Item 11: Is an individualised head model considered for each participant?
Pre-specified protocol	Head shape and tissue thickness varies considerably between individuals; therefore, head models should be personalised for each individual – i.e. from MRI/DTI data. If not, realistic head models should be employed as opposed to a spherical model, as the head is not a simplistic sphere. Individualistic head models were considered.
Yes, individualistic-1	A realistic head model was employed.
No, realistic-0.75	A spherical head model was employed.
No, spherical-0.25 Unclear-0.5	The head model used was unclear, hence an average quality score of 0.5 is given.
Item 12: Has the head been maximally segmented into appropriate layers depending on the tissue type being measured?
Pre-specified protocol	As specified by sub-sections:
12a: scalp
Yes: muscle, fat skin- 1 Yes: 2 layers-0.5	The scalp was segmented into the 3 tissue layers of muscle, fat, skin
No-0	The scalp is considered as 2 layers (i.e. muscle + fat)
N/A	Scalp is considered one homogenous layer. If the study did not measure scalp conductivity, item 12a is not included in the Quality Assessment score.
12b: skull
Yes: four layers-1	The skull was segmented into spongiform, inner and outer compact bone with sutures.
Yes: three layers-0.66	Skull considered tri-layered; spongiform, inner and outer compact bone without sutures.
Yes: two layers-0.33	Skull segmented into spongiform and compact bone.
No: one layer-0	The skull was considered as one homogenous head layer.
N/A	If the study did not measure scalp conductivity, item 12b is not included in the Quality Assessment score.
12c: brain
Yes: GM + WM – 1	The brain was compartmented into grey and white matter.
No: homogenous-0.5	The brain was considered as a homogenous tissue.
No: scalp = brain-0	The brain was assumed to have the same conductivity as the scalp.
N/A	If the study did not measure brain conductivity, item 12c is not included in the Quality Assessment score.
12d: WM anisotropy
Yes: anisotropic-1	WM was modelled as anisotropic
No- isotropic-0	WM was modelled as isotropic, or this was not mentioned in the study, therefore WM was assumed to be modelled as isotropic
N/A	If the study did not measure WM conductivity, item 12d is not included in the Quality Assessment score.
Item 13: Were no assumptions made for the conductivity value of any tissue type?
Pre-specified protocol	Conductivity values for all reported tissue types were empirically measured rather than assumed from prior literature (i.e. CSF is often assumed to model the remaining tissues).
Yes-1	No assumptions were made
No-0	Conductivity was assumed for one or more tissue types.