Lecture 1&2 - Introduction, Methods, Neural Time Series Analysis Flashcards
What is cognition?
“the faculty of knowing”; set of processes: perceive and process stimuli from outside and inside, store and retrieve (key-) information, hold memory, decide upon and execute actions to achieve goals; often without conscious experience
mind
subjective sense of self
cognitive functions
specific sort of information processing
PLATO (Introspection)
- Nativist (all knowledge available at birth)
- Rationalist (logic/introspection leading to knowledge)
- nature
ARISTOTELE (Empiricism)
- Empiricist (knowledge stems from observation)
- data&hypothesizing (leading to new knowlegde)
- nuture
WILLIAM JAMES (Psychologist/Philosopher)
- Associationism (activation of part of memory acitvating associated elements, may spread to other memory)
HERMAN EBBINGHAUS
- towards experimental psychology; used himself as research object
learning curve; asymptotic learning
forgetting curve; exponential
-> relearning makes things stick in mind
IVAN PAVLOV
- studies on animals
- classical conditioning (pairings)
- > can be overwritten with extinction learning (gradual decrease inresponse to a conditioned stimulus that occurs when the stimulus is presented without reinforcement)
EDWARD THORNDIKE
- instrumental conditioning; learning that certain action leads to certain outcome (positive or negative); law of effect (strenghten the positive, weaken the behavior leading to negative outcomes)
- > certain actions selected (survival of the fittest principle)
Behaviorism (SKINNER)
- examining how changes in stimulus presentation shape how individuals adapt their behavior to the demands of the environement (operant conditioning)
-> everything is stimulus response
(contradictory; cognitivism also concerns the inside (what happens between stimulus and reponse), looking at internal states affecting behavior; cognitive models -> psychological constructs; explain diverse phenomena without reference to their ultimate cause in brain)
-> touches up on operationism; psychological concept only in terms of experimental manipulations that evoke them, ignoring complex mental states, making experiments easier but reduces psychological scope (cannot explainn the structural and generative properties of mental phenomena (ex. language)
Cognitive Science
- making use of computational science (“mind as computer”)
- more insights into perception, memory and motor performance
- explore the complex mental life
- experimental approach (humans, animals, computer simulations of cognitive functions)
Golgi
- silver staining method (golgy staining)
- reticular theory (all neurons in brain and spinal cord from continous information network)
Ramony Cajal
- neuron doctrine; nervous system made of discrete individual cells
- leads to localization of function; different brain regions for different cogntivie functions
Homunculus
- representational map of entire body due to somatopie, which is the relationship of the different (adjacent) parts of the body
- > measuring brain activity when performing a task; studying cognitive changes when brain has been perturbed somehow (recorded via electrodes)
Brain pertubation approach
-> measuring taks performance after brain got pertubated
pertubations = influencing cognivitve function through variety of mechanisms, coming from brain damaged (brain lesions) or get induced (temporary (reversible lesion)/virtual, with drugs effecting neurotransmitters (pharmacological manipulation)
- single lesion can have diverse effects on cognitive functions due to different durations the artery was blocked (other parts might compensate)
- Diaschisis = if one brain part is damaged, others are not normally feeded anymore and also stop functioning as they usually do (highly interconnected brain structure)
-> can lead to wrongly attributing the lost functionality to the lesioned area
- investigated with MRI or DTI (diffusion tensor imaging)
Neuromonitoring approach
-> manipulate cognitive process and measure neural vairbale (from brain)
electric recording of single units
- EEG and MEG recording, MRI and CT (X-Ray), or fMRI and PET can investigate this
electrical and magnetic field recordings
- EEG
- MEG
structural imaging
- MRI
- CT
functional imaging
- fMRI
- PET
intracranial stimulation
- microstimulation in the brain
- rTMS (repetitive, series of pulses)
- tDCS (direct, spatial coarsebess)
(magnetic field generated over a region of the scalp by passing intense, rapidly varying, electrical current through a set of coils, producing extraneous flow of current transiently interacting with local neural processing, disruptive form brain limited to underlying area)
trade-off between methods in cognitive neuroscience?
spatial vs temporal resolution
- different deepness scales (micrometers)
- different layers of the brain (from single cell to neuron to the whole brain)
- different timing scales
pharmacology for pertubation
- chemical componds that work on the brain; certain ones for particular parts/functions
- neurotransmitters (having dedicated receptors); change layout of proteins and therefore enable opening/closing
- hormones & neuropetides
- exegenous compounds
agonist
stimulates receptors
antagonist
blocks receptors
plasticity of the brain
if one area is damaged brain can compensate (ex. blind people hear very well)
Association
brain region being involved in certain tasks, and that part is damaged conclusions can be drawn what this brain area is for (seeing impairments)
Dissociation
function related to particular structure in brain (specific region damaged)
complements imaging
shows which brain area is active for certain task, not necessarily that it is particular required for the brain function (means, that it is also active)
optogenetic modulation
shining laser light onto specific part, specialized for it to manipulate brain part with the laser lights (laser-activated channels in neurons)
-> can activate or inhibit
deep brain stimulation (DBS)
electrodes into brain, used to stimulate just the brain area where electrode sit, it’s pretty precise, patients can turn it on and off
-> over time it will attract inflammation, brain wants to get rid of it
transcranial magnetic stimulation (outside the brain)
and TDCS; anode - positive, cathode - negative
Applying magnetic field induced electrical current in the brain (magnetic fields), affectsing the neurons
- > very broad, not as accurate
- > having short lasting effect
- > repetitive stimulation, frequency determines effect
Neuromonitoring (meaning)
recording from inside the skull
PET
= positron emission tomography
- positrons can be build into molecules (decay over time)
- injected into bloodstream
- > Brain uses lot of energy which it gets from glucose, more active areas will use more
- > Gamma rays to locate which areas use up a lot of glucose, measuring the glucose distribution (giving picture where glucose lights up)
MRI
= magnetic resonance imaging
- induces strong magnetic field (send resonant frequency radio pulse)
- > Aligns all protons in the hydrogen atoms (water, it is all over the brain) aligned to the field, a radio frequency pulse can be measured, measuring the duration of how long it takes until protons are back in the original orientation, telling about the distribution of the protons
- > Taking a lot of sequential slices (plane by plane) and reconstruct the brain by putting all the slices together to get at 3D volume
fMRI
= functional metabolic imaging
- concerns deoxygenated blood
- event-related, block-designed
- contrast maps between codnitions, pooled accross statistical maps, statistical parametric mapping (SPM)
- > Blood is differently active in fMRI considering blood still has oxygene or not, amount of oxygen used can be seen and tells about energy consumption of particular brain area (blood-oxygenation level dependent (BOLD))
- > it has a little bit of a delay and cannot be picked up directly (low temporal resolution), response takes 4-8 seconds
repetition suppression
- neural circuits show exhaustion
- > reduction in signal for similar stimuli
- can be used to look for overlap in semantic items (less reduction for dissimilar stimuli)
neural time-series
-> recordings of ongoing brain activity (any sort of neural data which can be represented over time)
event related/block design
contrasting two conditions, blocking time for no particular vs. particual event
electrical signals in brain
-> reflexes that keep heart going for example
The neuron
build: cell body, spikes going our of it, dendrites, soma, myelins, synapse
- action potential (electrical signals) are the outputs of the neuron, produced in axon, electrical signal is send down the axon, either triggering a muscle directly or passing a signal (triggering another neuron)
- dendrites are the input places of the cell; the inputs have different weights, if there is a certain amount activated at the same time, meaning a certain threshold is exceeded, the potential gets passed on (meaning the activation function is either zero or one, nothing in-between) -> synapses are located on dendrite spines
- soma is the cell body with the dentrites going up from it (protein synthesis in the soma; transmitters travel via transport to the axon terminals)
- myelins on the axon ensure that electrodes cannot escape while traveling down the axon
- all neuron connections are over the synpase (connections are plastic - can change over time)
glial cells
- outnumber neurons 10:1
- > other celss to neurons aiding the nevous system
- astrocytes (blood-brain barrier); attached to blood vessels, ensuring “nothing wrong” goes inside the brain
- oligodendrocytes (myelination of neurons); white matter insolating to keep those signals/charges seperate
- microglial cells (fight infections in the brain); infections cause swelling, space gets narrowed, immune response is caused
membrane potential of neurons
- all neurons have limbic system allowing for different charges in- and outside of the neuron, sustaining neural activity
- resting membrane potential: -60mV inside; maintained by Na+/K+ exchange pump (K+ large inside, Na+ large outside) and active processes (energy costs through ATP)
- > Ions (Na+ and CI-) are permeable to this membrane through gates (protein structures); can be opened or closed (permeability for certain ion changes)
- > ATP puts A- out of the cell and Na+ into the cell (ongoing exchange); if this porcess stops information cannot be stored anymore (neurons lack energy)
electrical charge in the brain
- > osmotic or diffusion gradient; K+ wants to get out and Na+ wants to get into the cell (when they diffuse, they cause changes in the electrical potential)
- when K+ is equally on both sides there is no change in concnetration needed -> when the concentration inside increases, K+ can go out, diffusion gradient pushes K+ out of cell -> since they are positively charged, outside becomes more positive than the inside -> potential difference can be measured (measured as the membrane potential)
- note: CI- cannot diffuse
concentration ratio of one (resting potential)
-> there is no charge difference and not diffusion gradient
concentration of 10 (resting potential depends on concentration difference)
- > diffusion pushes out K+ ions; leaving negatively charged protein inside
- > outside becomes posiitve relative to inside; negative membrane potential (Vm), attracts K+ back into the cell
action potential (spike) - overview
- > intracellular potential
- permeability changes overt the course of the action potential
- travels along the axon (action potential only goes one way, channels which just have been active need to regenerate first taking to long to pass action potential back)
- generated in axon
action potential - permeability
- in resting state K+ ions dominate
- neurotransmitter binds to receptors, opening Na+ channel
- > permeability increases in sodium generating AP (until depolarization -> regeneration)
action potential - generation
- passive propagation of currents (potentials from dendrites to soma)
- acitve regeneration of APs at the nodes of Ranview (meaning the smaller part of the axon the action potential is going down on)
synaptic transmission
- > action potential reaches synapse (neurochemical conjunction of an axon and a synapse)
- littlw vesicles of neurotransmitters are released; chemicals go out in the little space between the cells (the synapse)
- the next cells opens channels to bind the neurotransmitters, maybe leading to next AP in postsynaptic cell
- neurotransmitter get cleared from the synapse and recycled
- an electrical circuit is created in this process (dipole) which can be measured with EEG
- > process: Ca++ influxes though voltage-gated channels, vesicles dock and bin with the membrane, exocytosis of neurotransmitters, transmitter binds postsynaptic receptor (presynaptic autoreceptors), degradation or reputake of neurotransmizzers clears the synapse
recording neurons in the brain
- single neurons close to electrode
- local field potential from larger area (measuring several cells in one area)
- parallel orientation of dendrites sums to an electrical field (due to the diploes all neurons are organized in the same way in the cortex, facing in the same direction, whereby the positive pole is directing more inside the brain (can be captured by EEG; fields weaken with distance, making EEG not very precise, since there is overlap in the recordings of nearby channels)
LPF, EEG and MEG
- accessibility from easy to hard: EEG -> MEG -> LFP
- high temporal resoltuion (good for quick dynamic of cognitive processes) -> 4ms per AP
- can measure whole brain (cortex) at ones when enough channels are available (simultaneous recordings from mutliple spatial locations) -> excludes deep structures
- low spatial resolution; electrical field potentials have to be strong enough to get up the scalp and be able to be captured by the electrodes on the head (the folded shape of the cortex migh cancel out electrical fields)
event-related potentials
- > taking all signals, sum them up and get ERP
- relating potentials to particular cognitive events (responses are delayed, so clear time stamps are needed, allowing for temporal filtering)
- > time-locked average brain responses to a certain trigger; requires precise temporal alignment, many trials repetitions and contrasting conditions
problems with these measuements (defining specific cognitive event for brain area)
- mass activity of groups of neurons is transformed non-linearily in electric fields
- many cogntive operations migtht be active at one point
- there might be exogenous electrical pertubation
- > the brain is always active; noise in the brain (source seperation needs to take place)
- > temporal and spatial filtering can be applied to contrast control conditions, conduct baseline subtractions and estimate source logalizations through comparison of simultaneous spatial sources
- EOGH
2. EOGV
- electrooculography horizontal -> saccades
- electrooculography vertical -> blinks
(measuring the eye to eliminate brlinking, which is noise in the EEG data (showns as a drop))
