Yozu, A. | bioRxiv Science

bioRxiv2026

Impaired Motor Awareness of Balance Control is Associated with Postural Instability in Parkinson's Disease

BackgroundBalance instability is a major contributor to disability and falls in people with Parkinsons disease (PwP) and is often insufficiently explained by motor impairment alone. Altered awareness of motor control has been suggested to contribute to sensorimotor dysfunction in PwP, but its relationship with balance performance is poorly understood. ObjectiveTo determine whether awareness of balance control, assessed using a control detection task (CDT), differs between healthy controls (HC) and PwP, and whether CDT performance is associated with balance-related measures. MethodsHealthy older adults (n=20) and PwP (n=22) performed a standing version of the CDT based on center-of-pressure (COP) control, using a force plate. CDT accuracy was used as the primary outcome measure. Static balance during quiet standing was assessed using the COP trajectory length and rectangular area. Dynamic standing balance was assessed using the Index of Postural Stability (IPS). Group differences were examined by independent-samples t-tests. Correlations between CDT accuracy and balance measures were analyzed. ResultsThe PwP group showed significantly lower CDT accuracy. Higher CDT accuracy was associated with better static balance in the HC group and the combined sample, and with higher IPS primarily in the PwP group. ConclusionsMotor awareness during postural tasks is altered in PwP and is associated with balance control. These findings suggest that balance instability in Parkinsons disease may involve altered balance-related action-outcome monitoring in addition to motor dysfunction.

neuroscience↗

bioRxiv2023

Role of the medial agranular cortex in unilateral spatial neglect

Unilateral spatial neglect (USN) results from impaired attentional networks and can affect various sensory modalities, such as visual and somatosensory. The rodent medial agranular cortex (AGm), located in the medial part of the forebrain from rostral to caudal direction, is considered a region associated with spatial attention. The AGm selectively receives multisensory input with the rostral AGm receiving somatosensory input and caudal part receiving visual input. Our previous study showed slower recovery from neglect with anterior AGm lesion using the somatosensory neglect assessment. Conversely, the functional differences in spatial attention across the entire AGm locations (anterior, intermediate, and posterior parts) are unknown. Here, we investigated the relationship between the severity of neglect and various locations across the entire AGm in a mouse stroke model using a newly developed program-based analysis method that does not require human intervention. Among the various lesion positions, acute severity was higher with the lesion in the intermediate rostrocaudal position. On the other hand, the recovery from USN-like behavior after this phase tended to be slower in cases with more rostral lesions in the AGm. Additionally, no motor paralysis was observed in any of the mice with lesions in each AGm. These results suggest that the intermediate rostrocaudal position of the AGm may significantly influence selection of the direction, regardless of the areas to which it is connected. On the contrary, recovery from USN-like behavior may be dependent on the areas to which it is connected. HighlightsLesion of the rodent medial agranular cortex (AGm) results in unilateral spatial neglect (USN). In the acute phase, the severity was higher with lesions in the intermediate AGm position. Recovery from somatosensory USN tended to be slower with rostral AGm lesions. Recovery from USN may depend on sensory modalities associated with the connected areas. Our results revealed location-dependent differences in attentional functions within the AGm.

animal behavior and cognition↗