Giovanni Bertolini | University of Zurich, Switzerland (original) (raw)

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Papers by Giovanni Bertolini

Journal of Neurology

Concussed patients with chronic symptoms commonly report dizziness during exposure to environment... more Concussed patients with chronic symptoms commonly report dizziness during exposure to environments with complex visual stimuli (e.g. supermarket aisles, busy crossroads). Such visual induced dizziness is well-known in patients with vestibular deficits, in whom it indicates an overreliance on visual cues in sensory integration. Considering that optokinetic after-nystagmus (OKAN) reflects the response of the central network integrating visual and vestibular self-motion signals (velocity storage network), we investigated OKAN in 71 patients [17 (23.9%) females, 30.36 ± 9.05 years old] who suffered from persistent symptoms after a concussion and presented clinical signs suggesting visual dependence. Data were retrospectively compared with 21 healthy individuals [13 (61.9%) females, 26.29 ± 10.00 years old]. The median values of the slow cumulative eye position and of the time constant of OKAN were significantly higher in patients than in healthy individuals (slow cumulative eye position...

Brain and cognition, 2018

Line bisection studies generally find a left-to-right shift in bisection bias with increasing dis... more Line bisection studies generally find a left-to-right shift in bisection bias with increasing distance between the observer and the target line, which may be explained by hemispheric differences in the processing of proximo-distal information. In the present study, the segregation between near and far space was further characterized across the motor system and contextual cues. To this aim, 20 right-handed participants were required to perform a manual bisection task of simple lines presented at three different distances (60, 90, 120 cm). Importantly, the horizontal spatial location of the line was manipulated along with the viewing distance to investigate more deeply the hemispheric engagement in the transition from near to far space. As the motoric component of the manual task producing activations of left premotor and motor areas may be partially responsible for the observed transition, participants were also involved in an ocular bisection task. Further, participants were require...

Frontiers in neurology, 2017

Faster trains require tilting of the cars to counterbalance the centrifugal forces during curves.... more Faster trains require tilting of the cars to counterbalance the centrifugal forces during curves. Motion sensitive passengers, however, complain of discomfort and overt motion sickness. A recent study comparing different control systems in a tilting train, suggested that the delay of car tilts relative to the curve of the track contributes to motion sickness. Other aspects of the motion stimuli, like the lateral accelerations and the car jitters, differed between the tested conditions and prevented a final conclusion on the role of tilt delay. Nineteen subjects were tested on a motorized 3D turntable that simulated the roll tilts during yaw rotations experienced on a tilting train, isolating them from other motion components. Each session was composed of two consecutive series of 12 ideal curves that were defined on the bases of recordings during an actual train ride. The simulated car tilts started either at the beginning of the curve acceleration phase (no-delay condition) or with...

Journal of neurology, Jan 28, 2017

Motion sickness is associated with a variety of autonomic symptoms, presumably due to proximity o... more Motion sickness is associated with a variety of autonomic symptoms, presumably due to proximity or functional interconnectivity between the autonomic centers in the brainstem and the vestibular system. A direct influence of the vestibular system on cardiovascular variables, defined as the vestibulo-sympathetic reflex, has been reported previously. Our aim was to investigate the sudomotor components of the autonomic responses associated with motion sickness during passive cross-coupling stimulation ("roll while rotating"). Healthy subjects (n = 17) were rotated at 40°/s around an earth-vertical yaw axis alone and in combination with sinusoidal roll oscillations (0.2 Hz). Motion sickness was assessed verbally every minute using a 1-10 scale, while recording DC and AC skin conductance levels (SCL) from the forehead. Yaw rotation alone provoked neither motion sickness nor variations of forehead sweating. Yet during cross-coupling stimulation all subjects reported motion sickne...

Journal of neurophysiology, 2017

Accurate and precise estimates of direction of gravity are essential for spatial orientation. Acc... more Accurate and precise estimates of direction of gravity are essential for spatial orientation. According to Bayesian theory, multisensory vestibular, visual and proprioceptive input is centrally integrated in a weighted fashion based on the reliability of the component sensory signals. For otolithic input, a decreasing signal-to-noise ratio was demonstrated with increasing roll-angle. We hypothesized that the weights of vestibular (otolithic) and extra-vestibular (visual/proprioceptive) sensors are roll-angle dependent and predicted an increased weight of extra-vestibular cues with increasing roll-angle, potentially following the Bayesian hypothesis. To probe this concept, the subjective visual vertical (SVV) was assessed in different roll-positions (≤±120°, steps=30°, n=10) with/without presenting an optokinetic stimulus (velocity=±60°/s). The optokinetic stimulus biased the SVV towards the direction of stimulus-rotation for roll-angles ≥±30° (p<0.005). Offsets grew from 3.9±1.8°...

The Journal of Physiology, 2016

Annals of the New York Academy of Sciences, Jun 1, 2009

Investigative ophthalmology & visual science, 2016

Impairment of visual acuity (VA) can be seen early on in various diseases and has a major impact ... more Impairment of visual acuity (VA) can be seen early on in various diseases and has a major impact on patients' daily activities. Zebrafish is an important model for studying visual disorders. We developed a new method in zebrafish larva to easily and precisely measure the VA, which should allow for better estimation of affected vision such as after genetic manipulation or pharmacologic intervention. We used an optokinetic reflex (OKR) paradigm with a staircase technique to estimate VA of zebrafish larva. Consistent eye displacements were used as the indicator for OKR. We measured VA and determined the dependence of VA on clockwise and counterclockwise horizontal stimulus directions. Visual acuity in zebrafish larva was estimated to be 0.179 ± 0.013 cyc/deg binocularly and 0.129 ± 0.008 cyc/deg (left eye) and 0.128 ± 0.012 cyc/deg (right eye) monocularly. We found within single subjects spatial frequency thresholds that showed highly significant differences between the two horizon...

Frontiers in Neurology, 2016

Journal of neurophysiology, Jan 13, 2016

Inferring object orientation in the surroundings heavily depends on our internal sense of directi... more Inferring object orientation in the surroundings heavily depends on our internal sense of direction of gravity. Previous research showed that this sense is based on the integration of multiple information sources, including visual, vestibular (otolithic) and somatosensory signals. The individual noise characteristics and contributions of these sensors can be studied using spatial orientation tasks, such as the subjective visual vertical (SVV) task. A recent study reported that patients with complete bilateral vestibular loss perform similar as healthy controls on these tasks, from which it was conjectured that the noise levels of both otoliths and body somatosensors are roll-tilt dependent. Here, we tested this hypothesis in ten healthy human subjects by roll-tilting the head relative to the body to dissociate tilt-angle dependencies of otolith and somatosensory noise. Using a psychometric approach, we measured bias and variability in perceived orientation of a briefly flashed line ...

Journal of Neurology, 2015

Cognition, Jan 8, 2015

The present study examined whether traveling through serially-ordered verbal memories exploits ov... more The present study examined whether traveling through serially-ordered verbal memories exploits overt visuospatial attentional resources. In a three-phase behavioral study, five single-digits were presented sequentially at one spatial location in phase 1, while recognition and verbal recall were tested in phases 2 and 3, respectively. Participants' spontaneous eye movements were registered along with the verbal responses. Results showed that the search and the retrieval of serially-ordered information were mediated by spontaneous ocular movements. Specifically, recognizing middle items of the memorized sequence required longer inspection times and, importantly, a greater involvement of overt attentional resources, than recognizing the serially first-presented item and, to a lesser extent, the last-presented item. Moreover, serial order was found to be spatially encoded from left-to-right, as eye position during vocal responses deviated the more to the right, the later the serial ...

Journal of neurophysiology, 2014

The subjective visual vertical (SVV) indicates perceived direction of gravity. Even in healthy hu... more The subjective visual vertical (SVV) indicates perceived direction of gravity. Even in healthy human subjects, roll angle-dependent misestimations, roll overcompensation (A-effect, head-roll > 60° and <135°) and undercompensation (E-effect, head-roll < 60°), occur. Previously, we demonstrated that, after prolonged roll-tilt, SVV estimates when upright are biased toward the preceding roll position, which indicates that perceived vertical (PV) is shifted by the prior tilt (Tarnutzer AA, Bertolini G, Bockisch CJ, Straumann D, Marti S. PLoS One 8: e78079, 2013). Hypothetically, PV in any roll position could be biased toward the previous roll position. We asked whether such a "global" bias occurs or whether the bias is "local". The SVV of healthy human subjects (N = 9) was measured in nine roll positions (-120° to +120°, steps = 30°) after 5 min of roll-tilt in one of two adaptation positions (±90°) and compared with control trials without adaptation. After a...