cog neuroscience Flashcards
whats useful about a damaged brain
helps us understand how a healthy brain works
N400 electrophysiological signal [how locating processes is valuable]
the N400 electrophysiological signal is triggered when we hear a completely unexpected word in a sentence; this is useful for language psych in measuring when prediction occurs in speech comprehension/planning
recording study method
a study in which behaviour is changed or manipulated, and the effect on the brain is measured
- CORRELATIONAL technique
strength of recording study technique
greater design flexibility and control, offers high temporal and spatial resolution of brain activity
inference studies
changing the state of the brain and measuring the effect on behaviour [EX: comparing brain damage ppts to control group]
- CAUSAL inference
limitation of inference studies
in brain damage, the brain often reorganises itself and has high plasticity, meaning that the function may not be completely impaired, and will be unique for every ppt
two types of stroke
ischemic - blockages in blood vessels cut off blood supply to the brain
hemmorrhagic - the wall of a blood vessel bursts, disrupting flow to brain
single dissociation
looking at one case of impairment; weak inference for exploring if two processes are different
double dissociation
two contrasting cases of impairment; strong inference for concluding that two processes are independent and can also help locating
association
cases with similar performance on all tasks (whether this is impairment or normality)
fractionation assumption
the assumption that brain damage can selectively affect different cognitive and neural systems
transparency assumption
the assumption that brain lesions can affect existing cognitive systems but do not create new ones
universality assumption
the assumption that all cognitive systems are basically the same
critique of transparency assumption
neural plasticity is common, so new pathways are often formed after brain damage
critique of universality assumption
individual differences are too prominent to assume that cognitive systems are the same - ppl have variation in cognitive ability & cognitive strategies
two proposed models of reading irregular words
connectionist ‘triangle’ model - to read irregular words, we use their semantics
dual-route cascaded model - to read irregular words, we use their lexical representation, not their semantics
lesion-symptom mapping
find ppts with similar impairments, acquire structural brain scans, identify specific areas & create a lesion overlap map
lesion overlap map
map of the brain where the areas with the most correlation between ppts is darker (works on a gradient)
lesion overlap map in reading
study looked at specific reading deficits; found that poor irregular word reading was correlated with damage to the anterior temporal lobe
how are lesion overlap maps useful in a clinical setting
can predict the statistical probability of specific brain injuries causing specific deficits
limits of using natural lesions (3)
- can only use between-subjects design, which can be influenced by individual differences
- brain damage frequently extends to multiple areas
- neural plasticity = possible reorganisation of function, so ppts may not have completely lost certain functions
transcranial magnetic stimulation
a rapidly changing magnetic field is applied to the head, and temporarily disrupts brain functions
= temporary virtual lesions
what principle does transcranial magnetic stimulation work off of
electromagnetic induction
= the electric charge of one coil creates a magnetic field which induces an electric charge in the second coil (second coil = brain)
strengths of transcranial magnetic stimulation (3)
- ppts can act as their own control in within-person design, reducing the effect of individual differences
- we can know and test what their normal brain function is like’
- no complications from damage or plasticity
limits of transcranial magnetic stimulation (3)
- only stimulates 2-3cm below skull = cannot reach deeper structures
- higher cognitive functions have less noticeable effects, so exps need careful design
- cannot study long term processes such as learning
how do atoms communicate
by passing on action potentials
this is called firing or spiking
how do EEGs work [electroencephalography]
records changing action potentials
measures microvolts, which are the response of many neurons firing at once
limitations of using EEG (2)
poor spatial resolution (measures when rather than where)
it’s hard to filter out noise from random firing
how do ERPs work [event-related potential]
records positive and negative changes in voltage;
these events are named based on their polarity and extent
how do MEGs work [magnetoencephalography]
similar to EEG but maps brain activity using a magnetic field instead
strength of MEG
better spatial resolution than EEG
how does a PET scan work
positron emission tomography
a radioactive tracer is injected into the blood stream, this then flows to where brain activity is taking places and the decay emits positrons which are measured
limits of PET scans (3)
ppts become exposed to radiation
expensive and complex
the task has to last at least 1 minute for decay to be recorded
how does a structural MRI work
protons within atoms are always spinning
a magnetic field is used to align them
to take a pic, a frequency is sent out to knock them out of place
we then measure where and how quickly they realign
how does a functional MRI work
active neurons require more oxygenated blood, an fMRI measure the ratio of oxygenated : deoxygenated blood to see where activity is occurring
- this is called BOLD imaging
the brain is split into a grid of voxels to locate the BOLD contrast
limit of fMRI
poor temporal resolution as it is a slow process
blocked design in MRI
showing ppts stimuli in blocks (can lead to them expecting the stimuli and changing behaviour)
event-related design in MRI
changing the stimuli each time it is shown to reduce expectations and provoke a more realistic response
subtraction analysis for fMRI
the average of the brain’s ‘on’ activity minus the average of the brain’s ‘off’ activity
default mode network
the brain network activity while resting; it deactivates during specific tasks
multi-voxel pattern analysis (fMRI)
using algorithms to differentiate between patterns of activation to classify subsets of activity
= can tell us WHAT info is being coded (not just where/when)
