Document Detail

Detecting multimodality in saccadic reaction time distributions in gap and overlap tasks.
MedLine Citation:
PMID:  9652079     Owner:  NLM     Status:  MEDLINE    
In many cases the distribution of saccadic reaction times (SRT) deviates considerably from a unimodal distribution and may often exhibit several peaks. We present a statistical approach to determining the number and form of the individual peaks. The overall density of the reaction times fi(t), i = 1...M obtained in M different experiments with the same subject is described as the sum of K basis functions xk(t), k = 1...K with different weights and an error term. A change in the experimental conditions is assumed to cause a change in the weights, not in the basis functions. We minimize the square of the difference (measured data minus approximation), divided by the error of the data. Incrementing K step by step we determine the necessary number of basis functions. This method is applied to data of six subjects tested in different saccade tasks. We detect five different modes: two in the range 80-140 ms (express modes), two in the range 145-190 ms (fast-regular mode) and one at about 230 ms (slow-regular mode). These modes are located at about the same positions for different subjects. The method presented here not only proves statistically the existence of several modes in SRT distributions but also allows the distributions to be described by a few characteristic numbers that go beyond the mean values and standard deviations.
S Gezeck; J Timmer
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Biological cybernetics     Volume:  78     ISSN:  0340-1200     ISO Abbreviation:  Biol Cybern     Publication Date:  1998 Apr 
Date Detail:
Created Date:  1998-07-20     Completed Date:  1998-07-20     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  7502533     Medline TA:  Biol Cybern     Country:  GERMANY    
Other Details:
Languages:  eng     Pagination:  293-305     Citation Subset:  IM    
Brain Research Unit, University of Freiburg, Germany.
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MeSH Terms
Conditioning (Psychology) / physiology*
Data Interpretation, Statistical
Middle Aged
Models, Neurological*
Photic Stimulation
Reaction Time / physiology*
Saccades / physiology*

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