neuroskill-data-reference

# NeuroSkill Data Reference --- ## EXG Band Powers Relative power — values sum to approximately 1.0. Found under `scores.bands` in `status`, or as `rel_*` top-level keys in metric responses. | Field | Band | Range | What it means | |---|---|---|---| | `rel_delta` | δ 0.5–4 Hz | 0–1 | Deep sleep, unconscious processes. High during N3 sleep or drowsiness. | | `rel_theta` | θ 4–8 Hz | 0–1 | Drowsiness, meditation, creativity, memory encoding. High in ADHD (TBR). | | `rel_alpha` | α 8–13 Hz | 0–1 | Relaxed wakefulness, idle cortex, eyes-closed state. Drops on task engagement. | | `rel_beta` | β 13–30 Hz | 0–1 | Active thinking, focus, anxiety. High beta = cognitive effort or stress. | | `rel_gamma` | γ 30–100 Hz | 0–1 | Sensory binding, high-level cognition. Low in schizophrenia. | --- ## EXG Ratios & Indices | Field | Formula | What it means | |---|---|---| | `faa` | ln(αR) − ln(αL) | **Frontal Alpha Asymmetry.** Positive = approach motivation / positive affect. Negative = withdrawal / depression. | | `tar` | θ / α | **Theta/Alpha Ratio.** High = drowsy or meditative. | | `bar` | β / α | **Beta/Alpha Ratio.** High = alert, possibly anxious. | | `dtr` | δ / θ | **Delta/Theta Ratio.** High in deep sleep or pathological slowing. | | `tbr` | θ / β | **Theta/Beta Ratio.** Main ADHD biomarker. Healthy ~1.0; elevated ADHD >1.5. | | `pse` | (power law slope) | **Power Spectral Exponent.** Steeper = more 1/f, typical of rest. Flatter = active. | | `bps` | (regression slope) | **Band-Power Slope.** Similar to PSE; measures spectral tilt. | | `apf` | Hz | **Alpha Peak Frequency.** 8–12 Hz typical; shifts with age and cognitive state. | | `sef95` | Hz | **Spectral Edge Frequency 95%.** Frequency below which 95% of power falls. | | `spectral_centroid` | Hz | **Spectral Centroid.** Weighted average frequency — rises with cognitive load. | | `coherence` | 0–1 | **Inter-channel coherence.** High = coordinated brain activity. | | `mu_suppression` | 0–1 | **Mu rhythm suppression.** Increases with motor imagery or observed action. | | `laterality_index` | −1 to 1 | **Hemispheric laterality.** Left vs. right hemispheric dominance. | | `snr` | dB | **Signal-to-Noise Ratio.** > 10 dB = good signal; < 5 dB = noisy. | --- ## Core Scores 0–1 range unless noted. Computed per 5-second epoch by the on-device model. | Field | What it means | |---|---| | `focus` | Sustained attention. Driven by frontal beta and suppressed alpha. | | `relaxation` | Calm, low-arousal state. High alpha, low beta. | | `engagement` | Active cognitive engagement. Composite of beta, theta, alpha suppression. | | `meditation` | Meditative depth. High frontal alpha, stable theta, low beta. | | `mood` | Valence estimate. Positive FAA and alpha balance → positive mood. | | `cognitive_load` | Mental effort. High theta + beta, low alpha. | | `drowsiness` | Sleepiness. High delta + theta, alpha intrusions. | --- ## Complexity Measures Nonlinear EXG measures — higher complexity generally means a more flexible, awake brain state. | Field | What it means | |---|---| | `hjorth_activity` | Signal variance (power). | | `hjorth_mobility` | Mean frequency estimate. | | `hjorth_complexity` | Signal shape complexity — how much the signal changes its frequency. | | `permutation_entropy` | Ordinal pattern entropy. Near 1 = complex/random; near 0 = highly ordered. | | `higuchi_fd` | Fractal dimension. ~1.5–1.8 during healthy wakefulness. | | `dfa_exponent` | Detrended fluctuation. ~0.5 = white noise; ~1.0 = long-range correlations. | | `sample_entropy` | Regularity — lower = more predictable/periodic signal. | | `pac_theta_gamma` | Phase-Amplitude Coupling (θ–γ). Linked to working memory and attention. | --- ## PPG / Heart Rate Variability Derived from the Muse PPG sensor (forehead). | Field | Unit | What it means | |---|---|---| | `hr` | bpm | Heart rate. | | `rmssd` | ms | Root mean square of successive differences — parasympathetic HRV. High = relaxed. | | `sdnn` | ms | Standard deviation of NN intervals — overall HRV. | | `pnn50` | % | % of successive differences > 50 ms — parasympathetic index. | | `lf_hf_ratio` | ratio | Low/High frequency power ratio — sympathetic vs. parasympathetic balance. High = stress. | | `respiratory_rate` | bpm | Estimated breathing rate from PPG. | | `spo2_estimate` | % | Estimated blood oxygen saturation (research only). | | `perfusion_index` | % | Ratio of pulsatile to static IR signal — peripheral perfusion quality. | | `stress_index` | 0–100 | Composite stress index. High HR + low HRV + high LF/HF → high stress. | --- ## Motion & Artifacts | Field | What it means | |---|---| | `stillness` | 0–1. Head movement score; 1 = no motion. | | `head_pitch` | Degrees forward/backward tilt. | | `head_roll` | Degrees left/right tilt. | | `nod_count` | Number of detected vertical head nods. | | `shake_count` | Number of detected horizontal head shakes. | | `blink_count` | Number of detected eye blinks (from frontal electrodes). | | `blink_rate` | Blinks per minute. | | `jaw_clench_count` | Number of detected jaw clenches (EMG artifact). | | `jaw_clench_rate` | Jaw clenches per minute. | --- ## Sleep Stages Used in `sleep` and `status.sleep`. | Stage | Code | EXG signature | |---|---|---| | Wake | `0` | High beta, present alpha when eyes closed | | N1 | `1` | Slow eye movements, alpha fades, theta begins | | N2 | `2` | Sleep spindles (12–15 Hz bursts), K-complexes, dominant theta | | N3 | `3` | High-amplitude delta > 50% of epoch — deep/slow-wave sleep | | REM | `4` | Low-amplitude mixed frequency, sawtooth waves, suppressed delta | --- ## Consciousness Metrics From `consciousness`. All 0–100 (higher = better). | Metric | What it measures | Reference (verified DOI) | |---|---|---| | `lzc` | Lempel-Ziv Complexity proxy — signal diversity; drops under anesthesia | Casali et al. (2013) · doi:[10.1126/scitranslmed.3006294](https://doi.org/10.1126/scitranslmed.3006294) | | `wakefulness` | Inverse drowsiness — high alpha relative to theta | Klimesch (1999) · doi:[10.1016/s0165-0173(98)00056-3](https://doi.org/10.1016/s0165-0173(98)00056-3) | | `integration` | Composite of coherence × PAC × spectral entropy — cortical integration | Tononi (2004) · doi:[10.1186/1471-2202-5-42](https://doi.org/10.1186/1471-2202-5-42) | > **Consciousness:** ≥ 50 = green, 25–50 = yellow, < 25 = red. --- ## References All DOIs below are verified against the Skill application reference list (`HelpReferences.svelte`). Only papers present in that list are cited here. | # | Citation | DOI | |---|---|---| | [64] | Monastra, V. J., Lubar, J. F., Linden, M. (2001). The development of a quantitative electroencephalographic scanning process for ADHD. *Neuropsychology*, 15(1), 136–144. | doi:10.1037/0894-4105.15.1.136 | | [66] | Demerdzieva, A., Pop-Jordanova, N. (2015). Relation Between Frontal Alpha Asymmetry and Anxiety in Young Patients with Generalized Anxiety Disorder. *PRILOZI*, 36(2), 157–177. | doi:10.1515/prilozi-2015-0064 | | [67] | Stewart, J. L., Coan, J. A., Towers, D. A., Allen, J. J. B. (2014). Resting and task-elicited prefrontal EXG alpha asymmetry in depression. *Psychophysiology*, 51(5), 446–455. | doi:10.1111/psyp.12191 | | [68] | Perlis, M. L., Merica, H., Smith, M. T., Giles, D. E. (2001). Beta EXG activity and insomnia. *Sleep Medicine Reviews*, 5(5), 365–376. | doi:10.1053/smrv.2001.0151 | | [69] | Bjørk, M. H., Stovner, L. J., Engstrøm, M. et al. (2009). Interictal quantitative EXG in migraine: a blinded controlled study. *The Journal of Headache and Pain*, 10(5), 331–339. | doi:10.1007/s10194-009-0140-4 | | [70] | Gloss, D. S., Nolan, S. J., Staba, R. (2014). The role of high-frequency oscillations in epilepsy surgery planning. *Cochrane Database of Systematic Reviews*. | doi:10.1002/14651858.cd010235.pub2 | | [71] | Dauvilliers, Y. (2007). Narcolepsy with Cataplexy: Hypocretin and Immunological Aspects. In: *Neuroimmunology of Sleep* (Springer), pp. 337–352. | doi:10.1007/978-0-387-69146-6_20 | | [72] | Jeong, J. (2004). EXG dynamics in patients with Alzheimer's disease. *Clinical Neurophysiology*, 115(7), 1490–1505. | doi:10.1016/j.clinph.2004.01.001 | | [73] | Spironelli, C., Fusina, F., Bortolomasi, M., Angrilli, A. (2021). EXG Frontal Asymmetry in Dysthymia, Major Depressive Disorder and Euthymic Bipolar Disorder. *Symmetry*, 13(12), 2414. | doi:10.3390/sym13122414 | | [74] | Uhlhaas, P. J., Singer, W. (2010). Abnormal neural oscillations and synchrony in schizophrenia. *Nature Reviews Neuroscience*, 11(2), 100–113. | doi:10.1038/nrn2774 | | [75] | Casali, A. G., Gosseries, O., Rosanova, M. et al. (2013). A Theoretically Based Index of Consciousness Independent of Sensory Processing and Behavior. *Science Translational Medicine*, 5(198), 198ra105. | doi:10.1126/scitranslmed.3006294 | | [6] | Klimesch, W. (1999). EXG alpha and theta oscillations reflect cognitive and memory performance. *Brain Research Reviews*, 29(2–3), 169–195. | doi:10.1016/s0165-0173(98)00056-3 | | [76] | Tononi, G. (2004). An information integration theory of consciousness. *BMC Neuroscience*, 5, 42. | doi:10.1186/1471-2202-5-42 |