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Brain Cogn. 2014 Mar;85:259-70. doi: 10.1016/j.bandc.2014.01.005. Epub 2014 Jan 30.

A model of curved saccade trajectories: spike rate adaptation in the brainstem as the cause of deviation away.

Author information

1
Cognitive Psychology, Faculty of Psychology and Education, Vrije Universiteit Amsterdam, Van der Boechorststraat 1, 1081 BT Amsterdam, The Netherlands. Electronic address: w.kruijne@vu.nl.
2
Experimental Psychology, Helmholtz Institute, Utrecht University, Heidelberglaan 2, 3584 CS Utrecht, The Netherlands.
3
Cognitive Psychology, Faculty of Psychology and Education, Vrije Universiteit Amsterdam, Van der Boechorststraat 1, 1081 BT Amsterdam, The Netherlands.

Abstract

The trajectory of saccades to a target is often affected whenever there is a distractor in the visual field. Distractors can cause a saccade to deviate towards their location or away from it. The oculomotor mechanisms that produce deviation towards distractors have been thoroughly explored in behavioral, neurophysiological and computational studies. The mechanisms underlying deviation away, on the other hand, remain unclear. Behavioral findings suggest a mechanism of spatially focused, top-down inhibition in a saccade map, and deviation away has become a tool to investigate such inhibition. However, this inhibition hypothesis has little neuroanatomical or neurophysiological support, and recent findings go against it. Here, we propose that deviation away results from an unbalanced saccade drive from the brainstem, caused by spike rate adaptation in brainstem long-lead burst neurons. Adaptation to stimulation in the direction of the distractor results in an unbalanced drive away from it. An existing model of the saccade system was extended with this theory. The resulting model simulates a wide range of findings on saccade trajectories, including findings that have classically been interpreted to support inhibition views. Furthermore, the model replicated the effect of saccade latency on deviation away, but predicted this effect would be absent with large (400 ms) distractor-target onset asynchrony. This prediction was confirmed in an experiment, which demonstrates that the theory both explains classical findings on saccade trajectories and predicts new findings.

KEYWORDS:

Brainstem; Curvature; Long lead burst neurons; Saccade deviation; Spike rate adaptation; Superior colliculus

PMID:
24486387
DOI:
10.1016/j.bandc.2014.01.005
[Indexed for MEDLINE]

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