The foc.us tDCS Headset, Part 2, Electrode Basics

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(foc.us tDCS headset showing “built-on” electrodes and sponges)

Impressive – But…

I continue to be very impressed with the new foc.us tDCS headset.  It brings to the table a huge array of features in a package that is relatively user-friendly (and will become more-so when its iOS and Android apps are available.)  If your interest is learning enhancement or treatment of depression, the headset alone is probably all you need.  So far, I have found it easy to use and reliable.

The accessory kit adds capabilities for placing electrodes in other locations on the head and shoulders for treatment of chronic pain, experimenting with “savant” learning, and other research projects. In this blog post, I want to briefly summarize the basics of electrode use using the “built-on” and accessory electrodes. I have also included a summary of basic operation for those curious about using the headset (or those having trouble understanding the manual.)

Electrode Placement

The “built-on” electrodes place the anode above the left eye and high on the left forehead (two sponges.)  The cathode is in the same positions but on the right side.  These positions, while perhaps not “ideal” in the eyes of some are probably close enough to published locations for learning enhancement and depression treatment for many or most users.  For depression, some have a preference for moving the cathode off to the right shoulder, but that requires the accessory kit. The headset itself is quite capable and will probably satisfy the needs of most.

Using the External Electrodes

You have to give foc.us some applause.  They designed a LOT of capability in to a fairly inexpensive package.  This is the first really versatile tDCS device that has a clean, simple design, has high ease-of-use – and doesn’t cost a fortune as many other “commercial” offerings do.  tDCS is now within reach of many more who really need it! For those not satisfied with the built-on electrodes, you can do your own thing for special treatments or research with the accessory kit.  It includes necessary wires (and other items) along with a small number of “TENS” style stick-on electrodes.

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(Cathode wire plugged into the back of the headset)

Important: The Wires

The kit includes a two-wire (anode & cathode) lead with good length, allowing placement pretty much as you see fit.  Uniquely, there is a single wire anode and single wire cathode included too. These are very useful when you want to use the built-on anode (or cathode) and have the opposite charge applied at a different location.  As mentioned, for depression, users may prefer the built-on anode, but want the cathode placed on the right shoulder.  The single cathode wire makes this simple to do.

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(Leads plug in to the back of the headset)

CAUTION: Voltage continues to be available via the built-on electrodes even if one of the accessory leads is plugged in.  You will need to remove the appropriate sponges (cathode or anode) when using an accessory wire.  So for example, a person seeking to treat depression would leave the anode (left) sponges in place, remove the cathode sponges (right side), and then use the cathode wire to place an electrode on the right shoulder.

If you leave sponges out, you need to be VERY CAREFUL that skin cannot come in contact with the copper plate inside the sponge holder (from an odd skin-wrinkle or tag.) If it does, a burn could result. An accessory CAP of some kind would be a nice safety feature – to cover the unused sponge holders. Perhaps the iOS/Android apps will allow disabling unused built-on electrodes – we’ll have to wait and see.  Safety caps would still be a good idea.

CAUTION: The plus and minus marking on the anode and cathode leads is BARELY visible and could easily lead to an error.  I suggest MARKING the leads in some much more visible manner (I used red and black zip-ties for the purpose.)

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(Can you see the minus sign on the back of the electrode clip?)

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(You will want to clearly mark lead polarity. Zip ties work.)

Coming in Part 3

In my next blog post I’ll have more information on operation, use, electrode placements, and more.  Please feel free to send along any questions or comment.  I’ll try to address those in the next post or two.  brent@speakwisdom.com

FYI: Summary of Basic Operation

Make sure the headset is charged

  1. Switch in “W” position
  2. Green light indicates charging

Turn it ON

  1. Flick the switch to the “O” position
  2. Touch the sensor (center back of the headset) for TWO SECONDS to activate it
  3. If you touch the sensor for three seconds or longer, the headset enters pairing mode (fine if desired, otherwise, switch to “W” then back to “O” and return to 1. above.)

To BEGIN a tDCS Session Already Configured

  1. Touch the sensor ONCE
  2. A four second count-down begins (time to put the headset on!) Current then ramps up to the desired level (more below.)
  3. Current will automatically ramp down at the end of the session

To END a tDCS Session

  1. Touch the sensor
  2. Switch to the “W” position to turn off the headset

Changing Session Settings

Set Mode

  1. Turn the headset on (switch set to “O”)
  2. Hold the sensor for two seconds to activate the headset
  3. Tap the sensor TWICE
  4. The headset will cycle through its four modes
    1. DC Sine-Wave – Logo brightness will rise and fall over 5 seconds
    2. Constant DC (DEFAULT) – Logo remains on for 5 seconds
    3. Pulsed Current (0.5 mA min) – Logo brightens and dim in 5 seconds
    4. Random Noise (0.5 mA to max random) – Logo brightness changes erratically
  5. When the logo reaches the state you desire, touch the sensor ONCE

Current Setting

  1. Next, the Logo will glow for three seconds at each of the below. Press the Logo to select.
    1. 0.5
    2. 1.0
    3. 1.5
    4. 2.0 (Only settable for use with external electrodes)
  2. Once current is set, foc.us headset returns to the ready state. You can begin a tDCS session by touching the sensor ONCE or…

To Confirm Settings

  1. Touch the sensor THREE times and the above Logo displays will appear for confirmation.

Factory Reset

  1. Touch and hold the sensor for 30 seconds.
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11 comments on “The foc.us tDCS Headset, Part 2, Electrode Basics

  1. Thanks for all the educating you do regarding TDCS! Maybe my commentary could be relevant to someone. I bought a pair of these foc.us devices on premise that it might benefit my reading comprehension (I’m a ferocious reader). I understand a side benefit might be improved mood. I don’t have clinical depression but who doesn’t like feeling more optimistic 🙂

    When I position the device as diagrammed in the manual with the lower electrodes .5” above my eyebrows & the other electrodes on my forehead I get overt phosphenes. Only when I position the lower electrodes 2″ above my eye socket (1.5″ above my eyebrow) do I not observe phosphenes. This happens even on the lowest current selection. My concern is both the upper electrodes don’t even place on my forehead. Rather they sit over top my hair just after where my hair line begins. Fortunately I’m a male that shaves his head, so conductance is a non-issue. Can you comment on how focused/diffuse a device like this might be? Or possibly the depth of neural pathways that could be reached with meaningful excitation?

    I gather the phosphenes are coming from my optic nerve which runs straight back to the visual cortex. Are some people’s optic nerves just way more sensitive than others? I’d read your post “A Very Simple Current Regulated tDCS Device” where you indicated some people observe phosphenes upon starting or ending their session. It seems like a long shot, but might it be the case that placement lower on my forehead (consequently lower on my PFC) be more advantageous with negligible risk to my optic nerve on premise that the optic nerve is extremely resilient and will filter out the noise from the stimulus after a short time causing the phosphenes to subside? …and there is no residual damage to the optic nerve? I’d say I only kept it positioned as diagrammed in the manual on 3 attempts for 4-6 pulses/phosphenes before taking it off. Even when I did move it up so high on my forehead, I infrequently observed very very subtle phosphenes but not enough to cause concern.

  2. Hi Daniel,

    I read that they occur more frequently when the electrodes are positioned too close to the eyebrow (duh)…

    I also read somewhere that phosphenes were a fairly common and transitory “side effect” for most studied. I got the very clear impression that no long-term damage was associated with tDCS among those who complained of phosphenes. Still, they can be quite unsettling.

    I get them whenever I adjust the headset and a contact is removed from my forehead. They’re freaky to be sure, but I don’t think they’re anything to be concerned with.

    Oh yeah, great blog by the way.

    Christian Hunter
    Austin, TX

  3. how have u been cleaning the 4 electrode plates and the external electrodes?
    noticing a buildup of the same blue on Foc.us on the plates, suspecting salt buildups…

  4. I’ve received my FOC.US kit and accessories. Overall I’m underwhelmed. While constructed reasonably well and packaged nicely, I find the documentation lacking and the operation, as you described it, a bit limited. For example, instead of asking the user to detect different flashing rates of an LED, it could have separate, small LEDs for each of the four functions, leaving no uncertainty as to which was selected. My options kit came with NO documentation; I’d be lost without your review – thanks, Brent.

  5. I have used the foc.us headset three times now–I only use on odd days so as to follow the 48 hours between session guideline without having to “remember ” the last session . I have not experienced any phosphenes thankfully –but after each session I experience slight vertigo which lasts all day– primarily when I turn my head quickly. I’m trying to determine if electrode placement is at fault or if it’s just a common side effect for some individuals. I am a petite female and I’m curious if I need to somehow adjust the headset so that my electrode placement resembles more accurately like that depicted in the manual .There no way for all four electrodes to be on the same plane -forehead -as depicted in the enclosed instructions … However, your photo with the styrofoam bust seems more realistic. It appears the top two electrodes rest more on the top of the skull.

    So, has anyone else experienced dizziness following a tDCS session?
    Does head circumference have anything to do with proper placement?
    And, thanks very much for the information here. I agree the kit lacks comprehensive instructions and zero in the accessory kit. It just arrived today so tomorrow I may onto a new setup.

    • I have not heard of any extenede periods of dizziness before – but everyone has slightly different physiology – so unique reactions are always possible. If the built-on electrodes are not lining up well, you may want to consider switching to external electrodes for more exact placement. I love the foc.us headset and often use mine with external electrodes for flexibility and the comfort of using Amrex 3×3 sponge electrodes.

      Brent

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