Research in the Ashton
Graybiel Spatial Orientation Laboratory covers human
spation orientation, motor control, and adaptation. Basic
mechanisms and their practical implications are both of
interest. Unique approaches include 1) emphasis on intersensory
and sensory-motor interactions, 2) recognition of the intimate
relationship between moment-to-moment control and long-term
adaptation, and 3) exploitation of non-terrestrial conditions,
such as space flight, artificial gravity and virtual environments
and of clinical populations with loss of vision, proprioception,
or vestibular function.
Our research on control of reaching movements illustrates
these themes. Some stages of making goal directed reaching
movements are localizing a target, planning a path, and
generating the forces necessary to move. From a mechanical
perspective, combinations of muscle length and force produce
posture and movement. A traditional experimental approach
to inferring the nature of neural control involves unexpectedly
perturbing movement trajectories and observing the resulting
errors. We have developed a new perturbation paradigm employing
a rotating room facility located in our laboratory that
simulates an "artificial gravity" environment.
Our paradigm involves comparing movements made in a normal
stationary environment to ones made in the rotating room.
The centrifugal force field generated during rotation may
be similar enough to the terrestrial gravitational field
for a rotating space vehicle to be used for generating "artificial
gravity". However, rotation also leads to Coriolis forces
that are potential source of side effects that could prohibit
the use of rotation for artificial gravity. For example
reaching movements made in a rotating room generate Coriolis
forces that are directly proportional to the cross product
of the room's angular velocity and the arm's linear velocity
within the room. Our research has investigated the implications
of Coriolis force perturbations for astronaut performance
and health during long duration space missions in a rotating
space vehicle, and we have also made use of the Coriolis
force perturbations for basic research.
Coriolis force perturbations in the rotating room are
transient (only present when the arm is moving), unexpected
and unique because they act without local contact. We have
found that reaching movements are deviated, in endpoint
and path, in the direction of Coriolis forces in the rotating
room, whereas traditional perturbation techniques have not
resulted in endpoint errors. Adaption to Coriolis forces
occurs within 10-20 movements such that straight, accurate
reaches are again possible, and mirror-image aftereffects
occur when rotation stops. The pattern of findings has shown
that 1) the field of candidate control variables for movement
execution does not include muscle stiffness, 2) proprioception
is paramount in trajectory monitoring and adaptation, 3)
the relevant proprioceptive information includes a strong
cutaneous component in addition to muscle spindle, joint
and tendon signals, 4) cutaneous inputs from perturbations
during movement execution are utilized in different ways
from cutaneous signals generated by contact with surfaces
at movement termination, 5) posture and movement involve
separate control elements, 6) the nervous system represents
and utilizes detailed "expectations" about the forces that
will be encountered during a reaching movement, and 7) the
movement plan is more dynamic than we and others originally
assumed.
Other problems being actively investigated include 1)
the role of Coriolis and other unusual forces in eye-head
coordination and calibration, 2) vestibular, and proprioceptive
influences on visual and auditory localization, 3) haptic,
visual, auditory and vestibular factors in perceived body
orientation, position sense, static posture and locomotion,
4) causes and ways of alleviating motion sickness disorientation
and misorientation in space flight, artificial gravity and
virtual environments.
Selected publications
DiZio, P., and Lackner, J.R. (1995) Motor adaptation to
Coriolis force perturbations of reaching movements: endpoint
but not trajectory adaptation transfers to the non-exposed
arm. Journal of Neurophysiology 74(4): 1787-1792.
[abstract]
Leslie KR, Stickgold R, DiZio P, Lackner JR, Hobson JA.
(1997) The effect of optokinetic stimulation on daytime
sleepiness. Arch Ital Biol. 135(3):219-28.
[abstract]
DiZio P, Li W, Lackner JR, Matin L. (1997) Combined influences
of gravitoinertial force level and visual field pitch on
visually perceived eye level. J Vestib Res. 7(5):381-92.
[abstract]
Easton RD, Greene AJ, DiZio P, Lackner JR. (1998) Auditory
cues for orientation and postural control in sighted and
congenitally blind people. Exp Brain Res. 118(4):541-50.
[abstract]
Lackner JR, DiZio P. (1998) Gravitoinertial force background
level affects adaptation to coriolis force perturbations
of reaching movements. J Neurophysiol. 80(2):546-53.
[abstract]
Lackner JR, DiZio P. (1998) Adaptation in a rotating artificial
gravity environment. Brain Res Rev. 28(1-2):194-202.
[abstract]
Lackner JR, DiZio P, Jeka J, Horak F, Krebs D, Rabin E.
(1999) Precision contact of the fingertip reduces postural
sway of individuals with bilateral vestibular loss. Exp
Brain Res. 126(4):459-66. [abstract]
Rabin E., Bortolami S.B., DiZio P., Lackner J.R. (1999)
Haptic stabilization of posture: changes in arm proprioception
and cutaneous feedback for different arm orientations.
J Neurophysiol. 82(6):3541-9. [abstract]
Lackner JR, DiZio P. (2000) Human orientation and movement
control in weightless and artificial gravity environments.
Exp Brain Res. 130(1):2-26. [abstract]
Cohn JV, DiZio P, Lackner JR. (2000) Reaching during virtual
rotation: context specific compensations for expected coriolis
forces. J Neurophysiol. 83(6):3230-40. [abstract]
Lackner JR, DiZio PA.(2000) Aspects of body self-calibration.
Trends Cogn Sci. 4(7):279-288. [abstract]
Lackner JR, DiZio P. (2000) Artificial gravity as a countermeasure
in long-duration space flight. J Neurosci Res. 62(2):169-76.
[abstract]
DiZio P, Lackner JR. (2000) Congenitally blind individuals
rapidly adapt to coriolis force perturbations of their reaching
movements J Neurophysiol. 84(4):2175-80. [abstract]
Lackner JR, Rabin E, DiZio P. (2000) Fingertip Contact
Suppresses the Destabilizing Influence of Leg Muscle Vibration.
J Neurophysiol. 84(5):2217-2224. [abstract]
Lackner JR, Rabin E, DiZio P. Stabilization of posture
by precision touch of the index finger with rigid and flexible
filaments. Exp Brain Res, 139: 454-464, 2001.
[abstract]
DiZio P, Lackner JR, Held RM, Shinn-Cunningham B, Durlach
NI. Gravitoinertial force magnitude and direction influence
head-centric auditory localization. J. Neurophysiol.,
85: 2455-2460, 2001. [abstract]
DiZio, Paul and James R. Lackner. Coriolis-force-induced
trajectory and endpoint deviations in the reaching movements
of labyrinthine-defective subjects. J. Neurophysiol.
85: 784-789, 2001. [abstract]
Last update: Thursday, September 6, 2001. E-mail comments
or questions to the webmaster.
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