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	Author	Friedman, Jason; SKM, Varadhan; Zatsiorsky, Vladimir M.; Latash, Mark L.
	Title	The sources of two components of variance: an example of multifinger cyclic force production tasks at different frequencies			Type	Journal Article
	Year	2009	Publication	Experimental Brain Research	Abbreviated Journal	Exp Brain Res
	Volume	196	Issue	2	Pages	263-277
	Keywords
	Abstract	In a multifinger cyclic force production task, the finger force variance measured across trials can be decomposed into two components, one that affects the combined force output (“bad variance”) and one that does not (“good variance”). Previous studies have found similar time patterns of “bad variance” and force rate leading to an approximately linear relationship between them. Based on this finding and a recently developed model of multifinger force production, we expected the “bad variance” during cyclic force production to increase monotonically with the rate of force change, both within a cycle and across trials at different frequencies. Alternatively, “bad variance” could show a dependence on task frequency, not on actual force derivative values. Healthy subjects were required to produce cyclic force patterns to prescribed targets by pressing on unidimensional force sensors, at a frequency set by a metronome. The task was performed with only the index finger, and with all four fingers. In the task with all four fingers, the “good variance” increased approximately linearly with an increase in the force magnitude. The “bad variance” showed within-a-cycle modulation similar to that of the force rate. However, an increase in the frequency did not lead to an increase in the “bad variance” that could be expected based on the natural relationships between action frequency and the rate of force change modulation. The results have been interpreted in the framework of an earlier model of multifinger force production where “bad variance” is a result of variance of the timing parameter. The unexpected lack of modulation of the “bad variance” with frequency suggests a drop in variance of the timing parameter with increased frequency. This mechanism may serve to maintain a constant acceptable level of variance under different conditions.
	Address	Department of Kinesiology, The Pennsylvania State University, University Park, PA 16802, USA
	Corporate Author				Thesis
	Publisher		Place of Publication		Editor
	Language	English	Summary Language		Original Title
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume		Series Issue		Edition
	ISSN	1432-1106	ISBN		Medium
	Area		Expedition		Conference
	Notes	PMID:19468721			Approved	no
	Call Number	Penn State @ write.to.jason @			Serial	15
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	Author	Shaklai, S.; Mimouni-Bloch, A.; Levin, M.; Friedman, J.
	Title	Development of finger force coordination in children			Type	Journal Article
	Year	2017	Publication	Experimental Brain Research	Abbreviated Journal
	Volume	235	Issue	12	Pages	3709–3720
	Keywords
	Abstract	Coordination is often observed as body parts moving together. However, when producing force with multiple fingers, the optimal coordination is not to produce similar forces with each finger, but rather for each finger to correct mistakes of other fingers. In this study, we aim to determine whether and how this skill develops in children aged 4-12 years. We measured this sort of coordination using the uncontrolled manifold hypothesis (UCM). We recorded finger forces produced by 60 typically developing children aged between 4 and 12 years in a finger-pressing task. The children controlled the height of an object on a screen by the total amount of force they produced on force sensors. We found that the synergy index, a measure of the relationship between “good” and “bad” variance, increased linearly as a function of age. This improvement was achieved by a selective reduction in “bad” variance rather than an increase in “good” variance. We did not observe differences between males and females, and the synergy index was not able to predict outcomes of upper limb behavioral tests after controlling for age. As children develop between the ages of 4 and 12 years, their ability to produce negative covariation between their finger forces improves, likely related to their improved ability to perform dexterous tasks.
	Address
	Corporate Author				Thesis
	Publisher		Place of Publication		Editor
	Language		Summary Language		Original Title
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume		Series Issue		Edition
	ISSN	1432-1106	ISBN		Medium
	Area		Expedition		Conference
	Notes				Approved	no
	Call Number	Shaklai2017			Serial	86
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	Author	Dempsey-Jones, H.; Wesselink, D.B.; Friedman, J.; Makin, T.R.
	Title	Organized Toe Maps in Extreme Foot Users			Type	Journal Article
	Year	2019	Publication	Cell Reports	Abbreviated Journal	Cell Reports
	Volume	28	Issue	11	Pages	2748-2756.e4
	Keywords
	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.
	Address
	Corporate Author				Thesis
	Publisher	Elsevier	Place of Publication		Editor
	Language		Summary Language		Original Title
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume		Series Issue		Edition
	ISSN	2211-1247	ISBN		Medium
	Area		Expedition		Conference
	Notes	doi: 10.1016/j.celrep.2019.08.027			Approved	no
	Call Number				Serial	99
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	Author	Lerner, O.; Friedman, J.; Frenkel-Toledo, S.
	Title	The effect of high-definition transcranial direct current stimulation intensity on motor performance in healthy adults: a randomized controlled trial			Type	Journal Article
	Year	2021	Publication	Journal of NeuroEngineering and Rehabilitation	Abbreviated Journal	J NeuroEngineering Rehabil
	Volume	18	Issue		Pages	103
	Keywords
	Abstract
	Address
	Corporate Author				Thesis
	Publisher		Place of Publication		Editor
	Language		Summary Language		Original Title
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume		Series Issue		Edition
	ISSN	1743-0003	ISBN		Medium
	Area		Expedition		Conference
	Notes				Approved	no
	Call Number				Serial	109
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	Author	Ezrati, O.; Friedman, J.; Dar, R.
	Title	Attenuation of access to internal states in high obsessive-compulsive individuals might increase susceptibility to false feedback: Evidence from a visuo-motor hand-reaching task			Type	Journal Article
	Year	2019	Publication	Journal of Behavior Therapy and Experimental Psychiatry	Abbreviated Journal	Journal of Behavior Therapy and Experimental Psychiatry
	Volume	65	Issue		Pages	101445
	Keywords	Obsessive-compulsive disorder; Movement; Agency; Proprioception; Proxies
	Abstract	Background and objectives The Seeking Proxies for Internal States (SPIS) model of obsessive-compulsive disorder (OCD) posits that obsessive-compulsive (OC) individuals have attenuated access to their internal states. Hence, they seek and rely on proxies, or discernible substitutes for these internal states. In previous studies, participants with high OC tendencies and OCD patients, compared to controls, showed increased reliance on external proxies and were more influenced by false feedback when judging their internal states. This study is the first to examine the effects of false feedback on performance of hand movements in participants with high and low OC tendencies. Method Thirty-four participants with high OC tendencies and 34 participants with low OC tendencies were asked to perform accurate hand reaches without visual feedback in two separate sessions of a computerized hand-reaching task: once after valid feedback training of their hand location and once with false-rotated feedback. We assessed the accuracy and directional adaptation of participants' reaches. Results As predicted, high OC participants evidenced a larger decrease in their hand positioning accuracy after training with false feedback compared to low OC participants. Limitations The generalization of our findings to OCD requires replication with a clinical sample. Conclusions These results suggest that in addition to self-perceptions, motor performance of OC individuals is prone to be overly influenced by false feedback, possibly due to attenuated access to proprioceptive cues. These findings may be particularly relevant to understanding the distorted sense of agency in OCD.
	Address
	Corporate Author				Thesis
	Publisher		Place of Publication		Editor
	Language		Summary Language		Original Title
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume		Series Issue		Edition
	ISSN	0005-7916	ISBN		Medium
	Area		Expedition		Conference
	Notes				Approved	no
	Call Number				Serial	95
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