Modulation of Saccadic Curvature by Spatial Memory and Associative Learning
The way the eye travels during a saccade typically does not follow a straight line but rather shows some curvature instead. Converging empirical evidence has demonstrated that curvature results from conflicting saccade goals when multiple stimuli in the visual periphery compete for selection as the...
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|Summary:||The way the eye travels during a saccade typically does not follow a straight line but rather shows some curvature instead. Converging empirical evidence has demonstrated that curvature results from conflicting saccade goals when multiple stimuli in the visual periphery compete for selection as the saccade target (Van der Stigchel, Meeter, & Theeuwes, 2006). Curvature away from a competing stimulus has been proposed to result from the inhibitory deselection of the motor program representing the saccade towards that stimulus (Sheliga, Riggio, & Rizzolatti, 1994; Tipper, Howard, & Houghton, 2000). For example, if participants are instructed to perform a saccade towards a defined target stimulus and to ignore a simultaneously presented nearby distractor stimulus, a saccade landing on the target typically exhibits curvature away from the distractor (e. g. Doyle & Walker, 2001).
The present thesis reports how trajectories of saccadic eye movements are affected by spatial memory and associative learning. The final objective was to explore if the curvature effect can be used to investigate associative learning in an experimental paradigm where competing saccade targets are retrieved from associative memory rather than being sensory events. The thesis incorporates manuscripts on the following working steps to accomplish this objective: The first manuscript presents the computer software that was written in order to derive measure of saccadic curvature from the recorded eye movement traces. The second manuscript replicates and extends prior reports on the effect of (non-associative) spatial working memory on saccade deviations (Theeuwes, Olivers, & Chizk, 2005). The third manuscript uses a novel associative learning task to demonstrate that changes in saccadic curvature during associative learning comply with the acquisition and extinction of competing associations as predicted by the Rescorla-Wagner model (Rescorla & Wagner, 1972), originally put forward to explain classical conditioning in animals.|