# Brain-machine interfaces

**URL:** <http://discourse.iapct.org/t/brain-machine-interfaces/1951>\
**Category:** CSG2004\
**Created:** [January 19, 2004, 12:37am UTC](http://discourse.iapct.org/t/brain-machine-interfaces/1951 "2004-01-19T00:37:42Z")\
**Posts on this page:** 5\
**Page:** 1

<div class="post-metadata">

**Author:** ![Philip\_Runkel](http://discourse.iapct.org/letter_avatar_proxy/v4/letter/p/8dc957/32.png) [@Philip\_Runkel](http://discourse.iapct.org/u/Philip_Runkel)\
**Post date:** [January 19, 2004, 12:37am UTC](http://discourse.iapct.org/t/brain-machine-interfaces/1951/1 "2004-01-19T00:37:42Z")

</div>

from Phil Runkel on 18 Jan 04, replying to Rick Marken’s of 17 Jan 04 at 08:28:29:

Thanks for your story about using GSR to control your perception of the size of a square on a computer screen and for your use of it to comment on the news item about the monkey who was doing something similar. I have not read the original article(s) about the monkey (and I guess neither have you), so maybe we are speculating beyond our facts, but after reading your message, I had a thought that I want to ask about.

Neural sensors detect changes in electrical voltage. Voltage can be affected by electrical potentials produced by neurons, and also by the conductivity of local chemicals (as in GSR). When I read that the experimenters were using neural sensors, I thought of all the “experiments” in which the experimenters ask the subject to watch a movie of a football game (let’s say), and find that the electrical voltage in the XYZ area is changing, and declare that they now know that football is controlled, or mediated, or processed, in the XYZ area.

As you pointed out, your excited thoughts produced changes in your GSR. Maybe if you attached a GSR sensor in your armpit, and watched an exciting football game, you could announce that the area for control, or mediation, or processing of football is the armpit!

Am I oversimplifying?

--Phil R.

---

<div class="post-metadata">

**Author:** ![Martin\_Taylor2](http://discourse.iapct.org/letter_avatar_proxy/v4/letter/m/b4bc9f/32.png) [@Martin\_Taylor2](http://discourse.iapct.org/u/Martin_Taylor2)\
**Post date:** [January 19, 2004, 6:12am UTC](http://discourse.iapct.org/t/brain-machine-interfaces/1951/2 "2004-01-19T06:12:14Z")

</div>

Martin Taylor 2004.01.19.0107]

> From Phil Runkel on 18 Jan 04, replying to Rick Marken's of 17 Jan  
> 04 at 08:28:29:
> 
> Thanks for your story about using GSR to control your perception of  
> the size of a square on a computer screen and for your use of it to  
> comment on the news item about the monkey who was doing something  
> similar.....  
> As you pointed out, your excited thoughts produced changes in your  
> GSR. Maybe if you attached a GSR sensor in your armpit, and watched  
> an exciting football game, you could announce that the area for  
> control, or mediation, or processing of football is the armpit!
> 
> Am I oversimplifying?

Probably. It's a matter of degrees of freedom.

Many years ago, I watched a demonstration of controlling the location  
of a cursor on a screen using head-mounted sensors (EEG). You  
couldn't do that with GSR, because it's a 2-dimensional problem.

But your point is reasonable. Activity in an area only shows that  
there is some correlation, not that the area is THE functional area  
for the behaviour studied. Activity there might only be an  
inconsequential side-effect of the real important brain work.

Martin

---

<div class="post-metadata">

**Author:** ![Richard\_Marken2](http://discourse.iapct.org/letter_avatar_proxy/v4/letter/r/edb3f5/32.png) [@Richard\_Marken2](http://discourse.iapct.org/u/Richard_Marken2)\
**Post date:** [January 19, 2004, 5:06pm UTC](http://discourse.iapct.org/t/brain-machine-interfaces/1951/3 "2004-01-19T17:06:36Z")

</div>

[From Rick Marken (2004.01.19.0900)]

> From Phil Runkel on 18 Jan 04, replying to Rick Marken�s of 17 Jan 04 at  
> 08:28:29:
> 
> Thanks for your story about using GSR to control your perception of the  
> size of a square on a computer screen and for your use of it to comment  
> on the news item about the monkey who was doing something similar. I  
> have not read the original article(s) about the monkey (and I guess  
> neither have you), so maybe we are speculating beyond our facts, but  
> after reading your message, I had a thought that I want to ask about.

I think I saw a news report on this work. As I recall, it showed the hookup  
between monkey's and cursor (the monkey's did a one dimensional tracking  
task) and it also showed a monkey controlling the cursor by "brain waves".

The interesting part of the work is that the researchers manage to transfer  
the monkeys from controlling the cursor using their hand to controlling it  
using their brain. I think they gradually decrease the influence of the  
monkeys' hand and increase the influence of the monkeys' brain waves on the  
cursor. It's quite an impressive demonstration of animal training.

I forget whether, when the cursor is influenced only by brain waves, the  
monkey stops using the hand. My guess is that some monkeys do stop using the  
hand and some don't, even though it is ineffective. It would depend on where  
reorganization end up. If someone knows what happens maybe they could let us  
know. I think it would be an interesting test of the reorganization model of  
PCT. I think the prediction of the reorganization model would be that  
continued use of the hand would occur in about 1/2 the monkeys.

> Neural sensors detect changes in electrical voltage. Voltage can be  
> affected by electrical potentials produced by neurons, and also by the  
> conductivity of local chemicals (as in GSR). When I read that the  
> experimenters were using neural sensors, I thought of all the  
> �experiments� in which the experimenters ask the subject to watch a  
> movie of a football game (let�s say), and find that the electrical  
> voltage in the XYZ area is changing, and declare that they now know that  
> football is controlled, or mediated, or processed, in the XYZ area.
> 
> As you pointed out, your excited thoughts produced changes in your GSR.  
> Maybe if you attached a GSR sensor in your armpit, and watched an  
> exciting football game, you could announce that the area for control, or  
> mediation, or processing of football is the armpit!

As Martin Taylor said, it is a degrees of freedom issue. When gross measures  
of the amplitude of physiological activity, GSR or brain waves, is used as  
the means of influencing the controlled variable, there is really only one  
df (amplitude) available for control.

Always great to hear from you, Phil.

Best regards

Rick

> **···**
>
> --  
> Richard S. Marken  
> MindReadings.com  
> Home: 310 474 0313  
> Cell: 310 729 1400

---

<div class="post-metadata">

**Author:** ![Philip\_Runkel](http://discourse.iapct.org/letter_avatar_proxy/v4/letter/p/8dc957/32.png) [@Philip\_Runkel](http://discourse.iapct.org/u/Philip_Runkel)\
**Post date:** [January 19, 2004, 7:35pm UTC](http://discourse.iapct.org/t/brain-machine-interfaces/1951/4 "2004-01-19T19:35:14Z")

</div>

To Martin Taylor and Rick Marken: Thanks for your replies to my query  
about the armpit. Helps keep me reasonably close to the track. --P

---

<div class="post-metadata">

**Author:** ![Dick\_Robertson](http://discourse.iapct.org/letter_avatar_proxy/v4/letter/d/2acd7d/32.png) [@Dick\_Robertson](http://discourse.iapct.org/u/Dick_Robertson)\
**Post date:** [January 20, 2004, 1:26pm UTC](http://discourse.iapct.org/t/brain-machine-interfaces/1951/5 "2004-01-20T13:26:07Z")

</div>

[From Dick Robertson,2004.01.19.1830CDT]

Philip Runkel wrote:

> &nbsp;&nbsp;&nbsp;Part 1.1 Type: Plain Text (text/plain)  
> From Phil Runkel on 18 Jan 04, replying to Rick Marken�s of 17 Jan 04  
> at  
> 08:28:29:
> 
> Thanks for your story about using GSR to control your perception of  
> the  
> size of a square on a computer screen and for your use of it to  
> comment  
> on the news item about the monkey who was doing something similar....

> As you pointed out, your excited thoughts produced changes in your  
> GSR.  
> Maybe if you attached a GSR sensor in your armpit, and watched an  
> exciting football game, you could announce that the area for control,  
> or  
> mediation, or processing of football is the armpit!

I love it. Thanks, Phil

Best,

Dick R

> **···**
>
> >