Normalized stability time analysis within the boundaries between adults with and without fear of falling

BACKGROUND

The unilateral stance test, measured by the center of pressure (COP), has been widely used to identify balance deficits. However, there is a critical gap in understanding the specific COP thresholds on postural stability in adults with a fear of falling (FOF).

AIMS

To investigate the normalized stability time, which was defined as the ratio of time spent within stability boundaries to the total test duration, under different visual conditions and specific thresholds between adults with and without FOF.

METHODS

Twenty-one older adults with FOF and 22 control subjects completed the unilateral limb standing test in eyes-open and eyes-closed conditions. Normalized stability times were computed based on five pre-determined COP sway range thresholds: 10 mm, 15 mm, 20 mm, 25 mm, and 30 mm.

RESULTS

Receiver operating characteristic analysis determined the diagnostic accuracy of FOF. There were significant differences in the effects of both visual conditions (F = 46.88, p = 0.001) and threshold settings (F = 119.38, p = 0.001) on stability time between groups. The FOF group significantly reduced normalized stability time at the 10 mm COP threshold under eyes-closed conditions (t = - 1.95, p = 0.03).

DISCUSSION

The findings highlight the heightened sensitivity of the 10 mm COP threshold in identifying group variances in postural stability when eyes are closed. Moreover, the FOF group displayed a marked reduction in stability duration based on visual scenarios and normalized thresholds.

CONCLUSION

The study highlights the need to account for both COP boundaries and visual conditions in adults with FOF. When assessing postural control during unilateral stances, clinicians must also give attention to non-visual cues.

Investigating the Impact of Visual Input on Voice Production in Virtual Reality

OBJECTIVE

This study explored the independent effects of visual input on voice production using virtual reality. Specifically, its effects on acoustic voice parameters and vocal status ratings, with the hypothesis that larger (a virtual lecture hall and theater compared to an office) and more full virtual rooms (75% of the capacity compared to 45%) would result in changes to the voice parameters and vocal status ratings.

METHODS

Voice production from 30 vocally healthy participants was recorded in six virtual reality conditions. After each condition, the participants provided vocal status ratings. The voice recordings were processed to calculate mean and standard deviation of sound pressure level and fundamental frequency, mean pitch strength, time dose, and cepstral peak prominence smoothed. The effects of the virtual reality conditions on these voice acoustic parameters and the vocal status ratings were analyzed.

RESULTS

The full virtual reality rooms resulted in significantly higher vocal fatigue and vocal discomfort ratings. The larger virtual reality rooms were significantly related to increases in mean and the standard deviation of sound pressure level, mean pitch strength, and cepstral peak prominence smoothed.

CONCLUSIONS

This study demonstrated that visual size and visual fullness input during speech tasks have distinct effects on voice production and self-reported vocal status. Visual size is related to voice acoustic outcomes, while visual fullness is related to self-reported outcomes.

Effects of limited previously acquired information about falling height on lower limb biomechanics when individuals are landing with limited visual input

BACKGROUND

Inhibitions in the acquisition of accurate information about the environment can affect control of the lower extremities and lead to anterior cruciate ligament injury. This study aimed to clarify the effects of limited prior knowledge of the height of the fall, as well as limited visual input, on lower limb and trunk motion and ground reaction force during landing.

METHODS

Twenty healthy university students were recruited. Drop landings from a 30-cm platform were measured under three conditions: (1) unknown, without prior knowledge of the height of the fall and without visual input; (2) known, with prior knowledge of the height of the fall and without visual input; and (3) control, with prior knowledge of the height of the fall and visual input.

FINDINGS

In the unknown condition, the peak ground reaction force for the vertical and posterior directions was significantly higher than that in the known and control conditions; leg and knee stiffness, ankle joint work, and joint flexion motion of the knee, ankle, and trunk after landing were decreased as well. In the known condition, there were no significant differences in leg and knee stiffness and vertical ground reaction force compared to the control condition.

INTERPRETATION

The results of this study indicate that the risk of anterior cruciate ligament injury during landing increases when individuals have limited visual input and prior knowledge of the height of the fall. This finding suggests that an accurate perception of the surrounding environment may help prevent anterior cruciate ligament injuries.

Visual input shapes the auditory frequency responses in the inferior colliculus of mouse

The integration of visual and auditory information is important for humans or animals to build an accurate and coherent perception of the external world. Although some evidence has shown some principles of the audiovisual integration, little insight has been gained into its functional purpose. In this study, we investigated the functional influence of dynamic visual input on auditory frequency processing by recording single unit activity in the central nucleus of the inferior colliculus (ICc). Results showed that the auditory responses of ICc neurons to sound frequencies could be enhanced or suppressed by visual stimuli even though the same visual stimuli induced no neural responses when presented alone. For each ICc neuron, the most effective visual stimuli were located in the same azimuth as for auditory stimuli and preceded for ∼20 ms. Additionally, visual stimuli could steepen or flatten the frequency tuning curves (FTCs) of ICc neurons by various visual effects at each responsive frequency. The modulation degree of auditory FTCs was dependent on the minimal thresholds (MTs) of ICc neurons, i.e., with MTs increasing, the modulation degree decreased. Due to the non-homogeneous distribution of MTs which was lowest at 10 kHz, visual modulation of auditory FTCs exhibited a frequency-specific manner, the closer it reached the characteristic frequency (CF) of 10 kHz, the greater modulation. Thus, visual modulation of auditory frequency responses in ICc is dependent not only on the visual stimulus but also on the auditory characteristics of ICc neurons. These results suggest a moment-to-moment visual modulation of auditory frequency responses that in real time increase auditory frequency sensitivity to audiovisual stimuli. Furthermore, in the long term such modulation could serve to instruct auditory adaptive plasticity to maintain necessary and accurate auditory detection and perceptual behavior.

Multisensory factors in postural control: Varieties of visual and haptic effects

Background Previous work on balance control in children and adults highlights the importance of multisensory information. Work in this vein has examined two principal input sources - the role of visual and haptic information on balance. Recent work has explored the impact of a different form of haptic input - object holding - on balance in young infants. Research question This experiment examined the impact of simultaneous visual input and haptic input on balance in children and adults, employing two novel forms of haptic input. Methods Static balance was measured in 3-5 year olds, 7-9 year olds, and young adults, in the presence of all possible combinations of manipulated visual input (eyes open, eyes closed) and haptic input (no touch, object hold, touch an unstable support, touch a stable support). Results Analysis of postural stability (mean velocity) indicated that stability was influenced by visual input, haptic input, and age group. For visual input stability increased in eyes open versus eyes closed conditions. For haptic input, stability systematically increased with increasing levels of fixed haptic input (e.g., no touch, object hold, unstable touch, stable touch). Stability also increased as a function of increasing age group. There were no interactions between the factors. Significance The finding that the two novel forms of haptic input - object hold and touch with an unstable support surface - increased stability relative to no touch input, but not as much as touch with a stable support, indicates that children use haptic information in a self-referential fashion for controlling posture. The failure to observe any interactions between visual and haptic inputs with age suggests that multisensory processing is generally additive across development, and has implications for the occurrence of sensory weighting across developmental epochs.

Influence of both cutaneous input from the foot soles and visual information on the control of postural stability in dyslexic children

Dyslexic children show impaired in postural stability. The aim of our study was to test the influence of foot soles and visual information on the postural control of dyslexic children, compared to non-dyslexic children. Postural stability was evaluated with TechnoConcept^® platform in twenty-four dyslexic children (mean age: 9.3±0.29years) and in twenty-four non-dyslexic children, gender- and age-matched, in two postural conditions (with and without foam: a 4-mm foam was put under their feet or not) and in two visual conditions (eyes open and eyes closed). We measured the surface area, the length and the mean velocity of the center of pressure (CoP). Moreover, we calculated the Romberg Quotient (RQ). Our results showed that the surface area, length and mean velocity of the CoP were significantly greater in the dyslexic children compared to the non-dyslexic children, particularly with foam and eyes closed. Furthermore, the RQ was significantly smaller in the dyslexic children and significantly greater without foam than with foam. All these findings suggest that dyslexic children are not able to compensate with other available inputs when sensorial inputs are less informative (with foam, or eyes closed), which results in poor postural stability. We suggest that the impairment of the cerebellar integration of all the sensorial inputs is responsible for the postural deficits observed in dyslexic children.

Interactions between dorsal and ventral streams for controlling skilled grasp

The two visual systems hypothesis suggests processing of visual information into two distinct routes in the brain: a dorsal stream for the control of actions and a ventral stream for the identification of objects. Recently, increasing evidence has shown that the dorsal and ventral streams are not strictly independent, but do interact with each other. In this paper, we argue that the interactions between dorsal and ventral streams are important for controlling complex object-oriented hand movements, especially skilled grasp. Anatomical studies have reported the existence of direct connections between dorsal and ventral stream areas. These physiological interconnections appear to be gradually more active as the precision demands of the grasp become higher. It is hypothesised that the dorsal stream needs to retrieve detailed information about object identity, stored in ventral stream areas, when the object properties require complex fine-tuning of the grasp. In turn, the ventral stream might receive up to date grasp-related information from dorsal stream areas to refine the object internal representation. Future research will provide direct evidence for which specific areas of the two streams interact, the timing of their interactions and in which behavioural context they occur.

Influence of transcutaneous electrical nerve stimulation on weight distribution in lower leg muscles

[Purpose] The purpose of this study was to compare the effects of transcutaneous electrical nerve stimulation (TENS), with and without visual input, on weight distribution following exercise-induced fatigue in the dorsiflexor and plantar flexor muscles of the ankle. [Subjects and Methods] This study had a cross-sectional design. Nineteen healthy adults (10 males, 9 females; mean age 21±0.8 years) were recruited to participate in a single group repeated measurements study lasting three days. On the first day, following exercise-induced fatigue, the standing position was maintained for 30 minutes, after which the postural sway was measured with eyes open (EO) and eyes closed (EC). On the second day, TENS was applied to the ankle dorsiflexors in the standing position for 30 minutes following exercise-induced fatigue. On the last day, TENS was applied to the plantar flexors, and the postural sway was measured with EO and EC following the same exercise-induced fatigue. [Results] On level terrain, with and without visual input, there was a significant difference between the baseline values and those following TENS on the tibialis anterior. On uneven terrain (simulated by a cushion), with and without visual input, there was a significant difference between the baseline values and those following TENS on the gastrocnemius. [Conclusion] Clinically, during walking on a flat surface for only a short period of time, TENS should be applied to the tibialis anterior. If walking training is performed on a variety of terrains for a longer time, TENS should be applied to the gastrocnemius.

Interactions between dorsal and ventral streams for controlling skilled grasp

The two visual systems hypothesis suggests processing of visual information into two distinct routes in the brain: a dorsal stream for the control of actions and a ventral stream for the identification of objects. Recently, increasing evidence has shown that the dorsal and ventral streams are not strictly independent, but do interact with each other. In this paper, we argue that the interactions between dorsal and ventral streams are important for controlling complex object-oriented hand movements, especially skilled grasp. Anatomical studies have reported the existence of direct connections between dorsal and ventral stream areas. These physiological interconnections appear to be gradually more active as the precision demands of the grasp become higher. It is hypothesised that the dorsal stream needs to retrieve detailed information about object identity, stored in ventral stream areas, when the object properties require complex fine-tuning of the grasp. In turn, the ventral stream might receive up to date grasp-related information from dorsal stream areas to refine the object internal representation. Future research will provide direct evidence for which specific areas of the two streams interact, the timing of their interactions and in which behavioural context they occur.

•

The dorsal and ventral streams are both involved in skilled grasping movements.

•

Ventral areas feed dorsal areas with information about object identity.

•

Grasps of increased complexity require gradually higher recruitment of ventral areas.

•

Dorsal stream inputs could fine tune object representations stored in ventral areas.