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87 Cards in this Set
- Front
- Back
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what is a voxel
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a volume pixel. at 3T about 2mm^3
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what is T1 imaging
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structural imaging. high resolution. distinguish types of tissues
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what is T2* imaging
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function measuring. finding activity, trough the BOLD signal.
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what is Field of View
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size of all stacked slices.
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what is the matrix size?
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number of pixels in a slive
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what is axial view
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view in the horizontale plane
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what is coronal view
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view in the vertical plane, parallel to ones position (perpendicular to which way your looking)
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what is sagittal
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also vertical, but parellel in which way you are looking
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how do hydrogen atoms generate a magnetic field
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they spin around, they are charged. hence they act as a magnetic dipole and they ave a magnetic field
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how do protons get in position in B0 magnetic field
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magnetics field want to align, so protons in a relatively strong field of the MRIs baseline (B0) tend all to go in line with the B0 signal.
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how do we get a signal from protons in MRI
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a radiofrequency pulses at the same frequency as the protons turning, and knocks the protons away from the B0 magnetic field. after this knock they slowly go back to align with the B0 field.
the speed of returning to the alignment with b0 is different for tissues this is known as T1 relaxation time. when protons return to align with the B0 field, they emit radiowaves, which are measurable. |
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what is a T2 signal
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protons influence each others field. decay can be faster because protons influence each other.
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what is T2*
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protons are also influences by other small factors, making them differ. in human body heamoglobin with its Fe can effectivly disturb the relaxation time. this is measurable as a activation of a part of the brain
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how localize signal?
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the gradient in magnetic field makes for a gradient in larmor frequencys. so the location is depending n the frequency.
a mixed signal can be fourier transformated, and the different fequencys tell us where the signal is from |
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what is Positron emission tomography
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PET is where you inject a radioactive tracer and follow it, seeing where there is increased bloodflow ergo increased activity.
it has less temporal resolution than MRI |
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what is BOLD signal?
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blood oxygen level dependent contrast.
goes up when brain area is used. is the indirect measurement of brain activity, and its relative! |
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what better. PET or MRI
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PET bit outdated, but stil has advantages over MRI:
sound can't be done in MRI can move while in PET, so speech but MRI better spatial and temporal |
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how does BOLD signal work. from cell activation to signal
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neuron active use more oxygen
oxygen depleted locally (can be measured as initial dip) vasodilation, more blood + oxygen. oxygenrich blood = heamoglobin with oxygen oxygen of heame, Fe becomes 'free' and has magnetic field, which increases the T2* relaxatino time of protons. so Deoxygenated heamoglobin can be picked up nicely. |
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how goes the heamodynamic respons
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the BOLD signal of a respons starts with a dip (use of oxygen) then huge overcompensation of allot of oxygen flow, and after that a undershoot because increased flow.
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heamodynamic respons varies in...
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across subjects, sessions, brain regions, stimuli.
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what kind of noise can you get in a mri experiment?
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thermal noise (electron motion)
signal drift (random variations in magnetic strength) slice timing (different timing for slices) subject noise (movements, respiration and heartbeat) variability (biological variation between sessions, voxels or subjects) |
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biggest disadvantage for MRI
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with high spatial resolution comes a problem. small spatial distortions can screw up the results. like small movements, or just variation between brains
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steps to overcome noise.
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-correct for movements (realignment
-slice timing correction -stereotactic normalization (coregistration / segment/normalise) -smoothing |
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what is smoothing
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giving each voxel next to active voxel a slight increased signal, following a guassian distribution. this way signal to noise ratio is enhanced. spatial extent increased, easier to normalize/compare
makes more blurry, but active parts better distinguishable. although, inactivated neuron next to active in a moasic like pattern will be less easy distinguishable. but these areas are not common, if existent at all |
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what is stereotactic normalization
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map image on a template brain.
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what is the mathmetical terms of the General linear model?
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GLM:
y=X*b+e y = the eventual date X = design matrix (what can we explain) b = how much do we explain e = error (not explainable) X, design matrix is allot of regressors for things we know that happen: nuisances, task related stuff, |
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3 types of contrasting made with eventual data from the GLM
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one condition contrast (one condition vs baseline)
two condition constrast (condition 1 vs condition 2) parametric (varying between the marges of the conditions) with a fixed contrast, the activation can be mapped |
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what can be called the 2nd level statistics
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group statistics. one subjects doesnt say anything about the whole population, so generalise multiple subjects. in this case, use statistical tests like t-test or anova for reliability of subject results
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what is episodic memory
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first person memory, of a specific moment in time and place.
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what is semantic memory
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knowledge of something. actual information. (in contrast to episodic: episodic = visiting paris. semantic = knowing paris is capital of france)
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what is declarative memory?
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memory that you are able to talk about. consciously accesible
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non declarative memory?
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not consciously accesible. procedural memory, like skills
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how goes from sensory input to long term memory?
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sensory input -> sensory store -(attention)-> short term memory -(rehearsal)-> long term memory
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what is the sensory store?
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very limited capacaty for a particular sensor. mostly big picture kinda stuff, but details wil be ignored fast (the engine at the airplane disapearing).
its sensitive to interference. integrates information over time |
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how sensory to STM?
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via attention. when focussing on a particular thing, it will be more in the awareness of ones mind. for (instance when not focussing on the gorilla, you will not notice it walking through the basketball throwers).
attention will focus on one thing and neglect others. |
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what short term memory (STM)
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limited memory, more of a awareness of something kind of thing. limited to abour 5 to 9 'chunks' (differs))
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what plasticity?
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brain is able to chance its connection between neurons, therefor chancing itself. happens throughout life (more in childhood).
whole brain is capable of plasticity |
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2 kinds of long term memory
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declarative and non-declarative
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anterograde amnesia?
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can't make new memories (from after injury)
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retrograde manesia
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can't remember old stuff (before injury)
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what is affected mostly in amnesia?
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episodic and semantic memory.
short-term mostly spare non-declarative mostly spared |
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name 5 brain structures that are often associated wit memory impairedness when dmg
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fornix
thalamus hippocampus mammillary body frontal lobe |
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how can amnesia occur
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injury, surgery, stroke, virus
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what regions are thought to be infolved in imaging
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aLIPC (anterior left inferior prefrontal cortex)
hippocampus parahippocampal cortex prirhinal cortex |
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role frontal lobes in memorY?
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maintaining information in working memory
selecting information in the environment to focus on provide cues and strategies for memoy retrieval evaluate the content of memories |
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why emotions?
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guide behavior
shape social interactions enhance cognitive process promote morallity |
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what conscious emotions
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subjective feeling
i'm angry! i'm happy! |
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what preconscious
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bodily 'emotions'
responses of body, more autonomous stuff |
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do emotions cause physical changes? does this work other way araound?
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yes.
other way around? maybe. (pencil in mouth = laugh) however there are more emotions than body functions, and the mind is quicker than the body. |
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jamen-lange theory of emotion
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feel something because physical change
(prolly a wrong theory --> adrenaline inject experiment from Schachter and Singer) |
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cannon-bard theory of emotion
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physical and emotion simultaneously
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schachter-singer two-factor theory of emotion
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emotion = arousal + cognition
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what are the six basic, universal emotional expressions (bij paul ekman)
and why are these so universal? |
happy, sad, disgust, fear, angry, surprise
seen in infants, and across cultures |
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are there differences between spontaneous and posed facial expressions?
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yes.
parkinsons = posed remains intact, but spontaneous affected lesion frontal cortex = affected posed, spontaneous intact. |
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name the, unofficial "emotional brain"
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papez circuit
amygdala hippocampus hypothalamus cingulate cortex orbitofrontal cortex anterior nucleus of thalamus |
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what emotino for amygdala
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fear.
kluver-bucy syndrrome = lesioned amygdala in monkeys makes them tame and fearless lesions in amygdala in humans make them not recognize fear |
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what is low and high road of emotions (LeDoux)
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low road is seeing stuff, thalamus, getting on V1 cortex, so in percept, and then having fear respons.
high road is thought to be a sort of fear reflex. instantly from thalamus to amygdala and getting a faster respons fear is important |
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what can happen when frontal lobe damage
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sociopath.
impaired decisions, irresponsible, egocentric, insensitive, impulsive |
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psychopath?
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impaired fear
driven to reward, by any means. no empathy |
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how measure emotions
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questionnaires
skin conductance response heartbeat breathing pupil dilation muscle cotnraction imaging (mri/eeg/meg) |
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what plays role in fear condition
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amygdala.
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what active in exlusion?
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anterior cingulate cortex --> same as physical pain.
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what do emotion do with cognition
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can enhance. fearfull pictures better remembered. arousing pictures also better remembered.
amotional context of picture can state different memory responses |
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short term memory + amygdala?
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no amygdala = higher digit span? so yeah
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whats so special about language
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30 segments/s recognition in speech (non speech 5 seg/s)
passive knowledge of words incredible (50k words) |
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phonological lexicon
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store of speech sounds that make up known words.
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lexical acces
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matching a perceptual description of word (acoustic form) to its stored set of words (in phonological lexicon)
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what are two kind of meanings of spoken word
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the semantic meaning of a word itself
the pragmatic meaning, what is actually intended with what is said semantic interpretation thought to precede pragmatic |
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what is N400 and how is it influenced in speech?
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a particular waveform noticed in EEG, which peaks at 400 ms when something happens with words.
when either the semantic knowledge, or the pragmatic knowledge doesn't fit. rather slow! 400 ms! |
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where do semantic and pragmatic violations turn up in the fMRI
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broca's area. left inferior prefrontal cortex.
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on what 3 ways are words in the lexical system organised?
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semantics
categorical (animal vs fruits/veggys) sensory vs functional |
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how are semantic features organized
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knowledge of words seems to be networked
collins and cuinlan: hierarchical organisation |
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categorical organisation?
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categories of words seem to bee organised in brain.
lesion patients: both show to be error prone for certain categories. |
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where goes dopamine?
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prefrontal cortex and basal ganglia
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where goes serotonine?
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more over the entire brain. not very specific like dopamine.
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less dopamine?
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better attention switching
actually whole attention setting is inhibited, so switching is easier. but cant stay attentionated very well also! |
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less serotonine?
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impaired reversal learning.
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what cognition?
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cognition is the ability to give a specific respons to a specific stimuli in a specific context.
not just a stimulus - response |
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way to study ognitive control
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wisconsin card sorting task
get stack of cards, and rules. rules chance, and match the cards according to the rules. |
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what selective attention
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able to prioritize certain types of information over others when wanted.
has to be flexible and robust. |
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reversals
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able to chance the association between things fast.
like stimulus - reward, to other stimulus - reward |
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what areas of brain for cognition
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lateral prefrontal cortex
orbital prefrontal cortex anterior cingulate cortex. (medial cortex) |
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how dopamine made?
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tyrosine -> dopa -> dopamine
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D1 receptor activation?
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excitatory
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D2 receptor activiation
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inhibitory
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wisconsin card sorting test, what test?
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(categories formed) test ability to learn and discover rules
(perseverative errors) ability to change behavior |
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awesome man
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thanks
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