Changes In Sensory Information Research Articles

Postural control measured before and after simulated ankle inversion landings among individuals with chronic ankle instability, copers, and controls

BackgroundPostural control measured during single-leg stance and single-leg hop stabilization has been used to estimate sensorimotor function in CAI individuals and copers. To date, studies have not used postural control tasks as a way of measuring responses to sudden changes in sensory information after simulated ankle inversion landings. Research questionA cross-sectional study was performed to identify any differences in static and dynamic postural control before and after simulated ankle inversion landings among individuals with chronic ankle instability (CAI), copers, and healthy controls. MethodsNineteen CAI individuals, 19 copers, and 19 controls participated in this study. Participants performed 3 static and dynamic balance tasks before and after simulated ankle inversion landings onto a 25° tilted platform from a height of 30 cm. The main outcome measures were the center of pressure (COP) velocity and range from the single-leg stance, as well as the dynamic postural stability index from the single-leg hop stabilization. The Wilcoxon signed-rank test was used to compare posttest and pretest differences in static and dynamic postural control between groups. ResultsIn the static postural control measures, the CAI group had a higher difference in COP velocity and COP range in the frontal plane (p < 0.05 and p < 0.05, respectively) than the coper group. In the dynamic postural control measures, the CAI group demonstrated a higher difference in the vertical stability index (p < 0.05) than the healthy control group. SignificanceCAI individuals have persistent worse postural control after somatosensory modulation due to their inability to adapt to sudden somatosensory modulation. Relative to CAI individuals, copers may have different abilities not only the integration of somatosensory input about ankle inversion modulation, but also the adaptation of the entire motor control system, preventing recurrent ankle sprains after an initial LAS. Therefore, somatosensory modulation may be the indicator of understanding CAI and coper.

Handling Qualities Assessment and Performance Evaluation for Unmanned Aerial Systems and Pilots

When fly-by-wire controls first appeared, much research focused on how to evaluate control laws and bare airframes for airworthiness given the reliance on electronic augmentation. Similarly, handling qualities and methods of evaluation for novel flying vehicles have been discussed whenever novel designs are developed. In the last 20 years, with the proliferation of unmanned aircraft systems (UAS), much research has focused on transferring existing methods of performance evaluation and airworthiness assessment to accommodate the unique feature of many UAS. However, the changes in sensory information and pilot experience levels require examining the aircraft and pilots together in a holistic manner. In this work, the authors present the results of a broad study focused on evaluation of both pilot skill and aircraft performance in a holistic way. In this study, the skill of the remote pilot is considered as well as the effectiveness of the electronic flight control system because the evaluation is conducted on the system at-large as opposed to considering each piece individually. An evaluation approach using mission-task-elements (MTEs), like that used within Aeronautical Design Standard-33 Handling Qualities Requirements for Military Rotorcraft (ADS-33), is developed and presented for UAS. In the study, new UAS pilots were evaluated before, during, and after an intensive training program using qualitative measures (like Cooper–Harper rating) and quantitative measurements (like elapsed time) of their performance while flying the prescribed MTEs. The techniques described can provide insight into pilot performance, airframe airworthiness, and effectiveness of stability systems in an efficient test program and the results are inherently easy to understand in the context of MTEs.

Perception of leaning backward while standing and patellar movement.

[Purpose] The purpose of this study was to investigate the relationship between the patellar movement and the standing backward leaning perceptibility. [Subjects and Methods] Fourteen volunteers who were confirmed presence of upward patellar movement during backward leaning from the quiet standing posture participated in this study. The quiet standing position, the standing backward leaning position at patellar movement onset and standing position perceptibility were measured. The position of the center of pressure in the anteroposterior direction in standing is represented as the percentage distance from the hindmost point of the heel in relation to the foot length (%FL). [Results] The mean value of the center of pressure on anteroposterior direction positions in quiet standing was 43.2%FL. The patellar movement onset position was 35.1%FL. The individual mean value of standard deviations for the onset position was 2.5%FL. The absolute error at the onset position is specifically and significantly small. [Conclusion] For the subjects whose patellas move during backward leaning in this study, the standing position near the onset position was perceived accurately, probably by the substantial change in sensory information associated with the onset of patellar movement while backward leaning.

Modulation of shark prey capture kinematics in response to sensory deprivation

The ability of predators to modulate prey capture in response to the size, location, and behavior of prey is critical to successful feeding on a variety of prey types. Modulating in response to changes in sensory information may be critical to successful foraging in a variety of environments. Three shark species with different feeding morphologies and behaviors were filmed using high-speed videography while capturing live prey: the ram-feeding blacktip shark, the ram-biting bonnethead, and the suction-feeding nurse shark. Sharks were examined intact and after sensory information was blocked (olfaction, vision, mechanoreception, and electroreception, alone and in combination), to elucidate the contribution of the senses to the kinematics of prey capture. In response to sensory deprivation, the blacktip shark demonstrated the greatest amount of modulation, followed by the nurse shark. In the absence of olfaction, blacktip sharks open the jaws slowly, suggestive of less motivation. Without lateral line cues, blacktip sharks capture prey from greater horizontal angles using increased ram. When visual cues are absent, blacktip sharks elevate the head earlier and to a greater degree, allowing them to overcome imprecise position of the prey relative to the mouth, and capture prey using decreased ram, while suction remains unchanged. When visual cues are absent, nurse sharks open the mouth wider, extend the labial cartilages further, and increase suction while simultaneously decreasing ram. Unlike some bony fish, neither species switches feeding modalities (i.e. from ram to suction or vice versa). Bonnetheads failed to open the mouth when electrosensory cues were blocked, but otherwise little to no modulation was found in this species. These results suggest that prey capture may be less plastic in elasmobranchs than in bony fishes, possibly due to anatomical differences, and that the ability to modulate feeding kinematics in response to available sensory information varies by species, rather than by feeding modality.

Auditory change-related cerebral responses and personality traits

The rapid detection of changes in sensory information is an essential process for survival. Individual humans are thought to have their own intrinsic preattentive responsiveness to sensory changes. Here we sought to determine the relationship between auditory change-related responses and personality traits, using event-related potentials. A change-related response peaking at approximately 120ms (Change-N1) was elicited by an abrupt decrease in sound pressure (10dB) from the baseline (60dB) of a continuous sound. Sixty-three healthy volunteers (14 females and 49 males) were recruited and were assessed by the Temperament and Character Inventory (TCI) for personality traits. We investigated the relationship between Change-N1 values (amplitude and latency) and each TCI dimension. The Change-N1 amplitude was positively correlated with harm avoidance scores and negatively correlated with the self-directedness scores, but not with other TCI dimensions. Since these two TCI dimensions are associated with anxiety disorders and depression, it is possible that the change-related response is affected by personality traits, particularly anxiety- or depression-related traits.

A Dynamic Evidential Fusion Network for Decision Making in Multi- Robot System

In smart environments, a multi-robot system is difficult to achieve a high confidence level of information for reliable decision making. The pieces of sensed information obtained from a multi-robot system have different degrees of uncertainty. Generated contexts about the situation of the environment can be conflicting even if they are acquired by simultaneous operations. In particular, unpredictable temporal changes in sensory information reduce the confidence level of information then lead to wrong decision making.

A model of task-specific focal dystonia

Task-specific focal dystonia is a task-specific movement disorder which manifests itself as a loss of voluntary motor control in extensively trained movements. The condition is most frequent in musicians. Until today, the aetiology of focal hand dystonia is not completely understood, but there is growing evidence for an abnormal cortical processing of sensory information, as well as degraded representation of motor functions. It was demonstrated that in the somatosensory cortex the topographical location of sensory inputs from individual fingers is corrupted. Occasionally, a change in sensory information of the hand may at least temporarily improve the condition. This phenomenon is called sensory trick. In this paper, we propose a model of encoding of sensory stimuli which could explain the task specificity of cortical representations of the fingers or other effectors in the context of dystonia. In the framework of this model a sensory stimulus is encoded as a signal vector of higher dimension. A part of its components directly represents the sensory stimulus, while the remaining components describe the context. This model does not only account for the task specificity, but may also explain some characteristics of the retraining process in this disorder.

A Dynamic Evidential Fusion Network for Decision Making in Multi- Robot System

In smart environments, a multi-robot system is difficult to achieve a high confidence level of information for reliable decision making. The pieces of sensed information obtained from a multi-robot system have different degrees of uncertainty. Generated contexts about the situation of the environment can be conflicting even if they are acquired by simultaneous operations. In particular, unpredictable temporal changes in sensory information reduce the confidence level of information then lead to wrong decision making. In order to solve this problem, we propose a reasoning method based on Dynamic Evidential Fusion Network (DEFN). First, we reduce conflicting information in multi-sensor networks using Evidential Fusion Network (EFN). Second, we improve the confidence level of information using Temporal Belief Filtering (TBF) and Normalized Weighting technique. We distinguish a sensor reading error from sensed information. Finally, we compare our approach with a fusion process based on Dynamic Bayesian Networks (DBNs) using paired observations so as to show the improvement of our proposed method.

Changes in presumed motor cortical activity during fatiguing muscle contraction in humans

Changes in sensory information from active muscles accompany fatiguing exercise and the force-generating capacity deteriorates. The central motor commands therefore must adjust depending on the task performed. Muscle potentials evoked by transcranial magnetic stimulation (TMS) change during the course of fatiguing muscle activity, which demonstrates activity changes in cortical or spinal networks during fatiguing exercise. Here, we investigate cortical mechanisms that are actively involved in driving the contracting muscles. During a sustained submaximal contraction (30% of maximal voluntary contraction) of the elbow flexor muscles we applied TMS over the motor cortex. At an intensity below motor threshold, TMS reduced the ongoing muscle activity in biceps brachii. This reduction appears as a suppression at short latency of the stimulus-triggered average of rectified electromyographic (EMG) activity. The magnitude of the suppression was evaluated relative to the mean EMG activity during the 50 ms prior to the cortical stimulus. During the first 2 min of the fatiguing muscle contraction the suppression was 10 +/- 0.9% of the ongoing EMG activity. At 2 min prior to task failure the suppression had reached 16 +/- 2.1%. In control experiments without fatigue we did not find a similar increase in suppression with increasing levels of ongoing EMG activity. Using a form of TMS which reduces cortical output to motor neurones (and disfacilitates them), this study suggests that neuromuscular fatigue increases this disfacilitatory effect. This finding is consistent with an increase in the excitability of inhibitory circuits controlling corticospinal output.

Never Resting Brain: Simultaneous Representation of Two Alpha Related Processes in Humans

Brain activity is continuously modulated, even at “rest”. The alpha rhythm (8–12 Hz) has been known as the hallmark of the brain's idle-state. However, it is still debated if the alpha rhythm reflects synchronization in a distributed network or focal generator and whether it occurs spontaneously or is driven by a stimulus. This EEG/fMRI study aimed to explore the source of alpha modulations and their distribution in the resting brain. By serendipity, while computing the individually defined power modulations of the alpha-band, two simultaneously occurring components of these modulations were found. An ‘induced alpha’ that was correlated with the paradigm (eyes open/ eyes closed), and a ‘spontaneous alpha’ that was on-going and unrelated to the paradigm. These alpha components when used as regressors for BOLD activation revealed two segregated activation maps: the ‘induced map’ included left lateral temporal cortical regions and the hippocampus; the ‘spontaneous map’ included prefrontal cortical regions and the thalamus. Our combined fMRI/EEG approach allowed to computationally untangle two parallel patterns of alpha modulations and underpin their anatomical basis in the human brain. These findings suggest that the human alpha rhythm represents at least two simultaneously occurring processes which characterize the ‘resting brain’; one is related to expected change in sensory information, while the other is endogenous and independent of stimulus change.

Angiotensin II in the brain and the autonomic control of the kidney

The kidney plays a central role in ensuring cardiovascular homeostasis, in that it functions to ensure that the variation in fluid intake is matched to that lost through normal everyday metabolism. The autonomic nervous system, via the renal sympathetic nerves, allows kidney function to be adjusted dynamically in response to changes in sensory information arising from the cardiovascular system, the soma, viscera and the higher cortical centres. At the level of the kidney, the sympathetic nerves innervate the vascular and tubular components, thereby regulating renal haemodynamics and fluid reabsorption. The processing of sensory information by the central nervous system involves nuclei associated with cardiovascular control and it is these nuclei which are influenced by angiotensin II generated locally in the brain. The angiotensin II appears to act in a neuromodulatory fashion or as a neurotransmitter. There is now sound evidence that the baroreflex control of sympathetic outflow to the kidney, at least, is under tonic inhibitory control by brain angiotensin II, which also facilitates the impact of the somatosensory system in mediating sympatho-excitation. The significance of brain angiotensin II in mediating reflex activation of the sympathetic nerves from other sensory systems has not yet been defined and needs to be resolved. Interestingly, it may be that deficits in the production of brain angiotensin II at these nuclei could contribute in part to the genesis of hypertension.

Expected and unexpected head yaw movements result in different modifications of gait and whole body coordination strategies.

During locomotion we routinely make voluntary head movements, similar to those made during steering tasks, in order to scan our environment and obtain information about objects in the environment and our proximity to these objects. Given the importance that head segment orientation during locomotion has received in the recent literature, two studies were designed to investigate responses following a voluntarily generated and an unexpected, externally applied head turn. During a voluntary head turn, an efferent copy of the head movement could cancel the sensory effects of the head turn, effectively isolating the movement response to that segment. Alternatively, if the steering synergy is a part of our motor repertoire, as has been suggested, movement of the head could automatically release a steering "synergy" of segmental control and coordination. A unique head mounted air-jet apparatus, designed and developed at the University of Waterloo, was used for both studies to ensure that auditory stimuli and the physical presence of the apparatus on the head were similar for participants of the two experiments. During certain points in the gait cycle, this device was triggered and a short burst of compressed air (350 ms) was released to cue participants to make a voluntary head turn (Experiment 1). The same device was triggered in Experiment 2; however, in this experiment compressed air was released for a longer duration (1,500 ms) which resulted in an unexpected and quick turn of the participants' head to either the left or right. In these experiments, vision was also manipulated in certain trials with liquid crystal display glasses that occluded vision for the duration of the head turn. Data from the first experiment indicates that a subset of the steering synergy previously observed is released following the voluntary head movement; however, the travel trajectory path is preserved, suggesting that sensory input resulting from the head movement is partially nullified by the central nervous system. Overall safety is ensured by maintaining the same travel path. In the second experiment, an unexpected perturbation was applied to the head during locomotion to determine how the absence of an efferent copy of the movement pattern influences the level of control over body segments during locomotion. Whole body responses similar to those observed during steering tasks were observed following application of this unexpected head perturbation. It is proposed that the CNS interprets an unexpected yaw movement of the head as a change in the frame of reference, and global modifications of the walking trajectory, similar to that observed during steering tasks, are made in the perceived new direction of travel. Collectively this work extends our understanding of how the CNS establishes a head based orientation frame for locomotion. The CNS interprets and integrates anticipated and unexpected changes in sensory information from the head segment and subsequently modifies locomotion patterns according to the perceived whole body orientation in space. The sequence of control following these head movements appears to be part of a movement repertoire that is not immutable; maintaining whole body stability during locomotion is paramount.

Perceived Standing Position after Reduction of Foot-Pressure Sensation by Cooling the Sole

We investigated the influence of the reduction of foot-pressure sensation by cooling the sole of the foot, at 1 degree C for 30 or 40 minutes, on the perception of standing position varied in the anteroposterior direction. The subjects were 16 healthy undergraduates. Firstly, for 4 of the subjects, cooling the sole of the foot decreased sensory information from the mechanoreceptors in the sole, by testing for an increase in the threshold for two-point discrepancy discrimination on the sole of the foot and for the disappearance of postural change with vibration to the sole. Next, the perception of standing position was measured by reproduction of a given standing reference position involving forward or backward leaning under both normal and cooled conditions of the feet. Standing position was varied in relation to the location of the center of foot pressure, defined as distance from the heel in percentage of the length of the foot. The reference positions, representing various locations of the center of foot pressure, were set at 10% increments from 20% to 80% of the length of the foot. With eyes closed, the subject first experienced the reference position and then attempted to reproduce it. The mean location of the center of foot pressure in the quiet standing posture was 45.7%. At the 40%, 50%, and 60% reference positions, those closest to quiet standing, absolute errors of reproduction were significantly larger than at other reference positions in both the normal and the cooled conditions. They were significantly larger in the cooled than in the normal condition. The 50% and 60% reference positions were reproduced significantly further forward in the cooled than in the normal condition. These results may be explained as due to an absence of marked changes in sensory information from both muscular activity and foot pressure when moving to reference positions close to the quiet standing posture.

PERCEIVED STANDING POSITION AFTER REDUCTION OF FOOT-PRESSURE SENSATION BY COOLING THE SOLE

We investigated the influence of the reduction of foot-pressure sensation by cooling the sole of the foot, at 1°C for 30 or 40 minutes, on the perception of standing position varied in the anteroposterior direction. The subjects were 16 healthy undergraduates. Firstly, for 4 of the subjects, cooling the sole of the foot decreased sensory information from the mechanoreceptors in the sole, by resting for an increase in the threshold for two-point discrepancy discrimination on the sole of the foot and for the disappearance of postural change with vibration to the sole. Next, the perception of standing position was measured by reproduction of a given standing reference position involving forward or backward leaning under both normal and cooled conditions of the feet. Standing position was varied in relation to the location of the center of foot pressure, defined as distance from the heel in percentage of the length of the foot. The reference positions, representing various locations of the center of foot pressure, were set at 10% increments from 20% to 80% of the length of the foot. With eyes closed, the subject first experienced the reference position and then attempted to reproduce it. The mean location of the center of foot pressure in the quiet standing posture was 45.7%. At the 40%, 50%, and 60% reference positions, those closest to quiet standing, absolute errors of reproduction were significantly larger than at other reference positions in both the normal and the cooled conditions. They were significantly larger in the cooled than in the normal condition. The 50% and 60% reference positions were reproduced significantly further forward in the cooled than in the normal condition. These results may be explained as due to an absence of marked changes in sensory information from both muscular activity and foot pressure when moving to reference positions close to the quiet standing posture.

Local sensation changes and altered hip muscle function following severe ankle sprain.

Changes in sensory information have been shown to influence muscle function locally. Some clinicians, however, believe that the influence may be more extensive. To investigate this clinical concept, subjects with severe ankle sprain were assessed for local sensation changes and proximal hip/back muscle function. Of a total of 361 potential subjects whose medical histories were assessed, 20 men (age 18-35 years) who had previously sustained a severe unilateral ankle sprain and 11 matched "control" subjects with no previous lower-limb injury participated in the study. Using this experimental model, tests of vibration sensation in the ankle (indicating sensation changes) as well as surface electromyography of muscle recruitment patterns for hip extension (indicating muscle function proximally) of the biceps femoris, gluteus maximus, and lumbar erector spinae muscles were made on both sides of the unilaterally injured and matched control subjects. Significant decreases in vibration perception and significant delays in gluteus maximus muscle recruitment during hip extension were found in the injured group. The author concludes that both local sensory and proximal muscle function changes are associated with unilateral severe ankle sprain.