Sustained division of the attentional spotlight

A Corrigendum to this article was published on 04 December 2003


By voluntarily directing attention to a specific region of a visual scene, we can improve our perception of stimuli at that location1. This ability to focus attention upon specific zones of the visual field has been described metaphorically as a moveable spotlight or zoom lens that facilitates the processing of stimuli within its ‘beam’2,3. A long-standing controversy has centred on the question of whether the spotlight of spatial attention has a unitary beam or whether it can be divided flexibly to disparate locations2,4,5,6. Evidence supporting the unitary spotlight view has come from numerous behavioural3,7,8,9,10 and electrophysiological11,12 studies. Recent experiments, however, indicate that the spotlight of spatial attention may be divided between non-contiguous zones of the visual field for very brief stimulus exposures (<100 ms)13,14. Here we use an electrophysiological measure of attentional allocation (the steady-state visual evoked potential) to show that the spotlight may be divided between spatially separated locations (excluding interposed locations) over more extended time periods. This spotlight division appears to be accomplished at an early stage of visual-cortical processing.

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Figure 1: Schematic diagram of stimulus sequences, electrode positions and typical SSVEPs for attended (dashed lines) and unattended (solid line) conditions.
Figure 2: Mean SSVEP amplitudes at each position under the four experimental conditions and normalized amplitudes averaged across the 8.7 Hz and 20.3 Hz SSVEPs.
Figure 3: Spline-interpolated isocontour maps of the grand average attend minus unattend amplitude under conditions of attending to separated locations.


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We thank N. Williams, H. Messmer and C.-M. Giabbiconi for help in data recording. This work was supported by the Deutsche Forschungsgemeinschaft and by NIMH.

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Correspondence to M. M. Müller.

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Müller, M., Malinowski, P., Gruber, T. et al. Sustained division of the attentional spotlight. Nature 424, 309–312 (2003).

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