Visual tracking, optokinetic aging

Ed Krug EdKrug at AOL.COM
Sun Mar 29 03:25:37 EST 1998

Hello Michael

In you message (below) the question was provoked of why aren't the very old
dyslexic?  I suggest that the answer to the question is that a character
recognition system, correctly established, has an array of character
additional recognition assets and a habit of correct recognition.
Deterioration of that system has to be extreme before it looses the ability to
correctly identify symbols.  The developing system, such as in a dyslexic
child, doesn't have the array of tools and subtle clues of proper character
recognition.  Additionally, the inherent flexability of the young system (aka
human) allows the child to make different identifications of the visual input.
This involves the issue of the amount of additional confirming data a
developing system needs to correctly identify visual (or any other) input.
That is to say that a child, dyslexic or not, requires more clues to identify
something than a practiced adult does.  If the confidence of the child is
shaken then the dyslexia becomes more severe.  The actual visual imput doesn't
change, just the willingness of the system to trust the input.  In molecular
biology terms, the stringency of the adult system is less; s/he will trust the
limited clues whereas the more stringent (less confident and less practiced)
child will reject the limited clues and go random.  

All that is just another way of saying that the blurring speed and tracking
ability of young versus old has to be measured and evaluated indenpendently of
the dramatic higher order differences between the two populations.

Edward C. Krug Ph.D.

In a message dated 98-03-26 06:59:47 EST, Michael.Hogan at UCG.IE writes:

>Have any of you come across any studies which have looked at 
>optokinetic tracking and the blurring speed (visual tracking limits) 
>in the elderly population.  Lewinson (1990) used a 3-D optical 
>scanner (basically a projector) to test the blurring speed of young 
>dyslexic and non-dyslexic groups.  He suggested that this tracking 
>ability was a measure of cerebellar functioning and found it to 
>correlate with measures of Romberg balance.  Also, both cerebellar 
>abilities had discriminative validity and distinguised dyslexic and 
>non-dyslexic groups.
>Aging is associated with declines in balance and visual tracking (if 
>you want references ask me, I'll send you a chapter).  But I have not 
>found studies which specifically use the blurring speed methodology.

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