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Cognitive Neuroscience Samenvatting
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HC 1:Cognition: knowlegde/ function (visual perception, attention, memory etc.)
Neuroscience: the research/ methods (fMRI, EEG etc.)
Cognitive Neuroscience: defining networks in information processes using neuroscientific
methods → measure and manipulate the brain
Franz Joseph Gall: areas on the skull represent skills and function
- So an indent or bump in the skull meant there was a certain function there
- Measure the inconsistencies on the skull
Phrenology: study of measuring the skull
Brain anatomy: the connections between neurons
Brain elements: hormones and neurotransmitters
- Medication and nutrition (like food) can influence this
Brodman: the first one to map the brain based on cell types (43x)
- Cells that are close to each other in location have similar functions
- Every neuron has its own function
- The structure and the location of the cell was related to its function
Motor neuron: communication for movement/ vision/ audio through central and peripheral
system
- Every neuron has 4 aspects:
1. Input: forms connections through dendrites
2. Output: presynaptic terminals
3. Transfer: axon
4. Modulator: cell neuron, processes information
- Only neuron that has myelin sheathing → protects the axon → because it is a relatively
long neuron so it needs to travel a long distance
Pyramidal neuron: has many dendrites so can make many connections (forebrain)
Cerebellum: is used for coordination
- Also has many dendrites and many connections (needed for coordination)
Bipolar neurons: used for sensory signals
- Has two extensions → only one dendrite
Electrophysiology: uses electrodes in brain cells and measures the electricity inside the cells
- This way you can detect brain activity through action potentials (the firing of the cell)
- Lots of activity when the stimulus is located in the receptive field
TMS/ tDCS: external shocks that are send into the brain (by researchers) to research functions
of certain areas in the brain
Neural pruning: the process of altering and changing neurons
Temporal resolution: how fast something is
- EX: how fast does the brain process certain information/ how fast can EEG measure
brain activity
Spatial resolution: location where activity is taking place (in brain or in environment)
EEG: electro-encephalography
- Measures potential differences due to neural activity
- Continuous recording of the voltage difference
, - Voltage happens when a neuron fires (action potentials)
- To have a good EEG reading you need: mass and synchronizes activity, activity needs to
be close to the skull and there needs to be a quiet surrounding
- Can’t measure only one neuron, only from a group of neurons
- Neurons need to fire in the same direction at the same time → then the EEG will
pick up the activity through the skull
- LFP: local field potential → synchronized synaptic current (summation of neurons)
- Activity on the outside of a cell due to cell activity
- Small waves on the results are brain activity and big waves are muscle movements
- ERP: event-related potential
- Activity in the brain due to a stimulus
- The baseline consist of the time period before the stimulus
- Advantages of EEG: high temporal resolution, safe (does not harm the brain)
- Disadvantages of EEG: not very precise spatial resolution
- PSP: post synaptic potential
- Created by voltage differences in the neuron
- The beginning is negative and the end is positive (the difference)
- Inhibitory: decreases chance that surrounding neurons will fire
- Excitatory: activates other neurons to fire and sends electrical signals through
brain
Mass activity: many neurons with the same alignment
Synchronized activity: neurons are grouped together and fire together
Gyri: cortical peaks (bumps in the brain)
- This is where EEG has the best results
MEG: magnetoencephalography (magnetic field)
- Has a better localisation than EEG
- Less diortations because it does not need to be on the skull, can measure deeper into
the brain
- Sensitive for the cortical valleys
- But EEG is cheaper and measures more neurons at the same time
EEG brain state (arousal)
1. Beta: when the participant is concentrating and paying attention/ relaxed (16-31 Hz)
2. Gamma: extreme concentration (32 Hz) → low amplitude (high arousal/ high frequency)
3. Alpha: person is relaxed, and not paying attention (8-15 Hz)
4. Theta: drowsy, sleepy (4-7 Hz)
5. Delta: deep sleep (<4Hz) → high amplitude (low arousal/ low frequency)
Slow waves → low arousal
Fast waves → high arousal
- Always a mixture of different frequency waves, some are more dominant based on
arousal
- Frequency reflects different arousal states
Theta/Beta ratio: reflects different type of arousal state
- Low ratio is more arousal
- High ratio is less arousal
, - ADHD patients are hyperactive because they have a high ratio which means they are
less aroused → try to compensate
Epochs: activity moment in EEG when stimulus is being shown
- All the result combined will result in an ERP
- Needs many trials to get an average
HC 2:
MRI: magnetic resonance imaging
- Interactions of magnetic field with tissue
- Measures the (magnetic) parts of the brain tissue
- Imaging technique: a reconstruction of the brain
- Good spatial resolution, EEG has better temporal resolution
Structural MRI: shows tissue based on magnetic properties (gray/ white matter)
- Also used for surgical planning because you can see the location of the brain very well
- Used for analysis of tissue change (EX: gray matter grows during developement)
- Localized structures for operations
- Shows fluid in the brains
- Creates images of the different tissue types
DWI: diffusion weighted imaging
- Measures direction of water movement
- Compares water responses to magnetic field in different directions
- Can find the direction of neurons in the brain by the diffusion of water→ what
connections are there between the neurons
- Maps direction of neural pathways
fMRI: functional MRI
- How tissue magnetic interactions change over time
- Looks at the change in oxygenated blood flow
- It infers that neural activity changes because when a stimulus is shown, blood will flow to
the part of the brain that needs to work to process this information
- Advantages: high spatial resolution, safe, easy interpretation, easy access
- Disadvantages: indirect measure of neural activity, bad temporal resolution, because of
loudness → low signal to noise ratios
- Images changes in brain activity with a task of stimulus
BOLD: blood oxygenation level dependent
- Blood either is deoxyhemoglobin (not oxygenated) or oxyhemoglobin (oxygenated) this
is what makes it magnetic
- Oxyhemoglobin will increase after a stimulus is shown, but first there will be an loss of
oxygen and signal will be lost, then there in a blood flow of oxygenated blood
(overcompensation)
- Blood response follows neural activity
Neural activity in fMRI:
1. MUA: multi unit activity: action potentials (spikes)
2. LFP: slow electrical signals/ subthreshold activity
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