[Eeglablist] EEGLabList280223/question on EEG epoch length for electrical stimulation study

[David Mayor]

Dear EEGLabList Community

We have a question on EEG epoch length for our electrical stimulation study.

We are investigating the EEG effects of transcutaneous 
electroacupuncture stimulation of the hands (‘TEAS’) at different 
frequencies. 66 participants attended for 4 sessions. Stimulation was 
made up of alternating positive and negative (biphasic) rectangular 
pulses,pulse duration 256 microseconds, at 2.5, 10, 80 or 160 pulses per 
second, with a different frequency applied in each session. EEG was 
recorded each time for 40 minutes (8 x 5-minutes) – before, during and 
after 20 minutes of TEAS.

We wish to assess how epoch length impacts measures such as cordance, 
the Hjorth parameters, a number of nonlinear indices computed using the 
CEPS toolbox (Mayor et al. 2021, 2023), and some connectivity measures 
from the HERMES toolbox (Niso et al. 2013).

We have two main questions:

1. Should we avoid multiples of the stimulation frequency periodicities 
when setting epoch length in order to compute FFT or other measures?

2. Should epochs overlap or not? (see Benjamin et al. 2021)

A related question might be whether microstate durations (or other 
microstate parameters) vary with stimulation, as they do for needle 
acupuncture (Si et al. 2021).

Your comments and contributions would be welcome.

Thank you for your time.

Best regards

David Mayor and Tony Steffert

University of Hertfordshire & The Open University, UK

https://urldefense.com/v3/__http://electroacupuncture.qeeg.co.uk/__;!!Mih3wA!CCFCoQXUUdVCtgnfXg64SGMEhLLtbuFPGLbmL0u84LfrMlON9Qhf6L4C-LOIopNIbQGqsA5PNvuhUm0vNTdGsAPQ7IwYdmhi_Agl4A$ 

References:

Benjamin L, Dehaene-Lambertz G, Fló A. Remarks on the analysis of 
steady-state responses: Spurious artifacts introduced by overlapping 
epochs. Cortex. 2021 Sep 1;142:370-8.

Mayor D, Panday D, Kandel HK, Steffert T, Banks D. CEPS: An open access 
MATLAB graphical user interface (GUI) for the analysis of complexity and 
entropy in physiological signals. Entropy. 2021 Mar 8;23(3):321.

Mayor D, Steffert T, Datseris G, Firth A, Panday D, Kandel H, Banks D. 
Complexity and entropy in physiological signals (CEPS): Resonance 
breathing rate assessed using measures of fractal dimension, heart rate 
asymmetry and permutation entropy. Entropy. 2023 Feb 6;25(2):301.

Niso G, Bruña R, Pereda E, Gutiérrez R, Bajo R, Maestú F, Del-Pozo F. 
HERMES: Towards an integrated toolbox to characterize functional and 
effective brain connectivity. Neuroinformatics. 2013 Oct;11:405-34.

Si X, Han S, Zhang K, Zhang L, Sun Y, Yu J, Ming D. The temporal 
dynamics of EEG microstate reveals the neuromodulation effect of 
acupuncture with /deqi/. Frontiers in Neuroscience. 2021 Oct 7;15:715512.