scholarly journals The Effects of Virtual Height Exposure on Postural Control and Psychophysiological Stress Are Moderated by Individual Height Intolerance

2022 ◽  
Vol 15 ◽  
Author(s):  
Diana Bzdúšková ◽  
Martin Marko ◽  
Zuzana Hirjaková ◽  
Jana Kimijanová ◽  
František Hlavačka ◽  
...  
Keyword(s):  
Visual Information ◽  
Emotional State ◽  
Balance Control ◽  
Electrodermal Activity ◽  
Low Frequency ◽  
Ground Level ◽  
Body Sway ◽  
Psychophysiological Stress ◽  
Study Participants ◽  
Fear Of Heights

Virtual reality (VR) enables individuals to be exposed to naturalistic environments in laboratory settings, offering new possibilities for research in human neuroscience and treatment of mental disorders. We used VR to study psychological, autonomic and postural reactions to heights in individuals with varying intensity of fear of heights. Study participants (N = 42) were immersed in a VR of an unprotected open-air elevator platform in an urban area, while standing on an unstable ground. Virtual elevation of the platform (up to 40 m above the ground level) elicited robust and reliable psychophysiological activation including increased distress, heart rate, and electrodermal activity, which was higher in individuals suffering from fear of heights. In these individuals, compared with individuals with low fear of heights, the VR height exposure resulted in higher velocity of postural movements as well as decreased low-frequency (<0.5 Hz) and increased high-frequency (>1 Hz) body sway oscillations. This indicates that individuals with strong fear of heights react to heights with maladaptive rigidity of posture due to increased weight of visual input for balance control, while the visual information is less reliable at heights. Our findings show that exposure to height in a naturalistic VR environment elicits a complex reaction involving correlated changes of the emotional state, autonomic activity, and postural balance, which are exaggerated in individuals with fear of heights.

scholarly journals Processing time of addition or withdrawal of single or combined balance-stabilizing haptic and visual information

2015 ◽  
Vol 114 (6) ◽  
pp. 3097-3110 ◽  
Author(s):  
Jean-Louis Honeine ◽  
Oscar Crisafulli ◽  
Stefania Sozzi ◽  
Marco Schieppati
Keyword(s):  
Steady State ◽  
Visual Information ◽  
Time Course ◽  
Balance Control ◽  
Body Sway ◽  
Integration Time ◽  
Peroneus Longus ◽  
Time Period ◽  
Sensory Modalities ◽  
Posture Stabilization

We investigated the integration time of haptic and visual input and their interaction during stance stabilization. Eleven subjects performed four tandem-stance conditions (60 trials each). Vision, touch, and both vision and touch were added and withdrawn. Furthermore, vision was replaced with touch and vice versa. Body sway, tibialis anterior, and peroneus longus activity were measured. Following addition or withdrawal of vision or touch, an integration time period elapsed before the earliest changes in sway were observed. Thereafter, sway varied exponentially to a new steady-state while reweighting occurred. Latencies of sway changes on sensory addition ranged from 0.6 to 1.5 s across subjects, consistently longer for touch than vision, and were regularly preceded by changes in muscle activity. Addition of vision and touch simultaneously shortened the latencies with respect to vision or touch separately, suggesting cooperation between sensory modalities. Latencies following withdrawal of vision or touch or both simultaneously were shorter than following addition. When vision was replaced with touch or vice versa, adding one modality did not interfere with the effect of withdrawal of the other, suggesting that integration of withdrawal and addition were performed in parallel. The time course of the reweighting process to reach the new steady-state was also shorter on withdrawal than addition. The effects of different sensory inputs on posture stabilization illustrate the operation of a time-consuming, possibly supraspinal process that integrates and fuses modalities for accurate balance control. This study also shows the facilitatory interaction of visual and haptic inputs in integration and reweighting of stance-stabilizing inputs.

scholarly journals CARACTERIZAÇÕES ANATÔMICA E FÍSICO-MECÂNICA DA MADEIRA DE Liquidambar sp.

FLORESTA ◽  
2015 ◽  
Vol 45 (4) ◽  
pp. 723 ◽  
Author(s):  
Thaís Pereira Freitas ◽  
Lairo David Feuchard ◽  
José Tarcísio Silva Oliveira ◽  
Juarez Benigno Paes ◽  
Marina Donária Chaves Arantes
Keyword(s):  
Specific Gravity ◽  
Dimensional Stability ◽  
Mechanical Characterization ◽  
Great Influence ◽  
Low Frequency ◽  
Ground Level ◽  
Espírito Santo ◽  
Vessel Elements ◽  
Espirito Santo

Este trabalho teve como objetivo a caracterização anatômica e físico-mecânica da madeira de Liquidambar sp. Para tanto, foram utilizadas três árvores com oito anos de idade, provenientes de um arboreto localizado do município de Guaçuí, Espírito Santo. As características anatômicas analisadas foram as dimensões das fibras (comprimento, diâmetro total e do lume e espessura da parede), dos elementos de vasos (diâmetro tangencial e frequência) e dos raios (altura, largura e frequência). Para a caracterização físico-mecânica foram avaliadas a massa específica (básica, aparente a 12% de umidade e anidra), as contrações totais lineares e volumétrica, a resistência à flexão estática, à compressão paralela às fibras, ao cisalhamento e dureza Janka. Constatou-se frequência vascular numerosa com vasos de pequeno diâmetro tangencial, raios heterocelulares ocorrendo em baixa frequência, e fibras libriformes longas de paredes delgadas a espessas. A massa específica básica da madeira proveniente de discos retirados a 1,30 m do nível do solo foi de 0,48 g cm-3, sendo considerada média, a estabilidade dimensional foi considerada baixa, e houve grande influência da umidade nos valores de resistência da madeira. AbstractAnatomical and physical-mechanical characterization of Liquidambar sp. wood. This research aimed to improve anatomical, physical and mechanical characterization of Liquidambar sp.wood. Three trees were obtained, at eight years of age, from an arboretum located in Guaçuí, Espírito Santo State, Brazil. The analyzed variables were dimensions of the fibers (length, total diameter and diameter of the lumen and wall thickness), the vessel elements (tangential diameter and frequency), and ray (height, width and frequency). The specific gravity (basic, at 12% moisture content and dry), and total volumetric and linear shrinkages, resistance to bending, compression parallel to the fibers, shear and Janka hardness. For anatomical description it was found numerous vessels often with small tangential diameter, heterocellular rays occurring at low frequency, and long libriform fibers with thick to thin walls. The specific gravity of wood from disks taken at 1.30 m from ground level was 0.48 g cm-3, wich we considered average, the dimensional stability was low, and there was great influence of moisture in the resistance values in wood.Keywords: Anatomy; specific gravity; dimensional stability; mechanical strength.

scholarly journals MobiLab – A Mobile Laboratory for On-Site Listening Experiments in Virtual Acoustic Environments

2019 ◽  
Vol 105 (5) ◽  
pp. 875-887
Author(s):  
Florian Pausch ◽  
Janina Fels
Keyword(s):  
Ambient Noise ◽  
Low Frequency ◽  
Mobile Laboratory ◽  
Noise Levels ◽  
Acoustic Parameters ◽  
Research Areas ◽  
Test Conditions ◽  
Acoustic Environments ◽  
Study Participants ◽  
Insulation Performance

Virtual acoustic environments have demonstrated their versatility for conducting studies in various research areas as they allow easy manipulations of experimental test conditions or simulated acoustic scenes, while providing expansion possibilities to related interdisciplinary and multimodal fields. Although the evolution of auditory and cognitive models is consistently pursued, listening experiments are still considered the gold standard, usually necessitating a large amount of resources, including travel expenses of study participants. In order to facilitate practical and efficient study execution, we therefore implemented a mobile hearing laboratory by acoustically optimising the interior of a caravan. All necessary technical facilities were integrated to perform listening experiments in virtual acoustic environments under controlled conditions directly on site, for example, in front of schools or senior residential centers. The design and construction of this laboratory are presented and evaluated based on insulation properties, selected room acoustic parameters, and interior ambient noise levels that are to be expected during operation at representative test sites. Limitations, particularly in low-frequency insulation performance, should provide incentives for further optimisations in similar future projects.

Effects of Cognitive Over Postural Demands on Upright Standing Among Young Adults

2020 ◽  
pp. 003151252097287
Author(s):  
Kell Grandjean da Costa ◽  
Erika K. Hussey ◽  
Eduardo Bodnariuc Fontes ◽  
Alekya Menta ◽  
John W. Ramsay ◽  
...  
Keyword(s):  
Young Adults ◽  
Balance Control ◽  
Healthy Adults ◽  
Body Sway ◽  
Cognitive Resources ◽  
Stance Control ◽  
Upright Standing ◽  
Measurement Units ◽  
Future Work ◽  
The Impact

A growing body of research has shown that static stance control (e.g., body sway) is influenced by cognitive demands (CD), an effect that may be related to competition for limited central resources. Measures of stance control have also been impacted by postural demands (PD) (e.g., stable vs. unstable stances). However, less is known of any possible interactions between PD and CD on static stance control in populations with intact balance control and ample cognitive resources, like young healthy adults. In this study, among the same participants, we factorially compared the impact of PD with and without CD on static stance control. Thirty-four healthy young adults wore inertial measurement units (IMU) while completing static stance tasks for 30 seconds in three different PD positions: feet apart, feet together, and tandem feet. After completing these tasks alone, participants performed these tasks with CD by concurrently completing verbal serial seven subtractions from a randomly selected three-digit number. For two dependent measures, path length and jerk, there were main effects of CD and PD but no interaction effect between these factors. For all other stance control parameters, there was only a PD main effect. Thus, adding a cognitive demand to postural demands, while standing upright, may have an independent impact on stance control, but CD does not seem to interact with PD. These results suggest that young healthy adults may be less sensitive to simple PD and CD due to their greater inherent balance control and available cognitive resources. Future work might explore more complex PD and CD combinations to determine the boundaries under which young adults’ resources are taxed.

scholarly journals Oscillatory Dynamics of Perceptual to Conceptual Transformations in the Ventral Visual Pathway

2018 ◽  
Vol 30 (11) ◽  
pp. 1590-1605 ◽  
Author(s):  
Alex Clarke ◽  
Barry J. Devereux ◽  
Lorraine K. Tyler
Keyword(s):  
Visual Information ◽  
Computational Models ◽  
Semantic Information ◽  
Low Frequency ◽  
Visual Pathway ◽  
Semantic Representations ◽  
Low Level ◽  
Oscillatory Dynamics ◽  
Incremental Model ◽  
Ventral Visual Pathway

Object recognition requires dynamic transformations of low-level visual inputs to complex semantic representations. Although this process depends on the ventral visual pathway, we lack an incremental account from low-level inputs to semantic representations and the mechanistic details of these dynamics. Here we combine computational models of vision with semantics and test the output of the incremental model against patterns of neural oscillations recorded with magnetoencephalography in humans. Representational similarity analysis showed visual information was represented in low-frequency activity throughout the ventral visual pathway, and semantic information was represented in theta activity. Furthermore, directed connectivity showed visual information travels through feedforward connections, whereas visual information is transformed into semantic representations through feedforward and feedback activity, centered on the anterior temporal lobe. Our research highlights that the complex transformations between visual and semantic information is driven by feedforward and recurrent dynamics resulting in object-specific semantics.

Impairments of Postural Balance in Surgically Treated Lumbar Disc Herniation Patients

2020 ◽  
Vol 36 (4) ◽  
pp. 228-234
Author(s):  
Ziva M. Rosker ◽  
Jernej Rosker ◽  
Nejc Sarabon
Keyword(s):  
Postural Balance ◽  
Center Of Pressure ◽  
Balance Control ◽  
The Body ◽  
Surface Velocity ◽  
Body Sway ◽  
Support Surface ◽  
Balance Task ◽  
Lateral Body ◽  
Unstable Support

Reports on body sway control following microdiscectomy lack reports on side-specific balance deficits as well as the effects of trunk balance control deficits on body sway during upright stances. About 3 weeks post microdiscectomy, the body sway of 27 patients and 25 controls was measured while standing in an upright quiet stance with feet positioned parallel on an unstable support surface, a tandem stance with the involved leg positioned in front or at the back, a single-leg stance with both legs, and sitting on an unstable surface. Velocity, average amplitude, and frequency-direction–specific parameters were analyzed from the center of pressure movement, measured by the force plate. Statistically significant differences between the 2 groups were observed for the medial–lateral body sway frequency in parallel stance on a stable and unstable support surface and for the sitting balance task in medial-lateral body sway parameters. Medium to high correlations were observed between body sway during sitting and the parallel stance, as well as between the tandem and single-legged stances. Following microdiscectomy, deficits in postural balance were side specific, as expected by the nature of the pathology. In addition, the results of this study confirmed the connection between proximal balance control deficits and balance during upright quiet balance tasks.

Tuning Perceptual Competition

2010 ◽  
Vol 103 (2) ◽  
pp. 1057-1065 ◽  
Author(s):  
Edmund Wascher ◽  
Christian Beste
Keyword(s):  
Visual Information ◽  
Relevant Information ◽  
Event Related Potential ◽  
Luminance Change ◽  
Orientation Change ◽  
Conflicting Information ◽  
Task Irrelevant ◽  
Study Participants ◽  
Dynamic Interplay ◽  
Relative Salience

The ability to notice relevant visual information has been assumed to be determined both by the relative salience of relevant information compared with distracters within a given display and by voluntary allocation of attention toward intended goals. A dominance of either of these two mechanisms in stimulus processing has been claimed by different theories. A central question in this context is to what degree and how task irrelevant signals can influence processing of target information. In the present study, participants had to detect a luminance change in various conditions among others against an irrelevant orientation change. The saliency of the latter was systematically varied and was found to be predictive for the proportion of detected information when relevant and irrelevant information were spatially separated but not when they overlapped. Weighting and competition of incoming signals was reflected in the amplitude of the N1pc component of the event-related potential. Initial orientation of attention toward the irrelevant element had to be followed by a reallocation process, reflected in an N2pc. The control of conflicting information additionally evoked a fronto-central N2 that varied with the amount of competition induced. Thus the data support models that assume that attention is a dynamic interplay of bottom-up and top-down processes that may be mediated via a common dynamic neural network.

scholarly journals Stable maintenance of multiple representational formats in human visual short-term memory

2020 ◽  
Vol 117 (51) ◽  
pp. 32329-32339
Author(s):  
Jing Liu ◽  
Hui Zhang ◽  
Tao Yu ◽  
Duanyu Ni ◽  
Liankun Ren ◽  
...  
Keyword(s):  
Visual Information ◽  
Short Term Memory ◽  
Temporal Dynamics ◽  
Low Frequency ◽  
Higher Order ◽  
Semantic Representations ◽  
Short Term ◽  
Term Memory ◽  
Visual Short Term Memory ◽  
Stable Maintenance

Visual short-term memory (VSTM) enables humans to form a stable and coherent representation of the external world. However, the nature and temporal dynamics of the neural representations in VSTM that support this stability are barely understood. Here we combined human intracranial electroencephalography (iEEG) recordings with analyses using deep neural networks and semantic models to probe the representational format and temporal dynamics of information in VSTM. We found clear evidence that VSTM maintenance occurred in two distinct representational formats which originated from different encoding periods. The first format derived from an early encoding period (250 to 770 ms) corresponded to higher-order visual representations. The second format originated from a late encoding period (1,000 to 1,980 ms) and contained abstract semantic representations. These representational formats were overall stable during maintenance, with no consistent transformation across time. Nevertheless, maintenance of both representational formats showed substantial arrhythmic fluctuations, i.e., waxing and waning in irregular intervals. The increases of the maintained representational formats were specific to the phases of hippocampal low-frequency activity. Our results demonstrate that human VSTM simultaneously maintains representations at different levels of processing, from higher-order visual information to abstract semantic representations, which are stably maintained via coupling to hippocampal low-frequency activity.

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