Ch. 3- Tools in Cognitive Neuroscience

Question 1

natural lesions

Answer 1

lesion due to stroke, brain tumors, brain injury, or degenerative disorders

goal=to examine behavioral and cognitive deficits and infer from them what that part of the brain is doing -> can allow for inference reg. relationship between brain and behavior

Question 2

limitations of natural lesions

Answer 2

1. assumes a mapping between anatomical and cognitive models
2. not possible to control size or location of lesion- damage doesn’t respect modules
3. originally not possible to know brain area affected until after death
4. assumes intact regions continue to fcn normally
5. brains are plastic and can lead to recovery of behavior
6. lesions do not allow us to determine temporal aspects of info processing

Question 3

experimental lesions

Answer 3

create small controlled lesions in animals to study its effects

Question 4

limitations of experimental lesions

Answer 4

1. difficult and time consuming to train animals
2. ethical concerns
3. avoid naive mapping of complex processes onto discrete brain regions

Question 5

benefits of experimental lesions

Answer 5

1. more control over the location & extent of lesion
2. better test hypothesis concerning specific regions and groups of regions
3. can do reversible lesions which are less invasive and permanent

Question 6

Transcranial Direct Current Stimulation (TDCS)

Answer 6

passes electrical current through brain between two scalp electrodes. Placement of electrodes can result in widespread of local inc in cortical exciteability

can be used to disrupt activity in a region to further understand its role

used as a tool to enhance performance and decrease deficits following brain injury and disease

Question 7

Transcranial Magnetic Stimulation (TMS)

Answer 7

pass a v strong electrical current through a coil that generates a magnetic field in the head -> interacts w neurons

Question 8

single pulse TMS

Answer 8

transiently influences neurons
brief effect
effective for mapping perceptual and motor areas, evaluating cortical excitability, and understanding temporal relationships

Question 9

repetitive TMS

Answer 9

results in longer term inc or dec in cortical excitability
useful for understanding how brain areas interact during cognition
can be used as a form of temporary lesion

Question 10

figure 8 coil

Answer 10

used to improve spatial specificity, results in more focused magnetic & electrical field

Question 11

advantages of TMS

Answer 11

1. noninvasive
2. temporary effects
3. can infer causality

Question 12

disadvantages of TMS

Answer 12

1. similar disad. as lesions
2. can’t reach deep structures
3. can indirectly activate large areas of cortex
4. don’t always know where you’re stimulating
5. has risks associated (seizure)

Question 13

EEG

Answer 13

measures electrical signals of the brain using electrodes on scalp
record potential (volts)= difference between two electrodes
v high temporal resolution (milliseconds)

Question 14

neural basis of EEG

Answer 14

affects pyramidal neurons of cortex- extracellular current flow is related to dendritic currents
requires a large number of synchronous neurons
reflects diff states of brain-can be used to determine how changes in brain state are related to behavior

Question 15

event related potential (ERP)

Answer 15

small signal that requires an averaging of data over multiple trials-> useful for investigating timing/reaction rate of brain

responses named according to polarity (P,N) and latency (100 ms, etc)

Question 16

inverse problem

Answer 16

you can’t determine a unique set of sources in the brain from an external pattern. activity -> brain area is flawed bc a lot of different brain areas can produce that activity

Question 17

MEG

Answer 17

relies on SQUIDS to detect v smol magnetic fields

better spatial resolution bc magnetic field is unimpeded by tissue

sensitive only to tangential sources, not to radial sources

suffers from inverse problem but simplifies it

Question 18

PET

Answer 18

decay of radioactive isotopes in blood that when positrons collide, will emit photons that are detectable by scanner

Question 19

advantages of PET

Answer 19

1. brain-based method of activity
2. can image deep structures
3. new isotopes are being generated to allow for imaging of diff compounds
4. many clinical uses

Question 20

disadvantages of PET

Answer 20

1. secondary measure of neural activity
2. invasive
3. limits # of exposure
4. v poor temporal resolution
5. only moderate spatial resolution

Question 21

fMRI

Answer 21

a measure of oxygenated blood flow

during inc activity, the amt of oxygen being delivered to the local area inc, and amt of oxygen removed from blood dec -> oxygen rich blood is LESS magnetic and results in larger BOLD signal

timescale of BOLD both delayed and extended- abt 11 seconds long

better temporal resolution than PET but still much less than EEG/MRI