The Experts below are selected from a list of 279 Experts worldwide ranked by ideXlab platform
J. Fukushima - One of the best experts on this subject based on the ideXlab platform.
-
Otolith-visual interaction in the control of eye movement produced by sinusoidal vertical Linear Acceleration in alert cats
Experimental Brain Research, 1991Co-Authors: K. Fukushima, J. FukushimaAbstract:1. Eye movement responses were examined in alert cats during sinusoidal vertical Linear Acceleration. Stimulus frequencies of 0.20–0.85 Hz with a constant amplitude of 10.5 cm (corresponding to 0.02–0.31 g) were used. A random visual pattern was presented to give sinusoidal vertical optokinetic stimuli of similar amplitude and frequency to the up-down motion of the cat. 2. Sinusoidal Linear Acceleration in the presence of a stationary visual pattern produced robust eye movement responses with near compensatory phase at all stimulus frequencies tested. With both eyes covered, a vertical Linear vestibulo-ocular reflex (LVOR) was frequently produced at a stimulus strength corresponding to 0.04–0.31 g. The evoked LVOR was always small, and the overall mean response phase values advanced by as much as 70 ° at frequencies below 0.56 Hz, indicating that the otolith signals activated by sinusoidal Linear Acceleration were not, by themselves, converted into compensatory eye position signals under these experimental conditions. 3. Optokinetic stimulation alone produced more lag of response phase as stimulus frequency increased, and the gain of evoked eye movement responses was smaller at higher stimulus frequencies compared to the gain during Linear Acceleration in the light. Bilateral labyrinthectomies resulted in a significant change of the eye movement responses during Linear Acceleration when visual inputs were allowed: there was more phase lag at higher stimulus frequencies and a decreased gain at all frequencies tested. These results indicate that the interaction of otolith and visual inputs produces robust eye movement responses with near compensatory phase during sinusoidal Linear Acceleration in the light.
-
Activity of eye movement-related neurons in and near the interstitial nucleus of Cajal during sinusoidal vertical Linear Acceleration and optokinetic stimuli
Experimental Brain Research, 1991Co-Authors: K. Fukushima, J. FukushimaAbstract:1. A total of 43 neurons that showed a close correlation with vertical eye movement with a burst-tonic or tonic type response during spontaneous saccades, were recorded within, and in the close vicinity of, the interstitial nucleus of Cajal (INC) in alert cats. Neuronal responses to sinusoidal vertical Linear Acceleration (0.2–0.85 Hz, amplitude 10.5 cm) and optokinetic stimuli (0.1–1.0 Hz, amplitude 10.5 cm), were examined. 2. All 43 eye movement-related neurons responded to sinusoidal vertical Linear Acceleration in the presence of a stationary visual pattern in correlation to robust eye movement responses with compensatory phase. Phase and gain values (re stimulus position) of response of individual cells were independent of the stimulus frequencies tested. Of these, 33 cells were examined during Linear Acceleration without visual input. Most cells (27/33) did not respond even when a weak Linear vestibulo-ocular reflex was present (6/27). The remaining 6 cells (6/33) responded to Linear Acceleration. Their mean phase values advanced by 80 ° and gain dropped by 55% compared to the responses with visual inputs. 3. Twenty eight of the 43 cells were examined during vertical optokinetic stimuli. The activity of all 28 cells was modulated in correlation to eye movement responses. Response phase showed more lag, and gain decreased as stimulus frequencies increased, similar to optokinetic eye movement responses. 4. The close correlation between the activity of eye movement-related neurons in the INC region and robust eye movements during Linear Acceleration with visual inputs and optokinetic stimuli suggest that these neurons are involved in some aspect of vertical eye position generation during such stimuli.
-
Otolith-visual interaction in the control of eye movement produced by sinusoidal vertical Linear Acceleration in alert cats.
Experimental brain research, 1991Co-Authors: K. Fukushima, J. FukushimaAbstract:1. Eye movement responses were examined in alert cats during sinusoidal vertical Linear Acceleration. Stimulus frequencies of 0.20-0.85 Hz with a constant amplitude of 10.5 cm (corresponding to 0.02-0.31 g) were used. A random visual pattern was presented to give sinusoidal vertical optokinetic stimuli of similar amplitude and frequency to the up-down motion of the cat. 2. Sinusoidal Linear Acceleration in the presence of a stationary visual pattern produced robust eye movement responses with near compensatory phase at all stimulus frequencies tested. With both eyes covered, a vertical Linear vestibulo-ocular reflex (LVOR) was frequently produced at a stimulus strength corresponding to 0.04-0.31 g. The evoked LVOR was always small, and the overall mean response phase values advanced by as much as 70 degrees at frequencies below 0.56 Hz, indicating that the otolith signals activated by sinusoidal Linear Acceleration were not, by themselves, converted into compensatory eye position signals under these experimental conditions. 3. Optokinetic stimulation alone produced more lag of response phase as stimulus frequency increased, and the gain of evoked eye movement responses was smaller at higher stimulus frequencies compared to the gain during Linear Acceleration in the light. Bilateral labyrinthectomies resulted in a significant change of the eye movement responses during Linear Acceleration when visual inputs were allowed: there was more phase lag at higher stimulus frequencies and a decreased gain at all frequencies tested. These results indicate that the interaction of otolith and visual inputs produces robust eye movement responses with near compensatory phase during sinusoidal Linear Acceleration in the light.
K. Fukushima - One of the best experts on this subject based on the ideXlab platform.
-
Otolith-visual interaction in the control of eye movement produced by sinusoidal vertical Linear Acceleration in alert cats
Experimental Brain Research, 1991Co-Authors: K. Fukushima, J. FukushimaAbstract:1. Eye movement responses were examined in alert cats during sinusoidal vertical Linear Acceleration. Stimulus frequencies of 0.20–0.85 Hz with a constant amplitude of 10.5 cm (corresponding to 0.02–0.31 g) were used. A random visual pattern was presented to give sinusoidal vertical optokinetic stimuli of similar amplitude and frequency to the up-down motion of the cat. 2. Sinusoidal Linear Acceleration in the presence of a stationary visual pattern produced robust eye movement responses with near compensatory phase at all stimulus frequencies tested. With both eyes covered, a vertical Linear vestibulo-ocular reflex (LVOR) was frequently produced at a stimulus strength corresponding to 0.04–0.31 g. The evoked LVOR was always small, and the overall mean response phase values advanced by as much as 70 ° at frequencies below 0.56 Hz, indicating that the otolith signals activated by sinusoidal Linear Acceleration were not, by themselves, converted into compensatory eye position signals under these experimental conditions. 3. Optokinetic stimulation alone produced more lag of response phase as stimulus frequency increased, and the gain of evoked eye movement responses was smaller at higher stimulus frequencies compared to the gain during Linear Acceleration in the light. Bilateral labyrinthectomies resulted in a significant change of the eye movement responses during Linear Acceleration when visual inputs were allowed: there was more phase lag at higher stimulus frequencies and a decreased gain at all frequencies tested. These results indicate that the interaction of otolith and visual inputs produces robust eye movement responses with near compensatory phase during sinusoidal Linear Acceleration in the light.
-
Activity of eye movement-related neurons in and near the interstitial nucleus of Cajal during sinusoidal vertical Linear Acceleration and optokinetic stimuli
Experimental Brain Research, 1991Co-Authors: K. Fukushima, J. FukushimaAbstract:1. A total of 43 neurons that showed a close correlation with vertical eye movement with a burst-tonic or tonic type response during spontaneous saccades, were recorded within, and in the close vicinity of, the interstitial nucleus of Cajal (INC) in alert cats. Neuronal responses to sinusoidal vertical Linear Acceleration (0.2–0.85 Hz, amplitude 10.5 cm) and optokinetic stimuli (0.1–1.0 Hz, amplitude 10.5 cm), were examined. 2. All 43 eye movement-related neurons responded to sinusoidal vertical Linear Acceleration in the presence of a stationary visual pattern in correlation to robust eye movement responses with compensatory phase. Phase and gain values (re stimulus position) of response of individual cells were independent of the stimulus frequencies tested. Of these, 33 cells were examined during Linear Acceleration without visual input. Most cells (27/33) did not respond even when a weak Linear vestibulo-ocular reflex was present (6/27). The remaining 6 cells (6/33) responded to Linear Acceleration. Their mean phase values advanced by 80 ° and gain dropped by 55% compared to the responses with visual inputs. 3. Twenty eight of the 43 cells were examined during vertical optokinetic stimuli. The activity of all 28 cells was modulated in correlation to eye movement responses. Response phase showed more lag, and gain decreased as stimulus frequencies increased, similar to optokinetic eye movement responses. 4. The close correlation between the activity of eye movement-related neurons in the INC region and robust eye movements during Linear Acceleration with visual inputs and optokinetic stimuli suggest that these neurons are involved in some aspect of vertical eye position generation during such stimuli.
-
Otolith-visual interaction in the control of eye movement produced by sinusoidal vertical Linear Acceleration in alert cats.
Experimental brain research, 1991Co-Authors: K. Fukushima, J. FukushimaAbstract:1. Eye movement responses were examined in alert cats during sinusoidal vertical Linear Acceleration. Stimulus frequencies of 0.20-0.85 Hz with a constant amplitude of 10.5 cm (corresponding to 0.02-0.31 g) were used. A random visual pattern was presented to give sinusoidal vertical optokinetic stimuli of similar amplitude and frequency to the up-down motion of the cat. 2. Sinusoidal Linear Acceleration in the presence of a stationary visual pattern produced robust eye movement responses with near compensatory phase at all stimulus frequencies tested. With both eyes covered, a vertical Linear vestibulo-ocular reflex (LVOR) was frequently produced at a stimulus strength corresponding to 0.04-0.31 g. The evoked LVOR was always small, and the overall mean response phase values advanced by as much as 70 degrees at frequencies below 0.56 Hz, indicating that the otolith signals activated by sinusoidal Linear Acceleration were not, by themselves, converted into compensatory eye position signals under these experimental conditions. 3. Optokinetic stimulation alone produced more lag of response phase as stimulus frequency increased, and the gain of evoked eye movement responses was smaller at higher stimulus frequencies compared to the gain during Linear Acceleration in the light. Bilateral labyrinthectomies resulted in a significant change of the eye movement responses during Linear Acceleration when visual inputs were allowed: there was more phase lag at higher stimulus frequencies and a decreased gain at all frequencies tested. These results indicate that the interaction of otolith and visual inputs produces robust eye movement responses with near compensatory phase during sinusoidal Linear Acceleration in the light.
Dora E. Angelaki - One of the best experts on this subject based on the ideXlab platform.
-
Computation of Linear Acceleration through an internal model in the macaque cerebellum
Nature Neuroscience, 2013Co-Authors: Jean Laurens, Hui Meng, Dora E. AngelakiAbstract:In this study, the authors recorded from the cerebellum while monkeys experienced an illusory perception of self-motion, and found that the neurons encoded the erroneous Linear Acceleration. Their findings provide evidence that the cerebellum might be involved in the implementation of internal models, as previously hypothesized by theorists. A combination of theory and behavioral findings support a role for internal models in the resolution of sensory ambiguities and sensorimotor processing. Although the cerebellum has been proposed as a candidate for implementation of internal models, concrete evidence from neural responses is lacking. Using unnatural motion stimuli, which induce incorrect self-motion perception and eye movements, we explored the neural correlates of an internal model that has been proposed to compensate for Einstein's equivalence principle and generate neural estimates of Linear Acceleration and gravity. We found that caudal cerebellar vermis Purkinje cells and cerebellar nuclei neurons selective for actual Linear Acceleration also encoded erroneous Linear Acceleration, as would be expected from the internal model hypothesis, even when no actual Linear Acceleration occurred. These findings provide strong evidence that the cerebellum might be involved in the implementation of internal models that mimic physical principles to interpret sensory signals, as previously hypothesized.
-
computation of Linear Acceleration through an internal model in the macaque cerebellum
Nature Neuroscience, 2013Co-Authors: Jean Laurens, Hui Meng, Dora E. AngelakiAbstract:In this study, the authors recorded from the cerebellum while monkeys experienced an illusory perception of self-motion, and found that the neurons encoded the erroneous Linear Acceleration. Their findings provide evidence that the cerebellum might be involved in the implementation of internal models, as previously hypothesized by theorists.
-
spatiotemporal processing of Linear Acceleration primary afferent and central vestibular neuron responses
Journal of Neurophysiology, 2000Co-Authors: Dora E. Angelaki, J. D. DickmanAbstract:Spatiotemporal convergence and two-dimensional (2-D) neural tuning have been proposed as a major neural mechanism in the signal processing of Linear Acceleration. To examine this hypothesis, we stu...
-
Response properties of pigeon otolith afferents to Linear Acceleration
Experimental brain research, 1997Co-Authors: Dora E. Angelaki, J. D. DickmanAbstract:In the present study, the sensitivity to sinusoidal Linear Accelerations in the plane of the utricular macula was tested in afferents. The head orientation relative to the translation axis was varied in order to determine the head position that elicited the maximal and minimal responses for each afferent. The response gain and phase values obtained to 0.5-Hz and 2-Hz Linear Acceleration stimuli were then plotted as a function of head orientation and a modified cosine function was fit to the data. From the best-fit cosine function, the predicted head orientations that would produce the maximal and minimal response gains were estimated. The estimated maximum response gains to Linear Acceleration in the utricular plane for the afferents varied between 75 and 1420 spikes s-1 g-1. The mean maximal gains for all afferents to 0.5-Hz and 2-Hz sinusoidal Linear Acceleration stimuli were 282 and 367 spikes s-1 g-1, respectively. The minimal response gains were essentially zero for most units. The response phases always led Linear Acceleration and remained constant for each afferent, regardless of head orientation. These response characteristics indicate that otolith afferents are cosine tuned and behave as one-dimensional Linear accelerometers. The directions of maximal sensitivity to Linear Acceleration for the afferents varied throughout the plane of the utricle; however, most vectors were directed out of the opposite ear near the interaural axis. The response dynamics of the afferents were tested using stimulus frequencies ranging between 0.25 Hz and 10 Hz (0.1 g peak Acceleration). Across stimulus frequencies, most afferents had increasing gains and constant phase values. These dynamic properties for individual afferents were fit with a simple transfer function that included three parameters: a mechanical time constant, a gain constant, and a fractional order distributed adaptation operator.
-
two dimensional spatiotemporal coding of Linear Acceleration in vestibular nuclei neurons
The Journal of Neuroscience, 1993Co-Authors: Dora E. Angelaki, G A Bush, Adrian A PerachioAbstract:Response properties of vertical (VC) and horizontal (HC) canal/otolith-convergent vestibular nuclei neurons were studied in decerebrate rats during stimulation with sinusoidal Linear Accelerations (0.2-1.4 Hz) along different directions in the head horizontal plane. A novel characteristic of the majority of tested neurons was the nonzero response often elicited during stimulation along the "null" direction (i.e., the direction perpendicular to the maximum sensitivity vector, Smax). The tuning ratio (Smin gain/Smax gain), a measure of the two-dimensional spatial sensitivity, depended on stimulus frequency. For most vestibular nuclei neurons, the tuning ratio was small at the lowest stimulus frequencies and progressively increased with frequency. Specifically, HC neurons were characterized by a flat Smax gain and an approximately 10-fold increase of Smin gain per frequency decade. Thus, these neurons encode Linear Acceleration when stimulated along their maximum sensitivity direction, and the rate of change of Linear Acceleration (jerk) when stimulated along their minimum sensitivity direction. While the Smax vectors were distributed throughout the horizontal plane, the Smin vectors were concentrated mainly ipsilaterally with respect to head Acceleration and clustered around the naso-occipital head axis. The properties of VC neurons were distinctly different from those of HC cells. The majority of VC cells showed decreasing Smax gains and small, relatively flat, Smin gains as a function of frequency. The Smax vectors were distributed ipsilaterally relative to the induced (apparent) head tilt. In type I anterior or posterior VC neurons, Smax vectors were clustered around the projection of the respective ipsilateral canal plane onto the horizontal head plane. These distinct spatial and temporal properties of HC and VC neurons during Linear Acceleration are compatible with the spatiotemporal organization of the horizontal and the vertical/torsional ocular responses, respectively, elicited in the rat during Linear translation in the horizontal head plane. In addition, the data suggest a spatially and temporally specific and selective otolith/canal convergence. We propose that the central otolith system is organized in canal coordinates such that there is a close alignment between the plane of angular Acceleration (canal) sensitivity and the plane of Linear Acceleration (otolith) sensitivity in otolith/canal-convergent vestibular nuclei neurons.
Shigeo Mori - One of the best experts on this subject based on the ideXlab platform.
-
Changes of vertical eye movements of goldfish for different otolith stimulation by Linear Acceleration.
Advances in space research : the official journal of the Committee on Space Research (COSPAR), 2003Co-Authors: A. Takabayashi, T. Ohmura-iwasaki, Shigeo MoriAbstract:Eye movements serves to hold the gaze steady or to shift the gaze to an object of interest. On Earth, signals from otoliths can be interpreted either as Linear motion or as tilt with respect to gravity. In microgravity, static tilt will no longer give rise to changes in otolith activity. However, Linear Acceleration as well as angular Acceleration stimulate the otolith organ. Therefore, during adaptation to microgravity, otolith-mediated response such as eye movements alter. In this study, we analyzed the eye movements of goldfish during Linear Acceleration. The eye movements during rectangular Linear Acceleration along the different body axis were video-recorded. The vertical eye rotations were analyzed frame by frame. In normal fish, leftward lateral Acceleration induced downward eye rotation in the left eye and upward eye rotation in the right eye. Acceleration from caudal to rostral evoked downward eye rotation in both eyes. When the direction of Acceleration was shifted 15 degrees left, the responses in the left eye disappeared. These results suggested that otolith organs in each side were stimulated differently.
-
Relationship between head orientation and torsional eye movements in goldfish during Linear Acceleration.
Advances in space research : the official journal of the Committee on Space Research (COSPAR), 2002Co-Authors: Akira Takabayashi, T. Ohmura, Shigeo MoriAbstract:Abstract We analyzed torsional eye movements of normal goldfish during sinusoidal Linear Acceleration, altering the orientation of the fish on the Linear accelerator in the yaw plane over a range of 90 degrees and in the pitch plane up to 30 degrees. We video-recorded changes of torsional eye movements associated with a body rotation in the yaw and pitch plane and analyzed them frame by frame. In normal fish, we observed clear torsional eye movements for stimuli of 0.1G Linear Accelerations along the body axis in the horizontal position. Torsion occurred in the opposite direction of resultant force produced by Linear Acceleration and gravity. Though the amplitude of these compensatory responses increased with increasing magnitude of Acceleration up to 0.5 G, the torsion angle did not fully compensate the angle calculated from gravity and Linear Acceleration. Furthermore, the torsion angle decreased as the longitudinal body axis deviated from the direction of Linear Acceleration. For the body axis perpendicular to the direction of Acceleration, torsional eye movement was still observed. When we tilted the fish in the pitch plane, compensatory eye torsion occurred. The response amplitude to Acceleration decreased for both head-up and head-down up to 30 degrees. These results suggested the existence of specific connections between the otolith organ and ocular muscles.
-
Muscle sympathetic outflow during horizontal Linear Acceleration in humans.
American journal of physiology. Regulatory integrative and comparative physiology, 2001Co-Authors: Jian Cui, Satoshi Iwase, Tadaaki Mano, Naomi Katayama, Shigeo MoriAbstract:To elucidate the effects of Linear Acceleration on muscle sympathetic nerve activity (MSNA) in humans, 16 healthy men were tested in a Linear accelerator. Measurements of MSNA, electrocardiogram, blood pressure, and thoracic impedance were undertaken during Linear Acceleration. Sinusoidal Linear Acceleration with peak values at +/-0.10, +/-0.15, and +/-0.20 G was applied in anteroposterior (+/-G(x), n = 10) or lateral (+/-G(y), n = 6) directions. The total activity and burst rate of MSNA decreased significantly during forward, backward, left, or right Linear Accelerations. The total activity of MSNA decreased to 50.5 +/- 6.9, 52.5 +/- 4.4, 71.2 +/- 9.6, and 67.6 +/- 8.2% from the baselines (100%) during Linear Accelerations with peak values at +/-0.20 G in the four directions, respectively. These results suggest that dynamic stimulation of otolith organs in horizontal directions in humans might inhibit MSNA directly in order to quickly redistribute blood to muscles during postural reflexes induced by passive movement, which supports the concept that the vestibular system contributes to sympathetic regulation in humans.
-
Muscle sympathetic nerve response to vestibular stimulation by sinusoidal Linear Acceleration in humans
Neuroscience letters, 1999Co-Authors: Jian Cui, Satoshi Iwase, Tadaaki Mano, Naomi Katayama, Shigeo MoriAbstract:Abstract To clarify the effects of natural otolith stimulation on muscle sympathetic nerve activity (MSNA) in humans, eight male volunteers were seated in a Linear accelerator (sled) during the recording of MSNA from the tibial nerve with microneurography, and also the recording of electrocardiogram, blood pressure measured with a Finapres device and thoracic impedance during movement. Sinusoidal Linear Acceleration with peak values of ±0.10, 0.15 and 0.20 Gx were applied to the sitting subjects in the anteroposterior direction. Both the total activity and the burst rate of MSNA decreased during the sinusoidal Linear Acceleration, whereas the average heart rate, thoracic impedance and mean arterial pressure did not change significantly. These results suggest that moderate sinusoidal Linear Acceleration in the anteroposterior direction may suppress MSNA in humans.
Bernard Cohen - One of the best experts on this subject based on the ideXlab platform.
-
Vertical (Z-axis) Acceleration alters the ocular response to Linear Acceleration in the rabbit
Experimental Brain Research, 2008Co-Authors: Jun Maruta, Theodore Raphan, John I. Simpson, Bernard CohenAbstract:Whether ocular orientation to gravity is produced solely by Linear Acceleration in the horizontal plane of the head or depends on both horizontal and vertical components of the Acceleration of gravity is controversial. Here, we compared orienting eye movements of rabbits during head tilt to those produced by centrifugation that generated centripetal Acceleration along the naso-occipital ( X -), bitemporal ( Y -) and vertical ( Z -) axes in a constant gravitational field. Sensitivities of ocular counter-pitch and vergence during pitch tilts were ≈25°/ g and ≈26°/ g , respectively, and of ocular counter-roll during roll tilts was ≈20°/ g . During X -axis centripetal Acceleration with 1 g of gravity along the Z -axis, pitch and vergence sensitivities were reduced to ≈13°/ g and ≈16°/ g . Similarly, Y -axis Acceleration with 1 g along the Z -axis reduced the roll sensitivity to ≈16°/ g . Modulation of Z -axis centripetal Acceleration caused sensitivities to drop by ≈6°/ g in pitch, ≈2°/ g in vergence, and ≈5°/ g in roll. Thus, the constant 1 g Acceleration along the Z -axis reduced the sensitivity of ocular orientation to Linear Accelerations in the horizontal plane. Orienting responses were also modulated by varying the head Z -axis Acceleration; the sensitivity of response to Z -axis Acceleration was Linearly related to the response to static tilt. Although the sign of the Z -axis modulation is opposite in the lateral-eyed rabbit from that in frontal-eyed species, these data provide evidence that the brain uses both the horizontal and the vertical components of Acceleration from the otolith organs to determine the magnitude of ocular orientation in response to Linear Acceleration.
-
perception of tilt somatogravic illusion in response to sustained Linear Acceleration during space flight
Experimental Brain Research, 2001Co-Authors: Gilles Clement, Theodore Raphan, Steven T Moore, Bernard CohenAbstract:During the 1998 Neurolab mission (STS-90), four astronauts were exposed to interaural and head vertical (dorsoventral) Linear Accelerations of 0.5 g and 1 g during constant velocity rotation on a centrifuge, both on Earth and during orbital space flight. Subjects were oriented either left-ear-out or right-ear-out (Gy centrifugation), or lay supine along the centrifuge arm with their head off-axis (Gz centrifugation). Pre-flight centrifugation, producing Linear Accelerations of 0.5 g and 1 g along the Gy (interaural) axis, induced illusions of roll-tilt of 20 degrees and 34 degrees for gravito-inertial Acceleration (GIA) vector tilts of 27 degrees and 45 degrees , respectively. Pre-flight 0.5 g and 1 g Gz (head dorsoventral) centrifugation generated perceptions of backward pitch of 5 degrees and 15 degrees , respectively. In the absence of gravity during space flight, the same centrifugation generated a GIA that was equivalent to the centripetal Acceleration and aligned with the Gy or Gz axes. Perception of tilt was underestimated relative to this new GIA orientation during early in-flight Gy centrifugation, but was close to the GIA after 16 days in orbit, when subjects reported that they felt as if they were 'lying on side'. During the course of the mission, inflight roll-tilt perception during Gy centrifugation increased from 45 degrees to 83 degrees at 1 g and from 42 degrees to 48 degrees at 0.5 g. Subjects felt 'upside-down' during in-flight Gz centrifugation from the first in-flight test session, which reflected the new GIA orientation along the head dorsoventral axis. The different levels of in-flight tilt perception during 0.5 g and 1 g Gy centrifugation suggests that other non-vestibular inputs, including an internal estimate of the body vertical and somatic sensation, were utilized in generating tilt perception. Interpretation of data by a weighted sum of body vertical and somatic vectors, with an estimate of the GIA from the otoliths, suggests that perception weights the sense of the body vertical more heavily early in-flight, that this weighting falls during adaptation to microgravity, and that the decreased reliance on the body vertical persists early post-flight, generating an exaggerated sense of tilt. Since graviceptors respond to Linear Acceleration and not to head tilt in orbit, it has been proposed that adaptation to weightlessness entails reinterpretation of otolith activity, causing tilt to be perceived as translation. Since Linear Acceleration during in-flight centrifugation was always perceived as tilt, not translation, the findings do not support this hypothesis.