Perceptual direction detection thresholds for yaw rotation about an earth-vertical axis were measured at seven frequencies (0.05, 0.1, 0.2, 0.5, 1, 2, and 5 Hz) in seven subjects in the dark. Motion stimuli consisted of single cycles of sinusoidal acceleration and were generated by a motion platform. An adaptive two-alternative categorical forced-choice procedure was used. The subjects had to indicate by button presses whether they perceived yaw rotation to the left or to the right. Thresholds were measured using a 3-down, 1-up staircase paradigm. Mean yaw rotation velocity thresholds were 2.8 deg s(-1) for 0.05 Hz, 2.5 deg s(-1) for 0.1 Hz, 1.7 deg s(-1) for 0.2 Hz, 0.7 deg s(-1) for 0.5 Hz, 0.6 deg s(-1) for 1 Hz, 0.4 deg s(-1) for 2 Hz, and 0.6 deg s(-1) for 5 Hz. The results show that motion thresholds increase at 0.2 Hz and below and plateau at 0.5 Hz and above. Increasing velocity thresholds at lower frequencies qualitatively mimic the high-pass characteristics of the semicircular canals, since the increase at 0.2 Hz and below would be consistent with decreased gain/sensitivity observed in the VOR at lower frequencies. In fact, the measured dynamics are consistent with a high pass filter having a threshold plateau of 0.71 deg s(-1) and a cut-off frequency of 0.23 Hz, which corresponds to a time constant of approximately 0.70 s. These findings provide no evidence for an influence of velocity storage on perceptual yaw rotation thresholds.

Active head turns to the left and right have recently been shown to influence numerical cognition by shifting attention along the mental number line. In the present study, we found that passive whole-body motion influences numerical cognition. In a random-number generation task (Experiment 1), leftward and downward displacement of participants facilitated small number generation, whereas rightward and upward displacement facilitated the generation of large numbers. Influences of leftward and rightward motion were also found for the processing of auditorily presented numbers in a magnitude-judgment task (Experiment 2). Additionally, we investigated the reverse effect of the number-space association (Experiment 3). Participants were displaced leftward or rightward and asked to detect motion direction as fast as possible while small or large numbers were auditorily presented. When motion detection was difficult, leftward motion was detected faster when hearing small number and rightward motion when hearing large number. We provide new evidence that bottom-up vestibular activation is sufficient to interact with the higher-order spatial representation underlying numerical cognition. The results show that action planning or motor activity is not necessary to influence spatial attention. Moreover, our results suggest that self-motion perception and numerical cognition can mutually influence each other.

BackgroundDelivering efficient and effective healthcare is crucial for a condition as burdensome as low back pain (LBP). Stratified care strategies may be worthwhile, but rely on early and accurate patient screening using a valid and reliable instrument. The purpose of this study was to evaluate the performance of LBP screening instruments for determining risk of poor outcome in adults with LBP of less than 3 months duration.MethodsMedline, Embase, CINAHL, PsycINFO, PEDro, Web of Science, SciVerse SCOPUS, and Cochrane Central Register of Controlled Trials were searched from June 2014 to March 2016. Prospective cohort studies involving patients with acute and subacute LBP were included. Studies administered a prognostic screening instrument at inception and reported outcomes at least 12 weeks after screening. Two independent reviewers extracted relevant data using a standardised spreadsheet. We defined poor outcome for pain to be ≥ 3 on an 11-point numeric rating scale and poor outcome for disability to be scores of ≥ 30% disabled (on the study authors' chosen disability outcome measure).ResultsWe identified 18 eligible studies investigating seven instruments. Five studies investigated the STarT Back Tool: performance for discriminating pain outcomes at follow-up was ‘non-informative’ (pooled AUC = 0.59 (0.55–0.63), n = 1153) and ‘acceptable’ for discriminating disability outcomes (pooled AUC = 0.74 (0.66–0.82), n = 821). Seven studies investigated the Orebro Musculoskeletal Pain Screening Questionnaire: performance was ‘poor’ for discriminating pain outcomes (pooled AUC = 0.69 (0.62–0.76), n = 360), ‘acceptable’ for disability outcomes (pooled AUC = 0.75 (0.69–0.82), n = 512), and ‘excellent’ for absenteeism outcomes (pooled AUC = 0.83 (0.75–0.90), n = 243). Two studies investigated the Vermont Disability Prediction Questionnaire and four further instruments were investigated in single studies only.ConclusionsLBP screening instruments administered in primary care perform poorly at assigning higher risk scores to individuals who develop chronic pain than to those who do not. Risks of a poor disability outcome and prolonged absenteeism are likely to be estimated with greater accuracy. It is important that clinicians who use screening tools to obtain prognostic information consider the potential for misclassification of patient risk and its consequences for care decisions based on screening. However, it needs to be acknowledged that the outcomes on which we evaluated these screening instruments in some cases had a different threshold, outcome, and time period than those they were designed to predict.Systematic review registrationPROSPERO international prospective register of systematic reviews registration number CRD42015015778.Electronic supplementary materialThe online version of this article (doi:10.1186/s12916-016-0774-4) contains supplementary material, which is available to authorized users.

Vestibular information helps to establish a reliable gravitational frame of reference and contributes to the adequate perception of the location of one's own body in space. This information is likely to be required in spatial cognitive tasks. Indeed, previous studies suggest that the processing of vestibular information is involved in mental transformation tasks in healthy participants. In this study, we investigate whether patients with bilateral or unilateral vestibular loss show impaired ability to mentally transform images of bodies and body parts compared to a healthy, age-matched control group. An egocentric and an objectbased mental transformation task were used. Moreover, spatial perception was assessed using a computerized version of the subjective visual vertical and the rod and frame test. Participants with bilateral vestibular loss showed impaired performance in mental transformation, especially in egocentric mental transformation, compared to participants with unilateral vestibular lesions and the control group. Performance of participants with unilateral vestibular lesions and the control group are comparable, and no differences were found between right-and left-sided labyrinthectomized patients. A control task showed no differences between the three groups. The findings from this study substantiate that central vestibular processes are involved in imagined spatial body transformations; but interestingly, only participants with bilateral vestibular loss are affected, whereas unilateral vestibular loss does not lead to a decline in spatial imagery.

A growing number of studies in humans demonstrate the involvement of vestibular information in tasks that are seemingly remote from well-known functions such as space constancy or postural control. In this review article we point out three emerging streams of research highlighting the importance of vestibular input: (1) Spatial Cognition: Modulation of vestibular signals can induce specific changes in spatial cognitive tasks like mental imagery and the processing of numbers. This has been shown in studies manipulating body orientation (changing the input from the otoliths), body rotation (changing the input from the semicircular canals), in clinical findings with vestibular patients, and in studies carried out in microgravity. There is also an effect in the reverse direction; top-down processes can affect perception of vestibular stimuli. (2) Body Representation: Numerous studies demonstrate that vestibular stimulation changes the representation of body parts, and sensitivity to tactile input or pain. Thus, the vestibular system plays an integral role in multisensory coordination of body representation. (3) Affective Processes and Disorders: Studies in psychiatric patients and patients with a vestibular disorder report a high comorbidity of vestibular dysfunctions and psychiatric symptoms. Recent studies investigated the beneficial effect of vestibular stimulation on psychiatric disorders, and how vestibular input can change mood and affect. These three emerging streams of research in vestibular science are—at least in part—associated with different neuronal core mechanisms. Spatial transformations draw on parietal areas, body representation is associated with somatosensory areas, and affective processes involve insular and cingulate cortices, all of which receive vestibular input. Even though a wide range of different vestibular cortical projection areas has been ascertained, their functionality still is scarcely understood.