Exam Flashcards
What is TMS?
A ‘non-invasive’ technique used to create ‘virtual cortical lesions’
What is neural noise?
Uses single-pulse TMS to disrupt cognitive processing
What is the ‘virtual lesion’ approach?
Repetitive TMS (rTMS) is used to interrupt or enhance cognitive processing
(able to inhibit functions for longer period)
What is the ‘probing excitability’ approach?
Uses single-pulse TMS to measure how strongly motor cortex ‘reacts’ to a pulse, i.e. how strong its output is after being stimulated
How is the ‘probing excitability’ approach measured?
Measured by recording motor evoked potentials (MEPs) using the electromyogram (EMG)
What is the ‘probing information transfer’ approach?
Uses two pulses, delivered in brief succession, questions how first pulse influences effect of the second
What is the formula for a t-value?
…….M – µ
t = ————
………Sm
t: t-statistic, which measures size of difference relative to variation in your sample data
M: Sample mean
μ: Average result you would expect if you could survey entire population
Sm: Standard error of mean, which is the standard deviation of the sampling distribution of the sample mean.
What is the one-sample experimental design?
One group with values coming from different people.
This is then compared to a single value
What is the independent-measures experimental design?
Two groups, each value comes from different person
What is the repeated-measures experimental design?
Single group which provides data for both conditions
What are the pros and cons of the one-sample design?
Advantages:
- Can be used to compare group data to known values
Disadvantages:
- May not always know population values
- May want to compare two groups, or to investigate change of behaviour over time
What are the pros and cons of the independent-measures design?
Advantages:
- The measurements are independent
- We don’t have to worry about learning effects due to repeated exposure
Disadvantages:
- People in different groups might be quite different in various ways
- We need large sample sizes to average out these effects, or we need to counterbalance factors that may influence results
- We cannot study behaviour over time
What are the pros and cons of the repeated-measures design?
Advantages:
- We don’t have to think about differences in baseline factors such as personality because this will affect both conditions equally
- We can study changes in behaviour over time
- We can usually test fewer people
Disadvantages:
- Measurements are not independent
- People know the treatment after the first conditions and can’t be naive in the second round. This might not work for all experiments
- We need to carefully counterbalance conditions to avoid unwanted order effects
How do we know if one sample t-test supports our hypothesis
If the result is in the most extreme 5% of the distribution
What type of test do we use when we have a non-directional hypothesis
A two-tailed t-test
What does the independent-measures t-test measure?
How two groups, exposed to different experimental conditions, differ on a particular measure
How does an independent measures t-test differ from a paired-samples t-test?
Independent measures test looks at two different groups under different conditions, paired-samples looks at same group under two different conditions
What is Cohen’s d?
Estimate of effect size that is independent of sample size
d is the mean difference divided by the standard deviation
What are the three cut-off values for Cohen’s d?
d = 0.2 small effect
d = 0.5 medium effect
d = 0.8 large effect
What does an r^2 value represent?
An estimate of the percentage of variation explained by the ‘treatment’
What are the three cut-off values for r^2 as suggested by Cohen?
r^2 = 0.01 small effect
r^2 = 0.09 medium effect
r^2 = 0.25 large effect
What is a confidence interval?
A range where we think the group average lies, based on sample data.
e.g. setting a 95% confidence interval means we can be sure our population mean was contained in this interval 95% of the time (M = 60, 95% CI [50, 70]
What are the three assumptions before t tests are completed?
a. The observations must be independent (people mustn’t influence each others results)
b. The populations from which samples are drawn must be normal (can be violated for larger sample sizes however)
c. If comparing two populations (independent-measures) samples must have equal variances
What are action potentials?
Electrical signals that occur when neurons are excited
What is the basilar membrane?
Structure in the inner ear that vibrates in response to sound, helping to convert sound waves into nerve signals
How do cochlear implants work?
Electrodes placed along basilar membrane, stimulation causes spiral ganglion cells to generate action potential
What are the purpose of rod and cone cells
Rod cells detect light and are used for night vision
Cone cells detect color and are used for daytime vision
What are the two types of colour-blindness?
Deuteranopia: green cones are absent
Protanopia: red cones are absent
What is the retinogeniculate pathway?
Transmits visual information from the retina to the LGN for detailed visual processing
What is the retinohypothalamic pathway?
Conveys light information from retina to the suprachiasmatic nucleus to regulate circadian rhythms
What are ganglion cells?
Neurons in the retina that receive visual information from photoreceptors and transmit it to the brain via the optic nerve
What is the retinotopic organisation of the primary visual cortex?
Cells close together get input from same region of retina
More cortical cells devoted to fovea than periphery
Blobs vs Interblobs
Blobs
- Colour
Interblobs
- Orientation
- Motion
- Depth
What is a cortical column module?
Process information in small region of space, but tile entire visual field
What is the two-streams hypothesis
Ventral stream
Computes detailed map of world from visual input
Dorsal stream transforms incoming visual information for action
What are the four types of ganglion cells?
Red-Green Opponent Ganglion Cells:
R-G: Excited by red light, inhibited by green light
G-R: Excited by green light, inhibited by red light
Yellow-Blue Opponent Ganglion Cells:
Y-B: Excited by yellow light, inhibited by blue light
B-Y: Excited by blue light, inhibited by yellow light
Damage to medial temporal-temporal does what?
Reduces ability to judge movement
What is motion blindness (akinetopsia)?
- caused by damage to MT
- see world in snapshots
- unable to judge speed
- can see biological motion
How are scenes processed?
Low Levels: Separate modules identify basic features
Middle Levels: These features are recombined
High Levels: Brain makes sense of info
What are the three levels of analysis in Marr’s approach?
Computational Level: What is the goal of recognition?
Algorithmic Level: How can the goal of recognition be executed?
Implementational Level: How can the algorithm be carried out by the brain?
What is the role of the inferior temporal cortex?
Synthesis of form, colour and depth
What are the functional modules in the ventral stream and their roles?
V4 - analysis of form; processing of colour constancy;
LO - object recognition
FFA - face recognition, object recognition
PPA - recognition of particular places
EBA - perception of body parts
