2 Neuroscience2.3 Basic techniques in neuroscience
2.3.1 Recording from the brain
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Written by Resident Doctor Committee · Published
What each method records
Method | Source of the signal | Temporal resolution | Spatial scale |
|---|---|---|---|
Single-unit recording | Voltage changes with spikes | Milliseconds | One neurone or a few nearby |
Scalp electroencephalography (EEG) | Summed synchronous postsynaptic currents in large cortical populations | Milliseconds | Usually centimetres |
Structural magnetic resonance imaging (MRI) | Tissue-dependent magnetic resonance contrast | Anatomical snapshot | Millimetres or less |
Functional imaging | BOLD haemodynamic change or tracer distribution | Seconds to minutes | Millimetres; regions and networks |
Microdialysis | Molecules diffusing across a probe membrane | Usually minutes | Region the probe samples |
BOLD signal reflects neurovascular coupling over seconds and does not record firing directly.
Limits and what each method answers
Method | Invasiveness and artefacts | Limit on inference | Best answers |
|---|---|---|---|
Single-unit | Invasive; drift and spike-sorting error | Selected cells and sites | Firing linked to stimuli or choices |
EEG | Non-invasive; muscle, eye and electrode artefacts | Ambiguity of source and reference | Timing, rhythms and event-related activity |
Structural MRI | Non-invasive; movement and scanner effects | Structure does not establish cause | Morphology and its associations |
Functional imaging | Movement; positron emission tomography (PET) needs tracer injection and radiation | Indirect signal and confounding | Task contrasts, networks and molecular targets |
Microdialysis | Invasive; tissue reaction and placement | Incomplete recovery; mixed sources | Local chemical responses |
The inverse problem of EEG is that different sources can produce similar scalp patterns.
Many trials in one cell or one participant do not replace replication across independent samples.
Analysis choices also affect reproducibility.
Combining methods
Methods complement each other: cells suggest mechanisms, EEG resolves timing, imaging maps networks and dialysis measures chemistry.
Agreement between methods strengthens inference, and controlled perturbation tests causal hypotheses.