[Abstract Title]. - Society for Neuroscience

was 71% more common, and hip angular displacements were 13 degree greater, when rocking
forward than backward. Similar trends were observed during hip rocking.
Conclusion: These observations indicate the nature of the ongoing task at the time of imbalance
influences the organization of the early-stage balance recovery response, and the subsequent
tendency to execute a step. Of particular interest is the use of a hip-dominated response when
accelerating backward and an ankle-dominant response when accelerating forward or when
stationary, which highlights the ability of the CNS to adapt the recovery response to the
biomechanical constraints and cognitive demands associated with ongoing activities.
References: [1] Talbot et al. 2005; [2] Horak & Nashner 1986; [3] Horak et al 1997
Disclosures: C.D. Murnaghan, None; S.N. Robinovitch, None.
Poster
275. Posture: Kinematics and Muscle Activity
Time: Sunday, November 16, 2008, 1:00 pm - 5:00 pm
Program#/Poster#: 275.15/JJ30
Topic: D.16.d. Kinematics and Muscle Activity
Support: CFI 10653/3103
HSFC
CIHR 77548
Title: Context-dependent characteristics of locomotor steering guided by optic flow
Authors: *J. R. BERARD 1,3 , J. FUNG 2,3 , A. LAMONTAGNE 2,3 ;
2 Physical and Occup. Therapy, 1 McGill Univ., Montreal, QC, Canada; 3 Jewish Rehabil. Hospital,
research site of CRIR, Laval, QC, Canada
Abstract: Optic flow is one of the visual cues used to guide locomotion whereby heading
direction is indicated by the focus of expansion (FOE) during typical, straight ahead walking.
Under some circumstances, however, the optic flow may be conflicting with other types of
sensory information whereby the heading direction may no longer correspond to the FOE
location. We investigated the context-dependent characteristics of visually guided locomotor
steering by manipulating 1) the type of optic flow; 2) the location of the FOE; and 3) the
instruction to use or disregard visual information presented. Subjects were evaluated while
walking overground and wearing a head mounted display (HMD; NVisor). The scene presented
in the HMD was of a large room with vertical and horizontal cues but no obstructions. Kinematic