Models
(see also: FDM-project,
also available in german)
3-loop model
The generation of a visually guided saccadic eye movement is a very
complex operation of the brain. There are 3 main pathways stem
connecting the retina of the eye with the efferent eye movement
generating system (EM):
- first loop: retina - striate visual cortex(V1) - superior colliculus - EM
- second loop: retina - V1 - prestriate visual cortex - frontal eye field - EM
- third loop: retina - V1 - prestriate visual cortex - parietal cortex
- frontal eye field.
Express saccades (80 ms - 120 ms in man) are generated according to the
first loop, fast regular saccades (140 ms - 170 ms in man) according to
the second loop, and slow regular saccades (180 ms - 250 ms in man)
according to the third loop.
literature:
- Fischer, B.: The preparation of visually guided saccades
Reviews in Physiology, Biochem. and Pharmacol., (1987) 106:1-35
- Fischer, B. and Boch, R.: Cerebral Cortex.
In: R. Carpenter (ed.): Eye Movements, Vol. 8: Vision and Visual Dysfunction.
- Fischer, B. and Weber, H.: Express saccades and visual attention
Behavioral and Brain Sciences, (1993) 16:553-610
neural network implemention
A neural network, consisting of 4 modules with 16 artificial but
realistic neurons was build in order to make computer simulations of the
3-loop model. Two transient-sustained input lines drive the network, the
impulses are poisson distributed. The model works completely
deterministically; its stochastic output is a consequence of the
stochastic properties of the input only. Simulations show how multimodal
distributions of saccadic reaction time are produced as a natural
consequence of the model structure. The gap effect on saccadic reaction
times is correctly produced by the model.
literature:
Fischer, B. and Gezeck, S. and Huber, W.:
The three-loop model: a neural network for the generation of
saccadic reaction times
Biol.Cybern. (1995) 72: 185-196
abstract
Detecting multimodality by a statistical methods
The excess mass test was used to analyse about 1000 data sets (of about
100 saccadic reaction times each) in order to detect the number and the
position of different peaks. With a simulation study the conservative
behaviour of this test was shown. Yet, the mean of number of peaks in
all distribution is nearly two. The distribution of the the position of
all peaks exhibits the express mode, the fast, and the slow regular
modes.
Author: Dr. Stefan Gezeck
back to Express Saccade Laboratory