[Eeglablist] How many electrodes tolerated for interpolation?

[fernandez luis]

> Hi Jinwon,
> 
> Accurate EEG channel interpolation is methodologically feasible across a broad spectrum of montage densities, including low-density configurations such as 19- and 32-channel systems, intermediate-density arrays such as 64 channels, and high-density systems such as 128 channels. Importantly, the methodological validity of interpolation does not primarily depend on the absolute number of electrodes, but on the availability of non-artifacted neighboring electrodes with adequate spatial distribution surrounding the channel to be reconstructed.
> 
>  
> EEG interpolation is a spatial estimation procedure in which the signal of an artifacted electrode is reconstructed using mathematically weighted contributions from the nearest clean surrounding electrodes. Accordingly, if the spatially adjacent electrodes are also artifacted, interpolation becomes unreliable or methodologically inappropriate, because the reconstruction process would be driven by distorted input data—violating key assumptions underlying spherical spline interpolation, inverse-distance weighting, and other spatial estimation algorithms.
> 
>  
> In low-density montages (e.g., 19 or 32 channels), interpolation remains technically feasible; however, the reduced spatial sampling inherently limits the anatomical precision and spatial granularity of the reconstructed signal. Nevertheless, interpolation in these systems can yield clinically acceptable results as long as the electrodes used as sources for reconstruction are clean, stable, and sufficiently distributed around the artifacted location.
> 
>  
> Intermediate-density systems such as 64-channel EEG offer improved spatial resolution that allows more accurate reconstruction of missing channels due to enhanced scalp coverage. High-density montages, particularly 128-channel EEG systems, provide dense and homogeneous spatial sampling, minimizing interpolation error and generating reconstructions that are more physiologically plausible and quantitatively reliable. This level of spatial resolution is advantageous for applications requiring high-fidelity scalp mapping, microstate analysis, connectivity estimation, and source localization.
> 
>  
> Despite differences in resolution across montage densities, a fundamental methodological requirement remains invariant: interpolation must be performed exclusively using clean, non-artifacted surrounding electrodes. Reconstruction based on artifacted neighbors compromises the physiological validity of the estimated signal and undermines the mathematical assumptions intrinsic to spatial interpolation algorithms.
> 
>  
> Technical Comparison: Conventional vs. High-Density EEG Interpolation
> 
>  
> 1. Interpolation in conventional EEG (19–32 channels)
> 
>  
> Low-density EEG systems rely on sparse spatial sampling, which imposes several methodological constraints:
> 
>  
> • Wide inter-electrode spacing  
> 
> • Higher vulnerability to local contamination  
> 
> • Reduced capacity to capture rapid spatial changes  
> 
> • Acceptable but limited reliability  
> 
>  
> 2. Interpolation in high-density EEG (64–128 channels)
> 
>  
> High-density EEG (HD-EEG) significantly enhances the reliability of interpolation due to:
> 
>  
> • Dense and homogeneous spatial sampling  
> 
> • Robustness to isolated corrupted channels  
> 
> • Improved modeling of spatial gradients  
> 
> • Near-physiological reconstruction in 128-channel systems  
> 
> Best 
> Luis Fernandez, MSc
> Clinical Neuropsychologist
> 

> El 17 nov 2025, a las 20:41, 장진원 via eeglablist <eeglablist at sccn.ucsd.edu> escribió:
> 
> Hi all,
> 
> I'm a clinical psychiatrist, so I am not really familiar with engineering
> concept of interpolation. I believe in high-density setting (128 channel)
> interpolation of a few channels are acceptable, but what if more than 10
> bad channels in 64 channel setting? Is it tolerable or detrimental for
> maintenance of true signal?
> 
> Best regards,
> Jinwon Chang
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