No subject

<pitcher at mrctr.upmc.edu>

An alternative hypothesis (which allows for real-time learning):

>What are the real implications of this study? One of the most
>important facts is that although both groups had identical 
>training sessions, they had different levels of learning of the 
>motor task because of what they did subsequent to practice. From 
>this fact alone one can conclude with some degree of certainty 
>that real-time, instantaneous learning is not used for learning 
>motor skills. How can one say that? One can make that conclusion 
>because if real-time learning was used, there would have been 
>continuous and instantaneous adjustment of the synaptic strengths 
>orconnection weights during practice in whatever net the brain was
>using to learn the motor task. This means that all persons trained
>in that particular motor task should have had more or less the 
>same "trained net," performance-wise, at the end of that training
>session, regardless of what they did subsequently. (It is assumed
>here that the task was learnable, given enough practice, and that
>both groups had enough practice.) With complete, permanent 
>learning (weight-adjustments) from "real-time learning," there 
>should have been no substantial differences in the learnt skill 
>between the two groups resulting from any activity subsequent to 
>practice. But this study demonstrates the opposite, that there 
>were differences in the learnt skill simply because of the nature 
>of subsequent activity. So real-time, instantaneous and permanent 
>weight-adjustment (real-time learning) is contradictory to the 
>results here.

The results are not contradictory to the idea of realtime
learning, if one can assume that the second group was
updating (learning in) the same part of the brain (network)
during the second training period as the first. It is well
demonstrated in most modalities that subsquent
'interference' training will degrade performance on
a newly learned skill. From the little bit I know of neural
networks, I'm guessing that the same could be shown with
models as well. The point is, if two groups of networks (or
brains) are trained in an identical fashion, then one group
is trained with a new skill in the same modality, the
initial learning will be 'overwritten' to some extent in
that group. The same sets of weights will need to be
updated.

Remember also that PET results are showing _relative_ blood
flow, so it cannot be assumed that the cerebellar activity
seen after learning was not present during the learning. On
the contrary, it was almost certainly necessary for the
motor activity to take place. The difference was that the
frontal cortex was also highly active, presumably
facilitating learning in the motor pathways.
Once a subject reached a certain level of proficiency with
the task, there would be less need for the frontal cortex 
to reinforce/facilitate the motor cortex activity, and 
those (motor) areas would appear to be most active.

------------------------------------------------------------