The influence of dual task on gait during galvanic vestibular or visual motion stimulation

Introduction: Gait performance is a multimodal process. Proprioceptive, visual and vestibular inputs have a great influence on gait. Galvanic vestibular stimulation (GVS) induces a body sway to anodal side of stimulation (Fitzpatrick et al., 2004). Visual motion stimulation (VMS) in roll also can induce gait deviation (Schneider et al., 2008). There is an effect on gait if additional concurrent cognitive tasks are required while walking, i.e. dual task. The more demanding the task, the greater is gait deviation. Not only cognitive tasks but also motor task can be modified (Paquet et al., 1998).

On this basis, we examined the gait deviation of healthy subjects. Firstly, subjects had to walk with only one or none stimulus. Secondly, they should perform all conditions with dual task.

Subjects and Methods:

9 healthy subjects (4 females, aged 26–36 years, mean 29,7±3,5, all right hander) were measured in a gym (10×6m). GVS was applied at mastoid processus (direct current, 0.9–2.5mA) with anodal side either on right or left processus. VMS was applied by a random dot pattern which was rotated constantly in roll at±15degree/s. At Dual task condition subjects had to subtract 13 from a given number. Each condition was performed three times while walking about 8m. Secondly, dual task was combined three times with GVS or VMS. As baseline all subjects did three runs without any stimulus.

Gait was detected by stereo camera system and a light-emitting diode fixed at the back of the subject.

Results:

1. In VMS, dual task had a significant influence on gait deviation (p=0,006) with a general shift to the right. Post-hoc Bonferroni-Test only revealed significance in neutral condition (p=0,009) with a deviation to the right.

2. In GVS, dual task did not have a significance influence on gait deviation (p=0.1) with a shift to the right only in GVS on the right side and neutral condition and quite the same deviation in GVS on the left side.

Conclusion: The deviation to the right in neutral condition during dual task might be due to the fact that arithmetic tasks are performed in right hemisphere in right hander. Sensory input might not be integrated properly on the right in this condition and therefore might enhance the effect of imbalance of dopamine system in hemispheres (Mohr et al., 2003,2004).

The greater influence of dual task on VMS than on GVS might be because the visual system possibly has a greater interaction with the cognitive system than vestibular system has.