Table 5 Neurophysiological measures and definitions
Measure | Category | Definition | Relevance to entrainment |
|---|---|---|---|
Phase-locking Index (PLI)71,72,73,74,123,124, Phase-locking value (PLV)75,76,77,95,99,100 | Phase consistency | A measure of the extent to which the instantaneous phase of two signals are synchronised146 | Measures the degree of neural synchrony to rhythmic stimuli |
Inter-trial phase consistency (ITPC)75,78, Inter-trial phase coherence (ITPC)79, Inter-trial coherence (ITC)80,81,96,125,126 | Phase consistency | The consistency in phase activity across trials that are time-locked to a specific event157 | Measures reliability of phase synchronisation to rhythmic stimuli |
Phase-locking factor (PLF)82 | Phase consistency | The degree to which the phases of oscillatory signals align across trials | Quantifies phase consistency in response to rhythmic stimuli |
Phase coherence (PC)97 | Phase consistency | The consistency of the phase differences between two or more brain signals at a given frequency | Measures the degree to which two signals are synchronised in response to rhythmic stimuli |
Phase consistency | The position within the cycle of a waveform at given points in time | Variability of phase can reflect synchronisation with rhythmic stimuli | |
Inter-hemispheric phase synchronisation (IHPS)95 | Phase consistency, coherence (regional) | The consistency of phase relationship between neural oscillations recorded from homologous regions in the left and right hemispheres of the brain95 | Reflects coordinated neural timing to rhythmic stimuli |
Global field synchronisation (GFS)85 | Phase consistency, coherence (regional) | Estimation of the amount of phase alignment across all brain regions as a function of frequency | Indicates the scale of wide-spread neural coherence in response to rhythmic stimuli |
Power | The magnitude of brain activity at a specific frequency | Measures the response strength to rhythmic stimuli | |
Power | Changes in the power spectrum of brain activity, specifically the degree of synchronisation or desynchronisation of neural oscillations across different frequencies, evoked by a stimulus158 | Measures power changes in response to rhythmic stimuli | |
Phase-locked power (PLP)87 | Power, phase consistency | The strength of neural activity at a specific frequency that is consistently aligned with a stimulus or event | Reflects the strength of consistent phase alignment to rhythmic stimuli |
Root-mean-square (RMS) power106 | Power | A statistical measure of the strength of a biosignal159, in this case, power | Quantifies magnitude of power change in response to rhythmic stimuli |
Single-trial power (STP)79 | Power | The analysis of brain activity based on individual trials of an EEG recording, rather than averaging power across multiple trials | Measures the quantity of neural activity in response to rhythmic stimuli at specific time points |
Power | The intensity of a signal simultaneously in time and frequency160 | Provides an estimation of time-varying magnitude of signal in a frequency band | |
Power difference between conditions89 | Power | The difference in signal magnitude associated with one experimental condition to another89 | Differentiates signal magnitude change between stimulus conditions |
Amplitude | The vertical distance or height of a waveform | Measures the response strength to rhythmic stimuli | |
Amplitude | A type of auditory-evoked potential that can be recorded from the scalp161 | Reflects brain response strength to rhythmic stimuli | |
Amplitude | The strength or magnitude of the magnetic field changes in the brain that are elicited by a specific stimulus or event | Measures neural response strength to rhythmic stimuli | |
Peak-to-peak (PtP) amplitude88 | Amplitude | The difference between the maximum voltage and the minimum voltage in a cycle, measuring the waveform’s overall variation88 | Shows neural response magnitude to rhythmic stimuli |
Amplitude | A statistical measure of the strength of a biosignal159, in this case, amplitude | Quantifies magnitude of power change in response to rhythmic stimuli | |
Amplitude | A steady-state evoked response that reflects the auditory processing of a sound’s envelope (fluctuations in amplitude over time) | Reflects the neural tracking of a sound envelope in response to rhythmic stimuli | |
Amplitude | The average amplitude of both phase-locked and non-phase-locked oscillations73 | Offers a measure of overall increase in signal intensity induced by rhythmic stimuli | |
Coherence95 | Coherence (regional) | The synchrony or similarity between two signals | Consistency of neural response to rhythmic stimuli across brain regions |
Coherence difference between conditions94 | Coherence (regional) | The difference in coherence between brain regions associated with one experimental condition to another94 | Differentiates cross-regional coherence change between stimulus conditions |
Cross-frequency coupling (CFC)82 | Coupling | The interaction between different frequency bands of brain oscillations | Shows the interaction between oscillations in response to rhythmic stimuli |
Phase-amplitude coupling (PAC)100 | Coupling | The interaction where the phase of a slower brainwave modulates the amplitude of a faster brainwave | Shows the coupling between oscillations in response to rhythmic stimuli |
Auditory-evoked potential (AEP)77 | Evoked response | Reflects change in electrical activity of the brain in response to auditory stimuli | Reflects time-locked brain responses to stimuli |
Signal quality | The strength of the desired brain signal relative to unwanted background noise | Measures the quality of the signal in response to rhythmic stimuli | |
Auditory steady-state response (ASSR) threshold105 | Response threshold | The minimum sound intensity that elicits a measurable, frequency-specific neural response105 | Reflects the sound level at which neural activity reliably synchs to rhythmic stimuli |
Temporal dynamics93 | Time-domain analysis | Time-dependent changes and patterns in physiological measures93 | Reflect time-related changes in response to rhythmic stimuli |
