[Eeglablist] interpolation, gradients

[Arnaud Delorme]

Dear Peter,

> May I have a few questions on interpolation methods implemented in eeglab.
> 1.       We have used topoplot to interpolate certain statistical parameters we gather from EEG electrodes. Is interpolation in topoplot done along the scalp surface or on some other surface – or volume?

The default interpolation in topoplot is planar (not spherical). Originally, this was because of constraints in speed of computation although now, it would not be that critical. You can look at spherical interpolation when using the headplot function.

> 2.       The question becomes even more important when we would like to calculate the gradient of the parameter in question. Is there a function in eeglab that would calculate gradients along the scalp surface?

There is a function called eeg_laplac() in EEGLAB (see also another function del2map).

> 3.       We would also like to calculate phase gradients. Is that implemented? 

Not to my knowledge although you might want to look at EEGLAB plugins.
Best wishes,

Arno