College aantekeningen
College aantekeningen Cognitive Neuroscience ()
- Instelling
- Universiteit Utrecht (UU)
Uitgebriede aantekeningen/samenvatting van de stof van college 1 t/m 6 van het vak Cognitive Neuroscience
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Voorbeeld 3 van de 24 pagina's
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Voorbeeld van de inhoud
Samenvatting CNS 1-6HC1
Bordmann was the first to map the cortex based on cell types (43x). The structure of the
brain and where neurons are located are related to the function they have.
Every neuron in the brain has 4 aspects. In at least most of them you see:
- They use dendrites to receive input from other neurons. Connection is possible with
multiple neurons.
- They use presynaptic terminals to give output to another neuron.
- They use axons for the transfer of an electric signal
- They use the cell nucleus to modulate inputs to eventually come with an output
Neurons are different from normal cells; axons and dendrites are specialized structures to
transmit and receive information through action potentials. They tend not to reproduce
after birth, but connections do alter. Therefore, neural activity gets worse once you become
older.
Each cell type has its own specific function:
- Motor neuron has myeline schedes around the axon to protect the axon and allow
to transfer the signal/potential much faster and over longer distances
- Pyramidal/cognition neuron has no/less scheding, but has dendrite branches going
out, connecting from the nucleus to transfer information and have input from other
neurons to modulate the signal that goes from the top to the bottom
- Purkinje/coordination neuron has a lot of dendrites to coordinate signals from a lot
of different inputs
- Retinal neuron is a one-way information processing system, so the neuron doesn’t
need that much feedback from other neurons and is a much simpler cell
,Damage to the anatomy (clinical neuropsychology) can lead to:
- Stroke;
o Hemorrhagic stroke: blood leads into brain tissue
o Ischemic stroke: clot stops blood supply to an area of the brain that causes
brain tissue to die
- Tumors or infections
- Trauma (football)
- Neural degeneration (Alzheimer)
- Epilepsy and lesions
- Genetic manifestations
Measuring brain activity can be done by measuring:
- Action potentials (electrophysiology)
- Local field potentials (electrophysiology)
- Electromagnetic fields at scalp (EEG/ERP)
- Manipulating neural activity (TMS/tDCS)
- Blood oxygenation (fMRI; PET; fNIRS)
The brain has several elements that can be measured:
- Neurotransmitters: can be measured where they are and with how many
- Hormones: can be measured in the blood
- Pharmacology: e.g. injection of testosterone
- Food supplements: e.g. choline acetylcholine
EEG: electroencephalography
- Electro: electromagnetic fields
- Encephalo: related to the brain
- Graphy: descriptive science
It measures potential differences due to neural activity; it measures where the voltage
differences come from. The moment a neuron becomes active, there is a flow of elements
with +/- charts. This causes a net response with a negative chart at one side of the neuron
and a positive chart at the other side voltage difference; a lot of neurons fire at the same
time. EEG measures voltage differences across the scalp.
- Reflects post-synaptic potentials (PSP): difference in voltage along axons
- Both inhibitory and excitatory PSP’s
- Reflects local field potential no single AP but a summation of many neurons
When is the measurement of the EEG good?
- Mass activity: many neurons with the same alignment
- Synchronized activity: not individual AP
- Close to the scalp: scalp and skull are bad conductors smears out the signal
- No noise sources
EEG electrode layout:
- 32-64 electrodes: enough for time-effects (temporal)
- 128 electrodes: enough for localization (rough spatial resolution)
, Advantages of EEG and MEG:
- EEG voltage potentials
o Timing: you can record signal activity at very high rate (high temporal resol)
o Measures brain states (frequencies) and temporal characteristics of brain
processes (event related potentials)
o Most sensitive to activity in gyri (cortical peaks)
- MEG magnetic field
o Similar measure, but direction is more important
o Better localization (less distortions by skull)
o Most sensitive to activity originating from sulci (cortical valleys)
- EEG = relative cheap, measures more neurons
- MEG = more expensive, better localization
EEG: MEG:
- EEG: low spatial resolution - MEG: (little bit less) low spatial resolution
- EEG: better temporal resolution - MEG: very low temporal resolution
HC2
Neural activity:
- LFP (local field potential): slow electrical signals from sub-threshold activity. Includes
synaptic activity and voltage-dependent membrane oscillations
earlier process
- MUA (multi-unit activity): action potentials, spikes
firing and output
Different types of MRI:
- Structural MRI: images different tissue types
- Diffusion MRI: maps the direction of neural pathways
- Functional MRI: images changes in brain activity with stimulus/task changes
They are all based on measuring the interaction of the tissue/blood with big magnetic
fields:
- Statistic field pulls atom spins into alignment
- Small gradient pushes spins out of alignment
- Energy released from realignment after gradient is measured to create images
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