Trajectory curvature in saccade sequences: spatiotopic influences vs residual motor activity

Megardon, Geoffrey, Ludwig, Casimir and Sumner, Petroc ORCID: https://orcid.org/0000-0002-0536-0510 2017. Trajectory curvature in saccade sequences: spatiotopic influences vs residual motor activity. Journal of Neurophysiology 118 (2) , pp. 1310-1320. 10.1152/jn.00110.2017

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Abstract

Saccades curve away from locations of previous fixation. Varying stimulus timing demonstrates the effects of both 1) spatiotopic representation and 2) motor residual activity from previous saccades. The spatiotopic effect can be explained if current models are augmented with an excitatory top-down spatiotopic signal. When decisions drive saccadic eye movements, traces of the decision process can be inferred from the movement trajectories. For example, saccades can curve away from distractor stimuli, which was thought to reflect cortical inhibition biasing activity in the superior colliculus. Recent neurophysiological work does not support this theory, and two recent models have replaced top-down inhibition with lateral interactions in the superior colliculus or neural fatigue in the brainstem saccadic burst generator. All current models operate in retinotopic coordinates and are based on single saccade paradigms. To extend these models to sequences of saccades, we assessed whether and how saccade curvature depends on previously fixated locations and the direction of previous saccades. With a two-saccade paradigm, we first demonstrated that second saccades curved away from the initial fixation stimulus. Furthermore, by varying the time from fixation offset and the intersaccadic duration, we distinguished the extent of curvature originating from the spatiotopic representation of the previous fixation location or residual motor activity of the previous saccade. Results suggest that both factors drive curvature, and we discuss how these effects could be implemented in current models. In particular, we propose that the collicular retinotopic maps receive an excitatory spatiotopic update from the lateral interparial region.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Psychology
Subjects:	B Philosophy. Psychology. Religion > BF Psychology
Uncontrolled Keywords:	Trajectory curvature in saccade sequences
Publisher:	American Physiological Society
ISSN:	0022-3077
Funders:	EPSRC, ESRC
Date of First Compliant Deposit:	12 June 2017
Date of Acceptance:	1 June 2017
Last Modified:	18 Nov 2023 17:27
URI:	https://orca.cardiff.ac.uk/id/eprint/101358

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