[Eeglablist] surface Laplacian

[ALEXANDER BENTLEY]

How can I perform a surface Laplacian on my data (129 X 300 X 180 - channels X timepoints X epochs)? I had a  look at the del2map and laplac2d functions... but both aren't clear as to how it is performed on the data. del2map requires a map and filename inputs. What is the map? Plus the filename I have of the electrode positions is GSN129.sfp and not a .loc file. Please help...