Article

Many patients with Parkinson's disease (PD) develop freezing of gait
(FoG), which may manifest as a hesitation or "getting stuck" when they attempt to
pass through a doorway. In two experiments, we asked whether FoG is associated
with (1) a deficit in internal representation of one's body size with respect to
a doorway and (2) a mismatch between imagined and actual walking times when
passing through a doorway. METHODS: 23 subjects with PD (11 with and 13 without
FoG) and 10 control subjects of similar age completed two experiments. In the
Passability experiment, subjects judged the passability of doorways with
different apertures scaled to their body widths. We compared passability
estimates across groups. In the Imagery experiment, subjects timed themselves
while: (1) imagining walking through doorways of different apertures and from
different distances and (2) actually walking in the same conditions they had just
imagined. We compared imagined and actual walking durations across groups and
conditions. RESULTS: In the Passability experiment, the estimated just-passable
doorway was wider, relative to body width, in PD subjects than in control
subjects, but there was no difference between PD subjects with and without FoG.
In the Imagery experiment, subjects in all groups walked more slowly through
narrow doorways than though wide doorways, and subjects with FoG walked much more
slowly through the narrowest doorways. PD subjects with FoG showed a large
discrepancy between actual and imagined time to pass through narrow doorways,
unlike PD subjects without FoG and control subjects. CONCLUSIONS: The equivalent
passability judgments in PD subjects with and without FoG indicate that FoG is
not specifically associated with a deficit in ability to internally represent
space with reference to body size. However, the large difference in duration
between actual and imagined walking through narrow doorways in subjects with FoG
suggests that PD subjects with FoG did not know how much they would slow down to
pass through narrow doorways. The observed discrepancy between imagined and
actual walking times may point to a specific problem that contributes to the
occurrence of FoG. These results also suggest that caution should be used when
interpreting brain imaging results from locomotor imagery studies with PD
subjects who have FoG.
CI - Copyright (c) 2011 Elsevier Ltd. All rights reserved.

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