S. Glasauer et al., GOAL-DIRECTED LINEAR LOCOMOTION IN NORMAL AND LABYRINTHINE-DEFECTIVE SUBJECTS, Experimental Brain Research, 98(2), 1994, pp. 323-335
When a subject is walking blindfolded straight ahead towards a previou
sly seen target, the brain must update an internal representation with
respect to the environment. This study examines whether the informati
on given by the vestibular system is necessary for this simple path in
tegration task and gives a quantitative description of locomotor behav
iour during the walk by comparing ten normal and seven bilateral labyr
inthine-defective (LD) subjects. Each subject performed 20 blindfolded
walks (EC) and ten walks with eyes open (EO) towards a target attache
d to the floor 4 m in front of them; these walks were made at differen
t velocities. The positions of head, trunk and feet were recorded usin
g a 3D motion analysis system. No significant difference was found bet
ween, normal and LD groups in-terms of the distance error of reaching
the target, while LD subjects showed a larger lateral error. Patch cur
vature, expressed as the standard deviation of the angle between the d
irection of one step and straight ahead, was found to be significantly
larger for LD subjects in the EC condition, demonstrating their insta
bility when walking without vision. Mean walking velocity was lower fo
r LD subjects than for normal subjects in both EC and EO conditions. B
oth groups walked faster with eyes open; LD subjects increased their v
elocity by increasing step length, normal subjects by increasing step
frequency. Head stabilisation in the frontal plane during locomotion w
as not significantly different between LD and normal subjects, whereas
both head and trunk rotation were slightly larger in LD subjects duri
ng blindfolded walking. The results show that bilateral LD subjects ar
e able to perform linear goal-directed locomotion towards memorised ta
rgets. Thus, the vestibular system does not appear to be necessary for
active linear path integration.