How to read a paper

Do not read a paper from the first word to the last. Read the abstract, then the figures with their captions, then the last paragraph of the introduction, then the methods only where a figure raised a question, then the discussion’s first paragraph. Write five lines. Fifteen minutes, most of the time.

The order

Abstract. What they did, what they found. Write one line: the claim.

Figures and captions, in order. A paper’s argument is its figures. The text explains them. Look at each one and ask what it is showing and whether it convinces you. The captions carry the methods you actually need. Write one line: which figure carries the paper.

Last paragraph of the introduction. This is where authors state what they did and why it is new. Compare to the abstract.

Methods, selectively. Only for the questions the figures raised. How many subjects? How was accuracy computed, and on what split? What was the sampling rateSampling rate How many measurements per second the ADC takes; EEG is usually 250 to 1000 per second. Related: Nyquist frequencyNyquist frequency Half the sampling rate; anything in the signal above it cannot be represented and will appear as something false. , AliasingAliasing A frequency above Nyquist masquerading as a lower one after sampling; nothing downstream can undo it. . Glossary entry, the reference, the filterFilter An operation that passes some frequencies and attenuates others; every filter also delays or distorts the timing of what it passes. Related: High-pass filterHigh-pass filter Removes slow drifts and DC offsets, passing everything above a cutoff; set it too high and you erase slow brain activity. , Low-pass filterLow-pass filter Removes fast content above a cutoff; the anti-alias filter is one, and so is the smoothing you apply to a noisy trace. , Notch filterNotch filter A very narrow filter that removes one frequency, usually 60 Hz mains hum; it also rings and distorts nearby content, so fix the hum at the source first. , Phase distortionPhase distortion Different frequencies being delayed by different amounts, which smears and shifts waveforms such as an ERP peak. . Glossary entry? In BCIBrain-computer interface (BCI) A system that turns measured brain activity into control of something outside the body, from a cursor to a wheelchair to a speech synthesizer. Related: DecoderDecoder The algorithm that maps neural signals to intended actions, such as a classifier or a Kalman filter. , Closed loopClosed loop A system in which the output feeds back to influence the input, such as a user adjusting their brain activity while watching the cursor it controls. . Glossary entry papers, the cross-validationCross-validation Testing a model on data it never saw during training, repeatedly, so the reported accuracy means something. Related: Data leakageData leakage Information from the test set sneaking into training, for example by shuffling trials from one session across both; it inflates accuracy and is the most common flaw in student BCI papers. , OverfittingOverfitting A model that has memorized its training data, including its noise, and fails on anything new. . Glossary entry paragraph is the one to find; that is where inflated numbers come from.

First paragraph of the discussion. The authors’ honest summary. Then the limitations paragraph, which is usually near the end and usually buried.

The five lines

Citation (first author, year, journal)
Claim: one sentence
Evidence: which figure, N, the number that matters
Doubt: what would make me distrust it
Use: what I would do with this

Put them in one file, in date order. That file becomes the literature review you will need for your first poster, and the thing you check before emailing a professor about their work.

What to read

The reading thread has a list per phase. The general rule: in Phase 1 and 2, read for the instruments (how did they record, what was the noise, what did the electrodesElectrode The conductor that turns ion currents in tissue into electron currents in a wire; its chemistry and contact quality set the noise you live with. Related: Silver/silver-chloride (Ag/AgCl)Silver/silver-chloride (Ag/AgCl) The standard electrode material for biopotentials, because its chemistry produces a stable, low-noise, low-drift interface with salty gel. , Electrode impedanceElectrode impedance How hard it is to push current through the skin-electrode contact, typically 5 to 50 kilohms with gel and megohms dry, higher at low frequencies. , Half-cell potentialHalf-cell potential The DC voltage that appears wherever a metal meets an electrolyte; two electrodes with different half-cell potentials produce an offset that can swamp the signal. . Glossary entry look like). In Phase 3, read for the methods (how was the decoderDecoder The algorithm that maps neural signals to intended actions, such as a classifier or a Kalman filter. Related: ClassifierClassifier An algorithm that assigns each trial a label, such as left hand or right hand, after being trained on labelled examples. , Kalman filterKalman filter An estimator that blends a prediction from a motion model with a noisy measurement, weighting each by how much it trusts it; the decoder behind most intracortical cursor control. , Brain-computer interface (BCI)Brain-computer interface (BCI) A system that turns measured brain activity into control of something outside the body, from a cursor to a wheelchair to a speech synthesizer. . Glossary entry trained and tested). In Phase 4 and later, read for the ideas.

Where to get papers

The university library gives you nearly everything. For the rest, most authors post preprints on bioRxiv or arXiv, and most will email a PDF if you ask politely. Google Scholar’s “all versions” link often finds a free copy.