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 3-Loop 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., 86:738-746 (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 non-parametrical 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, 1-35, 1987
(2)
B. Fischer, S. Gezeck, W. Huber: The three loop model for the generation of saccadic reaction times, Biological Cybernetics 72, 185-196, 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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