not a measure of neurons themselves
- requires an indirect inference that neurons are firing because that part of the brain is using more oxygen
cognitive neuroscience
brain stimulation techniques
to know if a particular part of your brain is important for a cognitive process we need to change the activity of that part of the brain and show that it changes behaviour
we need causality (not just correlation)
cognitive neuroscience
brain stimulation techniques
Transcranial magnetic stimulation (TMS)
An electromagnet which produces very powerdul and focal magnetic fields
short magenetic pules that briefly affect electrical activity in a localised patch of the brain tissue under the coil
If you put this on top of someones head you can produce a magnetic field that goes inside the skull
When it gets inside the skull depending on the type of magnetic field that you produce you can either:
- Induce electrical activity in the cells it passes through
- You can stop cells firing (give people brief brain injuries)
can have positive or negative task performance
This gives causality
Eg. Using fMRI find corrolation, then use TMS to see if you can abolish this process
○ This gives causal evidence
cognitive neuroscience
brain stimulation
advantages
causal evidence that a particular brain region is important for a cognitive function
mostly non-invasive
- safe and painless for healthy populations
