Altered Sensory Environments Research Articles

Contributing factors to postural stability in Prader-Willi syndrome

BackgroundPrader-Willi Syndrome (PWS) is a rare neurodevelopmental disorder affecting multiple functional parameters. This study examined postural stability and associated gait and neuromuscular factors in young adults with PWS. MethodsParticipants included 10 adults with PWS [7 M/3F; Body Fat % 40.61 ± 7.79]; ten normal weight (NW) adults [7 M/3F; Body Fat % 23.42 ± 7.0]; ten obese (OB) adults [7 M/3F; Body Fat % 42.40 ± 5.62]. Participants completed the Sensory Organization Test (SOT)®. Condition (C) specific and a composite equilibrium score (CES) were calculated (maximum = 100). Quadriceps strength was assessed using an isokinetic dynamometer. Three-dimensional gait analyses were completed along a 10 m walkway using a motion capture system and two force plates. A gait stability ratio (GSR) was computed from gait speed and step length (steps/m). ResultsThe PWS group had lower scores for C1, C3, C4 and CES compared to the NW (p < .039 for all) and lower scores for C4 and CES than the OB (p < .019 for both) groups, respectively. In C5 (eyes closed, sway-referenced support) and C6 (sway-referenced vision and support), 33.3% of participants with PWS fell during the first trial in both conditions (X2 [2] 7.436, p = .024) and (X2 [2] 7.436, p = .024) but no participant in the other groups fell. Those with PWS showed higher GSR than participants with NW (p = .005) and those with obesity (p = .045). ConclusionIndividuals with PWS had more difficulty maintaining standing balance when relying on information from the somatosensory (C3), visual-vestibular (C4) and vestibular systems (C5, C6). A more stable walk was related to shorter steps, slower velocity and reduced peak quadriceps torque. Participation in multisensory activities that require appropriate prioritization of sensory system(s) input for controlling balance in altered sensory environments should be routinely included. In addition, exercises targeting muscular force and power should be included as part of exercise programming in PWS.

Feeding in murky waters: acclimatization and landmarks improve foraging efficiency of zebrafish (Danio rerio) in turbid waters.

Fish inhabiting human-dominated ecosystems are prone to altered sensory environments in which they must live and function. Increased turbidity is one such change that they must deal with. We tested whether an increase in water turbidity and the presence of visual landmarks (coloured stones) affect the foraging efficiency of wild zebrafish. We also tested the influence of extended exposure to differing turbidity levels on the subsequent foraging efficiency of acclimatized individuals. Feeding latency (time taken to find food) increased significantly with increase in turbidity levels from a minimum of 4 s to ca 300 s. However, extended exposure of fish to varying levels of turbidity decreased feeding latencies in acclimatized conditions, indicating that acclimatization to the immediate visual environment plays an important role in determining foraging success. Most significantly, we found that feeding latencies in turbid conditions decreased significantly if visual landmarks were present. This demonstrates that zebrafish use visual landmark cues to navigate to foraging sites when visibility is impaired. This study has important implications on the role of behavioural plasticity and spatial learning in animals that allow them to cope with altered sensory environments such as episodes of enhanced turbidity that could be natural or anthropogenic.

Multimodal communication, mismatched messages and the effects of turbidity on the antipredator behavior of the Barton Springs salamander, Eurycea sosorum

Prey may use multiple sensory channels to detect predators, whose cues may differ in altered sensory environments, such as turbid conditions. Depending on the environment, prey may use cues in an additive/complementary manner or in a compensatory manner. First, to determine whether the purely aquatic Barton Springs salamander, Eurycea sosorum, show an antipredator response to visual cues, we examined their activity when exposed to either visual cues of a predatory fish (Lepomis cyanellus) or a non-predatory fish (Etheostoma lepidum). Salamanders decreased activity in response to predator visual cues only. Then, we examined the antipredator response of these salamanders to all matched and mismatched combinations of chemical and visual cues of the same predatory and non-predatory fish in clear and low turbidity conditions. Salamanders decreased activity in response to predator chemical cues matched with predator visual cues or mismatched with non-predator visual cues. Salamanders also increased latency to first move to predator chemical cues mismatched with non-predator visual cues. Salamanders decreased activity and increased latency to first move more in clear as opposed to turbid conditions in all treatment combinations. Our results indicate that salamanders under all conditions and treatments preferentially rely on chemical cues to determine antipredator behavior, although visual cues are potentially utilized in conjunction for latency to first move. Our results also have potential conservation implications, as decreased antipredator behavior was seen in turbid conditions. These results reveal complexity of antipredator behavior in response to multiple cues under different environmental conditions, which is especially important when considering endangered species.

A Comparison of Central Sensory Reception and Integration Abilities between Older Females with and without Fibromyalgia: A Pilot Study

Purpose: Impaired postural control has been reported in females with fibromyalgia syndrome (FMS). This study aimed to investigate a) differences in central sensory reception and integration abilities for postural control between older females with and without FMS, and b) the influence of a secondary cognitive task on postural control in altered sensory environments. Methods: The performances of 10 older females with FMS were compared to eight age-matched healthy females across single and dual task conditions using the Sensory Organization Test®. Results: No significant group differences were evident for Composite Equilibrium Score (CES) in the single task condition (p = 0.06) but a large effect size (Cohen’s d = 0.96) was obtained, suggesting a clinically relevant difference existed between groups with respect to general sensory reception and integration abilities. Single trial Equilibrium Scores (ESs) for both groups declined significantly in the more complex sensory conditions across both task conditions (p < 0.01) with a greater decline evident for the FMS group in sensory condition 4 in the dual-task condition (p = 0.04). The FMS group also experienced multiple falls in sensory conditions 5 and 6 across both task conditions with a significantly higher percentage of falls evident for the FMS group in condition 6 across both task conditions (p = 0.04). Conclusions: Overall postural stability was significantly lower in the FMS group when compared to an age-matched control group. Postural stability declined further in the FMS group when attempting to perform a secondary cognitive task in both sensory conditions that primarily relied on vestibular inputs for postural control. A greater focus on multisensory and dual-task training in a balance environment may benefit older females with FMS.

Changes in postural sway frequency and complexity in altered sensory environments following whole body vibrations

Studies assessing whole body vibration (WBV) have produced largely positive effects, with some neutral, on postural control with frequencies between 25 and 40Hz. However no conclusive evidence indicates that 25–40Hz elicits the optimal beneficial effects. To address this issue, a larger range of vibration intensity (10–50Hz at peak-to-peak amplitudes of 2 and 5mm) was employed while increasing the postural complexity (altered somatosensory and/or visual information) to assess acute effects of 4-min of WBV on postural control. Twelve healthy young adults underwent postural assessment at four time intervals (prior to, immediately following and 10 and 20min post WBV). Findings revealed both postural sway frequency and sway complexity/regularity were affected by WBV. Baseline posture demonstrated increased sway frequency (p=.04) following WBV with no changes in sway complexity. When the support surface was altered, changes in both the frequency and complexity of sway were elicited (p=.027, .002, respectively). When both somatosensory and visual information were altered delayed improvements in postural control were elicited (p=.05 and .01, for frequency and complexity, respectively). Given the differential acute effects as a function of postural task complexity, future longitudinal studies could determine the overall training effect on sway frequency and complexity.

Age-dependent differences in the time course of postural control during sensory perturbations

With research demonstrating that older adults are more likely to sustain a loss of balance than younger adults, the need for an account of age-related differences in postural control is apparent. Several measures of balance reported in the literature have assessed balance using an average or summative measure over the course of a trial, typically lasting several seconds. One limitation related to these measures is the inability to assess the time-course of postural control occurring throughout the trial. To this end, the current investigation assessed the temporal changes in balance both as a function of age and sensory environment. Postural control was assessed from 10 older adults (69.3+/-4.7 years) and 10 younger adults (22.1+/-1.7 years) over the course of fifteen seconds in three different sensory environments. The sensory manipulations involved sway-referenced rotation of the floor and/or the visual surround. Significant differences (p=0.001) in overall postural stability were observed between the two groups on all three sensory conditions. Additionally, time-course changes were observed between the two groups when the environment did not cause sensory conflict (sway-referenced floor or room only). However, when the environment created a situation of sensory conflict (sway-referenced floor and room) both groups followed the same time-course of postural changes. Interestingly, the time course of postural control for the older adults on the easiest condition was mimicked by the younger adults on a more challenging condition. However, when faced with sensory conflict there were no group differences in the time course of postural control. The findings suggest an age-related decline in the temporal control of posture in altered sensory environments.

Frequency spectral characteristics of standing balance in children and young adults

Past research has shown that spectral frequency characteristics of a balance control system may be useful for early detection of minor changes in the system. Since there is a lack of information regarding the frequency spectrum of children’s balance control system, this study was undertaken to investigate and compare the spectral frequency characteristics of standing balance control between children and young adults under altered sensory environments. Seventeen children (9 females, 8 males, mean age 7.8±0.9 years) and the same number of female and male young adults (mean age 21.1±1.3 years) were tested for standing balance under six sensory conditions. These conditions were created by crossing the three levels of the visual factor (open eye, closed eye, sway-referenced vision) with the two levels of the somatosensory factor (fixed foot support, compliant foot support). The median spectral frequencies of the shear forces in the anterior–posterior (A/P) and the medial–lateral (M/L) directions were used as dependent variables. The results showed that children had higher median spectral frequency of the A/P shear force than young adults and this difference was not affected by the somatosensory factor. The median spectral frequency in the M/L direction was not different between the groups. The higher rate of body mass vibration of children in the A/P direction implies that children may not have fully developed the ankle strategy for maintaining standing balance, but nonetheless have developed the same efficiency of using vision for their reference of standing balance.

Multisensory fusion: simultaneous re-weighting of vision and touch for the control of human posture

We examined the generally held belief that the postural control system is able to re-weight its available sensory inputs in order to optimize stance control in altered sensory environments. Our view is that previous accounts of sensory re-weighting provide only indirect evidence, which is subject to alternative explanations. The present results provide strong evidence for sensory re-weighting as the primary mechanism for changes observed in postural sway between conditions. Subjects were presented with small-amplitude, oscillatory visual and somatosensory stimuli at 0.20 and 0.28 Hz, respectively, in five conditions that manipulated the amplitudes of stimulus motion. Gain calculated in each trial with respect to each of the two stimuli was found to change systematically as stimulus motion amplitudes changed across condition. The observed pattern of gain rules out a constant-weight, linear account of posture and is consistent with the re-weighting hypothesis. Parameter fits of a third-order, linear stochastic model to postural sway trajectories in each condition showed that changes in gain across condition were primarily due to changes in coupling coefficients rather than changes in parameters that characterize the stability of the postural system. Visual gain was found to depend upon visual motion amplitude and touch gain was found to depend upon touch motion amplitude, indicating intra-modality dependencies. Visual gain also depended upon touch motion amplitude, indicating an inter-modality dependence. To our knowledge, simultaneous re-weighting of more than one sensory input has never been rigorously demonstrated. These techniques may be able to resolve the source of balance control deficits across populations with far more certainty than currently possible.

Het bewaren van statisch evenwicht in stand bij kinderen met spastische diplegische cerebrale parese in diverse sensorische situaties

Performance of static standing balance in children with spastic diplegic cerebral palsy under altered sensory environments [American Journal of Physical Medicine and Rehabilitation 1999;78(4):336-43]

ENTERING TRAIT AND CONTEXT INTO A COGNITIVE-TIMER MODEL FOR TIME ESTIMATION

Subjects were exposed to conditions of perceptual deprivation and perceptual overload, and were then asked to produce short intervals of time. It was hypothesized that the greater the variation in the sensory environment (i.e. perceptual overload vs perceptual deprivation), the shorter would be the time estimation obtained by this method of production. It was further assumed that the personality trait of Experience Seeking could moderate this influence of the altered sensory environments on the functioning of the cognitive timer. A trait–context interaction was uncovered, indicating this moderating effect. Furthermore, both trait and context effects were specific to the measure constant of the psychophysical function relating produced time to required time. These results are presented within a contextualistic approach to the study of subjective time.

Sensory organization of balance responses in children 3–6 years of age: a normative study with diagnostic implications

The effect of altered sensory environments on balance was studied in 82 healthy children between 3 and 6 years of age. The purpose was to obtain normative measurements of postural stability during early stages of development for use in clinical posturography. Subjects were tested in three visual conditions (eyes open, blind-folded, and sway-referenced visual enclosure) during stance on either a fixed or sway-referenced force platform (EquiTest). During sway-referenced conditions, spontaneous changes in the subject's center of force (COF) drove rotational displacements of the platform and/or visual surround. The gain of platform/COF or surround/COF displacement was altered from 0.00 to 1.5. An equilibrium score (ES) was calculated based on the amount of postural sway compared to the maximum sway possible without falling. A higher ES reflected greater postural stability. An improvement in postural stability was observed between 4 and 5 years of development when the sensory environment was fixed (sway referenced gain = 0.0). In a dynamic sensory environment, however, age-related improvements in postural stability were not uniform and depended upon the specific sensory condition. For example, while 6 year olds generally showed the greatest postural stability of any age group, all ages showed statistically equivalent equilibrium scores during stance on a compliant surface with eyes closed, at all sway gains. The ability to ignore misleading sensory inputs to maintain balance was observed at 3 years of age; 76% of the 3 year olds ( n = 16) were able to maintain stance in altered sensory environments at the 1.0 sway gain. In addition, postural stability was greater when visual inputs were sway-referenced compared to conditions that manipulated the support surface compliance. These data suggest that the predominance of visual-vestibular control of balance gives way to a somatosensory-vestibular dependence by age 3, but that the transition to adult-like balance responses is not complete for all sensory conditions even by age 6. The use of posturography to enhance the assessment of pediatric vestibular and sensory integration deficits is discussed.

Perceived Self-Orientation and Self-Motion in Microgravity, After Landing and During Preflight Adaptation Training

The research described in this paper is intended to support development and evaluation of preflight adaptation training (PAT) apparatus and procedures. Successful training depends on appropriate manipulation of visual and inertial stimuli that control perception of self-motion and self-orientation. For one part of this process, astronauts are trained to report their self-motion and self-orientation experiences. Before their space mission, they are exposed to the altered sensory environments produced by the PAT trainers. During and after the mission, they report their motion and orientation experiences. Subsequently, they are again exposed to the PAT trainers and are asked to describe relationships between their experiences in microgravity and following entry and their experiences in the trainers.

Subjective Time Estimation in Altered Sensory Environments

The influence of prior exposure to an altered sensory environment on subsequent subjective time estimation was the focus of the present study. It was hypothesized that the more varied the sensory environment (i.e., perceptual overload versus perceptual deprivation), the longer the time that is verbally estimated, and the shorter the time estimation obtained by the method of production. This hypothesis was supported for the data gathered by the latter method, but not by the former one, in a 3 x 4 factorial design employing 96 subjects, who were exposed to various combinations of auditory and visual stimulation. The conclusion drawn is that visual and auditory stimulation interact in their production of an altered sensory environment, and that the rate of functioning of the cognitive timer is environment dependent.

The induction of an altered state of consciousness as a function of sensory environment and experience seeking

This paper reports on the results of two experiments concerned with the induction of an altered state of consciousness (ASC) in the laboratory. In these experiments different conditions of sensory stimulation were operationally defined (altered sensory environments), and employed in an attempt to change the psychophysiological state of the subject, and thus induce an ASC. Visual and auditory sources of stimulation were used, and conditions of overload and deprivation were defined. The goal of the first study was to investigate how trait (experience seeking) and environment interact to codetermine subjective experience. In the second study, optimal conditions were employed for the induction of an ASC. Two groups of subjects, divided into ‘high’ and ‘low’ experience seekers by median split, were randomly allocated to these conditions and completed the experiment. It was found that more than 85% of high experience seekers, exposed to a condition of perceptual deprivation, experienced an ASC.

Comment: Sexually selected infanticide among female birds

Prey may use multiple sensory channels to detect predators, whose cues may differ in altered sensory environments, such as turbid conditions. Depending on the environment, prey may use cues in an additive/complementary manner or in a compensatory manner. First, to determine whether the purely aquatic Barton Springs salamander, Eurycea sosorum, show an antipredator response to visual cues, we examined their activity when exposed to either visual cues of a predatory fish (Lepomis cyanellus) or a non-predatory fish (Etheostoma lepidum). Salamanders decreased activity in response to predator visual cues only. Then, we examined the antipredator response of these salamanders to all matched and mismatched combinations of chemical and visual cues of the same predatory and non-predatory fish in clear and low turbidity conditions. Salamanders decreased activity in response to predator chemical cues matched with predator visual cues or mismatched with non-predator visual cues. Salamanders also increased latency to first move to predator chemical cues mismatched with non-predator visual cues. Salamanders decreased activity and increased latency to first move more in clear as opposed to turbid conditions in all treatment combinations. Our results indicate that salamanders under all conditions and treatments preferentially rely on chemical cues to determine antipredator behavior, although visual cues are potentially utilized in conjunction for latency to first move. Our results also have potential conservation implications, as decreased antipredator behavior was seen in turbid conditions. These results reveal complexity of antipredator behavior in response to multiple cues under different environmental conditions, which is especially important when considering endangered species.

Short-term sensory enrichment and artistic creativity.

In an effort to find brief and relatively simple methods of fostering creativity, Ss molded clay sculptures, first in a pretest condition and then 1 wk. later within either a 30-min. sensorily enriched environment or in the same control environment following 10-min. mild sensory deprivation. Following completion of both sculptures, Ss and six judges independently rated them for creativity. No environmental effects upon self-rated or judge-rated creativity were found. Correlations between self- and judge-ratings were low. The results suggest that effects on creativity by altered sensory environments may be difficult to produce.

Psychophysiological studies in altered sensory environments

The results of exploratory investigations suggested that disruptive psychological effects similar to those observed in experiments of longer duration could be produced when subjects were isloated for short periods in low sensory input environments if a high degree of uncertainty was produced by sharply limiting the information available to them about the nature or duration of the experiment. Body- and field-oriented subjects were then tested for 2 hr in a low sensory input experiment. The experimental “environment” was expected to highlight perceptual mode differences determined by Rod and Frame and Draw-A-Person Tests. Subjects who were field-oriented showed in contrast to body-oriented subjects: (1) most intense psychological discomfort; (2) higher incidence of visual and auditory imagery; (3) more evidence of disorganization of thought; and (4) greater discomfort with body sensations. In addition, the field-oriented subjects revealed: (1) less of an ability to discriminate somato-sensory cues which was most pronounced after the 2-hour experiment; and (2) EEG and skin resistance evidence of higher level of alerting during the experiment although both groups started at the same level of activity. Body- and field-oriented subjects were then tested in an identical experimental design except that subjects were given either a sedative, stimulant or placebo capsule immediately prior to their being isolated. The response patterns of both groups with a placebo was similar to that observed in the previous experiment. However, the response of the subjects to the sedative and to the stimulant was different in that the field subjects showed a decrease in central nervous system activation and a more relaxed psychological state as the experiment progressed and body subjects showed alerting to the stimulant and mixed response to densative. Hence, altering the internal state (psychological or physiological) of the two subjects changed their response patterns to the experimental environment. In another study the responses of subjects given LSD during a 2-hr low sensory input experiment were compared to responses of subjects given a placebo. The effects which were noted in the LSD subjects were very similar to the responses of field subjects in the previous study. It was thought that the effects produced by the drug on perceptual functions caused them to perceive and react similarly to field subjects. Possible neurol ormonal and neurophysiological differences in addition to perceptual mode and personality differences in body- and field-oriented subjects are discussed. The possible application of the experimental results to clinical diagnostic and therapeutic problems and the possible application to selection and training problems in aerospace research are reviewed.