oddball trackpad problem with injured finger

  • Thread starter Lloyd E. Sponenburgh
  • Start date
L

Lloyd E. Sponenburgh

Guest
I hope someone can answer this. It's just a matter of curiosity, but very
strange to me.

I _thought_ I understood how trackpads work.

However, about a year ago, I mostly amputated the tip of my right index
finger -- my trackpad finger.

The tip was very nicely re-attached, and has healed perfectly. You can
barely see a small scar.
It is: properly vascularized, no warmer or cooler than any other fingertip,
not drier nor damper than the others, and NOT covered with scarring or a
thicker callous than any other of my fingers.

It is, however, numb. The nerves are apparently healing or re-assigning
slowly, because slowly sensation is being restored.

The wierd thing is, though, it will NOT work a trackpad reliably. I have
learned to use my middle finger in the meantime.

When the incision first healed, the finger would not operate a trackpad
_at_all_. As sensation has slowly returned, it works erratically, and
better when I press really hard. But it takes much more pressure than a
"healthy" finger.

Does anyone have a clue what causes this?

Thanks,

LLoyd


--
"... He commands an audience's inattention. His voice is a high baritone
honk.
Even when directed at me, I can scarcely distinguish between the sounds of
his
speech and the noise of a fat man's fart." -- Anon
 
On Thu, 18 Jan 2007 10:21:46 -0500, "Lloyd E. Sponenburgh"
<lloydsp@mindspring.com> wrote:

I hope someone can answer this. It's just a matter of curiosity, but very
strange to me.

I _thought_ I understood how trackpads work.

However, about a year ago, I mostly amputated the tip of my right index
finger -- my trackpad finger.

The tip was very nicely re-attached, and has healed perfectly. You can
barely see a small scar.
It is: properly vascularized, no warmer or cooler than any other fingertip,
not drier nor damper than the others, and NOT covered with scarring or a
thicker callous than any other of my fingers.

It is, however, numb. The nerves are apparently healing or re-assigning
slowly, because slowly sensation is being restored.

The wierd thing is, though, it will NOT work a trackpad reliably. I have
learned to use my middle finger in the meantime.

When the incision first healed, the finger would not operate a trackpad
_at_all_. As sensation has slowly returned, it works erratically, and
better when I press really hard. But it takes much more pressure than a
"healthy" finger.

Does anyone have a clue what causes this?
Click to expand...
---
The nerves in your finger aren't sending the same information to
your brain that it was used to, so your brain is having to learn
what the "correct" pressure is. As your finger heals and your brain
relearns your finger, it'll all eventually work out.


--
JF
 
"John Fields" <jfields@austininstruments.com> wrote in message
news:bkjvq29kgojr3qk4irsf5iio9htg3ec8u5@4ax.com...
The nerves in your finger aren't sending the same information to
your brain that it was used to, so your brain is having to learn
what the "correct" pressure is. As your finger heals and your brain
relearns your finger, it'll all eventually work out.
Click to expand...
I'd have thought that. However, I'm an engineer by trade, and had to figure
out some details.

I press with my middle digit with a pressure on the pad of something under
5g, and the trackpad works correctly. With the index finger, it takes over
9g to _begin_ to move the cursor at all, and about 12g to move it
semi-reliably.

LLoyd
 
"Lloyd E. Sponenburgh" <lloydsp@mindspring.com> wrote in message
news:45afdd17$0$7891$4c368faf@roadrunner.com...
I press with my middle digit with a pressure on the pad of something under
5g, and the trackpad works correctly. With the index finger, it takes
over 9g to _begin_ to move the cursor at all, and about 12g to move it
semi-reliably.
Click to expand...
Let me re-iterate this, too. When the finger first healed, and was "dead
numb", it wouldn't move the cursor at all. It was like trying to trackpad
with a plastic stick.

LLoyd
 
Lloyd E. Sponenburgh wrote:

"Lloyd E. Sponenburgh" <lloydsp@mindspring.com> wrote in message
news:45afdd17$0$7891$4c368faf@roadrunner.com...
I press with my middle digit with a pressure on the pad of something
under
5g, and the trackpad works correctly. With the index finger, it takes
over 9g to _begin_ to move the cursor at all, and about 12g to move it
semi-reliably.

Let me re-iterate this, too. When the finger first healed, and was "dead
numb", it wouldn't move the cursor at all. It was like trying to trackpad
with a plastic stick.

LLoyd
Click to expand...
If you use a pencil to work the pad it wont work either. Its a very curious
point you have there (no pun intended).
 
Coyoteboy wrote:

Lloyd E. Sponenburgh wrote:
Click to expand...
I believe it works by capacitance. Your finger provides a much different
dielectric to the air between two layers or similar idea. If your finger is
not so sensitive maybe its the conductivity of the nerves in your finger
that determine the conductance of the finger which makes the pad track.
They certainly test for nerve damage with a nerve conductance test these
days...
 
"Coyoteboy" <coyoteboyspuduk@hotmail.com> wrote in message
news:KNidnSPaE8yQbTLYnZ2dnUVZ8tninZ2d@bt.com...
Coyoteboy wrote:

Lloyd E. Sponenburgh wrote:

I believe it works by capacitance. Your finger provides a much different
dielectric to the air between two layers or similar idea. If your finger
is
not so sensitive maybe its the conductivity of the nerves in your finger
that determine the conductance of the finger which makes the pad track.
They certainly test for nerve damage with a nerve conductance test these
days...
Click to expand...
Yeah.... I kind of thought that it was capacitance. And capacitance
shouldn't be affected by nerve conductance. But maybe there's something
else trackpads rely upon.

At least it works a keyboard! <G>

LLoyd
 
On Thu, 18 Jan 2007 15:52:17 -0500, "Lloyd E. Sponenburgh"
<lloydsp@mindspring.com> wrote:

"John Fields" <jfields@austininstruments.com> wrote in message
news:bkjvq29kgojr3qk4irsf5iio9htg3ec8u5@4ax.com...
The nerves in your finger aren't sending the same information to
your brain that it was used to, so your brain is having to learn
what the "correct" pressure is. As your finger heals and your brain
relearns your finger, it'll all eventually work out.

I'd have thought that. However, I'm an engineer by trade, and had to figure
out some details.

I press with my middle digit with a pressure on the pad of something under
5g, and the trackpad works correctly. With the index finger, it takes over
9g to _begin_ to move the cursor at all, and about 12g to move it
semi-reliably.
Click to expand...
---
OK, then:

http://docs.info.apple.com/article.html?artnum=17228


--
JF
 
Lloyd E. Sponenburgh wrote:

Yeah.... I kind of thought that it was capacitance. And capacitance
shouldn't be affected by nerve conductance. But maybe there's something
else trackpads rely upon.

At least it works a keyboard! <G

LLoyd
Click to expand...
Capacitance would be affected by nerve conduction - it would reduce the
dielectric value of the finger material.
 
You must log in or register to reply here.

Welcome to EDABoard.com

Sponsor

Back
Top