What a qEEG actually shows you.

The starting point: the brain is electrical

Every neuron in the cortex either fires or doesn't, hundreds of times a second. The summed effect of millions of these firings is the brain's electrical activity — and that activity has rhythms. Slow ones when you're drifting toward sleep. Faster ones when you're paying focused attention. Particular signatures when you're scanning the room for threat or settling into rest.

EEG, invented by Hans Berger in the 1920s, is the technology that records these rhythms. [1] A normal clinical EEG asks "is there a seizure focus?" and looks at the recording with the naked eye. Quantitative EEG — qEEG — does something different: it takes the same recording and processes it mathematically, plotting it against a database of healthy brains of similar age. [2]

What appears on the screen

When you sit through a qEEG at our clinic, the recording is 19-channel — meaning sensors at 19 standardised positions across the scalp, following the international 10–20 system. We record at rest with eyes closed, at rest with eyes open, and during a structured cognitive task (typically a continuous-performance test).

The raw recording is a tracing — a wavy line per channel, scrolling across the screen. That's what an old-fashioned clinical EEG showed and what neurologists still read for seizure focus. The quantitative output is layered on top of that. It includes:

• Spectral maps — colour-coded heat maps of how much energy is at each frequency, plotted across the scalp. Red usually means more activity than the norm; blue, less. [3]
• Coherence and phase measures — how synchronised activity is between different regions, which speaks to how the brain's networks are co-ordinating.
• Source-localised images — using a method called swLORETA, the surface recording is back-projected to estimate the cortical regions producing it. [4]
• Z-scores — how many standard deviations each metric sits from the age-matched normative database. ±2 SD is a meaningful deviation; ±3 SD is striking.

What the patterns tend to mean — and don't

Three things to be careful with here.

First, no qEEG pattern is a diagnosis. A qEEG showing excess slow-wave in the frontal midline, for instance, is consistent with attention difficulties — but it's also consistent with sleep deprivation, with certain medication effects, with traumatic brain injury, with mid-life cognitive change. The pattern is a pointer; the clinical formulation is the destination. [5]

Second, "looks normal" is genuinely informative. When the qEEG sits well within the normative envelope across all the metrics we look at, that doesn't mean we can't help — it means the patient's symptoms are likely being driven by something other than a primary cortical signature. Sleep, autonomic regulation, gut–brain inputs, life context. The conversation moves there.

Third, the interesting findings are usually relational, not absolute. One region looking unusual is one thing. The relationship between several regions, and how that relationship changes when cognitive load is applied, is often where the most useful clinical information lives.

The protocol, end to end

For patients curious about what to expect: a qEEG appointment runs about 60 minutes. Of that, the recording itself is 20–25 minutes. The remaining time is intake, sensor setup (a cap with 19 sensors, gel-applied for conduction), and clean-up.

The intake before recording is structured — medical and psychological history, sleep, lifestyle, current concerns, medications, prior workup. We use validated questionnaires appropriate to the presenting concern. None of this is incidental: the qEEG is read against the intake, not in isolation.

After the recording, the data is processed against the normative database (we use the Neuroguide platform, with swLORETA source localisation overlaid). Dr Ash reviews the report, integrates it with the intake, and writes a formulation. The patient receives that formulation in a sit-down conversation — typically the next visit — walking through the report on a screen, in plain language.

From there, if a programme is indicated, the qEEG findings inform the targets. We re-image at the midpoint and at conclusion of the programme, so we (and the patient) can see what's changed.

What it can't do

For clarity:

• qEEG does not diagnose epilepsy. Specialist clinical EEG and neurology referral are the appropriate path.
• qEEG does not replace structural imaging. Where MRI or CT is indicated — for stroke, tumour, structural anomaly — we refer.
• qEEG does not produce a "psychiatric diagnosis." It is a functional measurement, useful in clinical formulation, not a stand-alone diagnostic test.
• qEEG does not predict response to medication. Some research is exploring this, but it is not yet at the point of clinical utility.

The honest summary

A qEEG shows you how your brain is currently working — its rhythms, its synchronisation, its response to load — relative to a population of brains of similar age. That picture, on its own, is information. Combined with intake, autonomic markers, validated questionnaires, and clinical reasoning, it becomes a formulation.

The picture isn't the answer. But for many patients, it's the first time anyone has actually looked.

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About the author. Dr Ash Connell is a chiropractor (AHPRA CHI0001772308), board-certified in quantitative EEG (QEEG-D), and the founding clinician of The Healthy Brain Clinic. He practises from Geelong and Camperdown, Victoria, and online Australia-wide. Read his bio →

References

1. Berger H. (1929). Über das Elektrenkephalogramm des Menschen. Archiv für Psychiatrie und Nervenkrankheiten, 87(1), 527–570.
2. Thatcher RW. (2010). Validity and reliability of quantitative electroencephalography (qEEG). Journal of Neurotherapy, 14(2), 122–152.
3. Coben R, Evans JR (eds). (2010). Neurofeedback and Neuromodulation Techniques and Applications. Academic Press.
4. Pascual-Marqui RD. (2007). Discrete, 3D distributed, linear imaging methods of electric neuronal activity. arXiv preprint.
5. Hughes JR, John ER. (1999). Conventional and quantitative electroencephalography in psychiatry. Journal of Neuropsychiatry and Clinical Neurosciences, 11(2), 190–208.

Editorial note. This article was drafted by Dr Ash Connell with structural support from a large language model, then reviewed for clinical accuracy and AHPRA compliance before publication. Citations are real, peer-reviewed sources. The clinical interpretations are Dr Ash's own.