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Author Biess, A.; Flash, T.; Liebermann, D.G.
Title Riemannian geometric approach to human arm dynamics, movement optimization, and invariance Type Journal Article
Year 2011 Publication Physical Review. E, Statistical, Nonlinear, and Soft Matter Physics Abbreviated Journal Phys Rev E Stat Nonlin Soft Matter Phys
Volume 83 Issue 3 Pt 1 Pages (down) 031927
Keywords Arm/*physiology; Biomechanics; Computer Simulation; Humans; Kinetics; Male; Models, Biological; Models, Statistical; Models, Theoretical; *Movement; Psychomotor Performance/*physiology; Range of Motion, Articular/physiology; Reaction Time/physiology; Space Perception/*physiology; Torque
Abstract We present a generally covariant formulation of human arm dynamics and optimization principles in Riemannian configuration space. We extend the one-parameter family of mean-squared-derivative (MSD) cost functionals from Euclidean to Riemannian space, and we show that they are mathematically identical to the corresponding dynamic costs when formulated in a Riemannian space equipped with the kinetic energy metric. In particular, we derive the equivalence of the minimum-jerk and minimum-torque change models in this metric space. Solutions of the one-parameter family of MSD variational problems in Riemannian space are given by (reparameterized) geodesic paths, which correspond to movements with least muscular effort. Finally, movement invariants are derived from symmetries of the Riemannian manifold. We argue that the geometrical structure imposed on the arm's configuration space may provide insights into the emerging properties of the movements generated by the motor system.
Address Bernstein Center for Computational Neuroscience, DE-37073 Gottingen, Germany. armin@nld.ds.mpg.de
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Language English Summary Language Original Title
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ISSN 1539-3755 ISBN Medium
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Notes PMID:21517543 Approved no
Call Number Serial 29
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Author Finkbeiner, Matthew; Friedman, Jason
Title The flexibility of nonconsciously deployed cognitive processes: Evidence from masked congruence priming Type Journal Article
Year 2011 Publication PLoS ONE Abbreviated Journal
Volume 6 Issue 2 Pages (down) e17095
Keywords
Abstract Background

It is well accepted in the subliminal priming literature that task-level properties modulate nonconscious processes. For example, in tasks with a limited number of targets, subliminal priming effects are limited to primes that are physically similar to the targets. In contrast, when a large number of targets are used, subliminal priming effects are observed for primes that share a semantic (but not necessarily physical) relationship with the target. Findings such as these have led researchers to conclude that task-level properties can direct nonconscious processes to be deployed exclusively over central (semantic) or peripheral (physically specified) representations.

Principal Findings

We find distinct patterns of masked priming for “novel” and “repeated” primes within a single task context. Novel primes never appear as targets and thus are not seen consciously in the experiment. Repeated primes do appear as targets, thereby lending themselves to the establishment of peripheral stimulus-response mappings. If the source of the masked priming effect were exclusively central or

peripheral, then both novel and repeated primes should yield similar patterns of priming. In contrast, we find that both novel and repeated primes produce robust, yet distinct, patterns of priming.

Conclusions

Our findings indicate that nonconsciously elicited cognitive processes can be flexibly deployed over both central and peripheral representations within a single task context. While we agree that task level properties can influence nonconscious processes, our findings sharply constrain the extent of this influence. Specifically, our findings are inconsistent with extant accounts which hold that the influence of task-level properties is strong enough to restrict the deployment of nonconsciously elicited cognitive processes to a single type of representation (i.e. central or peripheral).
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Notes Approved no
Call Number Penn State @ write.to.jason @ Serial 22
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Author Awasthi, Bhuvanesh; Friedman, Jason; Williams, Mark
Title Faster, stronger, lateralized: Low spatial frequency information supports face processing Type Journal Article
Year 2011 Publication Neuropsychologia Abbreviated Journal
Volume 49 Issue 13 Pages (down) 3583-3590
Keywords
Abstract Distinct visual pathways are selectively tuned for processing specific spatial frequencies. Recently, Awasthi, Friedman and Williams (2011) reported fast categorisation of faces at periphery, arguing for primacy of low spatial frequency (LSF) information in face processing. However, previous studies have also documented rapid categorization of places and natural scenes. Here, we tested if the LSF advantage is face specific or also involved in place perception. We used visually guided reaching as a continuous behavioral measure to examine the processing of LSF and high spatial frequency (HSF) hybrids, presented at the periphery. Subjects reached out and touched targets and their movements were recorded. The trajectories revealed that LSF interference was both 95 ms earlier and stronger for faces than places and was lateralized to the left visual field. The early processing of LSF information supports the assumption that faces are prioritised and provides a (neural) framework for such specialised processing.
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Language Summary Language Original Title
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Notes Approved no
Call Number Penn State @ write.to.jason @ Serial 25
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Author Awasthi, Bhuvanesh; Friedman, Jason; Williams, Mark A
Title Processing of low spatial frequency faces at periphery in choice reaching tasks Type Journal Article
Year 2011 Publication Neuropsychologia Abbreviated Journal
Volume 49 Issue 7 Pages (down) 2136-2141
Keywords
Abstract Various aspects of face processing have been associated with distinct ranges of spatial frequencies. Configural processing of faces depends chiefly on low spatial frequency (LSF) information whereas high spatial frequency (HSF) supports feature based processing. However, it has also been argued that face processing has a foveal-bias (HSF channels dominate the fovea). Here we used reach trajectories as a continuous behavioral measure to study perceptual processing of faces. Experimental stimuli were LSF–HSF hybrids of male and female faces superimposed and were presented peripherally and centrally. Subject reached out to touch a specified sex and their movements were recorded. The reaching trajectories reveal that there is less effect of (interference by) LSF faces at fovea as compared to periphery while reaching to HSF targets. These results demonstrate that peripherally presented LSF information, carried chiefly by magnocellular channels, enables efficient processing of faces, possibly via a retinotectal (subcortical) pathway.
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Notes Approved no
Call Number Serial 24
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Author Zopf, Regine; Truong, Sandra; Finkbeiner, Matthew; Friedman, Jason; Williams, Mark A
Title Viewing and feeling touch modulates hand position for reaching Type Journal Article
Year 2011 Publication Neuropsychologia Abbreviated Journal
Volume 49 Issue 5 Pages (down) 1287–1293
Keywords
Abstract Action requires knowledge of our body location in space. Here we asked if interactions with the external world prior to a reaching action influence how visual location information is used. We investigated if the temporal synchrony between viewing and feeling touch modulates the integration of visual and proprioceptive body location information for action. We manipulated the synchrony between viewing and feeling touch in the Rubber Hand Illusion paradigm prior to participants performing a ballistic reaching task to a visually specified target. When synchronous touch was given, reaching trajectories were significantly shifted compared to asynchronous touch. The direction of this shift suggests that touch influences the encoding of hand position for action. On the basis of this data and previous findings, we propose that the brain uses correlated cues from passive touch and vision to update its own position for action and experience of self-location.
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Language Summary Language Original Title
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Notes Approved no
Call Number Penn State @ write.to.jason @ Serial 23
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