Subjective Postural Vertical Research Articles

The effect of subjective postural vertical on forward flexed posture in Parkinson's disease

BackgroundWe developed a novel method to measure the angle of subjective postural vertical (SPV) and showed that the SPV may be related to the exacerbation of the forward flexed posture. ObjectivesThe present study prospectively tested the effects of the subjective postural vertical on the exacerbation of the forward flexion of trunk (FFT) through long-term observation of Parkinson's disease patients. MethodsEvaluation of the posture included measuring FFT, the angle of lateral flexion of trunk, and the angle at the position that the patient subjectively perceived as the vertical position at a stationary upright position immediately after standing up at the time of initial observation, 6 months later, and 1 year later. ResultsThe SPV angles worsened significantly at 6 months and 1 year compared to the first measurements (9.3 ± 6.7° vs. 10.8 ± 8.2° and 10.6 ± 7.8°, P < 0.05), and the FFT angles worsened significantly at one year compared to the first measurements (11.1 ± 8.1° vs. 12.2 ± 8.8°, P = 0.004). Furthermore, using a hierarchical multiple regression model, the difference in SPV from the first visit to the first half year was considered a factor contributing to annual FFT change (P = 0.002). ConclusionsThis longitudinal study of a large number of cases suggested that changes in SPV may precede changes in FFT.

Misperception of body verticality in neurological disorders: A systematic review and meta-analysis.

The internal representation of verticality could be disturbed when a lesion in the central nervous system (CNS) affects the centers where information from the vestibular, visual, and/or somatosensory systems, increasing the risk of falling. The aim was to evaluate the vestibular and somatosensory contribution to the verticality pattern in patients with stroke and other neurological disorders. A literature search was performed in PubMed, Scopus, Web of Science, and CINAHL databases. Cross-sectional, case-control, and cohort studies comparing body verticality in patients with stroke or CNS diseases (CNSD) versus healthy controls were selected. Subjective postural vertical (SPV) in roll and pitch planes was used as the primary variable. Ten studies reporting data from 390 subjects were included. The overall effect for CNSD patients showed a misperception of body verticality in roll (standardized mean difference [SMD]=1.05; 95% confidence interval [CI].84-1.25) and pitch planes (SMD=1.03; 95% CI.51-1.55). In subgroup analyses, a high effect was observed in the perception of SPV both in roll and pitch planes in stroke (p=.002) and other CNSD (p<.001). These findings suggest a potential misperception of SPV in patients with stroke and other neurological disturbances. Patients with CNSD could present an alteration of vestibular and somatosensory contribution to verticality construction, particularly stroke patients with pusher syndrome (PS), followed by those with PS combined with hemineglect.

Do we need to consider head-on-body position, starting roll position and presence of visuospatial neglect when assessing perception of verticality after stroke?

ABSTRACT Background and Objective Considering various factors that influence the accuracy of the Subjective Visual Vertical (SVV) and Subjective Postural Vertical (SPV), standardization of assessment methods is needed. This retrospective study examined the contribution of Head-on-Body (HOB) position, starting roll position (SRP) and visuospatial neglect (VSN) to SVV and SPV constant errors (i.e. deviation from true vertical). Also, the contribution of HOB position and VSN presence to SVV and SPV variability (i.e. intra-individual consistency between trials) was assessed. Methods First-ever unilateral hemispheric stroke survivors (<85 years; <100 days post-stroke) were assessed with three HOB positions (neutral, contralesional, and ipsilesional) and seven starting positions (20°Contralesional to 20° ipsilesional) of the laser bar and tilt chair. Linear mixed models were selected to evaluate the contribution of HOB, SRP, and VSN to SVV/SPV constant errors and variability. Results Thirty-four subjects (24 VSN-/10 VSN+) were assessed. A tilted HOB position led to significantly higher constant errors for the SVV and SPV (the latter only in the VSN- group), and an increased SVV variability. SRP only significantly contributed to the SVV constant errors and only in the VSN- group. Furthermore, the presence of VSN resulted in a significantly higher SVV and SPV variability. Conclusions HOB position and the presence of SRP and VSN are important factors to consider during SVV and SPV measurements. Assessment with a neutral HOB position leads to more accurate results. HOB position and SRP influence the results of SVV and SPV differently in individuals with and without VSN, which highlights the relevance of VSN assessment.

Recovery process of vertical perception and activities of daily living in stroke patients: A retrospective cohort study.

Clarifications regarding the recovery process of the subjective postural vertical (SPV) and activities of daily living in stroke patients are required to help clinicians determine treatment plans. Therefore, we aimed to investigate the characteristics of the longitudinal recovery process of SPV and activities of daily living after stroke. Overall, 109 patients with stroke were enrolled. Clinical assessments included the SPV and total functional independence measure (FIM), initially and after 1 month. The mean and standard deviation of SPV indicated the directional and variability errors, respectively. Participants were categorized as follows: nondeviation group comprised directional and variability errors within the standard values, deviation of variability errors group comprised directional errors within the standard value and variability errors greater than the standard value, and deviation of both directional and variability errors group comprised directional and variability errors greater than the standard values. In addition, a two-way analysis of variance was performed for initial pre- and post-SPV, and pre- and posttotal FIM scores (p<.05). The deviation of variability errors group, and deviation of both directional and variability errors group, had larger SPV variability errors than did the nondeviation group. Furthermore, the deviation of variability errors group showed a significant improvement in variability errors after 1 month. There was a correlation between the initial SPV with eyes opened variability error and total FIM after 1 month in Pusher patients with unilateral spatial neglect in the deviation of both directional and variability errors group. SPV with eyes opened variability errors and initial FIM score may influence the independence of activities of daily living after 1 month in the recovery of patients with stroke with Pusher and unilateral spatial neglect.

Efficacy of lateral truncal tilt training with a wedge on postural vertical and activities of daily living in recovery phase after stroke: A randomized crossover trial.

The subjective postural vertical (SPV) is affected by training that requires participants to maintain balance; training to achieve sitting balance may also help SPV recovery and activities of daily living (ADLs). This study aimed to assess the medium-term effects of balance training on the postural vertical (PV) and ADLs in patients with stroke. Thirty-three patients with stroke were enrolled in this randomized crossover trial. The outcomes were SPV, SPV with eyes opened (SPV-EO), and the Functional Independent Measure (FIM) after the 14-day intervention of experimental or control training. Experimental training consisted of a maximum lateral truncal tilt to the paretic side at 0.25 Hz with or without a 10° wedge, repeated 60 times. Repeated-measures two-way analysis of variance was performed with two factors: intervention and the intervention period. There was no interaction between the control condition and the PV, but there was interaction between the intervention period and using a wedge for SPV variability errors. FIM showed an interaction between the intervention period and the use of a wedge. Balance training while sitting with a wedge significantly improved the SPV and FIM. This improved cognition and perception, which facilitate difficult dynamic tasks in ADLs.

Evaluation of subjective vertical perception among stroke patients: a systematic review.

Verticality misperception is relatively common among patients after stroke, and it may be evaluated in terms of (a) subjective visual vertical (SVV), (b) subjective haptic vertical (SHV) and (c) subjective postural vertical (SPV). To better understand these assessment methods, we conducted a systematic review of the methodological characteristics of different protocols for evaluating SVV, SHV and SPV among individuals after stroke. To standardize the methodological characteristics of protocols for evaluating verticality perception after stroke. We searched the following databases: PUBMED, regional BVS portal (MEDLINE, LILACS, IBECS, CUBMED, Psychology Index and LIS), CINAHL, SCOPUS, Web of Science, Science Direct, Cochrane Library and PEDro. Two review authors independently used the QUADAS method (Quality Assessment of Diagnostic Accuracy Studies) and extracted data. We included 21 studies in the review: most (80.9%) used SVV, eight (38.1%) used SPV and four (19.0%) used SHV. We observed high variability in assessments of verticality perception, due to patient positions, devices used, numbers of repetitions and angle of inclination for starting the tests. This systematic review was one of the first to explore all the methods of assessing verticality perception after stroke, and it provides crucial information on how to perform the tests, in order to guide future researchers/clinicians.

A perception bias of the gravitational vertical is confirmed in Adolescent Idiopathic Scoliosis.

Adolescent Idiopathic Scoliosis (AIS) is the most frequent spine deformity in adolescence. The cause of AIS remains unknown. Several studies show that AIS can be associated with a perception bias of gravitational vertical. In particularly, AIS patients with a right thoracic convexity exhibit deviation of the Subjective Postural Vertical. The origin of this disturbance could be located in trunk proprioceptive graciveptors. We wanted to verify this result with a population of lumbar and thoracolumbar AIS with left convexity. It was a multicenter, cross-sectional case-control study. Thirty adolescents with left lumbar or thoraco-lumbar AIS (age 14.3 ± 1.7 years; Cobb angle 27.6° ± 6.1°) and 30 controls matched for age (14.0 ± 1.5 years), were compared for Subjective Visual Vertical (SVV) measured in static and dynamic (optokinetic stimulation) conditions, and Subjective Postural Vertical (SPV). For SVV, there was no difference in the two groups, for static and dynamic conditions. The SPV was significantly different between the two groups (p < 0.0001). The SPV was shifted to the left for most of the AIS patients (med - 2.4°[- 3.6; - 1.7]) compared with controls (med 0°[- 0.5; 1.7]). Adolescents with AIS perceived verticality with significant greater uncertainty in postural modality than controls (p = 0.017). Our study confirms a significant directional bias in the orientation of SPV in left lumbar or thoraco-lumbar AIS. This confirmation paves the way to a new physiopathological model focused on trunk proprioception. III.

Dynamic arm movements attenuate the perceptual distortion of visual vertical induced during prolonged whole-body tilt.

Concurrent body movements have been shown to enhance the accuracy of spatial judgment, but it remains unclear whether they also contribute to perceptual estimates of gravitational space not involving body movements. To address this, we evaluated the effects of static or dynamic arm movements during prolonged whole-body tilt on the subsequent perceptual estimates of visual or postural vertical. In Experiment 1, participants were asked to continuously perform static or dynamic arm movements during prolonged tilt, and we assessed their effects on the prolonged tilt-induced shifts of subjective visual vertical (SVV) at a tilted position (during-tilt session) or near upright (post-tilt session). In Experiment 2, we evaluated how static or dynamic arm movements during prolonged tilt subsequently affected the subjective postural vertical (SPV). In Experiment 1, we observed that the SVV was significantly shifted toward the direction of prolonged tilt in both sessions. The SVV shifts decreased when performing dynamic arm movements in the during-tilt session, but not in the post-tilt session. In Experiment 2, as well as SVV, the SPV was shifted toward the direction of prolonged tilt, but it was not significantly attenuated by the performance of static or dynamic arm movements. The results of the during-tilt session suggest that the central nervous system utilizes additional information generated by dynamic body movements for perceptual estimates of visual vertical.

Multisensory Interactions in Head and Body Centered Perception of Verticality.

Percepts of verticality are thought to be constructed as a weighted average of multisensory inputs, but the observed weights differ considerably between studies. In the present study, we evaluate whether this can be explained by differences in how visual, somatosensory and proprioceptive cues contribute to representations of the Head In Space (HIS) and Body In Space (BIS). Participants (10) were standing on a force plate on top of a motion platform while wearing a visualization device that allowed us to artificially tilt their visual surroundings. They were presented with (in)congruent combinations of visual, platform, and head tilt, and performed Rod & Frame Test (RFT) and Subjective Postural Vertical (SPV) tasks. We also recorded postural responses to evaluate the relation between perception and balance. The perception data shows that body tilt, head tilt, and visual tilt affect the HIS and BIS in both experimental tasks. For the RFT task, visual tilt induced considerable biases (≈ 10° for 36° visual tilt) in the direction of the vertical expressed in the visual scene; for the SPV task, participants also adjusted platform tilt to correct for illusory body tilt induced by the visual stimuli, but effects were much smaller (≈ 0.25°). Likewise, postural data from the SPV task indicate participants slightly shifted their weight to counteract visual tilt (0.3° for 36° visual tilt). The data reveal a striking dissociation of visual effects between the two tasks. We find that the data can be explained well using a model where percepts of the HIS and BIS are constructed from direct signals from head and body sensors, respectively, and indirect signals based on body and head signals but corrected for perceived neck tilt. These findings show that perception of the HIS and BIS derive from the same sensory signals, but see profoundly different weighting factors. We conclude that observations of different weightings between studies likely result from querying of distinct latent constructs referenced to the body or head in space.

Comparison of two methods based on one psychophysical paradigm to measure the subjective postural vertical in standing

The perception of verticality can be altered with age or due to neurological diseases. Different procedures have been described to measure the subjective postural vertical (SPV). A deviation from the earth vertical was either described as a single position or as a sector defined by two positions representing the edges of the perceived verticality. In this study, for the first time, we investigated if these two methods produce equal values, and consequently can be merged to set normative values. SPV in standing was tested in 24 healthy young adults (28.4 (5.2) years of age, 12 women). Each participant performed both methods in the sagittal and the frontal plane. Absolute and constant error values were found to be similar for both methods in both planes with a mean difference of less than 0.3° (p > 0.148). The mean width of the SPV sector was 3.9° (0.9°) in the sagittal and 3.7° (1.4°) in the frontal plane, ranging in the mean from −5.5° to 8.1° in the sagittal and −5.3° to 4.3° in the frontal plane. SPV values significantly differed in range between both methods in both planes with a mean difference of more than 3.1° (p<0.002). Results show that both methods, SPVposition and SPVsector, produce equal error values when applied with otherwise similar methodological settings and can therefore be used alternatively or within the same meta-analysis. The SPVsector, however, led to wider range values and was less frequently rated as the preferred method to represent the participants’ subjective verticality.

Starting position effects in the measurement of the postural vertical for pusher behavior.

Pusher behavior (PB) is a severe lateral postural disorder that involves a disturbed subjective postural vertical (SPV) in the frontal plane. SPV is measured by determining the mean value and standard deviation of several trials beginning on both the contralesional- and ipsilesional-tilted positions. However, the postural representation, when passively tilted to the contralesional versus ipsilesional position, is different between patients with and without PB. Therefore, we hypothesized that SPV dependence on the starting position will be influenced by PB. For 53 patients with hemispheric stroke enrolled, SPV was measured using a non-motorized vertical board with eyes closed. The mean value (tilt direction) and standard deviation (variability) were calculated in four trials, each from two positions, with the patient tilted to the contralesional position (SPV-CL condition) and then to the ipsilesional position (SPV-IL condition). Patients were categorized into the non-pusher (n = 29) and pusher (n = 24) groups. In the SPV-CL trials, the tilt direction was significantly tilted contralesionally for the pusher group (-6.3° ± 1.6°) compared with that for the non-pusher group (-2.2° ± 1.8°; p < 0.001), with no significant difference in variability between the groups. In the SPV-IL trials, the tilt direction was not significantly different between the groups, but the variability was significantly higher in the pusher group (4.8° ± 2.0°) than in the non-pusher group (2.2° ± 1.3°; p < 0.001). The dependence of tilt direction and variability of SPV on the starting position in patients with PB differed from those noted in patients without PB. These results may help explain this abnormal posture and optimize neurological rehabilitation strategies for PB.

Perception of postural verticality in roll and pitch while sitting and standing in healthy subjects

Assessment of verticality perception is increasingly used in patients with disorders of upright body orientation, e.g. in pusher behavior after hemispheric stroke or in retropulsion in neurovascular or degenerative diseases. The subjective postural vertical (SPV) assesses the individual’s perceived upright body orientation in space and can be determined in a sitting or a standing position. As somatosensory input differs between sitting and standing, we suppose a different representation of verticality. Thus, the aim of this study was to compare the SPV while sitting and while standing, and to determine the influence of proprioceptive and visual stimulations on the SPV in both positions.Twenty healthy subjects (18–40 years, 9 female) participated in two experiments. In experiment 1 the SPV was assessed in the pitch and roll planes while sitting and standing. In experiment 2 we additionally applied somatosensory Achilles tendon vibration and visual optokinetic stimulation.Results of experiment 1 revealed no difference of the SPV error between sitting and standing. Though, we found an increased SPV variability while sitting. Experiment 2 showed no effect of sensory manipulation in the pitch plane, but an effect of optokinetic stimulation in the roll plane. The tilt in direction of the visual stimuli was more pronounced while sitting. Optokinetic stimulation also resulted in a larger SPV variability in roll, indicating larger insecurity in verticality estimation during stimulation.In conclusion, even though the SPV assessment while sitting and standing resulted in similar mean values, the larger variability and the higher sensitivity to visual stimuli while sitting suggest different strategies for verticality estimation while sitting and while standing.

Effect of dynamic visual motion on perception of postural vertical through the modulation of prior knowledge of gravity

To internally estimate gravitational direction and body orientation, the central nervous system considers several sensory inputs from the periphery and prior knowledge of gravity. It is hypothesized that the modulation of visual inputs, supplying indirect information of gravity, affects the prior knowledge established internally by other sensory inputs from vestibular and somatosensory systems, leading to the alteration of perceived body orientation relative to gravity. In order to test the hypothesis, we examined the effect of presenting a visual motion stimulus during a whole-body static tilt on the subsequent evaluation of the perceived postural vertical. Fifteen subjects watched a target moving along the body longitudinal axis directing from head to feet with constant downward acceleration (CA condition) or constant velocity (CV condition), or they did not receive any visual stimulation (NV condition) during the whole-body static tilt. Subsequently, the direction of the subjective postural vertical (SPV) was evaluated. The result showed that the SPV in the CA condition was significantly tilted toward the direction of the preceding tilt compared to that in the NV condition while those in the CV and NV conditions were not significantly different. The present result suggests that dynamic visual motion along body longitudinal axis with downward acceleration can modulate prior knowledge of gravity, and in turn this affects the perception of body verticality.

Effects of diagonally aligned sitting training with a tilted surface on sitting balance for low sitting performance in the early phase after stroke: a randomised controlled trial

Purpose To clarify the effects of diagonally aligned sitting training using a tilted surface on sitting balance for patients with low sitting performance in the early phase after stroke. Materials and methods This was an assessor-blinded randomised controlled trial. The experimental group used a surface tilted 10° backward and down toward the most affected side; the control group trained on a horizontal surface. Both groups were asked to move their trunk diagonally forward toward the least affected side. Participants performed the activity 40 times/session for seven sessions over 8 days. Sitting performances were assessed using the function in sitting test (FIST), subjective postural vertical (SPV) on the diagonal plane, and trunk impairment scale (TIS). Results Thirty-three stroke patients were randomly allocated into two groups. Treatment effects differed significantly: mean differences between groups for FIST (total score, static, dynamic, scooting, and reactive) were 8.96, 2.35, 3.01, 1.27, and 1.72 points, for the mean SPV value was 1.82°, and for the TIS (total score and static) were 1.87 and 1.58 points, respectively. These results were more favourable in the experimental group. Conclusions Diagonally aligned sitting training on a tilted surface improves sitting balance and modulates the SPV compared with a horizontal surface.

Role of somatosensory and/or vestibular sensory information in subjective postural vertical in healthy adults

The body's subjective postural vertical (SPV) has been thought to be affected by somatosensory information. How the SPV is perceived based on what types of somatosensory information has not been determined experimentally by manipulating somatosensory conditions. We investigated the effects of disturbing the somatosensory information from a seat pad and/or vestibular sensory information on the SPV in 15 healthy adults. Their SPV values were measured under four conditions (control, somatosensory, vestibular, and somatosensory + vestibular) in random order. The average and absolute SPV values were measured. In the somatosensory condition, a foam rubber pad was placed on the seating surface and the subject's SPV was measured. In the vestibular condition, the SPV was measured during galvanic vestibular stimulation (GVS). The somatosensory + vestibular condition was used to measure the SPV during combined somatosensory and vestibular stimulation. The mean SPV value was significantly increased in the somatosensory + vestibular condition compared to the other three conditions. The absolute value of SPV was significantly increased in the somatosensory and somatosensory + vestibular conditions compared to the control and vestibular conditions. There was no significant difference in the average or absolute SPV values in the vestibular condition compared to the other conditions. There was no significant difference between SPV errors when somatosensory information was disturbed or when somatosensory + vestibular information was disturbed. When the somatosensory information from the seat was disturbed, the SPV error increased, and it also shifted under the influence of the vestibular sensory information modulation. These results indicate that somatosensory information from the seat plays an important role in SPV in healthy adults.

Do Adolescents With Idiopathic Scoliosis Have an Erroneous Perception of the Gravitational Vertical?

Study designMulticenter, case-control study. ObjectivesDemonstrate altered perception of verticality in AIS compared with matched controls. Summary of background dataThe cause of adolescent idiopathic scoliosis (AIS) remains to be found. AIS is associated with neurosensorial anomalies, in particular, altered control of orthostatic posture. During kinetic activity, the upright posture, in humans, is determined in reference to the gravitational vertical (GV). We hypothesized that in AIS, there is a discordance in the perception of the GV and the true GV. In AIS, the longitudinal axis of the body would thus be misoriented because of an erroneous perception of the GV. MethodsThirty adolescents with right thoracic AIS (age 14.23 ± 1.75 years; Cobb angle 31.97°± 12.83°) and 30 controls matched for age (13.93 ± 1.85 years), body mass index, Tanner stage, and handedness were compared for subjective visual vertical (SVV) measured in static and dynamic (optokinetic stimulation) conditions, and subjective postural vertical (SPV). ResultsThere was no difference in the two groups, AIS and controls, for SVV. The SPV was significantly different between the two groups (p = .00023). The SPV was shifted to the right for most of the AIS patients (2.13°± 2.22°) compared with controls (–0.08°±1.40°). There was a significant correlation between SPV and clinical frontal tilt in the AIS patients. ConclusionOur findings demonstrate that patients with right thoracic AIS have an erroneous perception of the GV. In most AIS patients, SPV was shifted to the right, with no alteration of the SVV. AIS might be the consequence of a reoriented longitudinal body axis aligned with an erroneous vertical reference. The underlying mechanism might involve dysfunction of trunk graviceptors. The primary or secondary nature of this dysfunction remains an open question.

Test-retest reliability of and age-related changes in the subjective postural vertical on the diagonal plane in healthy subjects

The subjective postural vertical (SPV) reflects gravity perception when the eyes are closed. Changes in the SPV on both the frontal and sagittal planes occur in response to neurological disorders and aging; however, these changes on the diagonal plane are unclear. Here we examined test-retest reliability (n=16) of and age-related changes (n=38) in the SPV on the diagonal plane. Subjects sat on an electrical vertical board (EVB), which was used to measure the SPV on the diagonal plane. An experimenter controlled and moved the EVB seat at a constant speed on the diagonal plane and measured the seat's tilt using a digital inclinometer when subjects verbally reported that they had reached a true vertical position. Measurement was performed for eight trials, and the mean (tilt direction) and standard deviation (variability) were calculated. To determine test-retest reliability, the same experimenter repeatedly measured the SPV 1 week later. To assess age-related changes, tilt direction and variability were compared between the young (n=20) and elderly (n=18) groups. Test-retest reliability on the right and left diagonal planes was 0.61 or more. Moreover, tilt direction on the right diagonal plane - but not on the left diagonal plane - indicated a significant diagonally backward deviation in the elderly group compared with that in the young group. Variability was significantly higher in the elderly group on both planes. SPV measurement on the diagonal plane was indicated, and age-related changes were identified. Thus, future studies should assess the potential clinical applications of SPV in neurological disorders.

Normative data for human postural vertical: A systematic review and meta-analysis

Perception of verticality is required for normal daily function, yet the typical human detection error range has not been well characterized. Vertical misperception has been correlated with poor postural control and functionality in patients after stroke and after vestibular disorders. Until now, all the published studies that assessed Subjective Postural Vertical (SPV) in the seated position used small groups to establish a reference value. However, this sample size does not represent the healthy population for comparison with conditions resulting in pathological vertical. Therefore, the primary objective was to conduct a systematic review with meta-analyses of Subjective Postural Vertical (SPV) data in seated position in healthy adults to establish the reference value with a representative sample. The secondary objective was to investigate the methodological characteristics of different assessment protocols of SPV described in the literature. A systematic literature search was conducted using Medline, EMBASE, and Cochrane libraries. Mean and standard deviation of SPV in frontal and sagittal planes were considered as effect size measures. Sixteen of 129 identified studies met eligibility criteria for our systematic review (n = 337 subjects in the frontal plane; n = 187 subjects in sagittal plane). The meta-analyses measure was estimated using the pooled mean as the estimator and its respective error. Mean reference values were 0.12°±1.49° for the frontal plane and 0.02°±1.82° for the sagittal plane. There was a small variability of the results and this systematic review resulted in representative values for SPV. The critical analysis of the studies and observed homogeneity in the sample suggests that the methodological differences used in the studies did not influence SPV assessment of directional bias in healthy subjects. These data can serve as a reference for clinical studies in disorders of verticality.

Analysis of the subjective postural vertical on diagonal plane in elderly subjects and left hemiparetic patients after stroke

The subjective postural vertical (SPV) in healthy subjects is robustly maintained by integrating somatosensory and vestibular information, and extremely correct on frontal and sagittal plane. It is well-known that brain injury patients indicate disturbance of SPV on frontal or sagittal plane. On the other hand, stroke patients frequently fall paretic side and backward, but SPV on diagonal plane in normal subjects and stroke patients is unclear. The purpose of present study was to clarify the difference of SPV on diagonal plane between elderly subjects and stroke patients. The subjects comprised 14 elderly subjects (control group) and 10 left hemiparetic patients (LHP group). All subjects provided their written informed consent to take part in the study. SPV was measured using an electrical vertical board (EVB). The subjects sat on the EVB and were moved in the opposite direction from the left-backward or right-forward. The tilt of the seat when the subject feels and judges vertical position was recorded with a digital inclinometer. The mean (tilt direction) and standard deviation (variability) of eight trials were calculated. A true vertical position was considered 0°, diagonally backward and diagonally forward was treated as negative and positive, respectively. The values of SPV were compared between groups using the unpaired t-test ( P < 0.05). There was no difference between control group (66.8 ± 9.2 years [mean ± SD]) and LHP groups (67.5 ± 10.8 years) in age. In tilt direction, LHP group (−2.5 ± 0.7°) demonstrated significant tilt backward to the left than control group (−1.3 ± 1.4°). Variability was significantly higher in LHP (5.4 ± 2.0°) than control (2.5 ± 0.9°). In stroke patients, tilt direction deviated to the diagonally backward and the judgement of verticality was unstable. These results suggest a possibility to explain the tilt of sitting posture and the difficulty of transfer movement in stroke patients.

The effects of aging on the subjective vertical in the frontal plane in healthy adults.

[Purpose] To determine age-related differences in the subjective vertical in the frontal plane in healthy adults. [Subjects and Methods] The subjects were 26 healthy adults. For the subjective visual vertical (SVV), subjects were presented with a visual indicator in front of them that was rotated. For the subjective postural vertical-eyes open (SPV-EO) and subjective postural vertical (SPV), subjects sat in a seating device that was tilted right or left. The subjects gave a signal when they perceived true verticality. Each task was performed eight times. The items examined were the mean (tilt direction) and standard deviation (variability) of the eight trials, then the mean of four trials that started from the right or left side position. These items were compared between the young (age: 22–30 years [range]) and elderly (age: 60–74 years) groups. [Results] As for variability, the elderly group demonstrated significantly higher values of SPV-EO and SPV. As for the starting point effect, the elderly group demonstrated greater bias toward the starting direction than did the young group in SPV-EO and SPV in frontal plane. [Conclusion] The postural vertical was shown to change with age. Consideration of age-related changes and the starting point effect was indicated to be important.