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Summary Brain & Cognition - Interim I
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- Universiteit Van Amsterdam (UvA)
Summary of the lectures of Brain & Cognition for interim I
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Voorbeeld 2 van de 13 pagina's
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Summary Brain & Cognition ILecture 1: methods of cognitive neuroscience
Cognitive neuroscience: getting grip on the internal world, what happens between stimulus & response
Mental steps: 1. Encode, 2. Compare, 3. Decide, 4. Respond
CAVEAT 1: same brain region different functions
CAVEAT 2: sometimes processing happens parallel, sometimes serial
Convergence: theoretical concept proven with many neuroscientific techniques
Complementary: precision in time, space, one/many neurons measured, direct vs. indirect
measurements brain.
Each method has pros and cons
Brain activity measurements: correlational
Brain activity manipulations and brain damage: causal
Causal 1: human lesions
Caveat 1: rarely isolated to one area
Caveat 2: : different patients never exactly the same damage to same site
Causal methods 2: experimental lesions
Very accurate (animals) precise mapping function to behavior
But ethical? And takes a long time to train animals.
Causal 3: pharmacological
Coffee, cocaine, antidepressants, alcohol effect entire brain
Causal 4: intracranial stimulation
Direct electrical stimulation cortex or subcortical regions (subthalamus nucleus)
Weak stimulation improves brain function, strong leads to temporary or permanent lesion
Causal 5: optogenetics
Local & invasive technique (example rats with laser light)
Causal 6: TMS (= transcranial magnetic stimulation)
1
, Quite accurate (1cm). During task (“online”) makes you perform worse, before task (“offline”) makes
you perform better or worse.
Quite expensive, induces neural activity (action potentials) which can result in epileptic seizure.
Causal 7: TES (= transcranial electrical stimulation)
Spatially inaccurate, cheap and quite safe.
Electricity enters the brain under anode (+), makes it easier for neurons to produce action potential.
Exits the brain under cathode (- electrode), makes it harder for neurons to produce action potential.
Does not produce neural activity, but makes it easier (+) or harder (-) for brain region to become
active.
Causal method pros and cons
Method Pro Con
Human lesion No adaption needed Rarely isolated to one area,
difference between patients
Experimental lesion Very accurate Ethical issues, training takes
time
Pharmalogical “Easy” to do Influences entire brain
Optogenetics Precise Only animals, invasive, ethical
issues
Intracranial stimulation Precise Invasive
TMS Precise, rapid, induces action Expensive, heavy, chance of
potential epileptic seizure
TES Cheap, light weight, safe Imprecise, no control direction,
slow
Brain measurements
1. Single cell recordings: electrode put in vicinity of neuron receptive field action
potential
2. PET: radio active substance is given to patient movement blood brain active = more
blood
3. EEG/MEG: Individual neurons produce “graded potentials” (small depolarizations /
hyperpolarizations in membrane voltage). Local field potentials (LFP, large number produce
graded potentials at the same time) reflect combined input at the dendrites (input not output,
no action potential). Only cortex, because same cell orientation is needed.
Reasons oscillations EEG:
1. When excitatory neurons become active, they will also activate inhibitory neurons. These will
put a break on excitatory neurons, afterwards they will activate again.
2. “Pacemaker” cells in the brain stem and thalamus produce a concurrent neural drive in lots of
pyramidal neurons
3. Communication between brain areas happens in different frequency bands (high frequencies
often local communication, low frequencies global communication)
4. Fluctuations related to heartbeat and respiration
EEG is linear combination of sine waves, differ in: amplitude, frequency, phase + noise.
Frequency bands: gamma specialized processing, delta asleep & global.
EEG fantastic to image the entire brain at the same time and see which areas communicate to each
other.
Different approaches:
1. Event related potentials (ERP): multiple peaks, usually after stimulus repetition. Peaks:
coupled to different information processing steps, reflect the speed of information
processingand order of which brain regions become active.
2
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