title: Drawing ellipses in water: evidence for dynamic constraints in the relation between velocity and path curvature.
abstract: Several types of continuous human movements comply with the so-called Two-Thirds Power Law (2/3-PL) stating that velocity (V) is a power function of the radius of curvature (R) of the endpoint trajectory. The origin of the 2/3-PL has been the object of much debate. An experiment investigated further this issue by comparing two-dimensional drawing movements performed in air and water. In both conditions, participants traced continuously quasi-elliptic trajectories (period T = 1.5 s). Other experimental factors were the movement plane (horizontal/vertical), and whether the movement was performed free-hand, or by following the edge of a template. In all cases a power function provided a good approximation to the V-R relation. The main result was that the exponent of the power function in water was significantly smaller than in air. This appears incompatible with the idea that the power relationship depends only on kinematic constraints and suggests a significant contribution of dynamic factors. We argue that a satisfactory explanation of the observed behavior must take into account the interplay between the properties of the central motor commands and the visco-elastic nature of the mechanical plant that implements the commands.
authors.affiliation: Laboratory of Neuromotor Physiology, Santa Lucia Foundation, via Ardeatina, 306-00179, Rome, Italy.|Centre of Space BioMedicine, University of Rome Tor Vergata, 00133, Rome, Italy.
authors.forename: Giovanna
authors.initials: G
authors.lastname: Catavitello
authors.affiliation: Laboratory of Neuromotor Physiology, Santa Lucia Foundation, via Ardeatina, 306-00179, Rome, Italy. y.ivanenko@hsantalucia.it.
authors.forename: Yuri P
authors.initials: YP
authors.lastname: Ivanenko
authors.affiliation: Laboratory of Neuromotor Physiology, Santa Lucia Foundation, via Ardeatina, 306-00179, Rome, Italy.|Centre of Space BioMedicine, University of Rome Tor Vergata, 00133, Rome, Italy.|Department of Systems Medicine, University of Rome Tor Vergata, 00133, Rome, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Lacquaniti
authors.affiliation: Laboratory of Neuromotor Physiology, Santa Lucia Foundation, via Ardeatina, 306-00179, Rome, Italy.|Centre of Space BioMedicine, University of Rome Tor Vergata, 00133, Rome, Italy.
authors.forename: Paolo
authors.initials: P
authors.lastname: Viviani
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D009068:Movement / Q000502:physiology*; D014783:Viscosity; D014867:Water
chemical_list: D014867:Water
keywords: Drawing movements; Endpoint trajectory; Kinematic constraints; Two-thirds power law; Visco-elastic forces
references.citation: J Neurosci. 1985 Jul;5(7):1688-703
references.pmid: 4020415
references.citation: J Neurophysiol. 1998 Aug;80(2):696-714
references.pmid: 9705462
references.citation: Proc Natl Acad Sci U S A. 2015 Jul 21;112(29):E3950-8
references.pmid: 26150514
references.citation: J Neurosci. 2002 Sep 15;22(18):8201-11
references.pmid: 12223574
references.citation: Exp Brain Res. 2001 Jan;136(1):60-72
references.pmid: 11204414
references.citation: Neuroscience. 1986 Dec;19(4):1393-405
references.pmid: 3822127
references.citation: J Exp Psychol Hum Percept Perform. 1992 Aug;18(3):603-23
references.pmid: 1500865
references.citation: J Exp Psychol Hum Percept Perform. 1988 Nov;14(4):622-37
references.pmid: 2974873
references.citation: Eur J Neurosci. 2007 Oct;26(8):2391-403
references.pmid: 17953626
references.citation: Exp Brain Res. 2005 Apr;162(2):145-54
references.pmid: 15586276
references.citation: Science. 1992 Jun 19;256(5064):1692-5
references.pmid: 1609282
references.citation: J Exp Psychol Hum Percept Perform. 1985 Dec;11(6):828-45
references.pmid: 2934511
references.citation: Biol Cybern. 2007 Jun;96(6):577-601
references.pmid: 17406889
references.citation: Neurosci Lett. 2001 Jun 1;305(1):65-9
references.pmid: 11356309
references.citation: J Exp Psychol Hum Percept Perform. 1991 Feb;17(1):198-218
references.pmid: 1826312
references.citation: J Neurophysiol. 1996 Nov;76(5):2853-60
references.pmid: 8930238
references.citation: Neuroscience. 1982 Feb;7(2):431-7
references.pmid: 7078732
references.citation: Vision Res. 1997 Feb;37(3):347-53
references.pmid: 9135867
references.citation: PLoS Comput Biol. 2009 Jul;5(7):e1000426
references.pmid: 19593380
references.citation: Neuroscience. 1983 Sep;10(1):211-8
references.pmid: 6646421
references.citation: Nature. 1998 Aug 20;394(6695):780-4
references.pmid: 9723616
references.citation: Exp Brain Res. 2009 Apr;194(2):259-83
references.pmid: 19153724
references.citation: Biol Cybern. 1983;46(2):135-47
references.pmid: 6838914
references.citation: J Neurophysiol. 2009 Feb;101(2):1002-15
references.pmid: 19073811
references.citation: J Neurosci. 1997 May 15;17(10):3932-45
references.pmid: 9133411
references.citation: J Exp Psychol Hum Percept Perform. 1995 Feb;21(1):32-53
references.pmid: 7707032
references.citation: J Mot Behav. 1987 Dec;19(4):518-25
references.pmid: 15136275
references.citation: Biol Cybern. 2007 Feb;96(2):147-63
references.pmid: 17031664
references.citation: Biol Cybern. 1989;61(2):89-101
references.pmid: 2742921
references.citation: Science. 1994 Jul 22;265(5171):540-2
references.pmid: 8036499
references.citation: Acta Psychol (Amst). 1983 Oct;54(1-3):115-30
references.pmid: 6666647
references.citation: J Speech Lang Hear Res. 2002 Feb;45(1):127-42
references.pmid: 14748644
references.citation: Cortex. 2009 Mar;45(3):325-39
references.pmid: 18678364
references.citation: J Neurophysiol. 2008 Sep;100(3):1171-83
references.pmid: 18562557
references.citation: Neuroreport. 1997 Nov 10;8(16):3447-52
references.pmid: 9427305
references.citation: Exp Brain Res. 2013 Jun;227(4):535-46
references.pmid: 23649968
references.citation: Neuroreport. 2002 Jul 2;13(9):1171-4
references.pmid: 12151763