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Kevin C. Dieter, Bo Hu, David C. Knill, Duje Tadin; Visual smooth pursuit of proprioceptive signals is enhanced by task-irrelevant dynamic noise. Journal of Vision 2011;11(11):786. doi: 10.1167/11.11.786.
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© ARVO (1962-2015); The Authors (2016-present)
Smooth pursuit eye movements (SPEM) are an important mechanism for tracking behaviorally relevant objects as they move through the environment. Despite their obvious importance in tracking visual objects, studies have shown that it is possible to visually track stimuli in other modalities, albeit with greatly reduced gain (Berryhill, 2006). For example, SPEM is possible to a limited extent when tracking one's own hand in complete darkness, suggesting that proprioceptive information is available to the SPEM system. However, tracking of proprioceptive position is abolished if a stationary visual surface is presented between the observer and his/her hand (Watanabe & Shimojo, 1997), indicating that conflicting visual information either eliminates or effectively vetoes proprioceptive signals. Nevertheless, it may be possible for certain types of visual information to actually enhance these signals.
Here, we demonstrate that presentation of a dynamic random noise stimulus facilitates smooth pursuit of proprioceptive signals. Participants (n = 8) were asked to visually track their hand as they moved a slider along a one-dimensional track. There were four conditions: Hand Visible (dimly lit room), Hand Invisible (total darkness), Static Noise and Dynamic Noise. In the noise conditions, subjects moved their hands behind a mirror that displayed either dynamic or stationary white noise.
Replicating previous results, participants showed a limited ability to visually track proprioceptive signals alone (Hand Invisible), and this ability was eliminated by the presentation of static noise. Importantly, presenting dynamic visual noise markedly improved participants' ability to smoothly track their hand movements, resulting in a larger proportion of trials containing SPEM, higher gain in the pursuit signals, and fewer catch-up saccades during the dynamic noise condition.
Evidently, task-irrelevant motion information can improve visual smooth pursuit of proprioceptive signals. The addition of visual motion noise functionally unmasks the influence of proprioceptive inputs to the smooth pursuit system.
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