Gravity in the Brain as a Reference for Space and Time Perception

Lacquaniti, Francesco; Bosco, Gianfranco; Gravano, Silvio; Indovina, Iole; Scaleia, Barbara La; Maffei, Vincenzo; Zago, Myrka

doi:10.1163/22134808-00002471

Cited by 53 publications

(53 citation statements)

References 125 publications

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“…), another physical variable came into focus: (earth) gravity. Gravitational biases have been reported for free falling targets (McIntyre et al, 2001; Zago et al, 2005, 2008, 2010, 2011) as well as for parabolic trajectories (Bosco et al, 2012; Diaz et al, 2013; Delle Monache et al, 2014; de la Malla and López-Moliner, 2015; Lacquaniti et al, 2015, validated a gravity based model for parabolic interception brought forward in Gómez and López-Moliner, 2013), objects on ramps (Mijatović et al, 2014), and even for objects that move horizontally (De Sá Teixeira et al, 2013; De Sá Teixeira, 2016). Interestingly, there seem to be certain constraints as to when computations can access the internal representation of gravity; when the so called “idiotropic vector” along the vertical body axis, for example, is not aligned with the direction of gravity, the contribution of the internal representation of gravity decreases (De Sá Teixeira, 2014; De Sá Teixeira and Hecht, 2014).…”

Section: Gravity Information In Vision Related Processing: What Is Itmentioning

confidence: 97%

“…Furthermore, gravity has been suggested as a mediator between spatial and temporal cues (Lacquaniti et al, 2015): for example, participants judged more precisely the time that elapsed during the gravity-governed free fall of an object than for the same movement in upwards or horizontal directions (Moscatelli and Lacquaniti, 2011). What is more, biological motion is to a large extent dependent on the pendulum-like movements of the organism’s limbs, whose frequency and amplitude are in turn governed by gravity.…”

Section: Gravity Information In Vision Related Processing: What Is Itmentioning

confidence: 99%

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Gravity as a Strong Prior: Implications for Perception and Action

Jörges

López‐Moliner

2017

Front. Hum. Neurosci.

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In the future, humans are likely to be exposed to environments with altered gravity conditions, be it only visually (Virtual and Augmented Reality), or visually and bodily (space travel). As visually and bodily perceived gravity as well as an interiorized representation of earth gravity are involved in a series of tasks, such as catching, grasping, body orientation estimation and spatial inferences, humans will need to adapt to these new gravity conditions. Performance under earth gravity discrepant conditions has been shown to be relatively poor, and few studies conducted in gravity adaptation are rather discouraging. Especially in VR on earth, conflicts between bodily and visual gravity cues seem to make a full adaptation to visually perceived earth-discrepant gravities nearly impossible, and even in space, when visual and bodily cues are congruent, adaptation is extremely slow. We invoke a Bayesian framework for gravity related perceptual processes, in which earth gravity holds the status of a so called “strong prior”. As other strong priors, the gravity prior has developed through years and years of experience in an earth gravity environment. For this reason, the reliability of this representation is extremely high and overrules any sensory information to its contrary. While also other factors such as the multisensory nature of gravity perception need to be taken into account, we present the strong prior account as a unifying explanation for empirical results in gravity perception and adaptation to earth-discrepant gravities.

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Section: Gravity Information In Vision Related Processing: What Is Itmentioning

confidence: 97%

Section: Gravity Information In Vision Related Processing: What Is Itmentioning

confidence: 99%

Gravity as a Strong Prior: Implications for Perception and Action

Jörges

López‐Moliner

2017

Front. Hum. Neurosci.

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“…According to current views, the direction of gravity is estimated by combining retinal cues about the line orientation with static vestibular and somatosensory cues about body orientation, plus the prior assumption of an upright body orientation (Mittelstaedt 1983;Dyde et al 2006;MacNeilage et al 2007;De Vrijer et al 2008;Lacquaniti et al 2015;Alberts et al 2016;Kheradmand & Winnick 2017). Also, the perception of static body tilt results from multisensory fusion, vestibular inputs being integrated with proprioceptive inputs (Bringoux et al 2016), although the perception of body orientation is considered to be independent of the perception of vertical direction, with systematic errors smaller than those in SVV (Kaptein & Van Gisbergen, 2004;Kheradmand & Winnick 2017).…”

Section: Estimates Of Body and Gravity Directionsmentioning

confidence: 99%

“…When the task requires aligning a visual line to the vertical in the dark, the so‐called subjective visual vertical (SVV) (Lacquaniti et al . ; Kheradmand & Winnick ), the direction of gravity is estimated by combining retinal cues about the line orientation with vestibular and somatosensory cues about head and body orientation, plus the prior assumption of an upright head orientation (Mittelstaedt ; Dyde et al . ; MacNeilage et al .…”

Section: Introductionmentioning

confidence: 99%

Body orientation contributes to modelling the effects of gravity for target interception in humans

Scaleia

Lacquaniti

Zago

2019

The Journal of Physiology

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Key points It is known that interception of targets accelerated by gravity involves internal models coupled with visual signals. Non‐visual signals related to head and body orientation relative to gravity may also contribute, although their role is poorly understood. In a novel experiment, we asked pitched observers to hit a virtual target approaching with an acceleration that was either coherent or incoherent with their pitch‐tilt. Initially, the timing errors were large and independent of the coherence between target acceleration and observer's pitch. With practice, however, the timing errors became substantially smaller in the coherent conditions. The results show that information about head and body orientation can contribute to modelling the effects of gravity on a moving target. Orientation cues from vestibular and somatosensory signals might be integrated with visual signals in the vestibular cortex, where the internal model of gravity is assumed to be encoded. Abstract Interception of moving targets relies on visual signals and internal models. Less is known about the additional contribution of non‐visual cues about head and body orientation relative to gravity. We took advantage of Galileo's law of motion along an incline to demonstrate the effects of vestibular and somatosensory cues about head and body orientation on interception timing. Participants were asked to hit a ball rolling in a gutter towards the eyes, resulting in image expansion. The scene was presented in a head‐mounted display, without any visual information about gravity direction. In separate blocks of trials participants were pitched backwards by 20° or 60°, whereas ball acceleration was randomized across trials so as to be compatible with rolling down a slope of 20° or 60°. Initially, the timing errors were large, independently of the coherence between ball acceleration and pitch angle, consistent with responses based exclusively on visual information because visual stimuli were identical at both tilts. At the end of the experiment, however, the timing errors were systematically smaller in the coherent conditions than the incoherent ones. Moreover, the responses were significantly (P = 0.007) earlier when participants were pitched by 60° than when they were pitched by 20°. Therefore, practice with the task led to incorporation of information about head and body orientation relative to gravity for response timing. Instead, posture did not affect response timing in a control experiment in which participants hit a static target in synchrony with the last of a predictable series of stationary audiovisual stimuli.

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“…As we demonstrated herein, contextual effects could impact duration perception; it is therefore likely that time compression was less profound in grating conditions simply because contextual effects were weakened by the alternation of both orientation and motion direction on every stimulus presentation. The other intriguing possibility is that natural movies contain distinctive information specific to natural movements such as biological motion and gravitational fall (Carrozzo et al, 2010; Lacquaniti et al, 2015). In a pioneering study, Eagleman (2004) has shown that a small flash superimposed on a slow natural movie was perceived to be ∼30% shorter than if the flash was superimposed on a movie playing at a natural speed.…”

Section: Discussionmentioning

confidence: 99%

Relative Time Compression for Slow-Motion Stimuli through Rapid Recalibration

Kashiwakura

Motoyoshi

2017

Front. Psychol.

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A number of psychophysical studies have shown that moving stimuli appear to last longer than static stimuli. Here, we report that the perceived duration for slow moving stimuli can be shorter than for static stimuli under specific circumstances. Observers were tested using natural movies presented at various speeds (0.0× = static, 0.25× = slow, or 1.9× = fast, relative to original speed) and indicated whether test duration was perceived as longer or shorter than comparison movies presented at their original speed. While fast movies were perceived as longer than slow and static movies (in accordance with previous studies), we found that slow movies were perceived as shorter (i.e., time compressed) compared to static images. Similar results were obtained for artificial stimuli consisting of drifting gratings. However, time compression for slow stimuli disappeared if comparison stimuli were replaced by a white static disk that removed repetitive exposures to moving stimuli. Results suggest that duration estimation is modulated by contextual effects induced by the specific diet – or distribution – of prior visual stimuli to which observers are exposed. A simple model, which includes a rapid recalibration of human time estimation via adaptation to preceding stimuli, succeeds in reproducing our experimental data.

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Gravity in the Brain as a Reference for Space and Time Perception

Cited by 53 publications

References 125 publications

Gravity as a Strong Prior: Implications for Perception and Action

Gravity as a Strong Prior: Implications for Perception and Action

Body orientation contributes to modelling the effects of gravity for target interception in humans

Relative Time Compression for Slow-Motion Stimuli through Rapid Recalibration

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