Net Application; Measure From The Nasion To The Inion - Geodesic Sensor Net Technical Manual

6: Applying the GSN
This section describes how to locate and mark the vertex.
1 Ask the subject to use his or her index finger
to secure one end of the measuring tape to
the nasion.
Run the tape over the top of the head until it
2
reaches the inion, and note the distance
(Figure 6-3). Locate the halfway point and
use a china marker to draw a short line—
perpendicular to the tape—on the subject's
head.
Measure the distance between the
3
preauricular points, extending the
measuring tape across the top of the head
over the line made in Step 2 (Figure 6-4).
Locate the halfway point and draw a short
line—perpendicular to the tape—on the
subject's head. Note where this line crosses
the nasion–inion midpoint line. This
intersection is the location of the vertex,
now marked with an X.
Note: When marking the scalp, minimize discomfort to the subject by holding the china
marker so that its tip makes a shallow angle with the scalp surface. Gently move the tip
across the scalp with light pressure to make a line.

Net Application

This section discusses how to apply the Net and adjust it for a proper fit. Steps
include soaking the Net in electrolyte solution (if the GSN has sponge inserts),
holding the Net correctly before application, applying the Net safely to the subject's
head, adjusting the Net to the relevant skull landmarks, and verifying its position on
the head. All of these steps are necessary to ensure an accurate EEG recording.
Caution!: Ask the subject to remove earrings, glasses, barrettes, and hair ties.
Earrings can be especially uncomfortable with an HCGSN applied. Glasses can be
replaced after Net application, as needed.
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Geodesic Sensor Net Technical Manual
Figure 6-3. Measure from the
nasion to the inion
Figure 6-4. Measure between
the preauricular points
S-MAN-200-GSNR-001 • January 31, 2007