Friday, December 21, 2007

More on Learning

Also in reply to The Devil is in the Details:

Matthias, you mentioned:
attention is the driving force behind cortical plasticity - the same stimulus is able to produce two different outcomes - depending on how much attention is directed towards the stimulus.

Stimulus discrimination (paying attention to what and where a stimulus is applied) - changes the cortex in a completely different way than simple passive tactile stimulation.

I agree, and it seems things can get even more complex. What if the "stimulus" which focuses "attention" (simple choice about what to attend to? Locus of control? The illusion of free will?) inside as opposed to outside? Endogenous as opposed to exogenous?

The authors of this paper, Differences Between Intention-based and Stimulus-based Actions set out to see if there was a difference;
Abstract. Actions carried out in response to exogenous stimuli and actions selected endogenously on the basis of intentions were compared in terms of their behavioral(movement timing) and electrophysiological (EEG) profiles. Participants performed a temporal bisection task that involved making left or right key presses at the midpoint between isochronous pacing signals (a sequence of centrally-presented letters). In separate conditions, the identity of each letter either (1) prescribed the location of the subsequent key press response (stimulus-based) or (2) was determined by the location of the preceding keypress, in which case participants were instructed to generate a random sequence of letters (intention-based). The behavioral results indicated that stimulus-based movements occurred earlier in time than intention-based movements. The EEG results revealed that activity reflecting stimulus evaluation and response selection was most pronounced in the stimulus-based condition, whereas activity associated with the general readiness to act was strongest in the intention-based condition. Together, the behavioral and electrophysiological findings provide evidence for two modes of action planning, one mediated by stimulus-response bindings and the other by action-effect bindings. The comparison of our results to those of an earlier study (Waszaketal.,2005) that employed spatially congruent visuo-motor mappings rather than symbolic visuo-motor mappings suggests that intention-based actions are controlled by similar neural pathways in both cases, but stimulus-based actions are not.

Perhaps you would be interested in deconstructing this paper with me to determine how it is relevant to PT and especially to pain perception as it concerns us. I'm sure it is, but I think it might require a team effort. What do you think?

Certainly learning is involved, as we see in page 14 in the results section. The authors considered "the ideomotor approach" in which "intention-based actions arise automatically through the anticipation of their sensory effects" (bottom page 9, top page 10).

When I read it a few days ago, something fell into place that never had before. If the expectation or "mental representation" is that moving will cause pain, then it will. But.. if another idea is supplied, i.e., "Find a way to move without causing pain", then different mental representations could be built, learned, attended to, become an endogenous "stimulus".

At least, that's how I'm interpreting it at the moment. Our work is supposed to be all about helping people physically regain their "illusion of free will".. ability to move freely as they wish, without hurting. Mirror therapy is a visual movement illusion and works well to provide the "brain" with a new "idea", skin stretching provides a kinesthetic movement illusion and works well (at least clinically/anecdotally) to do the same... If this is useful, simply asking a patient to initiate, develop, then operate their own "illusion" of moving without hurting, could be an idea-seed they could create and develop in their brain.


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