Interdependence of movement and anatomy persists when amputees learn a physiologically impossible movement of their phantom limb

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Moseley & Brugger (2009) Proc. Natl Acad. Sci. USA doi:10.1073/pnas.0907151106 (2009)

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Resting position

We measured reaction time (RT) during left/right judgments of pictured hands, when the intact and phantom hands were positioned like this:

Moseley & Brugger (2009) Proc. Natl Acad. Sci. USA doi:10.1073/pnas.0907151106 (2009)

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Resting position

We measured RT during left/right judgments of pictured hands, when the intact and phantom hands were positioned like this*:

We were interested in RT’s for these pictures:

Image position

*The reason we do this is because the longer it takes to move between the position the hand is in and the position the hand in the photograph is in, the longer the reaction time to make a correct judgment becomes.

See Parsons LM. Integrating cognitive psychology, neurology and neuroimaging. Acta Psychol (Amst) 2001;107(1-3):155-181 to learn about this.

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Moseley & Brugger (2009) Proc. Natl Acad. Sci. USA doi:10.1073/pnas.0907151106 (2009)

Resting position

Image position

We grouped RT’s when the resting hand & the pictured hand were in the same position:

Moseley & Brugger (2009) Proc. Natl Acad. Sci. USA doi:10.1073/pnas.0907151106 (2009)

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Resting position

Image position

We grouped RT’s when the resting hand & the pictured hand were in the same position:We grouped RT’s when the resting hand & the pictured hand were in the same position and the opposite position

Moseley & Brugger (2009) Proc. Natl Acad. Sci. USA doi:10.1073/pnas.0907151106 (2009)

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Resting position

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Image position

I A I A I

This shows that, as we would predict, when the hand or phantom hand, was in the same position as the hand in the photograph was, the reaction time is fast. When it is in the opposite position (as far as the impossible movement is concerned) the reaction time is slow.

Moseley & Brugger (2009) Proc. Natl Acad. Sci. USA doi:10.1073/pnas.0907151106 (2009)

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Participants

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Moseley & Brugger (2009) Proc. Natl Acad. Sci. USA doi:10.1073/pnas.0907151106 (2009)

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4Amp.

RT (sec)

Resting position

Pre Post

Image position

Intact

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Successes were quicker when pictured hand was opposite to resting position, but ONLY for the phantom side and ONLY after training.

This shows the 4 subjects who said they could do the impossible movement with their phantom were not lying. That is, it shows that, now they can move from the resting position to the position shown in the photograph, using a very short trajectory (ie, the impossible way).

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Moseley & Brugger (2009) Proc. Natl Acad. Sci. USA doi:10.1073/pnas.0907151106 (2009)

Axis

Two reported a new axis in their phantom.

On the right: a drawing showing a new phantom hand with an axis through the wrist into the hand. Two participants reported this. In both, it slowed their reaction time to make a left/right judgment, but only if the resting position of the phantom was bent to one side and the image showed a hand bent the other way. This makes sense if you think that their is an axis effectively ‘blocking’ the movement. So, again, they weren’t lying!

Moseley & Brugger (2009) Proc. Natl Acad. Sci. USA doi:10.1073/pnas.0907151106 (2009) © GL Moseley

www.bodyinmind.com.au

Axis

Pre Post

* *

0

4RT (sec)

Resting position

Image position

Two reported a new axis in their phantom.

On the right: a drawing showing a new phantom hand with an axis through the wrist into the hand. Two participants reported this. In both, it slowed their reaction time to make a left/right judgment, but only if the resting position of the phantom was bent to one side and the image showed a hand bent the other way. This makes sense if you think that their is an axis effectively ‘blocking’ the movement. So, again, they weren’t lying!

Moseley & Brugger (2009) Proc. Natl Acad. Sci. USA doi:10.1073/pnas.0907151106 (2009) © GL Moseley

www.bodyinmind.com.au

Axis

Pre Post

* *

0

4RT (sec)

Resting position

Image position

Two reported a new axis in their phantom.

This impeded their capacity to move their hand sideways.

On the right: a drawing showing a new phantom hand with an axis through the wrist into the hand. Two participants reported this. In both, it slowed their reaction time to make a left/right judgment, but only if the resting position of the phantom was bent to one side and the image showed a hand bent the other way. This makes sense if you think that their is an axis effectively ‘blocking’ the movement. So, again, they weren’t lying!

Moseley & Brugger (2009) Proc. Natl Acad. Sci. USA doi:10.1073/pnas.0907151106 (2009) © GL Moseley

www.bodyinmind.com.au

So what? The physical characteristics of your body image may affect how your brain works your body.

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Moseley & Brugger (2009) Proc. Natl Acad. Sci. USA doi:10.1073/pnas.0907151106 (2009)