Biology subjects

Umeda, T.

Publications and source records attributed to Umeda, T..

5 recordsLinked to original sources

bioRxiv2026

Serial dependence in haptic perception during active manual exploration.

Serial dependence, whereby current perception is systematically biased toward the most recent sensory experience, has been demonstrated across multiple sensory modalities. However, whether serial dependence occurs during active haptic perception remains unknown. Moreover, because haptic perception of object geometry depends on hand movements for sensory acquisition (i.e., active touch), it remains unclear whether serial dependence, if any, originates from perceptual processing, movement, or both. Here, we investigated whether active haptic perception exhibits attractive serial dependence using a newly developed haptic device that let participants explore virtual slopes of different heights. Participants reported perceived slope heights, and we recorded their kinematics. Perceptual judgments were systematically attracted toward the most recently experienced slope, demonstrating serial dependence during active haptic perception. By contrast, none of the kinematic parameters exhibited corresponding serial dependence. These findings show that serial dependence extends to the somatosensory perceptual domain and suggest that the observed perceptual bias was not mediated by systematic changes in hand movements.

neuroscience↗

bioRxiv2025

Autogenic spinal excitatory circuit ensures skilled hand movements in primates

Skillful hand movements are a hallmark of primates, including humans, requiring sophisticated motor planning and execution. Challenging the longstanding paradigm that emphasizes the dominance of the cerebral cortex1, our study highlights a pivotal role for spinal excitatory reflex circuits in both planning and executing skillful hand movements. Using a combination of experimental approaches with behaving non-human primates and predictive simulation, we identified a group of excitatory spinal interneurons that orchestrate a closed-loop, positive feedback mechanism during voluntary wrist movements. This mechanism is characterized by a bidirectional interaction between inter-neuronal spiking and muscle activity, mediated by motoneuronal efferent signals and proprioceptive afferent signals from the same agonistic muscles. Furthermore, we demonstrate that the temporal profile of muscle activity during movement execution, including amplitude and duration, is pre-determined during motor planning at the spinal interneurons, functioning as a force-feedback gain within the excitatory circuit. These findings suggest that autogenic spinal excitatory circuits play a predominant role in shaping overall muscle activation during motor execution, provided the proper reflex gain is pre-set by higher neural systems during motor planning. Together, our findings provide a cellular-level perspective on how spinal reflex loops contribute to skilled voluntary movements in primates, extending over a century of spinal reflex research2.

neuroscience↗

bioRxiv2024

Simply crushed Zizyphi spinosi semen prevents neurodegenerative diseases and reverses age-related cognitive decline in mice

Neurodegenerative diseases are age-related disorders characterized by the cerebral accumulation of amyloidogenic proteins, and cellular senescence underlies their pathogenesis. Thus, it is necessary for preventing these diseases to remove toxic proteins, repair damaged neurons, and suppress cellular senescence. As a source for such prophylactic agents, we selected Zizyphi spinosi semen (ZSS), a medicinal herb used in traditional Chinese medicine. ZSS hot water extract ameliorated A{beta} and tau pathology and cognitive impairment in mouse models of Alzheimers disease and frontotemporal dementia. Non-extracted ZSS simple crush powder showed stronger effects than the extract and improved -synuclein pathology and cognitive/motor function in Parkinsons disease model mice. Furthermore, when administered to normal aged mice, the ZSS powder suppressed cellular senescence, reduced DNA oxidation, promoted brain-derived neurotrophic factor expression and neurogenesis, and enhanced cognition to levels similar to those in young mice. The quantity of known active ingredients of ZSS, jujuboside A, jujuboside B, and spinosin, was not proportional to the nootropic activity of ZSS. These results suggest that ZSS simple crush powder is a promising dietary material for the prevention of neurodegenerative diseases and brain aging. Impact statement Non-extracted simple crush powder of Zizyphi spinosi semen has not only disease-preventing effects but also brain-rejuvenating effects in mice.

neuroscience↗

bioRxiv2023

Future spinal reflex is embedded in primary motor cortex output

Mammals can execute intended limb movements despite the fact that spinal reflexes involuntarily modulate muscle activity. To generate appropriate muscle activity, the cortical descending motor output must coordinate with spinal reflexes, yet the underlying neural mechanism remains unclear. We simultaneously recorded activities in motor-related cortical areas, afferent neurons, and forelimb muscles of monkeys performing reaching movements. Motor-related cortical areas, primarily the primary motor cortex (M1), encode subsequent afferent activities attributed to forelimb movements. M1 also encodes a subcomponent of muscle activity evoked by these afferent activities, corresponding to spinal reflexes. Furthermore, selective disruption of the afferent pathway specifically reduced this subcomponent of muscle activity, suggesting that M1 output drives muscle activity not only through direct descending pathways but also through the "transafferent" pathway composed of descending plus subsequent spinal reflex pathways. Thus, M1 provides optimal motor output based on an internal forward model that prospectively computes future spinal reflexes.

neuroscience↗

bioRxiv2020

The primary motor cortex prospectively computes the spinal reflex

The spinal reflex transforms sensory signals to generate muscle activity. However, it is unknown how the motor cortex (MCx) takes the spinal reflex into account when performing voluntary limb movements. We simultaneously recorded the activity of the MCx, afferent neurons, and forelimb muscles in behaving monkeys. We decomposed muscle activity into subcomponents explained by the MCx or afferent activity using linear models. Long preceding activity in the MCx, which is responsible for subsequent afferent activity, had the same spatiotemporal contribution to muscle activity as afferent activity, indicating that the MCx drives muscle activity not only by direct descending activation but also by trans-afferent descending activation. Therefore, the MCx implements internal models that prospectively estimate muscle activation via the spinal reflex for precise movement control.

neuroscience↗