2 Neuroscience2.3 Basic techniques in neuroscience
2.3 Basic techniques in neuroscience
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Written by Resident Doctor Committee · Published
Recording versus perturbation
Recording brain activity shows only an association with behaviour or symptoms.
Perturbation by lesions, stimulation, drugs or optogenetics tests what changes when one component is altered.
Perturbation still needs controls, because effects spread through networks or recruit compensation, and natural lesions are not randomly allocated.
Comparing methods
Method | Signal | Time resolution | Spatial resolution |
|---|---|---|---|
Single-unit recording | Spikes | About 1 ms | Single cell |
Electroencephalography (EEG), magnetoencephalography (MEG) | Fields from neural currents | About 1 ms | Depends on source model |
Structural magnetic resonance imaging (MRI) | Tissue contrast | Snapshot | 1 mm or less |
Functional MRI | Haemodynamic response | Seconds | Millimetres |
Positron emission tomography (PET), single-photon emission computed tomography (SPECT) | Radiotracer distribution | Seconds to minutes | Several millimetres |
Microdialysis | Extracellular molecules | Minutes | Probe region |
Single-unit recording and microdialysis are invasive, functional MRI measures activity only indirectly, and PET and SPECT expose people to radiation.
Stem cells and organoids
Embryonic stem cells come from the inner cell mass of the blastocyst, so an embryo is destroyed to obtain them.
Induced pluripotent stem cells are reprogrammed from adult somatic cells, so no embryo is destroyed and the ethical objection falls away.
Induced pluripotent stem cells taken from a patient keep that patient's genetic information.
Brain organoids grown from pluripotent stem cells reach an architecture comparable to the mid-gestation (second-trimester) fetal brain, not a postnatal or adult brain.
Interpreting findings
A single cell cannot represent a whole network, and an average can hide opposing responses.
A reproducible group difference still needs separate validation before it is used to diagnose an individual.