Table 1.
Demographic, neuropsychiatric and virtual reality characteristics.
Figure 1.
A graphical depiction of the experimental paradigm. Patients used a set of footpedals to navigate a virtual corridor while lying on their back in a 3T MRI scanner. During the navigation of the corridor, either Direct (e.g. the word ‘WALK’) or Indirect (e.g. the word ‘RED’ written in the colour red) cues were presented on the bottom 1/3 of a computer screen. Patients were asked to interpret these cues and determine whether to continue walking or to stop and await the next cue based on a pre-learned rule. The experiment was designed with interspersed blocks of low cognitive load (left block) and high cognitive load (right block), in which Indirect and Direct cues were presented, respectively.
Table 2.
Brain areas showing the largest increased BOLD response in the second level analyses comparing a Complex WALK cue with a Simple WALK cue.
Figure 2.
Cortical surface rendering of the major areas of increased and decreased BOLD response during the comparison of the Indirect WALK cue and the Direct WALK cue. A similar pattern was seen when comparing PD patients with and without FOG. Colour intensity on the graph represents the t-value obtained from the 2nd-level analysis of each group (corrected with a false detection rate of p<0.05).
Figure 3.
Differences between two groups (patients without FOG > patients with FOG).
Slices of the brain representing the main regions of increased BOLD contrast in the comparison of patients without FOG > patients with FOG (corrected with a false detection rate of p<0.05) presented in the coronal (y = 6), sagittal (x = 32) and axial (z = −1) slices of a representative single T1 image. The major differences were found in the bilateral anterior insula, the bilateral ventral striatum and the pSMA. These differences were significant after controlling for group differences in motor severity, affective disturbance and impaired attentional set-shifting ability.
Figure 4.
Results of the Region-of-Interest Analysis when viewing an Indirect > Direct cue (patients without FOG > patients with FOG).
Results from the direct comparison of the contrast values from regions-of-interest between patients without FOG and patients with FOG. Error bars represent the estimated standard error for each value. Key: L = left; R = right; pSMA = presupplementary motor area; STN = subthalamic nucleus; AI = anterior insula; VS = ventral striatum. Significance levels: * – p<0.05; ** – p<0.01.