Table 1.
What differentiates PD with and without FoG?
| Title | Protocol | Metric | Findings | Interpretation (Hypothesis Supported) |
|---|---|---|---|---|
| Motor preparation rather than decision-making differentiates Parkinson's disease patients with and without freezing of gait (28) | Detection of differences in cognitive decision making by EEG recording during timed response target detection | Lateralized readiness potential (LRP) | Earlier onset in PDFoG+ compared with PDFoG– | Excessive recruitment of lateral premotor areas due to loss of automatic motor control (2nd) |
| LRP | Larger magnitude in PDFoG+ compared with PDFoG– | |||
| Frontal theta and beta oscillations during lower-limb movement in Parkinson's disease (117) | EEG recording during lower-limb pedaling | Theta (4–8) power | Attenuated in the mid-frontal location in PDFoG+ compared with PDFoG– | Associated with impairments in cognitive control (5th) |
| Beta (13–30 Hz) power | Increase in the frontal location in PDFoG+ compared with PDFoG– | Altered preparatory adjustments and motor plan execution through top-down signaling (5th or 3rd) | ||
| High beta activity in the subthalamic nucleus and freezing of gait in Parkinson's disease (26) | EEG and deep brain electrode recording during seated position | High-beta (21–35 Hz) | Higher STN activity during the OFF state in PDFoG+ compared with PDFoG– | Associated with interference in the frontal cortico-BG loops, which suggests a predisposition to freeze (2nd) |
| Attention modulation during motor preparation in parkinsonian freezers: A time-frequency EEG study (105) | Discriminatory attentional dual task, as mediated by oddball paradigm using EEG, for the time preceding gait initiation | Beta ERD | Not present in PDFoG+ compared with PDFoG– | Associated with impairments of the BG, as either hypersynchronized thalamocortical activity or reduced BG involvement (2nd) |
| Beta ERS | Prolonged in PDFoG+ compared with PDFoG– | A cortical marker of the high-power beta oscillations in the subthalamic nucleus during FoG (2nd) | ||
| Neuromodulation targets pathological not physiological beta bursts during gait in Parkinson's disease (111) | Walking in place and forward walking comparison of DBS frequency-setting effects while recording STN and EEG power coherence | Beta (13–30) burst | Prolonged in PDFoG+ compared with PDFoG– | Reflect beta-band oscillations in the STN, which are representative of FoG (2nd) |
| Bicycling suppresses abnormal beta synchrony in the parkinsonian basal ganglia (115) | Comparison of subthalamic features OFF medication during bicycling | Beta (13–35 Hz) | Reduced in PDFoG+ compared with PDFoG– | Reduces interference between cortico-BG loops, thus reducing FoG risk (2nd) |
| 18-Hz power | Increased at movement onset in PDFoG+ compared with PDFoG– | Indicates susceptibility to freezing caused by movement-inhibition throughout the motor network (2nd) | ||
| Subthalamic neural entropy is a feature of freezing of gait in freely moving people with Parkinson's disease (30) | STN activity comparison during stepping in place, forward walking, and instrumented walking | Beta (13–30) power | Decreased during stepping in PDFoG+ compared with PDFoG– | Compensatory mechanism adopted to overcome abnormal gait (2nd) |
| Sample entropy | Increased during forward walking in PDFoG+ compared with PDFoG– | Increase in error of the processing of sensorimotor information in the subthalamic outflow that results in abnormal gait patterns (1st or 2nd) |
Results and interpretation of studies that compare neural biomarkers of PDFoG+ vs. PDFoG–.