Oculomotor capture and inhibition of return: Evidence for an oculomotor suppression account of IOR

Previous research has shown that when subjects search for a particular target object the sudden appearance of a new object captures the eyes on a large proportion of trials. The present study examined whether the onset affects the oculomotor system even when the eyes move directly towards the target. Using a modified version of the oculomotor paradigm (see Theeuwes, Kramer, Hahn, & Irwin, 1998) we show that when the eyes moved to the target object, subsequent saccades were inhibited from moving to a location at which a new object had previously appeared (inhibition-of-return; IOR). Whether or not a saccade to the onset was executed had no effect on the size of the inhibition. In particular conditions, the trajectories of saccades to the target objects were slightly curved in the opposite direction of the onset. The data are interpreted in the context of a novel hypothesis regarding oculomotor IOR

Oculomotor capture by surprising onsets

The present study examined the effect of surprising onsets on oculomotor behaviour. Participants were required to execute a saccadic eye movement to a colour singleton target. After a series of trials an unexpected onset distractor was abruptly presented on the surprise trial. The presentation of the onset was repeated on subsequent trials. The results showed that the onset captured the eyes for 28% of the participants on the surprise trial, but this percentage decreased after repeated exposure to the onset. Furthermore, saccade latencies to the target were increased when a surprising onset was presented. After repeated exposure to the onset, latencies to the target decreased to the preonset level. The results suggest that when the onset is not part of participants' task set it has a strong effect on oculomotor behaviour. Once the task set has been updated and the onset no longer comes as a surprise its effect on oculomotor behaviour is dramatically reduced

Transfer of information into working memory during attentional capture

Previous research has shown that task-irrelevant onsets can capture spatial attention even when attending to the onset is inconsistent with our intentions. The present study investigated whether information acquired during attentional capture is transferred into working memory. To measure whether this is the case, 25% of visual search trials were followed by a distractor recognition task. The results showed that the onset letter was recognized more often than a nononset letter. In addition, the magnitude of attentional capture was positively correlated with the onset letter recognition advantage. The results suggest that attentional capture results in transfer of information into working memory

Programming of endogenous and exogenous saccades: Evidence for a competitive integration model

this article. Correspondence concerning this article should be addressed to Richard Godijn, Department of Cognitive Psychology, Vrije Universiteit, Van Der Boechorststraat 1, 1081 BT Amsterdam, the Netherlands. E-mail: [email protected] Journal of Experimental Psychology: Copyright 2002 by the American Psychological Association, Inc. Human Perception and Performance 2002, Vol. 28, No. 5, 1039--1054 0096-1523/02/$5.00 DOI: 10.1037//0096-1523.28.5.1039 1039 inhibitory (Figure 1B), but when two nearby locations are activated, the combined activation results in a relatively high peak somewhere between the two locations (Figure 1C). In accordance with Trappenberg et al. (2001), the execution of a saccade is triggered when the activation at a specific location in the saccade map reaches threshold. Trappenberg et al. (2001) developed a neural-field model based on the principle of competitive integration of exogenous and endogenous signals in the SC. Their model produced activity patterns very similar to activity patterns of cells in the SC. Furthermore, the saccade latencies of the model fit well with a range of oculomotor effects, such as the remote distractor effect. The remote distractor effect (e.g., Walker, Deubel, Schneider, & Findlay, 1997) refers to the finding that saccade latencies are longer when a target is presented simultaneously with a distractor but only when the distance between target and onset is relatively large. Furthermore, when the distractor is presented near the target, the eyes often land in between target and distractor (global effect or center-of-gravity effect; e.g., Coren & Hoenig, 1972; Findlay, 1982). These findings are consistent with the lateral inhibition structure of the competitive integration model. However, it is important to note ..

Spatial working memory and Inhibition of Return

Recently we showed that maintaining a location in spatial working memory affects saccadic eye movement trajectories, in that the eyes deviate away from the remembered location (Theeuwes, Olivers, & Chizk, 2005). Such saccade deviations are assumed to be the result of inhibitory processes within the oculomotor system. The present study investigated whether this inhibition is related to the phenomenon of inhibition of return (IOR), the relatively slow selection of previously attended locations as compared with new locations. The results show that the size of IOR to a location was not affected by whether or not the location was kept in working memory, but the size of the saccade trajectory deviation was affected. We conclude that inhibiting working memory–related eye movement activity is not the same as inhibiting a previously attended location in space. Working memory is a system that allows for the temporary storage of information until a task is completed (see, e.g., Baddeley, 1986). Awh and colleagues (Awh & Jonides, 2001; Awh, Jonides, & Reuter-Lorenz, 1998) provided evidence for a strong link between working memory and attention. For example, they showed that when a locatio

Spin-dependent thermoelectric transport coefficients in near-perfect quantum wires

Thermoelectric transport coefficients are determined for semiconductor quantum wires with weak thickness fluctuations. Such systems exhibit anomalies in conductance near 1/4 and 3/4 of 2e^2/h on the rising edge to the first conductance plateau, explained by singlet and triplet resonances of conducting electrons with a single weakly bound electron in the wire [T. Rejec, A. Ramsak, and J.H. Jefferson, Phys. Rev. B 62, 12985 (2000)]. We extend this work to study the Seebeck thermopower coefficient and linear thermal conductance within the framework of the Landauer-Buettiker formalism, which also exhibit anomalous structures. These features are generic and robust, surviving to temperatures of a few degrees. It is shown quantitatively how at elevated temperatures thermal conductance progressively deviates from the Wiedemann-Franz law.Comment: To appear in Phys. Rev. B 2002; 3 figure

TUNNELING SPECTROSCOPY OF QUANTUM CHARGE FLUCTUATIONS IN THE COULOMB BLOCKADE

We present a theory of Coulomb blockade oscillations in tunneling through a pair of quantum dots connected by a tunable tunneling junction. The positions and amplitudes of peaks in the linear conductance are directly related, respectively, to the ground state energy and to the dynamics of charge fluctuations. We study analytically both strong and weak interdot tunneling. As the tunneling decreases, the period of the peaks doubles, as observed experimentally. In the strong tunneling limit, we predict a striking power law temperature dependence of the peak amplitudes.Comment: 4 pages, revtex3.0, 1 figure uuencode

The Thermopower of Quantum Chaos

The thermovoltage of a chaotic quantum dot is measured using a current heating technique. The fluctuations in the thermopower as a function of magnetic field and dot shape display a non-Gaussian distribution, in agreement with simulations using Random Matrix Theory. We observe no contributions from weak localization or short trajectories in the thermopower.Comment: 4 pages, 3 figures, corrected: accidently omitted author in the Authors list, here (not in the article

Quantum Chaos in Open versus Closed Quantum Dots: Signatures of Interacting Particles

This paper reviews recent studies of mesoscopic fluctuations in transport through ballistic quantum dots, emphasizing differences between conduction through open dots and tunneling through nearly isolated dots. Both the open dots and the tunnel-contacted dots show random, repeatable conductance fluctuations with universal statistical proper-ties that are accurately characterized by a variety of theoretical models including random matrix theory, semiclassical methods and nonlinear sigma model calculations. We apply these results in open dots to extract the dephasing rate of electrons within the dot. In the tunneling regime, electron interaction dominates transport since the tunneling of a single electron onto a small dot may be sufficiently energetically costly (due to the small capacitance) that conduction is suppressed altogether. How interactions combine with quantum interference are best seen in this regime.Comment: 15 pages, 11 figures, PDF 2.1 format, to appear in "Chaos, Solitons & Fractals