Experimental Brain Research最新文献

We address the underexplored role of visual feedback in ensuring stability of pressing force produced in isometric conditions by the two hands. We considered the task as a two-level hierarchy (total force, F_TOT, and hand forces, F_HAND) and used the framework of the uncontrolled manifold hypothesis to quantify synergies stabilizing F_TOT and F_HAND. Young healthy persons performed steady-state forces with visual feedback and targets for the forces produced by each hand and/or for the total force. We quantified inter-trial and within-a-trial (across time windows) variance components affecting and not affecting F_TOT and F_HAND. Variables with visual feedback, F_TOT or F_HAND, showed force-stabilizing synergies reflected in the structure of variance, while variables without visual feedback failed to show such synergies. The synergies were consistently stronger when the feedback was continuous, compared to when the feedback disappeared when the cursor was inside the target. The results showed a strong dependence between variance that did not affect F_TOT (within the corresponding solution space) and variance that affected each F_HAND across the feedback conditions. Within-a-trial synergy indices were significantly lower than those in the inter-trial analysis. The data are interpreted as reflecting hierarchical control with synergies at both levels of the hierarchy, those that define F_TOT and F_HAND. These synergies get contributions from inter-trial force sharing variability and sensory feedback-based covariation of forces produced by the elements (fingers or hands) along individual trials. Combining inter-trial and within-a-trial analysis of variance may provide an important toolbox to explore cases of impaired control of action stability.

The hindlimb of the spinalized frog when supported on a flat surface, can produce a precise wiping reflex to remove a small piece of paper soaked in a weak acidic solution placed on the forelimb. By passively changing the forelimb position, one can modify the body schema and the coordinates of the skin irritant relative to the body, but the frog still manages to remove the irritant and accurately wipe the affected skin spot several times. Similarly, healthy humans are able to preserve movement precision of hammering despite a broad variability in arm movement leading to variability in the hammer trajectory (Bernstein's example of synergy). An explanation of the neural mechanisms underlying these synergies, heretofore unknown, is proposed in the present paper. This is done in the framework of the referent control theory (RCT), an extension of the equilibrium-point hypothesis that is applicable to many members of the biological kingdom including humans and frogs. The RCT is also helpful in solving the classical posture-movement problem and in explaining the directional tuning of neurons and the role of proprioception in action-perception coupling. Experimental tests of the RCT in future studies are proposed in comparison with other theories of action and perception. It is suggested that the RCT represents a paradigm shift in the understanding of action and perception by implying that they are controlled by specific parameters of physical and physiological laws.

Postoperative delirium is a major concern in elderly patients and is associated with early cognitive decline after anesthesia exposure. Sevoflurane anesthesia increases amyloid-β (Aβ) production, leading to neuroinflammation, blood-brain barrier (BBB) disruption, and postoperative delirium. Interleukin-17 (IL-17) is implicated in BBB breakdown, and Aβ deposits induce elevated expression. Hence, we explored the relationships between early postoperative cognitive alterations and Aβ deposits, IL-17 expression in the hippocampus, and BBB damage in aged rats after fracture surgery under sevoflurane anesthesia. Aged rats underwent fracture surgery under 3.6% sevoflurane for 2 h. Cognitive changes were assessed using fear conditioning and Y-maze tests, and hippocampal occludin and Ly6g expression were measured using Western blotting. Aβ42, IL-17, and MMP-9 levels were measured using enzyme-linked immunosorbent assays, and BBB disruption was evaluated using Evans Blue at 6, 12, and 24 h post-anesthesia. We intrathecally administered the γ-secretase inhibitor (DAPT) and IL-17 antiserum to inhibit Aβ42 deposition and IL-17 expression, respectively. We observed cognitive changes, hippocampal Aβ42, Ly6g, IL-17, occludin, and MMP-9 levels, and BBB disruption 24 h post-anesthesia. Further, we noticed decreased freezing and residence time in the new Y-maze arm in aged rats, increased Aβ42, IL-17, MMP-9, and Evans blue contents, and decreased occludin expression at 6 h post-anesthesia. These phenotypes worsened at 12 and 24 h. However, DAPT and IL-17 antiserum administration improved cognitive performance and various hippocampal parameters 24 h post-anesthesia. Our study suggests that early postoperative cognitive decline is likely linked to Aβ42 deposition, triggering neuroinflammation and BBB disruption via increased IL-17 expression.

Trigeminal neuralgia (TN) is characterized by intense and recurrent episodes of pain in the orofacial region, mainly affecting the second (V2) and third (V3) divisions of the trigeminal nerve. Recent studies suggest that TN may be associated with structural alterations in the limbic system, particularly the amygdala, a core region for the emotion-related network, involved in emotional aspects of pain and pain modulation. This study evaluated the volumetry of the amygdala and its nine nuclei in patients with TN compared to healthy controls. Structural Magnetic Resonance Imaging (MRI) data were analyzed from 111 TN patients and 48 healthy volunteers. MRI scans were acquired using a 3 T MRI scanner with high-resolution 3D T1w sequences (2022-2024) at the Federal Neurosurgical Center in Novosibirsk, Russia, and assessed via the OpenNeuro database. Amygdala volumetry was performed using FreeSurfer software. Morphometric analysis revealed significantly lower volumes of both the left (p = 0.02, η²p = 0.13) and the right amygdala (p = 0.005, η²p = 0.05) in TN patients, compared to healthy controls. Additionally, TN patients exhibited smaller bilateral volumes in the cortical nucleus of the amygdala as well as smaller volumes of the medial, accessory basal, and corticoamygdaloid transition nuclei of the right amygdala, when compared to the control group. Amygdala alterations may reflect impaired pain modulation in trigeminal neuralgia (TN), affecting sensory and affective aspects of pain.

The neural representation of the body is highly flexible and can be altered by integrating multisensory signals in the brain. The rubber hand illusion (RHI) is a widely used paradigm to investigate this phenomenon; participants experience ownership of a rubber hand and perceive their real hand as shifting toward the rubber hand's location, a phenomenon known as proprioceptive drift. Although individual differences in the extent of this drift are well documented, it remains unclear whether such differences are related to specific aspects of motor function. In this study, we examined the relationship between the magnitude of proprioceptive drift during the RHI and the ability of individuals to imitate and reproduce elbow movements. Our results revealed a significant correlation between the magnitude of proprioceptive drift and the accuracy of action reproduction but not imitation. These findings suggest that altered body representation may selectively influence the motor processes involved in action reproduction, highlighting the interplay between body ownership and motor control.

Visual motion signals are useful in predicting the future, and can affect the detectability and phenomenology of vision in various ways. Recent research has demonstrated that the disappearance position of a moving object is perceived as shifted in the direction of motion when the background consists of dynamic noise. This "twinkle-goes" illusion is thought to arise from a positional prediction overshoot that occurs because dynamic noise delays the accumulation of sensory evidence needed to register the disappearance. In Experiment 1, we examined the temporal dynamics of this illusion by measuring the illusory position shift using a probe at various positions along the motion trajectory and at different time points after the object's physical vanishing. The illusory position shift was nearly zero at the moment the moving object vanished, and subsequently gradually increased as a function of time up to ~ 120 ms after vanishing. In Experiment 2, motivated by prior reports of rhythmic fluctuations in both behavior and neural activity, we investigated whether neural theta oscillations were involved in the illusion. We found that the size of the illusory position shift correlated with the theta phase before vanishing. Taken together, these results suggest that the positional prediction of a moving object is slow-paced and rhythmically updated in synchrony with theta oscillations.

Signal Transducer and Activator of Transcription 1 (STAT1) is a nuclear transcription factor involved in multiple biological processes including the cell cycle, cell survival and immune response. However, the role and mechanism of STAT1 overexpression in learning and memory of young mice have not been investigated. Here, we indicated that STAT1 overexpression apparently induced cognitive defects of 2-month-old C57 mice. STAT1 overexpression in 2-month-old C57 mice markedly decreased spine density and the levels of synaptic associated protein including PSD95, SYN I and PSD93. Moreover, neuronal apoptosis was remarkably induced in STAT1-overexpression 2-month-old C57 mice by BCL-2/Bax signaling pathway. Furthermore, STAT1 overexpression in 2-month-old C57 mice apparently increased the proliferation of microglia and astrocytes, accompanied by a notable elevation in the mRNA levels of inflammatory factors including TNF-α, IL-1α, IL-6 and IL-18. In addition, STAT1 overexpression in 2-month-old C57 mice impaired mitochondrial function by increasing lipid peroxidation levels, decreasing ATP levels and superoxide dismutase activity. Proteomic analysis showed that protein expression profile of synapses, inflammation and mitochondria were all altered and that biological process of synaptic transmission, inflammatory response and fatty acid beta-oxidation were regulated via overexpressing STAT1 in 2-month-old C57 mice. Taken together, these findings suggest that STAT1 may be a pivotal risk factor for impaired cognitive ability.