Neural and Electromyographic Correlates of Wrist Posture Control

In identical experiments in and out of a MR scanner, we recorded functional magnetic resonance imaging and electromyographic correlates of wrist stabilization against constant and time-varying mechanical perturbations. Positioning errors were greatest while stabilizing random torques. Wrist muscle activity lagged changes in joint angular velocity at latencies suggesting trans-cortical reflex action. Drift in stabilized hand positions gave rise to frequent, accurately directed, corrective movements, suggesting that the brain maintains separate representations of desired wrist angle for feedback control of posture and the generation of discrete corrections. Two patterns of neural activity were evident in the blood-oxygenation-level-dependent (BOLD) time series obtained during stabilization. A cerebello-thalamo-cortical network showed significant activity whenever position errors were present. Here, changes in activation correlated with moment-by-moment changes in position errors (not force), implicating this network in the feedback control of hand position. A second network, showing elevated activity during stabilization whether errors were present or not, included prefrontal cortex, rostral dorsal premotor and supplementary motor area cortices, and inferior aspects of parietal cortex. BOLD activation in some of these regions correlated with positioning errors integrated over a longer time-frame consistent with optimization of feedback performance via adjustment of the behavioral goal (feedback setpoint) and the planning and execution of internally generated motor actions. The finding that nonoverlapping networks demonstrate differential sensitivity to kinematic performance errors over different time scales supports the hypothesis that in stabilizing the hand, the brain recruits distinct neural systems for feedback control of limb position and for evaluation/adjustment of controller parameters in response to persistent errors.

Download Full-text

Saccade Adaptation in Response to Altered Arm Dynamics

Journal of Neurophysiology ◽

10.1152/jn.00430.2003 ◽

2003 ◽

Vol 90 (6) ◽

pp. 4016-4021 ◽

Cited By ~ 19

Author(s):

Thrishantha Nanayakkara ◽

Reza Shadmehr

Keyword(s):

Feedback Control ◽

Real Time ◽

Internal Model ◽

Proprioceptive Feedback ◽

Hand Position ◽

Formidable Challenge ◽

Random Direction ◽

Intact Brain ◽

Saccade Adaptation ◽

The Brain

The delays in sensorimotor pathways pose a formidable challenge to the implementation of stable error feedback control, and yet the intact brain has little trouble maintaining limb stability. How is this achieved? One idea is that feedback control depends not only on delayed proprioceptive feedback but also on internal models of limb dynamics. In theory, an internal model allows the brain to predict limb position. Earlier we had found that during reaching, the brain estimates hand position in real-time in a coordinate system that can be used for generating saccades. Here we tested the idea that the estimate of hand position, as expressed through saccades, depends on an internal model that adapts to dynamics of the arm. We focused on the behavior of the eyes as perturbations were applied to the unseen hand. We found that when the hand was perturbed from stable posture with a 100-ms force pulse of random direction and magnitude, a saccade was generated on average at 182 ms postpulse onset to a position that was an unbiased estimate of real-time hand position. To test whether planning of saccades depended on an internal model of arm dynamics, arm dynamics were altered either predictably or unpredictably during the postpulse period. When arm dynamics were predictable, saccade amplitudes changed to reflect the change in the arm's behavior. We suggest that proprioceptive feedback from the arm is integrated into an adaptable internal model that computes an estimate of current hand position in eye-centered coordinates.

Download Full-text

Glia Not Neurons: Uncovering Brain Dysmaturation in a Rat Model of Alzheimer’s Disease

Biomedicines ◽

10.3390/biomedicines9070823 ◽

2021 ◽

Vol 9 (7) ◽

pp. 823

Author(s):

Ekaterina A. Rudnitskaya ◽

Tatiana A. Kozlova ◽

Alena O. Burnyasheva ◽

Natalia A. Stefanova ◽

Nataliya G. Kolosova

Keyword(s):

Alzheimer’S Disease ◽

Alzheimer's Disease ◽

Prefrontal Cortex ◽

Brain Structures ◽

Time Frame ◽

Oxys Rats ◽

Unknown Etiology ◽

Suitable Model ◽

Model Of Alzheimer’S Disease ◽

The Brain

Sporadic Alzheimer’s disease (AD) is a severe disorder of unknown etiology with no definite time frame of onset. Recent studies suggest that middle age is a critical period for the relevant pathological processes of AD. Nonetheless, sufficient data have accumulated supporting the hypothesis of “neurodevelopmental origin of neurodegenerative disorders”: prerequisites for neurodegeneration may occur during early brain development. Therefore, we investigated the development of the most AD-affected brain structures (hippocampus and prefrontal cortex) using an immunohistochemical approach in senescence-accelerated OXYS rats, which are considered a suitable model of the most common—sporadic—type of AD. We noticed an additional peak of neurogenesis, which coincides in time with the peak of apoptosis in the hippocampus of OXYS rats on postnatal day three. Besides, we showed signs of delayed migration of neurons to the prefrontal cortex as well as disturbances in astrocytic and microglial support of the hippocampus and prefrontal cortex during the first postnatal week. Altogether, our results point to dysmaturation during early development of the brain—especially insufficient glial support—as a possible “first hit” leading to neurodegenerative processes and AD pathology manifestation later in life.

Download Full-text

Perceptual decisions are biased toward relevant prior choices

Scientific Reports ◽

10.1038/s41598-020-80128-0 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Helen Feigin ◽

Shira Baror ◽

Moshe Bar ◽

Adam Zaidel

Keyword(s):

Sensory Information ◽

Irrelevant Stimulus ◽

Stimulus Feature ◽

Serial Dependence ◽

Low Level ◽

Subsequent Test ◽

Key Factor ◽

High Level ◽

Motor Actions ◽

The Brain

AbstractPerceptual decisions are biased by recent perceptual history—a phenomenon termed 'serial dependence.' Here, we investigated what aspects of perceptual decisions lead to serial dependence, and disambiguated the influences of low-level sensory information, prior choices and motor actions. Participants discriminated whether a brief visual stimulus lay to left/right of the screen center. Following a series of biased ‘prior’ location discriminations, subsequent ‘test’ location discriminations were biased toward the prior choices, even when these were reported via different motor actions (using different keys), and when the prior and test stimuli differed in color. By contrast, prior discriminations about an irrelevant stimulus feature (color) did not substantially influence subsequent location discriminations, even though these were reported via the same motor actions. Additionally, when color (not location) was discriminated, a bias in prior stimulus locations no longer influenced subsequent location discriminations. Although low-level stimuli and motor actions did not trigger serial-dependence on their own, similarity of these features across discriminations boosted the effect. These findings suggest that relevance across perceptual decisions is a key factor for serial dependence. Accordingly, serial dependence likely reflects a high-level mechanism by which the brain predicts and interprets new incoming sensory information in accordance with relevant prior choices.

Download Full-text

Increase in weighting of vision vs. proprioception associated with force field adaptation

10.1101/544189 ◽

2019 ◽

Author(s):

Brandon M. Sexton ◽

Yang Liu ◽

Hannah J. Block

Keyword(s):

Force Field ◽

Position Sense ◽

Multisensory Perception ◽

Hand Position ◽

Null Field ◽

Before And After ◽

Force Field Adaptation ◽

Perceptual Changes ◽

The Brain ◽

Straight Ahead

AbstractHand position can be encoded by vision, via an image on the retina, and proprioception (position sense), via sensors in the joints and muscles. The brain is thought to weight and combine available sensory estimates to form an integrated multisensory estimate of hand position with which to guide movement. Force field adaptation, a form of cerebellum-dependent motor learning in which reaches are systematically adjusted to compensate for a somatosensory perturbation, is associated with both motor and proprioceptive changes. The cerebellum has connections with parietal regions thought to be involved in multisensory integration; however, it is unknown if force adaptation is associated with changes in multisensory perception. One possibility is that force adaptation affects all relevant sensory modalities similarly, such that the brain’s weighting of vision vs. proprioception is maintained. Alternatively, the somatosensory perturbation might be interpreted as proprioceptive unreliability, resulting in vision being up-weighted relative to proprioception. We assessed visuo-proprioceptive weighting with a perceptual estimation task before and after subjects performed straight-ahead reaches grasping a robotic manipulandum. Each subject performed one session with a clockwise or counter-clockwise velocity-dependent force field, and one session in a null field to control for perceptual changes not specific to force adaptation. Subjects increased their weight of vision vs. proprioception in the force field session relative to the null field session, regardless of force field direction, in the straight-ahead dimension (F1,44 = 5.13, p = 0.029). This suggests that force field adaptation is associated with an increase in the brain’s weighting of vision vs. proprioception.

Download Full-text

The time frame of the brain AVM formation

Interventional Neuroradiology ◽

10.1177/1591019919845538 ◽

2019 ◽

Vol 25 (5) ◽

pp. 588-588

Author(s):

Masaki Komiyama

Keyword(s):

Time Frame ◽

Brain Avm ◽

The Brain

Download Full-text

Motor cost affects the decision of when to shift gaze for guiding movement

Journal of Neurophysiology ◽

10.1152/jn.00027.2019 ◽

2019 ◽

Vol 122 (1) ◽

pp. 378-388 ◽

Cited By ~ 3

Author(s):

F. Javier Domínguez-Zamora ◽

Daniel S. Marigold

Keyword(s):

Center Of Mass ◽

Relevant Information ◽

Lateral Direction ◽

Foot Placement ◽

Factors Affecting ◽

Direct Gaze ◽

Trial Basis ◽

Motor Actions ◽

The Cost ◽

The Brain

Frequent gait modifications are often required to navigate our world. These can involve long or wide steps or changes in direction. People generally prefer to minimize the motor cost (or effort) of a movement, although with changes in gait this is not always possible. The decision of when and where to shift gaze is critical for controlling motor actions, since vision informs the brain about the available choices for movement—in this case, where to step. Here we asked how motor cost influences the allocation of gaze. To address this, we had participants walk and step to the center of sequential targets on the ground. We manipulated the motor cost associated with controlling foot placement by varying the location of one target in the lateral direction on a trial-to-trial basis within environments with different numbers of targets. Costlier steps caused a switch from a gaze strategy of planning future steps to one favoring visual feedback of the current foot placement when participants had to negotiate another target immediately after. Specifically, costlier steps delayed gaze shifts away from the manipulated target. We show that this relates to the cost of moving the leg and redirecting the body’s center of mass from target to target. Overall, our results suggest that temporal gaze decisions are affected by motor costs associated with step-to-step demands of the environment. Moreover, they provide insight into what affects the coordination between the eyes and feet for the control of stable and accurate foot placement while walking. NEW & NOTEWORTHY Changes in gait allow us to navigate our world. For instance, one may step long or wide to avoid a spilled drink. The brain can direct gaze to gather relevant information for making these types of motor decisions; however, the factors affecting gaze allocation in natural behaviors are poorly understood. We show how the motor cost associated with a step influences the decision of when to redirect gaze to ensure accurate foot placement while walking.

Download Full-text

Impact of Frame Positioning Errors on Fuselage Panel Assembly Variation

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.433-435.847 ◽

2013 ◽

Vol 433-435 ◽

pp. 847-851

Author(s):

Wei Miao Yan ◽

Yun Bo Bi ◽

Xin Tian Fan ◽

Kun Peng Du ◽

Wei Wang

Keyword(s):

Finite Element ◽

Information Matrix ◽

Principal Component ◽

Element Model ◽

Position Errors ◽

Positioning Errors ◽

Influence Coefficients ◽

Assembly Accuracy ◽

Optimum Selection ◽

The Impact

This paper firstly establishes a finite element model of a fuselage panel, and then an assembly variation model is derived from the method of influence coefficients (MIC) and principal component analysis (PCA). With the calculation of Fisher information matrix and effective independence (EFI), 49 measurement points are extracted from a number of finite element nodes by the optimum selection method, and the mathematical relation between the position errors of measurement points and the positioning errors of frames is established, which is utilized to analyze the impact of positioning errors of each frame on fuselage panel assembly variation. Finally, the key frame that is important to ensure assembly accuracy and to improve the assembly process is determined.

Download Full-text

NMR spectroscopy and imaging of the neonatal brain

Biochemical Society Transactions ◽

10.1042/bst0280121 ◽

2000 ◽

Vol 28 (2) ◽

pp. 121-126 ◽

Cited By ~ 9

Author(s):

C. E. Cooper ◽

J. S. Wyatt

Keyword(s):

Blood Flow ◽

Brain Function ◽

Blood Oxygenation ◽

Cell Swelling ◽

Resonance Spectroscopy ◽

Neonatal Brain ◽

Cellular Processes ◽

Nmr Techniques ◽

The Brain ◽

Ischaemic Insult

Magnetic resonance spectroscopy and imaging provide unique information about the brain to the biochemist and the clinician. In particular, the ability to image metabolites other than water and to get detailed information about dynamic cellular processes (such as blood flow, blood oxygenation and cell swelling) is leading to many new insights into brain function and dysfunction. This review describes the use of old and new NMR techniques which demonstrate that mitochondrial dysfunction plays an important role in the cell death that occurs following an hypoxic-ischaemic insult to the neonatal brain.

Download Full-text

The Estimation of Angular Misalignments for Ultra Short Baseline Navigation Systems. Part I: Numerical Simulations

Journal of Navigation ◽

10.1017/s0373463313000222 ◽

2013 ◽

Vol 66 (4) ◽

pp. 561-578 ◽

Cited By ~ 6

Author(s):

Hsin-Hung Chen

Keyword(s):

Numerical Simulations ◽

Survey Method ◽

Alignment Error ◽

Navigation Systems ◽

Misalignment Angle ◽

Short Baseline ◽

Position Errors ◽

Positioning Errors ◽

Line Survey ◽

Survey Approach

Ultra Short Baseline (USBL) navigation systems are often faced with positioning errors arising from misalignments between sensors. This paper proposes a line survey method for USBL angular alignment calibration. In the scheme of USBL line survey, mathematical representations of positioning error arising from heading, pitch and roll misalignments are derived, respectively. The effect of each misalignment angle and how the differences can be used to calibrate each misalignment angle in turn are presented. An iterative algorithm that takes advantage of the geometry of position errors resulting from angular misalignments is developed for USBL calibration. Numerical simulations are provided to demonstrate the effectiveness of the USBL line survey approach. In addition, the effect of measurement error on the estimation of roll alignment error is evaluated and discussed.

Download Full-text