Bodywide fluctuations support manual exploration: Fractal fluctuations in posture predict perception of heaviness and length via effortful touch by the hand

Mangalam, Madhur; Chen, Ryan; McHugh, Terrence R.; Singh, Tarkeshwar; Kelty-Stephen, Damian G.

doi:10.1016/j.humov.2019.102543

Cited by 35 publications

(27 citation statements)

References 66 publications

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“…Greater flow of multifractality across all pairs of anatomical locations did not always resulted in more accurate judgments, but the flow of multifractal fluctuations across specific body segments played a crucial role in perceiving accurately. Hence, we cannot claim the simple wholesale conclusion that more multifractality entails higher accuracy [27,28]. Instead, dynamic touch hinges upon specific interplay amongst many degrees of freedom, each individually fluctuating multifractally-that is, with multiple fractal forms across time and fluctuation size-and the flow of these multifractal fluctuations may provide an essential medium for perceptual information [12,14].…”

Section: Discussionmentioning

confidence: 98%

“…The predictive role of fractal fluctuations appears to even extend across the body. When people manually heft a grasped object with their hands, the relatively distant measure of postural sway CoP at their feet has a fractal signature that helps predict the perceptual judgments [27,28]. Hence, fractal fluctuations provide a window into how specific patterns of movements spread across the entire body to support perceptual goals that seem-intuitively at least-specifically localized amidst the anatomical periphery.…”

Section: Modulating the Bodywide Flow Of Mechanical Fluctuations To Imentioning

confidence: 99%

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Multifractal signatures of perceptual processing on anatomical sleeves of the human body

Mangalam

Carver²,

Kelty-Stephen

2020

Preprint

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Research into haptic perception typically concentrates on mechanoreceptors and their supporting neuronal processes. This focus risks ignoring crucial aspects of active perception. For instance, bodily movements influence the information available to mechanoreceptors, entailing that movement facilitates haptic perception. Effortful manual wielding of an object prompts feedback loops at multiple spatiotemporal scales, rippling outwards from the wielding hand to the feet, maintaining an upright posture, and interweaving to produce a nonlinear web of fluctuations throughout the body. Here, we investigated whether and how this bodywide nonlinearity engenders a flow of multifractal fluctuations that could support perception of object properties via dynamic touch. Blindfolded participants manually wielded weighted dowels and reported judgments of heaviness and length. Mechanical fluctuations on the anatomical sleeves, from hand to the upper body, as well as to the postural center of pressure, showed evidence of multifractality arising from nonlinear temporal correlations across scales. The modeling of impulse-response functions obtained from vector autoregressive (VAR) analysis revealed that distinct sets of pairwise exchanges of multifractal fluctuations entailed accuracy in heaviness and length judgments. These results suggest that the accuracy of perception via dynamic touch hinges on specific flowing patterns of multifractal fluctuations that people wear on their anatomical sleeves.Research into haptic perception typically concentrates on mechanoreceptors and their supporting neuronal processes, such as mechanoreceptor physiology and neuronal processing of passive somatosensory feedback [1,2]. Despite the significant insights of this research, this focus risks ignoring crucial aspects of active perception. For instance, bodily movements influence the information available to mechanoreceptors, entailing that movement facilitates haptic perception [3][4][5]. The present work investigated how bodywide mechanical interactions facilitate "dynamic" or "effortful" perception of heaviness and length of manuallywielded, visually-occluded objects. Specifically, we test two possibilities: first, that statistical structure in mechanical fluctuations flows across disparate anatomical locations (i.e., beyond the wielding hand) to coordinate perceptual judgments and, second, that the structure of this flow of statistical regularities impacts the accuracy of these judgments. The bodywide multifractal tensegrity (MFT) may simplify the degrees-of-freedom problem of spatiotemporally organizing afferent activityThe human body is highly complex, consisting of an enormous number of components, connected, interacting, and evolving via networks spanning multiple space and time scales. In traditional treatments of nervous-system networks, mechanoreceptor activity specifying the states of joints, muscles, and tendons flow through the spinal neurons to the brain. The challenge for this treatment is how the central executive can organize spati...

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Section: Discussionmentioning

confidence: 98%

Section: Modulating the Bodywide Flow Of Mechanical Fluctuations To Imentioning

confidence: 99%

Multifractal signatures of perceptual processing on anatomical sleeves of the human body

Mangalam

Carver²,

Kelty-Stephen

2020

Preprint

Self Cite

View full text Add to dashboard Cite

show abstract

“…This organization entails a specifically multifractal geometry that embodies multiple scale-invariant patterns of behavior (e.g., microsaccades within the saccades that intersperse larger saccades by the eye and turns by the head) across time and across space. CoP fractality has repeatedly borne a consistent relationship to perceptual judgments of visual and haptic stimuli [24][25][26][27][28][29], and research into perceptual tasks (e.g., manually wielding an object to judge heaviness or length) while standing shows that a bodywide flow of fractal fluctuations precedes and shapes the verbal articulation of perceptual judgments [30,31]. Hence, a fractal flow within posture seems to support information flow and might provide a glimpse of the control policy emerging from bodily situation in task constraints.…”

Section: Perceptual Constraints On Postural Stability Could Reshape Imentioning

confidence: 95%

“…Visually fixating brings a prestressed quiet stance into one with informational coupling with the visual stimulus. Past work has repeatedly implicated fractal fluctuations in the head and upper torso for using visual information to organize action [28,29,[65][66][67][68]. Visual inspection of IRF plots indicated rare instances of effects from or responses from CoM fractality on or to SD (1 trial in the 50-, 135-, and 305-cm conditions), but the regression modeling indicated no stable relationship.…”

Section: Glimpses Of a Possible Control Policy For Visually Guided Qumentioning

confidence: 99%

Multifractal roots of suprapostural dexterity

Kelty-Stephen¹,

Lee

Carver

et al. 2020

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A growing consensus across otherwise disparate perspectives on perception and action is that visually guided postural control emerges from within task constraints. Task constraints generate physiological fluctuations across various parts of the body. These fluctuations foster exploration of the available sensory information. For instance, standard deviation (SD) and temporal correlations of bodily sway can indicate how richly postural control samples available mechanical and visual information. Too much or too little SD entails destabilization of posture. Temporal correlations show a similar relationship, but they have also been shown to support carrying sampled information to other aspects of the postural system. The present study shows that increasing visual constraints on posture reveals an adaptive relationship between SD and temporal correlations of postural fluctuations. In short, changing the viewing distance of a fixation target shows that temporal correlations self-correct themselves across time and diminish SD across time as well. Notably, these relationships were strong for all viewing distances except the most comfortable viewing and reaching distance. This self-correcting relationship allows the visual layout itself to press the postural system into a poise for engaging with objects and events in the surrounding.

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“…26 (iii) We used detrended fluctuation analysis 44 to compute Hurst's exponent, HfGn, indexing temporal correlations in original CoP PED series (CoP_PED_HfGn_Original) and shuffled versions of each series (CoP_PED_HfGn_Shuffled) using the scaling region: 4, 8, 12,… 1024. 34 Shuffling destroys the temporal structure of a signal. (iv) Multifractal spectrum width, Δ α, indexing the extent of multifractal temporal correlations in the signal.…”

Section: Canonical Indices Of Endogenous Postural Fluctuationsmentioning

confidence: 99%

Visual effort moderates postural cascade dynamics

Mangalam¹,

Lee

Newell

et al. 2020

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Standing still and focusing on a visible target in front of us is a preamble to many coordinated behaviors (e.g., reaching an object). Hiding behind its apparent simplicity is a deep layering of texture at many scales. The task of standing still laces together activities at multiple scales: from ensuring that a few photoreceptors on the retina cover the target in the visual field on an extremely fine-scale to synergies spanning the limbs and joints at smaller scales to the mechanical layout of the ground underfoot and optic flow in the visual field on the coarser scales. Here, we used multiscale probability distribution function (PDF) analysis to show that postural fluctuations exhibit similar statistical signatures of cascade dynamics as found in fluid flow. Critically, the oculomotor strain of visually fixating different distances moderates postural cascade dynamics. Visually fixating at a comfortable viewing distance elicited posture with a similar cascade dynamics as posture with eyes closed. Greater viewing distances known to stabilize posture showed more diminished cascade dynamics. In contrast, nearest and farthest viewing distances requiring greater oculomotor strain to focus on targets elicited a dramatic strengthening postural cascade dynamics, reflecting active postural adjustments. Critically, these findings suggest that vision stabilizes posture by reconfiguring the prestressed poise that prepares the body to interact with different spatial layouts.

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Bodywide fluctuations support manual exploration: Fractal fluctuations in posture predict perception of heaviness and length via effortful touch by the hand

Cited by 35 publications

References 66 publications

Multifractal signatures of perceptual processing on anatomical sleeves of the human body

Multifractal signatures of perceptual processing on anatomical sleeves of the human body

Multifractal roots of suprapostural dexterity

Visual effort moderates postural cascade dynamics

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