Abstract
This paper presents a computer simulation of the three-loop model for the temporal aspects of the generation of visually guided saccadic eye movements. The intention is to reproduce complex experimental reaction time distributions by a simple neural network. The operating elements are artificial but realistic neurones. Four modules are constructed, each consisting of 16 neural elements. Within each module, the elements are connected in an all-to-all manner. The modules are working parallel and serial according to the anatomically and physiologically identified visuomotor pathways including the superior colliculus, the frontal eye fields, and the parietal cortex. Two transient-sustained input lines drive the network: one represents the visual activity produced by the onset of the saccade target, the other represents a central activity controlling the preparation of saccades, e.g. the end of active fixation. 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 times are produced as a natural consequence of the model structure. The gap effect on saccadic reaction times is correctly produced by the model: depending only on the gap duration (all model parameters unchanged) express, fast-regular, and slow-regular saccades are obtained in different numbers. In agreement with the experiments, bi- or trimodal distributions are produced only for medium gap durations (around 200 ms), while for shorter or longer gaps the express mode disappears and the distributions turn bi- or even unimodal. The effect of varying the strength of the transient-sustained components and the ongoing activity driving the hierarchically highest module are considered to account for the interindividual variability of the latency distributions obtained from different subjects, effects of different instructions to the same subject, and the observation of express makers (subjects who produce exclusively express saccades). How the model can be extended to describe the spatial aspects of the saccade system will be discussed as well as the effects of training and/or rapid adaptation to experimental conditions.
Article PDF
Similar content being viewed by others
Explore related subjects
Discover the latest articles, news and stories from top researchers in related subjects.Avoid common mistakes on your manuscript.
References
Biscaldi M, Weber H, Fischer B, Stuhr V (1994) Mechanism of fixation in man: evidence from saccadic reaction times. In: Findlay J (ed) Eye Movement research: mechanisms, processes and applications. Elsevier, North-Holland, Amsterdam (in print)
Buhmann J, Schulten K (1986) Associative recognition and storage in a model network of physiological neurons. Biol Cybern 54:319–335
Dominey PF, Arbib MA (1992) A cortico-subcortical model for generation of spatially accurate sequential saccades. Cereb Cortex 2:153–175
Fischer B (1987) The preparation of visually guided saccades. Rev Physiol Biochem Pharmacol 106:1–35
Fischer B, Boch R (1983) Saccadic eye movements after extremely short reaction times in the monkey. Brain Res 260:21–26
Fischer B, Boch R (1991) Cerebral cortex. In: Carpenter R (ed) Vision and visual dysfunction Vol 8. Eye movements. Macmillan, London, pp 277–296
Fischer B, Ramsperger E (1984) Human express saccades: extremely short reaction times of goal directed eye movements. Exp Brain Res 57:191–195
Fischer B, Ramsperger E (1986) Human express saccades: effects of randomization and daily practice. Exp Brain Res 64:569–578
Fischer B, Weber H (1990) Saccadic reaction times of dyslexic and age-matched normal subjects. Perception 19:805–818
Fischer B, Weber H (1993) Express saccades and visual attention. Behav Brain Sci 16:553–567
Fischer B, Boch R, Ramsperger E (1984) Express-saccades of the monkey: effect of daily training on probability of occurrence and reaction time. Exp Brain Res 55:232–242
Fischer B, Weber H, Biscaldi M, Aiple F, Otto P, Stuhr V (1993) Separate populations of visually guided saccades in humans: reaction times and amplitudes. Exp Brain Res 92:528–541
Jüttner M, Wolf W (1992) Occurrence of human express saccades depends on stimulus uncertainty and stimulus sequence. Exp Brain Res 89:678–681
Kingstone A, Klein RM (1993) What are human express saccades? Percep Psychophys 54:260–273
Langer TP, Kaneko CR (1990) Brainstem afferents to the oculomotor omnipause neurons in monkey. J Comp Neurol 295:413–427
Mayfrank L, Mobashery M, Kimmig H, Fischer B (1986) The role of fixation and visual attention in the occurrence of express saccades in man. Eur Arch Psychiatry Neurol Sci 235:269–275
Mountcastle VB, Motter BC, Steinmetz MA, Sestokas AK (1987) Common and differential effects of attentive fixation on the excitability of parietal and prestriate (V4) cortical visual neurons in the macaque monkey. J Neurosci 7:2239–2255
Munoz DP, Wurtz RH (1992) Role of the rostral superior colliculus in active visual fixation and execution of express saccades. J Neurophysiol 67:1000–1002
Reulen JP (1984) Latency of visually evoked saccadic eye movements. I. Saccadic latency and the facilitation model. Biol Cybern 50:251–262
Robinson DA (1981) Control of eye movements. In: Brookhart JM, Mountcastle VB, Brooks VB, Geiger SR (eds) Handbook of physiology — the nervous system II. American Physiological Society, Bethesda, pp 1277–1320
Rohrer WH, Sparks DL (1993) Express saccades: the effect of spatial and temporal uncertainty. Vision Res 33:2447–2460
Saslow MG (1967) Effects of components of displacement-step stimuli upon latency for saccadic eye movement. J Opt Soc Am 57:1024–1029
Schiller PH, True SD, Conway JL (1980) Deficits in eye movements following frontal eye-field and superior colliculus ablations. J Neurophysiol 44:1175–1189
Wenban-Smith MG, Findlay JM (1991) Express saccades: is there a separate population in humans? Exp Brain Res 87: 218–222]
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Fischer, B., Gezeck, S. & Huber, W. The three-loop model: a neural network for the generation of saccadic reaction times. Biol. Cybern. 72, 185–196 (1995). https://doi.org/10.1007/BF00201483
Received:
Accepted:
Issue Date:
DOI: https://doi.org/10.1007/BF00201483