Academic journal article Perception and Psychophysics

Sensory Interactions in Bilateral Kinesthesia

Academic journal article Perception and Psychophysics

Sensory Interactions in Bilateral Kinesthesia

Article excerpt

Three experiments are reported that examine the masking effect on the detection of kinesthetic targets from noise presented simultaneously on the same hand or on a different hand as the target. Performance was facilitated when noise on the two hands was correlated versus uncorrelated or when it occurred on just one hand. The data are consistent with correlated input on the two hands being compared and used to reduce noise effects. Moreover, participants ignored uncorrelated noise from nontarget hands when they knew in which hand the targets would occur. There was no effect of shifts from uncorrelated to correlated noise 200 msec prior to targets, suggesting that such bottom-up changes were insufficient to induce comparison across the hands. In contrast, shifts from correlated to uncorrelated noise 200 msec prior to the target had performance at the same level as that with uncorrelated noise throughout the trial. This result indicates that the loss of correlation was detected within this interval and that when the target's location was known, participants were then able to switch attention to the target hand. The interactions between attentional filtering and the correlation on the processing of bilateral kinesthetic inputs are discussed.

Many of our interactions with our environment are accomplished with the use of both of our hands. Such use can involve different movements of the two hands to achieve a common goal, such as one hand stabilizing and turning an object while the other hand explores the object's surfaces (Lederman & Klatzky, 1987). It can also involve actions in which the movements of the hands are very similar; for instance, when judging the weight of a large object, we might lift and heft it with both hands. The coupled use of the arms is often studied in the context of movement control-that is, how we behave when we have to produce movements. A common finding is that control of the arms appears to be shared, or under a single command, when both arms are being used together. For instance, research has shown that although the movement of a single arm between two targets on a table is well described by Fitts's law in terms of its speed-accuracy relationships (Fitts, 1992), this law no longer applies under bimanual conditions. When the arms are moved simultaneously to targets of different distances, the movements are coordinated in time so that the hands arrive at their respective targets together (Kelso, Southard, & Goodman, 1979). This coupling across the hands persists even when an obstruction is placed in the path of one hand. The movement of the unobstructed hand is not only temporally coupled to that of the obstructed one, but it also shows a similar deviation in space, although with a lower amplitude (Kelso, Putnam, & Goodman, 1983). Coupling between the hands is not restricted to these relatively simple pointing situations, but is also found under conditions in which each hand may have a different functional task (e.g., one hand opening a drawer while the other reaches into it; Perrig, Kazennikov, & Wiesendanger, 1999), as well as in studies of bimanual force control (Semen & Wiesendanger, 2001a, 2001b). Researchers have suggested that such temporal and spatial coupling between the hands facilitates movement control by simplifying the organization needed to control two tasks to that of controlling just a single unit (Kelso et al., 1979).

Although the production of movement has an important role in creating this coordination, note that the sensations arising from these bilateral movements will, as a result, be coordinated in their spatiotemporal properties. One must ask whether the central nervous system might make use of this sensory consequence of the coupling system. That is, when we are presented with sensory inputs that are correlated in their changes over time, is there an assumption of a common cause? Does correlation in sensations across the hands change the way in which we process the sensations on each hand? …

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