Methods Flashcards
perturbation methods
change the brain -> causal relation
monitoring methods
measure the brain -> correlation
limitation van damage to the brain als info over cognition
experimenter heeft geen control:
- damage not focal (single lesion can have a diverse effect)
- not generalizable (not every patient is the same)
wat moet je doen om damage als exp. hogere validiteit te geven
groups of patients en dan kijken naar wat ze allemaal in gemeen hebben qua loss of function
lesions maken in animals als researcher limitations
- animals need time to learn
- animals not as complex behaviour
- ethical
- interpretation problems: diachisis (damage to one neuron leads to decreased activitiy in another neuron); damage to fiber tracts bv heeft een hoop andere gevolgen
wat zijn de 3 perpetuating methods
- lesions
- pharmacological
- brain stimulation
pharmacological perpetuations
interfere with neurotransmitters that influence a certain cogntion.
- chronic drug abusers
- trials met drugs
agonist
activates the same receptors
antagonist
deactivates the receptors
limitation of pharmacological
unspecific
Penfield wat deed hij
intracranial brain stimulation -> somatotopic organization
optogenetics
Genetic material responsible for making ligand-gated ion channels is extracted and inserted in a virus. This virus is injected in a brain area and will infect the targeted neurons. The inserted genetic material will lead to the production of channelrhodopsins in the membranes of the infected neurons. Dit is intracranial brain stimulation
voorbeeld extracranial brain stimulation
TMS
TMS
Strong current is sent through coil and produces a strong
magnetic field. This field induces a changing electrical field in the
underlying brain area and causes neuronal activity ( e.g. motor
activity).
-
Single pulse TMS : during the experiment, a TMS pulse is
delivered on each trial (e.g., when a stimulus is presented).
-
Repetitive TMS : before the start of the experiment, a train of
pulses is delivered that changes the underlying brain area for
longer duration.
The effect of TMS depends on the strength of the pulse. A strong
pulse causes temporary ‘lesions’; weaker pulses can sometimes
facilitate activation.
TMS + en -
+ great temporal resolution
- bad spatial resolution
- only superficial structures
- contractions in head and neck: hard to mimic for control condition and annoying
- heeeel soms epileptic seizure
Transcranial Electrical Stimulation (TES)
ook wel tDCS (transcranial Direct Current Stimulation).
small electrical current is applied directly
to the scalp. Effects can last for an extended period
and is used in research and to treat clinical
problems (e.g., depression).
maar niet duidelijk of dit ook echt sterk genoeg is.
monitoring methods
direct recordings
EEG
MEG
PET
fMRI
optical brain imaging
single cell recordings
electrical recordings directly in the brain (vooral animal research). laten zien met peristimulus histogram
tuning curves
a neuron is stimulated in different dimensions (bv orientation) en dan kijken hoe hij op verschillende versies reageert.
electroencephalography:
cap, electrical potential recordings outside of the skull
what do we measure with eeg
membrane potentials –> als veel neuronen op hetzelfde moment signalen krijgen (EPSP en IPSP) –> local field potential LFP -> sterke LFPs kunnen gemeten worden.
dus wat meet eeg wel en wat niet (2 dingen)?
niet: actiepotentialen en intracellular, maar wel: combined input to dendrites of neurons, dus extracellular
In welke orientation meet je EEG?
alleen als de electrode perpendicular is to the signal -> dus alleen in gyri.
wat voor 2 dingen kun je uit een EEG signaal halen
- oscillations: different waves with different frequencies (dus de verschillende waves uit de som halen)
- ERPs: event related potentials -> small voltage differences in an ongoing EEG wave, triggered by sensory and cognitive events (dus de verschillen tussen ‘standaard’ gaande wave, wanneer er iets gebeurd)
–> The EEG data is ‘cut’ in portions (called epochs ) and aligned to the onset of the
stimulus presentation. The epochs are averaged and the signal that is most common in all epochs remains.
