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Friedman, J., Raveh, E., Weiss, T., Itkin, S., Niv, D., Hani, M., et al. (2019). Applying Incongruent Visual-Tactile Stimuli during Object Transfer with Vibro-Tactile Feedback (Vol. 147).
Abstract: The application of incongruent sensory signals that involves disrupted tactile feedback is rarely explored, specifically with the presence of vibrotactile feedback (VTF). This protocol aims to test the effect of VTF on the response to incongruent visual-tactile stimuli. The tactile feedback is acquired by grasping a block and moving it across a partition. The visual feedback is a real-time virtual presentation of the moving block, acquired using a motion capture system. The congruent feedback is the reliable presentation of the movement of the block, so that the subject feels that the block is grasped and see it move along with the path of the hand. The incongruent feedback appears as the movement of the block diverts from the actual movement path, so that it seems to drop from the hand when it is actually still held by the subject, thereby contradicting the tactile feedback. Twenty subjects (age 30.2 +/- 16.3) repeated 16 block transfers, while their hand was hidden. These were repeated with VTF and without VTF (total of 32 block transfers). Incongruent stimuli were presented randomly twice within the 16 repetitions in each condition (with and without VTF). Each subject was asked to rate the difficulty level of performing the task with and without the VTF. There were no statistically significant differences in the length of the hand paths and durations between transfers recorded with congruent and incongruent visual-tactile signals – with and without the VTF. The perceived difficulty level of performing the task with the VTF significantly correlated with the normalized path length of the block with VTF (r = 0.675, p = 0.002). This setup is used to quantify the additive or reductive value of VTF during motor function that involves incongruent visual-tactile stimuli. Possible applications are prosthetics design, smart sport-wear, or any other garments that incorporate VTF.
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Friedman, J., & Korman, M. (2019). Observation of an expert model induces a skilled movement coordination pattern in a single session of intermittent practice. Sci Rep, 9(1), 4609.
Abstract: We tested how observation of a skilled pattern of planar movements can assist in the learning of a new motor skill, which otherwise requires rigorous long-term practice to achieve fast and smooth performance. Sixty participants performed a sequence of planar hand movements on pre-test, acquisition, post-test and 24 h post-training blocks, under 1 of 4 conditions: an observation group (OG), a slowed observation group (SOG), a random motion control group (RMCG) and a double physical training control group (DPTCG). The OG and SOG observed an expert model's right hand performing the study task intermittently throughout acquisition, RMCG observed random dots movement instead of a model. Participants in the DPTCG received extra physical practice trials instead of the visually observed trials. Kinematic analysis revealed that only in conditions with observation of an expert model there was an instant robust improvement in motor planning of the task. This step-wise improvement was not only persistent in post-training retests but was also apparently implicit and subject to further incremental improvements in movement strategy over the period of 24 hours. The rapid change in motor strategy was accompanied by a transient within-session increase in spatial error for the observation groups, but this went away by 24 h post-training. We suggest that observation of hand movements of an expert model coaligned with self-produced movements during training can significantly condense the time-course of ecologically relevant drawing/writing skill mastery.
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Dempsey-Jones, H., Wesselink, D. B., Friedman, J., & Makin, T. R. (2019). Organized Toe Maps in Extreme Foot Users. Cell Reports, 28(11), 2748–2756.e4.
Abstract: Although the fine-grained features of topographic maps in the somatosensory cortex can be shaped by everyday experience, it is unknown whether behavior can support the expression of somatotopic maps where they do not typically occur. Unlike the fingers, represented in all primates, individuated toe maps have only been found in non-human primates. Using 1-mm resolution fMRI, we identify organized toe maps in two individuals born without either upper limb who use their feet to substitute missing hand function and even support their profession as foot artists. We demonstrate that the ordering and structure of the artists’ toe representation mimics typical hand representation. We further reveal “hand-like” features of activity patterns, not only in the foot area but also similarly in the missing hand area. We suggest humans may have an innate capacity for forming additional topographic maps that can be expressed with appropriate experience.
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