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	Author	Kapur, Shweta; Friedman, Jason; Zatsiorsky, Vladimir M.; Latash, Mark L.
	Title	Finger interaction in a three-dimensional pressing task			Type	Journal Article
	Year	2010	Publication	Experimental Brain Research	Abbreviated Journal
	Volume	203	Issue	1	Pages	101-118
	Keywords
	Abstract	Accurate control of forces produced by the fingers is essential for performing object manipulation. This study examines the indices of finger interaction when accurate time profiles of force are produced in different directions, while using one of the fingers or all four fingers of the hand. We hypothesized that patterns of unintended force production among shear force components may involve features not observed in the earlier studies of vertical force production. In particular, we expected to see unintended forces generated by non-task fingers not in the direction on the instructed force but in the opposite direction as well as substantial force production in directions orthogonal to the instructed direction. We also tested a hypothesis that multi-finger synergies, quantified using the framework of the uncontrolled manifold hypothesis, will help reduce across-trials variance of both total force magnitude and direction. Young, healthy subjects were required to produce accurate ramps of force in five different directions by pressing on force sensors with the fingers of the right (dominant) hand. The index finger induced the smallest unintended forces in non-task fingers. The little finger showed the smallest unintended forces when it was a non-task finger. Task fingers showed substantial force production in directions orthogonal to the intended force direction. During four-finger tasks, individual force vectors typically pointed off the task direction, with these deviations nearly perfectly matched to produce a resultant force in the task direction. Multi-finger synergy indices reflected strong co-variation in the space of finger modes (commands to fingers) that reduced variability of the total force magnitude and direction across trials. The synergy indices increased in magnitude over the first 30% of the trial time and then stayed at a nearly constant level. The synergy index for stabilization of total force magnitude was higher for shear force components as compared to the downward pressing force component. The results suggest complex interactions between enslaving and synergic force adjustments, possibly reflecting the experience with everyday prehensile tasks. For the first time, the data document multi-finger synergies stabilizing both shear force magnitude and force vector direction. These synergies may play a major role in stabilizing the hand action during object manipulation.
	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		ISBN		Medium
	Area		Expedition		Conference
	Notes	in press			Approved	no
	Call Number	Penn State @ write.to.jason @			Serial	20
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	Author	Noy, L.; Alon, U.; Friedman, J.
	Title	Corrective jitter motion shows similar individual frequencies for the arm and the finger			Type	Journal Article
	Year	2015	Publication	Experimental Brain Research	Abbreviated Journal	Exp Brain Res
	Volume	233	Issue	4	Pages	1307-1320
	Keywords
	Abstract	A characteristic of visuomotor tracking of non-regular oscillating stimuli are high-frequency jittery corrective motions, oscillating around the tracked stimuli. However, the properties of these corrective jitter responses are not well understood. For example, does the jitter response show an idiosyncratic signature? What is the relationship between stimuli properties and jitter properties? Is the jitter response similar across effectors with different inertial properties? To answer these questions, we measured participants' jitter frequencies in two tracking tasks in the arm and the finger. Thirty participants tracked the same set of eleven non-regular oscillating stimuli, vertically moving on a screen, once with forward-backward arm movements (holding a tablet stylus) and once with upward-downward index finger movements (with a motion tracker attached). Participants' jitter frequencies and tracking errors varied systematically as a function of stimuli frequency and amplitude. Additionally, there were clear individual differences in average jitter frequencies between participants, ranging from 0.7 to 1.15 Hz, similar to values reported previously. A comparison of individual jitter frequencies in the two tasks showed a strong correlation between participants' jitter frequencies in the finger and the arm, despite the very different inertial properties of the two effectors. This result suggests that the corrective jitter response stems from common neural processes.
	Address
	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	0014-4819	ISBN		Medium
	Area		Expedition		Conference
	Notes	PMID:25630905			Approved	no
	Call Number				Serial	76
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	Author	Raveh, E.; Friedman, J.; Portnoy, S.
	Title	Visuomotor behaviors and performance in a dual-task paradigm with and without vibrotactile feedback when using a myoelectric controlled hand			Type	Journal Article
	Year	2018	Publication	Assistive Technology	Abbreviated Journal	Assistive Technology
	Volume	30	Issue		Pages	274-280
	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	1040-0435	ISBN		Medium
	Area		Expedition		Conference
	Notes				Approved	no
	Call Number				Serial	85
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	Author	Kaufman-Cohen, Y.; Levanon, Y.; Friedman, J.; Yaniv, Y.; Portnoy, S.
	Title	Home exercise in the dart-throwing motion plane after distal radius fractures: A Pilot Randomized Controlled Trial			Type	Journal Article
	Year	2020	Publication	Journal of Hand Therapy	Abbreviated Journal
	Volume		Issue		Pages
	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		ISBN		Medium
	Area		Expedition		Conference
	Notes				Approved	no
	Call Number				Serial	103
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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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