The phrase "a scalp position" is correct and usable in written English.
It can be used in contexts related to hairdressing, medical discussions, or discussions about headgear or helmets.
Example: "The stylist recommended a scalp position that would enhance the volume of my hair."
Alternatives: "a head position" or "a hair position".
These parameters make it possible to address the issues of "convergence" (TMS on several different scalp positions produce a MEP in the same target muscle), "divergence" (TMS on a single scalp position produce a MEP in different target muscles) and somatotopy of motor area (based mainly on hot-spot and centre-of-gravity positions).
When used in combination with structural and functional MRI images these "neuronavigation" systems allow for precise identification of the scalp position corresponding to a particular brain area [ 13].
When anchored to anatomical landmarks, these distances could be used to locate the scalp position corresponding to a specific region of neural activity identified using functional MRI.
First, subjects were seated comfortably and the coil was positioned using a coil-holder (Brainsight, Rogue Research Inc ,Quebec Canada), at the scalp position at which Standard TMS induced motor-evoked potentials (MEPs) of maximal peak-to-peak amplitude in the target right first dorsal interosseus (FDI) muscle.
Visual area V5 was chosen for this example as it can be readily localized using fMRI and the corresponding scalp position cannot be identified based on a single anatomical landmark.
A number of approaches can be used to identify the correct scalp position for stimulation.
First, stimuli were applied with suprathreshold intensity and the coil was moved in steps of 1 cm to determine the optimal scalp position for producing motor evoked potentials (MEP) of maximal amplitude (lowest threshold) in the contralateral target hand muscle.
Average amplitudes, within 100 ms window around the negative-peak-latencies, are presented separately in Table 2 for each condition, stimulus type, and scalp position.
The optimal scalp position for the induction of MEPs with the maximum amplitude in the right FDI muscle was individuated for each participant.
Using a slightly suprathreshold stimulus intensity, the coil was moved over the left hemisphere to determine the scalp position from which maximal amplitude MEPs were elicited from the FDI and the ADM muscles.
