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Hi, all,
I have my location file in .sfp format for EGI 64 channel sensor net.
I am wondering if there is a way to convert this .sfp file into .loc file ,which is supported by the offline analysis tool.

One more question is, after I run the offline analysis tool, I got result on high-frequency, as is shown in the figure. the figure is Left hand condition VS resting condition, based on 60 trials of each condition.
Condition 1: Imagine Left hand
Condition 2: Rest
sampling rate:1000 Hz
filter: 0.1-60 Hz.
What's the possible reason for that?

Thanks a lot!
Ran

Ryan,

you can use the EEGLAB functions readloc and writeloc to convert from and to .loc files in various formats.

Regarding the high-frequency correlations in your data, there has gamma band modulation been observed in ECoG data (J Neurosci. 2007 Feb 28;27(9):2424-32.
Spectral changes in cortical surface potentials during motor movement.
Miller KJ, Leuthardt EC, Schalk G, Rao RP, Anderson NR, Moran DW, Miller JW, Ojemann JG.). Maybe your amplifier's SNR is good enough to let some of that through to EEG as well.

Juergen

Hi, Juergen,

Thank you for the reply. That really helps.
So I used the readlocs and writelocs function and generated a loc file from sfp file.
After that, I tried to load it to the Eloc_helper, it constantly gave me an error about invalid eloc file.
I played around and found out that, the radius column I have here has some value greater than 0.5, which exceeds the requirement of the
Eloc_helper

r > settings.headRadius

.
Does it mean something was wrong when I did the conversion using EEGlab?
Thanks a lot!

Sincerely,
Ran

Hi Ryan,

Does it mean something was wrong when I did the conversion using EEGlab?

it appears EEGLAB is not as picky about electrode coordinates as OfflineAnalysis is, although I would guess that EEGLAB does not plot coordinates outside the head either.
You might need to rescale electrode coordinates by 0.5/r_max between the readloc and writeloc steps.

Best regards,
Juergen

Hi, Juergen,

Thank you for the help.
I was thinking about recaling too.
I will try that out.

Thanks,
Ran