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Exp Brain Res (2007) 181:297305 DOI 10.1007/s00221-007-0935-y
RESEARCH ARTICLE
Dual-target interference for the automatic pilot in the dorsal stream
Brendan D. Cameron Ian M. Franks James T. Enns Romeo Chua
Received: 19 October 2006 / Accepted: 27 February 2007 / Published online: 21 March 2007 Springer-Verlag 2007
Abstract When a target moves to a new location during a rapid aiming movement, the hand follows it, even when the participant intends not to. Pisella et al. (Nat Neurosci 3:729736, 2000) claim that the posterior parietal cortex, in the dorsal visual stream, is responsible for this automatic pilot. Here we study the limits of automaticity in the dorsal stream through analysis of aiming movements to two targets in sequence. Participants were given a goal of moving rapidly to two targets, with the Wrst movement being completed within approximately 200 ms. On 30% of trials, the Wrst or the second target jumped unpredictably to a new location at movement onset, allowing us to measure the automatic capture of the hand. The results showed that hand movements were less responsive to target jumps in a 2-target condition than in a 1-target control condition. This indicates that the automatic pilot is susceptible to interference from multiple visual inputs, implying that the dorsal stream is less eVective at guiding actions online when multiple targets are attended.
Keywords Pointing Dorsal stream Sequential aiming Automatic guidance Attention
Introduction
Online corrections to visually-guided movements are thought to be mediated by the dorsal visual stream (Pisella et al. 2000; Desmurget et al. 1999). This neural stream projects to the posterior parietal cortex (PPC), and has been shown to guide movements in the absence of conscious awareness (for a review, see Goodale and Westwood 2004). In fact, Milner and Goodales (1995) perception/action model of dual-stream visual processing relegates all conscious visual processing to the ventral stream (in the inferotemporal cortex), leaving the dorsal stream to carry out its tasks automatically. The robustness of this automaticity has been demonstrated by movement corrections to unperceived target perturbations (Goodale et al. 1986; Pelisson et al. 1986; Prablanc and Martin 1992) and by participants inability to inhibit corrections to perceived target perturbations (Pisella et al. 2000; Cressman et al. 2006). The PPC has, accordingly, been described as an automatic pilot...