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Freezing of gait (FOG) in Parkinson's disease (PD) can be triggered by sensomotor, cognitive or limbic factors. The limbic system's impact on FOG is attributed to elevated limbic load, characterized by aversive stimuli, potentially depleting cognitive resources for movement control, resulting in FOG episodes. However, to date, PD patients with and without FOG have not shown alterations of anticipatory postural adjustments during gait initiation after exposure to emotional images, possibly because visual stimuli are less immediately disruptive than auditory stimuli, which can more directly affect attention and the limbic system. This study aims to determine if step initiation is influenced by ecological auditory stimuli with emotional content in patients with FOG compared to those without. Forty-five participants, divided into 3 groups (15 PD with FOG, 15 PD without FOG in ON state, and 15 healthy subjects), stood on a force platform and were asked to step forward in response to neutral, pleasant, or unpleasant ecological auditory stimuli. Anticipatory postural adjustments were investigated in imbalance and unloading phases, while spatio-temporal parameters, including center of pressure (CoP) displacements, were computed for step initiation. PD with FOG showed a reduction of CoP displacements after listening to unpleasant stimuli. Conversely, pleasant stimuli facilitated CoP displacements in these subjects. No influence of affective stimuli on CoP displacements was found in the other two groups. Multiple regression analysis revealed that the behavioral pattern in PD with FOG, modulated by stimuli with affective valence, was mainly associated with the limbic area (i.e., depression). The findings showed that the emotional network plays a crucial role in the pathophysiology of freezing, generating probably interference with attentional reserves that trigger FOG., Competing Interests: Declarations. Competing interests: The authors declare no competing interests., (© 2024. The Author(s).)

Valence (positive and negative) and content (embodied vs non-embodied) characteristics of visual stimuli have been shown to influence motor readiness, as tested with response time paradigms. Both embodiment and emotional processing are affected in Parkinson's disease (PD) due to basal ganglia dysfunction. Here we aimed to investigate, using a two-choice response time paradigm, motor readiness when processing embodied (emotional body language [EBL] and emotional facial expressions [FACS]) vs non-embodied (emotional scenes [IAPS]) stimuli with neutral, happy, and fearful content. We enrolled twenty-five patients with early-stage PD and twenty-five age matched healthy participants. Motor response during emotional processing was assessed by measuring response times (RTs) in a home-based, forced two-choice discrimination task where participants were asked to discriminate the emotional stimulus from the neutral one. Rating of valence and arousal was also performed. A clinical and neuropsychological evaluation was performed on PD patients. Results showed that RTs for PD patients were longer for all conditions compared to HC and that RTs were generally longer in both groups for EBL compared to FACS and IAPS, with the sole exception retrieved for PD, where in discriminating fearful stimuli, RTs for EBL were longer compared to FACS but not to IAPS. Furthermore, in PD only, when discriminating fearful respect to neutral stimuli, RTs were shorter when discriminating FACS compared to IAPS. This study shows that PD patients were faster in discriminating fearful embodied stimuli, allowing us to speculate on mechanisms involving an alternative, compensatory, emotional motor pathway for PD patients undergoing fear processing., (© 2024. The Author(s).)

Motor imagery (MI) is the mental execution of actions without overt movements that depends on the ability to imagine. We explored whether this ability could be related to the cortical activity of the brain areas involved in the MI network. To this goal, brain activity was recorded using high-density electroencephalography in nineteen healthy adults while visually imagining walking on a straight path. We extracted Event-Related Desynchronizations (ERDs) in the θ, α, and β band, and we measured MI ability via (i) the Kinesthetic and Visual Imagery Questionnaire (KVIQ), (ii) the Vividness of Movement Imagery Questionnaire-2 (VMIQ), and (iii) the Imagery Ability (IA) score. We then used Pearson's and Spearman's coefficients to correlate MI ability scores and average ERD power (avgERD). Positive correlations were identified between VMIQ and avgERD of the middle cingulum in the β band and with avgERD of the left insula, right precentral area, and right middle occipital region in the θ band. Stronger activation of the MI network was related to better scores of MI ability evaluations, supporting the importance of testing MI ability during MI protocols. This result will help to understand MI mechanisms and develop personalized MI treatments for patients with neurological dysfunctions., (© 2024. The Author(s).)

The aim of this study was to investigate differences between usual and complex gait motor imagery (MI) task in healthy subjects using high-density electroencephalography (hdEEG) with a MI protocol. We characterized the spatial distribution of α- and β-bands oscillations extracted from hdEEG signals recorded during MI of usual walking (UW) and walking by avoiding an obstacle (Dual-Task, DT). We applied a source localization algorithm to brain regions selected from a large cortical-subcortical network, and then we analyzed α and β bands Event-Related Desynchronizations (ERDs). Nineteen healthy subjects visually imagined walking on a path with (DT) and without (UW) obstacles. Results showed in both gait MI tasks, α- and β-band ERDs in a large cortical-subcortical network encompassing mostly frontal and parietal regions. In most of the regions, we found α- and β-band ERDs in the DT compared with the UW condition. Finally, in the β band, significant correlations emerged between ERDs and scores in imagery ability tests. Overall we detected MI gait-related α- and β-band oscillations in cortical and subcortical areas and significant differences between UW and DT MI conditions. A better understanding of gait neural correlates may lead to a better knowledge of pathophysiology of gait disturbances in neurological diseases., (© 2022. The Author(s).)