The results that were reported by Tsushima et al. (Reports, 15 Dec. 2006, p. 1786) are surprising, since they contradict the general view that the influence of a subthreshold is smaller than that of a suprathreshold stimulus. Nevertheless, they are in line with previous findings that subthreshold stimuli often lead to relatively robust effects (1, 2). Therefore, it would be highly interesting to use their series of psychophysical and functional magnetic resonance imaging (fMRI) experiments on participants who are known to have specific problems with visual attention, for instance, participants with spatial neglect (3, 4). This research could give a better insight in the underlying brain mechanisms and could perhaps also lead to a better clinical understanding of spatial attention deficits. Tsushima et al. found, for instance, that for the subthreshold motion, activity in the visual cortex measured by functional magnetic resonance imaging was higher, but activity in the lateral prefrontal cortex was lower than with suprathreshold motion, suggesting that subthreshold irrelevant signals are not subject to effective inhibitory control.
Could a too-high threshold in patients with spatial neglect perhaps explain why these patients have spatial attention deficits? In my point of view, this would be an exciting next step from both a theoretical and a clinical perspective.
References
1. T. Watanabe, J. E. Nanez, Y. Sasaki, Nature 413, 844 (2001).
2. A. R. Seitz, T. Watanabe, Nature 422, 36 (2003).
3. G. Rees et al., Brain 123, 1624 (2000).
4. M. Corbetta et al., Nat. Neurosci. 8, 1603 (2005).
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