Alignment to natural and imposed mismatches between the senses

Abstract

Does the nervous system continuously realign the senses so that objects are seen and felt in the same place? Conflicting answers to this question have been given. Research imposing a sensory mismatch has provided evidence that the nervous system realigns the senses to reduce the mismatch. Other studies have shown that when subjects point with the unseen hand to visual targets, their end points show visual-proprioceptive biases that do not disappear after episodes of visual feedback. These biases are indicative of intersensory mismatches that the nervous system does not align for. Here, we directly compare how the nervous system deals with natural and imposed mismatches. Subjects moved a hand-held cube to virtual cubes appearing at pseudorandom locations in three-dimensional space. We alternated blocks in which subjects moved without visual feedback of the hand with feedback blocks in which we rendered a cube representing the hand-held cube. In feedback blocks, we rotated the visual feedback by 5° relative to the subject's head, creating an imposed mismatch between vision and proprioception on top of any natural mismatches. Realignment occurred quickly but was incomplete. We found more realignment to imposed mismatches than to natural mismatches. We propose that this difference is related to the way in which the visual information changed when subjects entered the experiment: the imposed mismatches were different from the mismatch in daily life, so alignment started from scratch, whereas the natural mismatches were not imposed by the experimenter, so subjects are likely to have entered the experiment partly aligned.

Errors in visuo-haptic and haptic-haptic location matching are stable over long periods of time

“…The results confirm that the matching errors are subjectdependent (Van Beers et al, 1998;Smeets et al, 2006;Sousa et al, 2010;Rincon-Gonzalez et al, 2011;Kuling et al, 2013;Van der Kooij et al, 2013;Kuling et al, 2014), and show that they are also very consistent across time. Previously, Rincon-Gonzalez et al (2011) found consistent visuo-haptic matching errors in a passive task, and Smeets et al (2006) reported very consistent matching errors in an active task.…”

“…Several studies have examined the errors that are found when matching a visually perceived with a haptically perceived position (visuo-haptic task; (Van Beers, Sittig, & Denier van der Gon, 1998;Smeets et al, 2006;Sousa, Brenner, & Smeets, 2010;Rincon-Gonzalez, Buneo, & Helms Tillery, 2011;Kuling, Brenner, & Smeets, 2013;Van der Kooij, Brenner, van Beers, Schot, & Smeets, 2013;Kuling, van der Graaff, Brenner, & Smeets, 2014;Kuling, Brenner, & Smeets, 2015). The matching errors are typically smaller for targets closer to the body (Van Beers et al, 1998), and they are not influenced by external forces (Kuling et al, 2013(Kuling et al, , 2015.…”

Visuomotor Adaptation: How Forgetting Keeps Us Conservative

“…It is well known that in such cases we readily adjust our movement planning so that performance errors are reduced, a phenomenon called adaptation (see [1–3] for reviews). A fascinating phenomenon has repeatedly been observed, but has not received much attention: adaptation levels off before biases are completely removed [4–14]. This is especially clear when subjects can only see their errors after their movement has ended (as in the tennis example), but even when subjects receive continuous visual feedback, they only partially adjust their movement plan and then correct for the remaining bias on the fly (e.g.…”

“…Doing so should result in biases eventually being removed completely, but this does not always happen (e.g. [4–14]). Moreover, when there is no feedback to learn from, because the visual feedback is removed (e.g.…”

“…Moreover, when there is no feedback to learn from, because the visual feedback is removed (e.g. [14,18,19]) or manipulated to indicate that there are no errors regardless of performance (‘error clamp’; [5,13,20]), errors gradually drift back towards a baseline state, a phenomenon that cannot be explained by learning alone.…”