Neural Variability in the Prefrontal Cortex as a Reflection of Neural Flexibility and Stability in Patients With Parkinson Disease

Abstract

Background and Objectives:Functional Near-Infrared Spectroscopy (fNIRS) studies provide direct evidence to the important role of the prefrontal cortex (PFC) during walking in aging and Parkinson's disease (PD). Most studies mainly explored mean HbO2 levels, while moment-to-moment variability measures have been rarely investigated. Variability measures can inform on flexibility that is imperative for adaptive function. We hypothesized that patients with PD will show less variability in HbO2 signals during walking compared to healthy controls.Methods:206 participants, 57 healthy controls (age: 68.9±1.0 years; 27 women) and 149 idiopathic PD patients (age: 69.8±0.6 years, 50 women, disease duration: 8.27±5.51 years) performed usual walking and dual-task walking (serial 3 subtractions) with an fNIRS system placed on the forehead. HbO2 variability was calculated using the standard deviation (SD), range, and mean detrended time series of fNIRS-derived HbO2 signal evaluated during each walking task. HbO2 variability was compared between groups and between walking tasks using mixed model analyses.Results:Higher variability (SD, range, mean detrended time series) was observed during dual-task walking, compared to usual walking (p<0.025), but this was derived from the differences within the healthy control group (group X task interaction: p<0.007). On the other hand, task repetition demonstrated reduced variability in healthy controls but increased variability in patients with PD (interaction group*walk-repetition: p<0.048). The MDS-UPDRS motor score correlated with HbO2 range (r=0.142, p=0.050) and HbO2 SD (r=0.173, p=0.018) during usual walking in all participants.Discussion:In this study, we suggest a new way to interpret changes in HbO2 variability. We relate increased HbO2 variability to flexible adaptation to environmental challenges and decreased HbO2 variability to the stability of performance. Our results show that both are limited in PD however, further investigation of these concepts is required. Moreover, HbO2 variability measures are an important aspect of brain function that adds new insights into the role of PFC during walking with aging and PD.Classification of Evidence:This study provides Class III evidence that patients with PD have more variability within Hb02 signals during usual-walking, compared to healthy controls, but not during dual-task walking.

Network-Based Transcranial Direct Current Stimulation May Modulate Gait Variability in Young Healthy Adults

“…Interestingly, while a non-significant trend toward reduced gait variability in the dual task condition was observed following tDCS, the effects of stimulation were noticeably less in this walking condition as compared to the others. We expect that this is because dual task performance likely depends upon still other cognitive networks (e.g., the fronto-parietal executive network) and the ability to effectively allocate ‘resources’ between the two tasks ( Lo et al, 2021 ; Maidan et al, 2022 ). On the other hand, it might also be that higher intensity or longer stimulation is needed to induce changes in cortical function that are sufficient to cause measurable differences in gait within more challenging conditions.…”

An fNIRS-Based Dynamic Functional Connectivity Analysis Method to Signify Functional Neurodegeneration of Parkinson’s Disease

“…Figure 11 shows the performance of the proposed method compared with three available methods using fNIRS [25], [26], [27]. The proposed method outperformed method 1, 2, and 3 with Accuracy = 0.7708 ± 0.1134 and F1 = 0.8152 ± 0.0959.…”

“…In addition to these modalities, functional near-infrared spectroscopy (fNIRS), an emerging neuroimaging technology, is increasingly applied to explore the brain functional neurodegeneration of PD patients in clinical walking tests [18], [19], [20] for its portability for task-related measurement, convenience to transfer and use, flexibility for experiments and tolerance to movement noises, etc [21], [22]. In [23], [24], [25], [26], and [27], researchers tried to analyze the difference between PD patients and healthy controls in clinical walking tests with mean, standard deviation, mean detrended time series, range, transition acceleration and angle of hemoglobin concentration changes.…”

Changes in cortical activation during upright stance in individuals with chronic low back pain: An fNIRS study

“…fNIRS is a novel neuroimaging technology that can determine the concentrations of oxygenated hemoglobin and deoxyhemoglobin in the local cortex by detecting optical parameters, indirectly reflecting neural activity (Sakudo, 2016). It has the advantages of portability, non-invasive nature, and low sensitivity to motion artifacts during dynamic balance tasks (Teo et al, 2018;Maidan et al, 2022). Although fNIRS has a lower temporal resolution than EEG, it is suitable to measure brain activity during upright stance tasks in this study, which did not require high temporal resolution.…”