Unique temporal profiles for planned and unplanned termination of movement in Parkinson’s Disease
Poster No:
2068
Submission Type:
Abstract Submission
Authors:
Apoorva Karekal1, Blake Sims1, Mackenzie Carnes1, Allison Prince1, Cinthia Munez1, Alexander Rockhill2, Kelsey Schultz1, Nicki Swann1
Institutions:
1University of Oregon, Eugene, OR, 2Oregon Health & Science University, Eugene, OR
First Author:
Co-Author(s):
Introduction:
Parkinson's Disease (PD) is a common movement disorder affecting millions worldwide. Individuals with PD have been shown to exhibit impaired inhibitory control, at times, leading to impulsivity and error, especially in tasks that demand high cognitive effort. Experimentally, inhibitory control is often assessed using a standard stop task. In this task participants respond to a go signal with a button press. However, on a minority of trials the go signal is followed by another stimuli (a "stop signal") indicating that participants should halt their initiated response. A challenge with the use of this task is that the cognitive process underlying the sudden need to inhibit a motor response is intertwined with the motor output itself. This complicates interpretation of behaviour and physiology during this task. To address this limitation, we have used a novel stop task called the continuous movement task (CMST), which assesses planned and unplanned inhibition of movement. Participants move a computer mouse during a countdown and halt the movement in response to a stop signal which occurs either at the end of the countdown or at an earlier, unpredictable, time. Here the process of suddenly having to inhibit a movement (unplanned stopping) can be directly compared with the planned stopping of movement - allowing a more clear isolation of the cognitive component. The goal of this study is to examine differences in planned and unplanned stopping as a measure of inhibitory control in PD.
Methods:
The continuous movement stop task (CMST) was assessed in a cohort of 25 healthy age-matched controls and 26 individuals with PD during acquisition of electroencephalogram (EEG). Individuals with PD arrived OFF medication (12 hours of medication abstention) and completed the CMST. Participants then took their medication and CMST was performed again (all in the same day). For healthy controls, subjects performed the CMST while EEG was measured in the same way. The CMST consists of 80 planned and unplanned stop trials.
In planned trials, subjects were required to move the cursor in a circular motion upon seeing the 'Go' cue, follow a countdown from 6-1, and stop moving the cursor when the 'stop' cue appeared on the computer screen. In unplanned trials, the 'stop' cue appeared at an unpredictable time before the countdown reached 1. The stop completion time (SCT) was assessed for both planned and unplanned trials, measured as the time from the appearance of the 'stop' cue to when the cursor movement came to a full stop. The go reaction time (GRT) was also measured as the time from the appearance of the 'go' cue to the initial movement of the cursor.
In planned trials, subjects were required to move the cursor in a circular motion upon seeing the 'Go' cue, follow a countdown from 6-1, and stop moving the cursor when the 'stop' cue appeared on the computer screen. In unplanned trials, the 'stop' cue appeared at an unpredictable time before the countdown reached 1. The stop completion time (SCT) was assessed for both planned and unplanned trials, measured as the time from the appearance of the 'stop' cue to when the cursor movement came to a full stop. The go reaction time (GRT) was also measured as the time from the appearance of the 'go' cue to the initial movement of the cursor.
Results:
Our findings demonstrate significant differences in SCT and GRT between groups, as revealed by paired t-tests. The SCT was significantly higher in unplanned than planned stop trials across all groups (p<0.01) (Figure 1). Additionally, individuals with PD, both OFF and ON medication, exhibited higher SCT compared to healthy controls in both planned and unplanned trials (p<0.05) (Figure 2). Conversely, the GRT was higher in individuals with PD OFF medication compared to those ON medication (p<0.05) and there was no difference between patients and controls. EEG findings are forthcoming.
·Stop completion time (SCT) between across healthy control and individuals with Parkinson's Disease ( ON and OFF medication state) for planned and unplanned trials
·Stop completion time (SCT) between planned and unplanned trials in healthy control and individuals with Parkinson's Disease ( ON and OFF medication state)
Conclusions:
These results indicate that SCT in unplanned stopping is slower than planned stopping and that this effect is present regardless of disease or medication status. Additionally, people with PD took longer to stop compared to controls - but did not take longer to go - perhaps corresponding to a deficit in inhibition. Finally, there was no difference in stop completion time in patients ON versus OFF medication in spite of significant slowing in go reaction time in patients off medication.
Disorders of the Nervous System:
Neurodegenerative/ Late Life (eg. Parkinson’s, Alzheimer’s) 2
Higher Cognitive Functions:
Executive Function, Cognitive Control and Decision Making
Motor Behavior:
Motor Planning and Execution 1
Motor Behavior Other
Keywords:
Cognition
Motor
Movement Disorder
1|2Indicates the priority used for review