User Tutorial:EEG Measurement Setup - Revision history

Ckong: /* Impedance */

2019-08-16T13:40:22Z

Impedance

← Older revision		Revision as of 13:40, 16 August 2019
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	==Noise Reduction==		==Noise Reduction==
	===Impedance===		===Impedance===
	Impedance between the scalp and electrodes, measured in <tt>kOhm</tt>, is a main factor of the recording signal quality. While introducing low frequency noise, high impedance can also indicate a poor conductivity between electrodes and the underneath skin. Rubbing the skin using a wood stick can break the ~~dead~~ tissue on the surface of the skin. For wet electrodes, sufficient gel can moist the skin throughout times, which lowers the impedance.		Impedance between the scalp and electrodes, measured in <tt>kOhm</tt>, is a main factor of the recording signal quality. While introducing low frequency noise, high impedance can also indicate a poor conductivity between electrodes and the underneath skin. Rubbing the skin using a wood stick can break the dry tissue on the surface of the skin and increase conductivity. For wet electrodes, sufficient gel can moist the skin throughout times, which lowers the impedance.

	To measure the current impedance,		To measure the current impedance,
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	*In the Source Signal module, right click.		*In the Source Signal module, right click.
	**Set ''Notch'' to <tt>60Hz</tt>		**Set ''Notch'' to <tt>60Hz</tt>


	===Grounding===		===Grounding===

Ckong: /* Noise Reduction */

2019-07-24T17:37:59Z

Noise Reduction

← Older revision		Revision as of 17:37, 24 July 2019
Line 61:		Line 61:
	==Noise Reduction==		==Noise Reduction==
	===Impedance===		===Impedance===
	Impedance between the scalp and electrodes, measured in kOhm is a main factor of the recording signal quality. While introducing low frequency noise, high impedance can also indicate a poor conductivity between electrodes and the underneath skin. Rubbing the skin using a wood stick can break the dead tissue on the surface of the skin. For wet electrodes, sufficient gel can moist the skin throughout times, which lowers the impedance.		Impedance between the scalp and electrodes, measured in <tt>kOhm</tt>, is a main factor of the recording signal quality. While introducing low frequency noise, high impedance can also indicate a poor conductivity between electrodes and the underneath skin. Rubbing the skin using a wood stick can break the dead tissue on the surface of the skin. For wet electrodes, sufficient gel can moist the skin throughout times, which lowers the impedance.

	To measure the current impedance,		To measure the current impedance,
Line 101:		Line 101:

	===Grounding===		===Grounding===
	Brain signal quality can also be interfered by surrounded electronics. Unshield power adapters of monitors or running cables in the nearby ~~wall~~ can induce noise to the raw signal. While filtering can take care of most noise, physically removing the source of noise can achieve higher signal quality. One good way is to ground the subject though the amplifier. The gUSBamp of our example has a grounding outlet on the back. Subject can also inspect the effect grounding by touching the metal case of the amplifier. Both can achieve a cleaner signal at the source level.		Brain signal quality can also be interfered by surrounded electronics. Unshield power adapters of monitors or running cables in the nearby walls can induce noise to the raw signal. While filtering can take care of most noise, physically removing the source of noise can achieve higher signal quality. One good way is to ground the subject though the amplifier. The gUSBamp of our example has a grounding outlet on the back. Subject can also inspect the effect of grounding by touching the metal case of the amplifier. Both can achieve a cleaner signal at the source level.

	==EEG Artifacts==		==EEG Artifacts==

Ckong: /* Noise Reduction */

2019-07-23T16:58:57Z

Noise Reduction

@@ Line 70: / Line 70: @@
 **Set ''NotchEnabled'' to <tt>0</tt>
 *In the operator module, click '''Set Config'''.
 To inspect current signal quality,
 *In the Source Signal module, right click.
 **Set ''High Pass'' to <tt>0.1Hz</tt>
@@ Line 83: / Line 85: @@
 Image:SourceSignalQualitySecond.PNG|Good Signal
 </gallery>
 ==EEG Artifacts==

Ckong: /* Impedance */

2019-07-23T16:41:59Z

Impedance

← Older revision		Revision as of 16:41, 23 July 2019
Line 70:		Line 70:
	**Set ''NotchEnabled'' to <tt>0</tt>		**Set ''NotchEnabled'' to <tt>0</tt>
	*In the operator module, click '''Set Config'''.		*In the operator module, click '''Set Config'''.
			To inspect current signal quality,
			*In the Source Signal module, right click.
			**Set ''High Pass'' to <tt>0.1Hz</tt>
			**Set ''Low Pass'' to ''off''
			**Set ''Notch'' to ''off''

	<gallery caption="Impedance Measurement" widths="~~300px~~" heights="300px" perrow="4">
			<gallery caption="Impedance Measurement" widths="600px" heights="300px" perrow="4">
	Image:MeasureElectrodeImpedanceFirst.PNG\|Electrode impedance before rubbing the skin and applying more gel		Image:MeasureElectrodeImpedanceFirst.PNG\|Electrode impedance before rubbing the skin and applying more gel
	Image:~~System~~.PNG\|~~Opening the System Properties~~		Image:SourceSignalQualityFirst.PNG\|Noisy Signal
	Image:~~DeviceManager~~.PNG\|~~Opening~~ the ~~Device Manager~~		Image:MeasureElectrodeImpedanceSecond.PNG\|Electrode impedance after rubbing the skin and applying more gel
	Image:~~COMCircled~~.PNG\|~~Identifying the COM Port~~		Image:SourceSignalQualitySecond.PNG\|Good Signal
	</gallery>		</gallery>

	==EEG Artifacts==		==EEG Artifacts==

Ckong at 16:25, 23 July 2019

2019-07-23T16:25:32Z

@@ Line 58: / Line 58: @@
 *While ensuring that '''Cz''' does not shift, adjust the cap such that the Fz-Cz-Pz line is on the midline; Fp1-Fp2 line is horizontal, and at the level of the Fpz mark; the O1-O2 line is horizontal, and at the level of the Oz mark.
 *You can now fix Ref and Gnd electrodes. These electrodes are attached in one of a few typical configurations.  One common configuration is to attach the Ref electrode to one earlobe, and the Gnd electrode to the mastoid on the same side of the head. Another possible configuration is to attach Ref to one mastoid and Gnd to the other mastoid.  This choice is influenced by the used cap technology, which may have dedicated electrodes outside the cap for reference and ground, or may have these electrodes embedded in the cap directly.
 ==EEG Artifacts==

Ckong: /* Electrode Placement */

2019-07-23T15:23:23Z

Electrode Placement

← Older revision		Revision as of 15:23, 23 July 2019
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	*Mark the vertex on the subject's scalp using a felt-tip pen or some other similar method. Begin by locating the nasion and inion on the subject as indicated in panel A of the figure above. Using a tape measure, find the distance between these two locations. The point half-way between the two points is the vertex. Make a mark at that point for later reference. (Other 10-20 points could be located in a similar manner.)		*Mark the vertex on the subject's scalp using a felt-tip pen or some other similar method. Begin by locating the nasion and inion on the subject as indicated in panel A of the figure above. Using a tape measure, find the distance between these two locations. The point half-way between the two points is the vertex. Make a mark at that point for later reference. (Other 10-20 points could be located in a similar manner.)
	*Mark scalp positions for Fpz and Oz. The Fpz position is above the nasion 10% of the distance from the nasion to the Inion. The Oz position is above the inion the same distance.		*Mark scalp positions for Fpz and Oz. The Fpz position is above the nasion 10% of the distance from the nasion to the Inion. The Oz position is above the inion the same distance.
	*Identify the Cz electrode on the EEG cap and place the cap to position the Cz electrode on the vertex.		*Identify the '''Cz''' electrode on the EEG cap and place the cap to position the Cz electrode on the vertex.
	*Keeping Cz fixed, slide the cap onto the head.		*Keeping Cz fixed, slide the cap onto the head.
	*While ensuring that Cz does not shift, adjust the cap such that the Fz-Cz-Pz line is on the midline; Fp1-Fp2 line is horizontal, and at the level of the Fpz mark; the O1-O2 line is horizontal, and at the level of the Oz mark.		*While ensuring that '''Cz''' does not shift, adjust the cap such that the Fz-Cz-Pz line is on the midline; Fp1-Fp2 line is horizontal, and at the level of the Fpz mark; the O1-O2 line is horizontal, and at the level of the Oz mark.
	*You can now fix Ref and Gnd electrodes. These electrodes are attached in one of a few typical configurations. One common configuration is to attach the Ref electrode to one earlobe, and the Gnd electrode to the mastoid on the same side of the head. Another possible configuration is to attach Ref to one mastoid and Gnd to the other mastoid. This choice is influenced by the used cap technology, which may have dedicated electrodes outside the cap for reference and ground, or may have these electrodes embedded in the cap directly.		*You can now fix Ref and Gnd electrodes. These electrodes are attached in one of a few typical configurations. One common configuration is to attach the Ref electrode to one earlobe, and the Gnd electrode to the mastoid on the same side of the head. Another possible configuration is to attach Ref to one mastoid and Gnd to the other mastoid. This choice is influenced by the used cap technology, which may have dedicated electrodes outside the cap for reference and ground, or may have these electrodes embedded in the cap directly.

Mellinger: /* Eye Blink Artifacts */

2012-09-10T11:59:53Z

Eye Blink Artifacts

← Older revision		Revision as of 11:59, 10 September 2012
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	visible in the frontopolar region, but propagating to all the electrodes of the montage, becoming weaker with distance from the front.		visible in the frontopolar region, but propagating to all the electrodes of the montage, becoming weaker with distance from the front.

	~~Blink~~ artifacts' frequency ~~content is negligible~~ in the alpha band, so they produce no		For blink artifacts, the power contained in their frequency components in the alpha band is negligible, so they produce no
	apparent effect on SMR data analysis (if their number is reasonable).		apparent effect on SMR data analysis (as long as their number is reasonable).
	At the same time, their amplitude is quite large so that time domain analyses (such as		At the same time, their amplitude is quite large so that time domain analyses (such as
	averaged P300 wave forms) can be strongly influenced by their presence.		averaged P300 wave forms) can be strongly influenced by their presence.

Mellinger: /* Electrode Placement */

2009-08-14T13:11:32Z

Electrode Placement

← Older revision		Revision as of 13:11, 14 August 2009
Line 52:		Line 52:
	Accurate placement of many electrodes on the scalp is time consuming and requires practice. EEG caps greatly facilitate this process. These caps are made of elastic fabric (often available in different sizes), and electrodes are already fixed in the proper configuration. One proven technique to place electrodes using such caps is the following:		Accurate placement of many electrodes on the scalp is time consuming and requires practice. EEG caps greatly facilitate this process. These caps are made of elastic fabric (often available in different sizes), and electrodes are already fixed in the proper configuration. One proven technique to place electrodes using such caps is the following:

	*Mark the vertex on the subject's scalp using a felt-tip pen or some other similar method. Begin by locating the nasion and inion on the subject as indicated in panel A of the figure above. Using a tape measure, find the distance between these two locations. The point half-way between the two		*Mark the vertex on the subject's scalp using a felt-tip pen or some other similar method. Begin by locating the nasion and inion on the subject as indicated in panel A of the figure above. Using a tape measure, find the distance between these two locations. The point half-way between the two points is the vertex. Make a mark at that point for later reference. (Other 10-20 points could be located in a similar manner.)
	points is the vertex. Make a mark at that point for later reference. (Other 10-20 points could be located in a similar manner.)
	*Mark scalp positions for Fpz and Oz. The Fpz position is above the nasion 10% of the distance from the nasion to the Inion. The Oz position is above the inion the same distance.		*Mark scalp positions for Fpz and Oz. The Fpz position is above the nasion 10% of the distance from the nasion to the Inion. The Oz position is above the inion the same distance.
	*Identify the Cz electrode on the EEG cap and place the cap to position the Cz electrode on the vertex.		*Identify the Cz electrode on the EEG cap and place the cap to position the Cz electrode on the vertex.

Mellinger: /* Electrode Placement */

2009-05-29T14:08:18Z

Electrode Placement

← Older revision		Revision as of 14:08, 29 May 2009
Line 58:		Line 58:
	*Keeping Cz fixed, slide the cap onto the head.		*Keeping Cz fixed, slide the cap onto the head.
	*While ensuring that Cz does not shift, adjust the cap such that the Fz-Cz-Pz line is on the midline; Fp1-Fp2 line is horizontal, and at the level of the Fpz mark; the O1-O2 line is horizontal, and at the level of the Oz mark.		*While ensuring that Cz does not shift, adjust the cap such that the Fz-Cz-Pz line is on the midline; Fp1-Fp2 line is horizontal, and at the level of the Fpz mark; the O1-O2 line is horizontal, and at the level of the Oz mark.
	*You can now fix Ref and Gnd electrodes. These electrodes are attached in one of a few typical configurations. One common configuration is to attach the Ref electrode to one earlobe, and the Gnd electrode to the mastoid on the same side of the head. Another possible configuration is to attach Ref to one mastoid and Gnd to the other mastoid. This choice is influenced by the used cap technology, which may have dedicated electrodes for reference and ground, or may have these electrodes embedded in the cap directly.		*You can now fix Ref and Gnd electrodes. These electrodes are attached in one of a few typical configurations. One common configuration is to attach the Ref electrode to one earlobe, and the Gnd electrode to the mastoid on the same side of the head. Another possible configuration is to attach Ref to one mastoid and Gnd to the other mastoid. This choice is influenced by the used cap technology, which may have dedicated electrodes outside the cap for reference and ground, or may have these electrodes embedded in the cap directly.

	==EEG Artifacts==		==EEG Artifacts==

Mellinger: /* Electrode Placement */

2009-05-29T14:02:53Z

Electrode Placement

← Older revision		Revision as of 14:02, 29 May 2009
Line 50:		Line 50:

	==Electrode Placement==		==Electrode Placement==
	~~Acquiring~~ EEG ~~from more than a single location provides spatial information that is useful~~ in ~~interpreting results~~, and ~~to identify signals and artifacts by their spatial distribution characteristics~~.		Accurate placement of many electrodes on the scalp is time consuming and requires practice. EEG caps greatly facilitate this process. These caps are made of elastic fabric (often available in different sizes), and electrodes are already fixed in the proper configuration. One proven technique to place electrodes using such caps is the following:
	~~Also, linear combinations of signals from different locations may be used~~ to ~~extract signals originating from certain locations.~~

	~~Attaching 16+2 (or worse 64+2) individual electrodes to the scalp of a subject is not~~		*Mark the vertex on the subject's scalp using a felt-tip pen or some other similar method. Begin by locating the nasion and inion on the subject as indicated in panel A of the figure above. Using a tape measure, find the distance between these two locations. The point half-way between the two
	~~a simple task. And doing it with high geometrical accuracy is a task for very~~		points is the vertex. Make a mark at that point for later reference. (Other 10-20 points could be located in a similar manner.)
	~~experienced technicians. The difficulty may be greatly alleviated using EEG caps. They are made of~~		*Mark scalp positions for Fpz and Oz. The Fpz position is above the nasion 10% of the distance from the nasion to the Inion. The Oz position is above the inion the same distance.
	~~elastic fabric (available in different sizes), and electrodes are already fixed in~~
	~~the proper configuration.~~

	~~Placing an EEG cap onto a subject is easy:~~
	*Mark the vertex on the subject's scalp using a felt-tip pen or some other similar method. ~~To do so, begin~~ by locating the nasion and inion on the subject as indicated in ~~subfigure (~~A) above. Using a tape measure, find the distance between these two locations. The point ~~midway~~ between the two points~~, or 50% of the distance,~~ is the vertex. Make a mark at that point for later reference. Other 10-20 points ~~can~~ be located in a similar manner. ~~Distances between points are reported, as percentages of the total distance, in subfigure (A~~) ~~above.~~
	*Mark scalp positions for Fpz and Oz.
	*Identify the Cz electrode on the EEG cap and place the cap to position the Cz electrode on the vertex.		*Identify the Cz electrode on the EEG cap and place the cap to position the Cz electrode on the vertex.
	*Keeping Cz fixed, ~~slip~~ the cap onto the head.		*Keeping Cz fixed, slide the cap onto the head.
	*While ensuring that Cz does not shift, adjust the cap such that:		*While ensuring that Cz does not shift, adjust the cap such that the Fz-Cz-Pz line is on the midline; Fp1-Fp2 line is horizontal, and at the level of the Fpz mark; the O1-O2 line is horizontal, and at the level of the Oz mark.
	**the Fz, Cz Pz line is on the midline;		*You can now fix Ref and Gnd electrodes. These electrodes are attached in one of a few typical configurations. One common configuration is to attach the Ref electrode to one earlobe, and the Gnd electrode to the mastoid on the same side of the head. Another possible configuration is to attach Ref to one mastoid and Gnd to the other mastoid. This choice is influenced by the used cap technology, which may have dedicated electrodes for reference and ground, or may have these electrodes embedded in the cap directly.
	**the Fp1-Fp2 line is horizontal, and at the level of the Fpz mark;
	**the O1-O2 line is horizontal, and at the level of the Oz mark.

	You can now fix Ref and Gnd electrodes. ~~Usually, Ref is~~ attached to one of the ~~earlobes~~, ~~or one of~~ the ~~mastoids, in form of a cup electrode using collodium (an adhesive chemical).~~
	~~Some caps have a~~ Gnd electrode ~~embedded~~ on ~~a scalp position; if this is not the case, Gnd is~~ the same ~~kind~~ of ~~electrode as~~ Ref, and ~~should be attached~~ to the ~~earlobe~~ or ~~mastoid opposing~~ the ~~Ref electrode~~.

	==EEG Artifacts==		==EEG Artifacts==