One of the most fascinating aspects of brain research
is the subject of language. As in many other cases, the
malfunctions that occur in different persons for various
reasons give us insight on the mechanisms that support
our ability to talk, read and listen. Following the work
of Plaut and associates, we deal with the dyslexia disorder,
which is the overall name for a large number of reading
disorders. A Boltzmann machine neural network scheme was
trained to implement the nonlinear mapping task of graphic
representation into semantic representation, which may
model the brain sections responsible for the translation
of a written word into meanings and syllables. After training,
various types of lesions were applied and the performance
of the network was tested in order to measure the effect
of each lesion on the error rate and type distribution
that were detected. The system's errors were classified
into several categories and the distribution of errors
between the categories was studied. Using the simulations,
it is demonstrated that a finite scheduling process in
the Boltzmann machine causes the distribution of the network's
errors to be unique and different from its expected error
distribution. The phenomenon is given a mathematical explanation
rooted in the statistical mechanics basics of the Boltzmann
machine. Test results suggest the localization of certain
reading functions within the network. Comparison is made
to relevant types of dyslexia and shows resemblance in
major symptoms as well as in certain known side effects.
(JINS, 2000, 6, 620–626.)