Necessary conditions for consciousness
shamimkhaliq at hotmail.comTakeThisOff
Thu Feb 15 12:56:46 EST 2001
these two quotes imply it's an aspect of central imagery/representation, not
peripheral processes, i think. but if you're interested it quotes some
reviews on the topic that might be interesting to read.
"Amputated subjects, for example, report feeling movements of their phantom
limb, and seem to have a clear image of their intended action (for complete
description, see Schilder, 1935). Similar feelings are reported by patients
with deafferented limbs (due to peripheral deafferentation or other causes).
They may describe their intended action in great detail while no actual
movements can be observed from the outside (e.g., Duchenne de Boulogne,
1855, Jeannerod et al, 1984). These data suggest that, in the condition of
executed action, the content of the motor representation would not reach
consciousness because it would be cancelled as soon as the corresponding
movement is executed (perhaps by the incoming signals generated by execution
itself). By contrast, in the condition of motor imagery, where execution is
purposively blocked or delayed, the representation would be protected from
cancellation and would become accessible to conscious processing. "
Patients who have been paralysed centrally report no effort trying to move
paralysed limbs (Mach, 1906 ; Gandevia, 1982 ), while patients or
participants paralysed peripherally use more effort to "move" their
paralysed limbs (Gandevia and McCloskey, 1977 ). Force judgements of
weakened muscles tend to be overestimated independent of actual muscular
tension (Holmes, 1922 ). There's an increase in duration of a goal-directed
movement when this movement becomes more difficult. This occurs even without
visual feedback (Prablanc et al, 1979 ) so it's not due to more time needed
to process visual feedback but neural coding of the movement during the
preparatory stage (Jeannerod, 1986a ; see Meyer et al, 1990 for a review).
Shamim Khaliq shamimkhaliq at hotmail.com <http://shamimkhaliq.50megs.com/>
Marcy <marcyatwork at hotmail.com> wrote in message
news:3GUh6.138768$V22.27989982 at news4.rdc1.on.home.com...
> Phantom limbs... Where is the information coming from? If the lower leg is
> amputated at the knee, does the sensation of an itchy foot come from the
> nerve endings at the tip of the knee (point of amputation), or an
> interpretation the brain is making based on the body image. If the latter
> true, how does this affect all sensations we feel? Can that be measured?
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