The ActiveTwo head cap was developed in cooperation with Dr. Peter Praamstra at the Behavioral Brain Sciences Center, University of Birmingham, United Kingdom. The head cap consists of an elastic cap with plastic electrode holders. The cap itself does not contain electrodes – only plastic electrode holders that receive the pin-type active electrodes. The caps have ear-slits for easy access to the ears. Head-caps are provided with an elastic / velcro chin strap for fixing the cap in place, but body harnesses with criss-cross chest straps are also available.
The fabric template of the standard caps is suitable for positioning electrodes at the positions in the expanded 5% system defined in Oostenveld R, Praamstra P.Clin Neurophysiol. 2001 Apr;112(4):713-9. Several variations on the standard head-cap are available, including caps with extra fabric at the sides and in back, balaclava-style (full-coverage) caps with fabric along the sides of the face and the neck and surgical-style caps with no chin strap or body harness.
Please note that the ActiveTwo head-cap and associated active electrodes are designed only for use with the ActiveTwo system. They cannot be used with other types of bioamplifiers.
Electrode holders do just what their name says — they hold the pin-type active electrodes in place. These holders are designed to be used with the elastic fabric material of the standard head caps we offer, but they can also be used in other types of head caps or even other types of garments for holding the pin-type electrodes on the body.
Each electrode holder consists of three parts: a flared base with gel cavity, top tab with recessed circular insert for label and a rubber X-ring that provides friction to hold the electrode in place. The holders can be disassembled and relocated in the cap to change electrode positions or they can be removed from an old cap and installed in a new cap.
Sizes and layouts
Caps are available in a wide range of sizes and with a variety of electrode position layouts:
|Size||Color||Head Circ.||# Sites||Std. Layout||Boys||Girls|
|Infa 6||Red||22-26 cm||32||10/20||premature infants|
|Infa 5||Blue||26-30 cm||32||10/20||premature infants|
|Infa 4||Yellow||30-34 cm||32||10/20||premature infants|
|Infa 3||Brown||34-38 cm||64||10/20||0 – 1 mo.||0 – 1.5 mo.|
|Infa 2/3||Pink/Brown||36-40 cm||64||10/20||0 – 2 mo.||.5 – 3 mo.|
|Infa 2||Pink||38-42 cm||64||10/20||1 – 3.5 mo.||1.5 – 5.5 mo.|
|Infa 1/2||Lt Blue/Pink||40-44 cm||64||10/20||2 – 6.5 mo.||3 – 9 mo.|
|Infa 1||Light Blue||42-46 cm||64||10/20||3.5 – 10.5 mo.||5.5 – 15.5 mo.|
|X-Small/Infa 1||Green/ Light Blue||44-48 cm||64||10/20||6.5 – 19 mo.||9 – 28 mo.|
|X-Small||Green||46-50 cm||128||10/20 or ABC||10.5 – > 36 mo.||15.5 – > 36 mo.|
|Small/X-Small||Yellow/Green||48-52 cm||128||10/20 or ABC||19 – > 36 mo.||28 – > 36 mo.|
|Small||Yellow||50-54 cm||256||10/20 or ABC||toddlers / children|
|Medium/Small||Red/Yellow||52-56 cm||256||10/20 or ABC||children / teens / small adults|
|Medium||Red||54-58 cm||256||10/20 or ABC||teens / adults|
|Large/Medium||Blue/Red||56-60 cm||256||10/20 or ABC||teens / adults|
|Large||Blue||58-62 cm||256||10/20 or ABC||large teens / adults|
|X-Large||Brown||62-66 cm||256||10/20 or ABC||exceptionally large adults|
Standard cap layouts for 16, 32 and 64 channels are based on the International 10/20 System. Layouts for 128, 160 and 256 channels have electrode positions that are radially equidistant from CZ.
Click on the images below to enlarge the view of each standard cap layout diagram:
|16 Channels||32 Channels||64 Channels|
|128 Channels||160 Channels||256 Channels|
Applying the head cap
The standard steps for applying the head cap and electrodes are:
|1 – Place the cap on the subject’s head.||2. Fill the electrode holders with electrode gel from a syringe.||3. Insert the electrodes, taking care to match the color-coded label on the electrode to that on the electrode holder.|
Because of the characteristics of the active electrode, high electrode impedance can be tolerated, so no skin preparation is required. Thus, the usual, unpleasant and time-consuming abrasion of the scalp is omitted. After the electrode holders are filled with gel, the active electrodes are plugged in the cap one by one. The procedure is fast and reliable, and allows high density EEG measurement with a minimum of preparation time and subject discomfort.
It is also possible to pre-assemble the head cap (insert electrodes into the electrode holders) and pre-gel the electrodes for placement on subjects with shorter hair (e.g. infants). This shortens application time by eliminating the need to apply gel and insert electrode while the subject waits.
Custom head caps
Surgical-style caps with slightly lower coverage on the sides and in the back of the head are available upon request. The surgical-style cap incorporates an elastic band at the lower border of the cap, which eliminates the need for a chin-strap or body harness. The surgical style cap also provides slightly lower coverage in temporal and occipital areas.
A special full-coverage head cap (not pictured here) for use with 128 and 256 channel systems was developed in conjunction with Dr. Scott Makeig and colleagues at the Swartz Center for Computational Neuroscience in La Jolla, CA. This cap provides coverage in the cheek and neck regions that is expected to be useful for better identification of signals by means of independent component analysis (ICA). For details about this special cap configuration, contact Dr. Scott Makeig.
Different electrode layouts are possible on client specification. It is also possible to assemble your own cap layout.
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ActiveTwo Head Cap Large(Blue) 256 Electrode Holders, Equiradial ABC
ActiveTwo Head Cap Small/Medium (Yellow/Red) 256 Holders, Equiradial ABC
ActiveTwo Head Cap X-Large (Brown) 256 Electrode Holders, Equiradial ABC
ActiveTwo Head Cap Small (Yellow) 256 Electrode Holders, Equiradial ABC
ActiveTwo Head Cap Large (Blue) 160 Electrode Holders, Equiradial ABC
ActiveTwo Head Cap X-Small (Green) 160 Electrode Holders, Equiradial ABC
ActiveTwo Head Cap Medium (Red) 160 Electrode Holders, Equiradial ABC
ActiveTwo Head Cap Medium/Large (Red/Blue) 160 Layout Equiradial ABC
ActiveTwo Head Cap X-Small (Green) 128 Electrode Holders, Equidistant ABC
ActiveTwo Head Cap Small (Yellow) 128 Electrode Holders, Equidistant ABC
ActiveTwo Head Cap Medium/Large (Red/Blue) 128 Holders, Equidistant
ActiveTwo Head Cap Large (Blue) 128 Holders, Equidistant
ActiveTwo Head Cap Medium (Red) 128 Holders, Equidistant
ActiveTwo Head Cap Small/Medium (Yellow/Red) 128 Holders, Equidistant
ActiveTwo Head Cap Large (Blue) 128 Electrode Holders, 1020
ActiveTwo HeadCap Medium/Large (Red/Blue) 128 Holders, 1020 extended