Levodopa Facilitates Prefrontal Cortex Activation During Dual Task Walking in Parkinson Disease

Abstract

Background. Although dopaminergic medication improves dual task walking in people with Parkinson disease (PD), the underlying neural mechanisms are not yet fully understood. As prefrontal cognitive resources are involved in dual task walking, evaluation of the prefrontal cortex (PFC) is required. Objective. To investigate the effect of dopaminergic medication on PFC activity and gait parameters during dual task walking in people with PD. Methods. A total of 20 individuals with PD (69.8 ± 5.9 years) and 30 healthy older people (68.0 ± 5.6 years) performed 2 walking conditions: single and dual task (walking while performing a digit vigilance task). A mobile functional near infrared spectroscopy system and an electronic sensor carpet were used to analyze PFC activation and gait parameters, respectively. Relative concentrations of oxygenated hemoglobin (HbO2) from the left and right PFC were measured. Results. People with PD in the off state did not present changes in HbO2 level in the left PFC across walking conditions. In contrast, in the on state, they presented increased HbO2 levels during dual task compared with single task. Regardless of medication state, people with PD presented increased HbO2 levels in the right PFC during dual task walking compared with single task. The control group demonstrated increased PFC activity in both hemispheres during dual task compared with single task. People with PD showed increases in both step length and velocity in the on state compared with the off state. Conclusions. PD limits the activation of the left PFC during dual task walking, and dopaminergic medication facilitates its recruitment.

Cortical Activity Underlying Gait Improvements Achieved With Dopaminergic Medication During Usual Walking and Obstacle Avoidance in Parkinson Disease

“…20,23,54 Taken together, our findings show that dopaminergic medication may facilitate PFC activation during challenging walking tasks. 24…”

“…HbO 2 concentration signals were averaged per region of interest (left and right PFC) and normalized by dividing them by corresponding signal amplitude (from minimum to maximum) value of the whole experiment. 24,39 We averaged left and right PFC signals for subsequent analyses. 10-13 Each of the 5 trials was divided into 2 phases: (1) a baseline period, 15 s before the instruction to start walking (the 5 s immediately before the instruction were excluded), and (2) experimental task, from 5 to 25 s walking.…”

“…The baseline HbO 2 concentration was subtracted from the HbO 2 concentration during the experimental task. 10,12,24…”

“…23 In addition, we recently demonstrated that dopaminergic medication facilitates PFC activation during dual-task walking in people with PD. 24 Thus, we hypothesized that people with PD in the off state would not increase PFC activity during obstacle avoidance (relative to unobstructed walking), whereas both people with PD in the on state and healthy older adults would present increased PFC activity. Because PD involves excessive GABAergic inhibition in thalamocortical neurons, which leads to slower cortical activity, 25,26 we expected that people with PD in the off state would present higher power at lower EEG frequencies (α power) and lower power at higher EEG frequencies (β and γ) in motor/sensorimotor areas during walking when compared with healthy older adults.…”

Executive Control of Walking in People With Parkinson’s Disease With Freezing of Gait

“…Measures of PFC activity obtained using fNIRS are reliable 23 and can differentiate healthy older adults and clinical populations, such as people with PD. 13,23,24 Existing studies focusing on FoG mainly characterize the executive control of turning. [25][26][27] People with PD with FoG have increased PFC activity while turning in place in comparison to nonfreezers.…”