Abstract
Background: Patients with Parkinson’s disease (PD) commonly show spatially asymmetric behaviors, such as veering while attempting to walk in a straight line. While there is general agreement that the lateral motor dysfunction contributes to asymmetric behaviors in PD, it is dispute regarding whether the spatial perception is also biased. In addition, it is not clear whether PD impairs the speed of spatial information process, i.e., the efficiency of information process.Objectives: To assess the visuospatial representation and efficiency of spatial information processing in hemi-PD.Methods: Two saccadic tasks were employed: non-spatial cue evoked saccade and spatial cue evoked saccade. In the former task, an identical visual stimulus (appeared on the body mid-sagittal plane) was artificially associated with a fixed saccadic target (left or right) in a given session. In the latter task, subjects were instructed to make a rightward or leftward saccade based on the perceived location of a visual cue (left vs. right side of the body mid-sagittal plane). We estimated the location of subjective straight ahead (SSA) for each subject by using a psychometric fitting function to fit the location judgment results, enabling evaluation of the symmetry of representation between the left and right hemifields. In addition, since the locations of saccadic targets were same in these two tasks, thus, for each individual subject, the elongated saccadic reaction time (SRT) in the latter task, comparing with the former one, mainly reflects the time spent on judgment of the spatial location of visual cue, i.e., spatial perception. We also assessed the efficiency of spatial perception between two hemispheres, through comparing the normalized SRT (i.e., SRT difference between two tasks) between trials with leftward and rightward judgments.Results: Compared with healthy control subjects (HCs), the SSA was shifted to the contralesional side in both left onset PD (LPD, lesion of right substantia nigra) and right onset PD (RPD, lesion of left substantia nigra) patients. The process of spatial information was significantly longer when a spatial cue appeared in the contralesional hemifield.Conclusions: Patients with hemi-PD showed biased visuospatial representation between left and right hemifields and decreased the efficiency of spatial information processing in the contralesional side. Such results indicate that the hemi-PD impairs both spatial representation and the efficiency of spatial information process, which might contribute to asymmetric behaviors.
Highlights
The classical motor symptoms of Parkinson’s disease (PD) include bradykinesia, muscular rigidity, rest tremor and postural and gait impairment (Kalia and Lang, 2015)
Since eye position can strongly affect the spatial judgment (Morgan, 1978; Jeannerod and Biguer, 1989; Barbeito and Simpson, 1991; Lewald and Ehrenstein, 2000), it is possible that the opposite subjective straight ahead (SSA) deviation between right onset PD (RPD) and left onset PD (LPD) was related to the deviation of eye position during location judgment of the visual cue, even though subjects were required to maintain fixation straight ahead
We calculated the eye position of each subject while the visual cue appeared at the location that was nearest to the SSA (HC, −0.5◦; RPD, 0.5◦; LPD −1.0◦), and compared the difference in eye positions among subjects of three groups (HC, LPD and RPD) when they made same directional judgment
Summary
The classical motor symptoms of Parkinson’s disease (PD) include bradykinesia, muscular rigidity, rest tremor and postural and gait impairment (Kalia and Lang, 2015). Patients with PD commonly exhibit spatially asymmetric behaviors (Lee et al, 2001b; Amick et al, 2006), such as veering while attempting to walk straight ahead (Ren et al, 2015). Patients with Parkinson’s disease (PD) commonly show spatially asymmetric behaviors, such as veering while attempting to walk in a straight line. While there is general agreement that the lateral motor dysfunction contributes to asymmetric behaviors in PD, it is dispute regarding whether the spatial perception is biased. It is not clear whether PD impairs the speed of spatial information process, i.e., the efficiency of information process
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
