Structure Analysis and Modelling of Saccadic Reaction Time Distributions

 Dr. S. Gezeck, Brain Research Unit, Institute for Biophysics
 Dr. M. Biscaldi, Brain Research Unit, Institute for Biophysics
 Prof. Dr. B. Fischer, Brain Research Unit, Institute for Biophysics
 Dr. J. Timmer, FDM, Institute of Physics
 Prof. Dr. J. Honerkamp, FDM, Institute of Physics
Finished Work:
At first the 3Loop model of saccade generation (1), that is based on
neurological findings, was simulated. After setting the internal
constants of the model, it produced realistic reaction time distributions
under different physical conditions (2).
Present and future Work:
In order to develop an analytic stochastic model of saccade generation
the analytic behaviour of a stochastic driven neural network should be
analysed.
Nonparametrical methods are used to investigate the number of basic
functions in empirical reaction time distributions. The excess mass
estimator (Müller and Sawitzki, J. of the Am. Statist. Assoc.,
86:738746 (1991) ) is used to determine the number and position of the
modes (3). All peaks can be classified in three classes postulated in
(1).
The nonparametrical factor analysis is developed to investigate the
number and the shape of basis functions that occur in about 20
distributions. The main idea is that the bins forming one peak scale
parallel. The basis functions could be classified in the same classes
found in (3), but often appear two peaks of the same class in the
empirical distributions.
Saccadic variables should be measured of healthy subjects with different
ages. A classification should be performed. Starting with the
correlation matrix of the variables a model should be developped.
Psychometric and saccadic variables of dyslexics and controls should
be measured to investigate the influence of weakness of reading and writing
to saccadic variables. A classification should be performed.
References:
 (1)
 B. Fischer:
The preparation of visually guided saccades,
Rev. Phys. Biochem. Pharm 106, 135, 1987
 (2)
 B. Fischer, S. Gezeck, W. Huber:
The three loop model for the generation of saccadic reaction times,
Biological Cybernetics 72, 185196, 1995
abstract
 (3)
 Gezeck S., Fischer B., Timmer J,:
Saccadic reaction times: a statistical analysis of multimodal distributions,
submitted to: Vision Research
Author: Stefan Gezeck
Express Saccade Laboratory
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