The analysis of the performances of the upper limb is considered very important in view of long-t... more The analysis of the performances of the upper limb is considered very important in view of long-term presence of the humans in weightlessness conditions. This paper outlines the main features, utilization scope and capabilities of Hand Posture Analyzer (HPA), a set of instruments designed and developed by Kayser Italia in the frame of a contract with Italian Space Agency(ASI), to carry out research on the upper limb in micro-gravity conditions during space flights. The upper limb functionality and efficiency holds an even greater importance on orbit than down on earth. Early utilization of HPA on the International Space Station (ISS) will focus on the analysis of reaching, grasping and launch of objects and on the assessment of muscular performance degradation in weightlessness.
We review studies on catching that reveal internalization of physics for action control. In catch... more We review studies on catching that reveal internalization of physics for action control. In catching free-falling balls, an internal model of gravity is used by the brain to time anticipatory muscle activation, modulation of reflex responses, and tuning of limb impedance. An internal model of the expected momentum of the ball at impact is used to scale the amplitude of anticipatory muscle activity. [Barlow; Hecht; Shepard]
X and Y raw centroid and tail positions of individual Drosophila melanogaster larvae (n=42) in th... more X and Y raw centroid and tail positions of individual Drosophila melanogaster larvae (n=42) in the overshoot condition (orbiting around an odor source) tracked at 7Hz and at the spatial resolution specified in the file— see manuscript for more details
We report the discovery that the locomotor trajectories of Drosophila larvae follow the power-law... more We report the discovery that the locomotor trajectories of Drosophila larvae follow the power-law relationship between speed and curvature previously found in the movements of human and non-human primates. Using high-resolution behavioural tracking in controlled but naturalistic sensory environments, we tested the law in maggots tracing different trajectory types, from reaching-like movements to scribbles. For most but not all flies, we found that the law holds robustly, with an exponent close to three-quarters rather than to the usual two-thirds found in almost all human situations, suggesting dynamic effects adding on purely kinematic constraints. There are different hypotheses for the origin of the law in primates, one invoking cortical computations, another viscoelastic muscle properties coupled with central pattern generators. Our findings are consistent with the latter view and demonstrate that the law is possible in animals with nervous systems orders of magnitude simpler than in primates. Scaling laws might exist because natural selection favours processes that remain behaviourally efficient across a wide range of neural and body architectures in distantly related species
3. ABSTRACT The vertebrate nervous system evolved in an environment where the stimulus to the bod... more 3. ABSTRACT The vertebrate nervous system evolved in an environment where the stimulus to the body's multiple gravireceptive senses invariably changed whenever the orientation of the body was altered. Experiments conducted in orbital flight allow us to remove static gravireceptor cues to the orientation of the head, body, and limbs. In this way we can better understand the role of gravity in fundamental sensory, motor, and cognitive processes subserving spatial orientation and movement control in daily life on earth. The goal of the ...
Moving and interacting with the environment require a reference for orientation and a scale for c... more Moving and interacting with the environment require a reference for orientation and a scale for calibration in space and time. There is a wide variety of environmental clues and calibrated frames at different locales, but the reference of gravity is ubiquitous on Earth. The pull of gravity on static objects provides a plummet which, together with the horizontal plane, defines a three-dimensional Cartesian frame for visual images. On the other hand, the gravitational acceleration of falling objects can provide a time-stamp on events, because the motion duration of an object accelerated by gravity over a given path is fixed. Indeed, since ancient times, man has been using plumb bobs for spatial surveying, and water clocks or pendulum clocks for time keeping. Here we review behavioral evidence in favor of the hypothesis that the brain is endowed with mechanisms that exploit the presence of gravity to estimate the spatial orientation and the passage of time. Several visual and non-visual (vestibular, haptic, visceral) cues are merged to estimate the orientation of the visual vertical. However, the relative weight of each cue is not fixed, but depends on the specific task. Next, we show that an internal model of the effects of gravity is combined with multisensory signals to time the interception of falling objects, to time the passage through spatial landmarks during virtual navigation, to assess the duration of a gravitational motion, and to judge the naturalness of periodic motion under gravity.
Noise defined as random disturbances is ubiquitous in both the external environment and the nervo... more Noise defined as random disturbances is ubiquitous in both the external environment and the nervous system. Depending on the context, noise can degrade or improve information processing and performance. In all cases, it contributes to neural systems dynamics. We review some effects of various sources of noise on the neural processing of self-motion signals at different stages of the vestibular pathways and the resulting perceptual responses. Hair cells in the inner ear reduce the impact of noise by means of mechanical and neural filtering. Hair cells synapse on regular and irregular afferents. Variability of discharge (noise) is low in regular afferents and high in irregular units. The high variability of irregular units provides information about the envelope of naturalistic head motion stimuli. A subset of neurons in the vestibular nuclei and thalamus are optimally tuned to noisy motion stimuli that reproduce the statistics of naturalistic head movements. In the thalamus, variabil...
Motion direction and luminance contrast are two central features in the representation of visual ... more Motion direction and luminance contrast are two central features in the representation of visual motion in humans. In five psychophysical experiments, we showed that these two features affect the perceived speed of a visual stimulus. Our data showed a surprising interaction between contrast and direction. Participants perceived downward moving stimuli as faster than upward or rightward stimuli, but only at high contrast. Likewise, luminance contrast produced an underestimation of motion speed, but mostly when the stimuli moved downward. We explained these novel phenomena by means of a theoretical model, accounting for prior knowledge of motion dynamics.
ABSTRACTNoisy galvanic vestibular stimulation has been shown to improve vestibular perception in ... more ABSTRACTNoisy galvanic vestibular stimulation has been shown to improve vestibular perception in healthy subjects. Here, we sought to obtain similar results using more natural stimuli consisting of small-amplitude motion perturbations of the whole body. Thirty participants were asked to report the perceived direction of antero-posterior sinusoidal motion on a MOOG platform. We compared the baseline perceptual thresholds with those obtained by applying small, stochastic perturbations at different power levels along the antero-posterior axis, symmetrically distributed around a zero-mean. At the population level, we found that the thresholds for all but the highest level of noise were significantly lower than the baseline threshold. At the individual level, the threshold was lower with at least one noise level than the threshold without noise in 87% of participants. Thus, small, stochastic oscillations of the whole body can increase the probability of detecting subthreshold vestibular ...
<p>A: Distribution histogram of the responses (pooled over participants). B: CDFs for each ... more <p>A: Distribution histogram of the responses (pooled over participants). B: CDFs for each participant and for the population. Same format as in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0093020#pone-0093020-g002" target="_blank">Figure 2B</a>.</p
Raw data related to "Visuomotor Interactions and Perceptual Judgments in Virtual Reality Sim... more Raw data related to "Visuomotor Interactions and Perceptual Judgments in Virtual Reality Simulating Different Levels of Gravity"
X and Y raw centroid and tail positions of individual Drosophila melanogaster larvae (n=41) in th... more X and Y raw centroid and tail positions of individual Drosophila melanogaster larvae (n=41) in the dispersal condition (foraging in the absence of olfactory cues) tracked at 7Hz and at the spatial resolution specified in the file— see manuscript for more details
We report the discovery that the locomotor trajectories of <i>Drosophila</i> larvae f... more We report the discovery that the locomotor trajectories of <i>Drosophila</i> larvae follow the power-law relationship between speed and curvature previously found in the movements of human and non-human primates. Using high-resolution behavioural tracking in controlled but naturalistic sensory environments, we tested the law in maggots tracing different trajectory types, from reaching-like movements to scribbles. For most but not all flies, we found that the law holds robustly, with an exponent close to third-fourth rather than to the usual two-third found in almost all human situations, suggesting dynamic effects adding on purely kinematic constraints. There are different hypotheses for the origin of the law in primates, one invoking cortical computations, another viscoelastic muscle properties coupled with central pattern generators. Our findings are consistent with the latter view and demonstrate that the law is possible in animals with nervous systems orders of magnitude simpler than in primates. Scaling laws might exist, because natural selection favours processes that remain behaviourally efficient across a wide range of neural and body architectures in distantly related species.
Gravity is a physical constraint all terrestrial species have adapted to through evolution. Indee... more Gravity is a physical constraint all terrestrial species have adapted to through evolution. Indeed, gravity effects are taken into account in many forms of interaction with the environment, from the seemingly simple task of maintaining balance to the complex motor skills performed by athletes and dancers. Graviceptors, primarily located in the vestibular otolith organs, feed the Central Nervous System with information related to the gravity acceleration vector. This information is integrated with signals from semicircular canals, vision, and proprioception in an ensemble of interconnected brain areas, including the vestibular nuclei, cerebellum, thalamus, insula, retroinsula, parietal operculum, and temporo-parietal junction, in the so-called vestibular network. Classical views consider this stage of multisensory integration as instrumental to sort out conflicting and/or ambiguous information from the incoming sensory signals. However, there is compelling evidence that it also contr...
The analysis of the performances of the upper limb is considered very important in view of long-t... more The analysis of the performances of the upper limb is considered very important in view of long-term presence of the humans in weightlessness conditions. This paper outlines the main features, utilization scope and capabilities of Hand Posture Analyzer (HPA), a set of instruments designed and developed by Kayser Italia in the frame of a contract with Italian Space Agency(ASI), to carry out research on the upper limb in micro-gravity conditions during space flights. The upper limb functionality and efficiency holds an even greater importance on orbit than down on earth. Early utilization of HPA on the International Space Station (ISS) will focus on the analysis of reaching, grasping and launch of objects and on the assessment of muscular performance degradation in weightlessness.
We review studies on catching that reveal internalization of physics for action control. In catch... more We review studies on catching that reveal internalization of physics for action control. In catching free-falling balls, an internal model of gravity is used by the brain to time anticipatory muscle activation, modulation of reflex responses, and tuning of limb impedance. An internal model of the expected momentum of the ball at impact is used to scale the amplitude of anticipatory muscle activity. [Barlow; Hecht; Shepard]
X and Y raw centroid and tail positions of individual Drosophila melanogaster larvae (n=42) in th... more X and Y raw centroid and tail positions of individual Drosophila melanogaster larvae (n=42) in the overshoot condition (orbiting around an odor source) tracked at 7Hz and at the spatial resolution specified in the file— see manuscript for more details
We report the discovery that the locomotor trajectories of Drosophila larvae follow the power-law... more We report the discovery that the locomotor trajectories of Drosophila larvae follow the power-law relationship between speed and curvature previously found in the movements of human and non-human primates. Using high-resolution behavioural tracking in controlled but naturalistic sensory environments, we tested the law in maggots tracing different trajectory types, from reaching-like movements to scribbles. For most but not all flies, we found that the law holds robustly, with an exponent close to three-quarters rather than to the usual two-thirds found in almost all human situations, suggesting dynamic effects adding on purely kinematic constraints. There are different hypotheses for the origin of the law in primates, one invoking cortical computations, another viscoelastic muscle properties coupled with central pattern generators. Our findings are consistent with the latter view and demonstrate that the law is possible in animals with nervous systems orders of magnitude simpler than in primates. Scaling laws might exist because natural selection favours processes that remain behaviourally efficient across a wide range of neural and body architectures in distantly related species
3. ABSTRACT The vertebrate nervous system evolved in an environment where the stimulus to the bod... more 3. ABSTRACT The vertebrate nervous system evolved in an environment where the stimulus to the body's multiple gravireceptive senses invariably changed whenever the orientation of the body was altered. Experiments conducted in orbital flight allow us to remove static gravireceptor cues to the orientation of the head, body, and limbs. In this way we can better understand the role of gravity in fundamental sensory, motor, and cognitive processes subserving spatial orientation and movement control in daily life on earth. The goal of the ...
Moving and interacting with the environment require a reference for orientation and a scale for c... more Moving and interacting with the environment require a reference for orientation and a scale for calibration in space and time. There is a wide variety of environmental clues and calibrated frames at different locales, but the reference of gravity is ubiquitous on Earth. The pull of gravity on static objects provides a plummet which, together with the horizontal plane, defines a three-dimensional Cartesian frame for visual images. On the other hand, the gravitational acceleration of falling objects can provide a time-stamp on events, because the motion duration of an object accelerated by gravity over a given path is fixed. Indeed, since ancient times, man has been using plumb bobs for spatial surveying, and water clocks or pendulum clocks for time keeping. Here we review behavioral evidence in favor of the hypothesis that the brain is endowed with mechanisms that exploit the presence of gravity to estimate the spatial orientation and the passage of time. Several visual and non-visual (vestibular, haptic, visceral) cues are merged to estimate the orientation of the visual vertical. However, the relative weight of each cue is not fixed, but depends on the specific task. Next, we show that an internal model of the effects of gravity is combined with multisensory signals to time the interception of falling objects, to time the passage through spatial landmarks during virtual navigation, to assess the duration of a gravitational motion, and to judge the naturalness of periodic motion under gravity.
Noise defined as random disturbances is ubiquitous in both the external environment and the nervo... more Noise defined as random disturbances is ubiquitous in both the external environment and the nervous system. Depending on the context, noise can degrade or improve information processing and performance. In all cases, it contributes to neural systems dynamics. We review some effects of various sources of noise on the neural processing of self-motion signals at different stages of the vestibular pathways and the resulting perceptual responses. Hair cells in the inner ear reduce the impact of noise by means of mechanical and neural filtering. Hair cells synapse on regular and irregular afferents. Variability of discharge (noise) is low in regular afferents and high in irregular units. The high variability of irregular units provides information about the envelope of naturalistic head motion stimuli. A subset of neurons in the vestibular nuclei and thalamus are optimally tuned to noisy motion stimuli that reproduce the statistics of naturalistic head movements. In the thalamus, variabil...
Motion direction and luminance contrast are two central features in the representation of visual ... more Motion direction and luminance contrast are two central features in the representation of visual motion in humans. In five psychophysical experiments, we showed that these two features affect the perceived speed of a visual stimulus. Our data showed a surprising interaction between contrast and direction. Participants perceived downward moving stimuli as faster than upward or rightward stimuli, but only at high contrast. Likewise, luminance contrast produced an underestimation of motion speed, but mostly when the stimuli moved downward. We explained these novel phenomena by means of a theoretical model, accounting for prior knowledge of motion dynamics.
ABSTRACTNoisy galvanic vestibular stimulation has been shown to improve vestibular perception in ... more ABSTRACTNoisy galvanic vestibular stimulation has been shown to improve vestibular perception in healthy subjects. Here, we sought to obtain similar results using more natural stimuli consisting of small-amplitude motion perturbations of the whole body. Thirty participants were asked to report the perceived direction of antero-posterior sinusoidal motion on a MOOG platform. We compared the baseline perceptual thresholds with those obtained by applying small, stochastic perturbations at different power levels along the antero-posterior axis, symmetrically distributed around a zero-mean. At the population level, we found that the thresholds for all but the highest level of noise were significantly lower than the baseline threshold. At the individual level, the threshold was lower with at least one noise level than the threshold without noise in 87% of participants. Thus, small, stochastic oscillations of the whole body can increase the probability of detecting subthreshold vestibular ...
<p>A: Distribution histogram of the responses (pooled over participants). B: CDFs for each ... more <p>A: Distribution histogram of the responses (pooled over participants). B: CDFs for each participant and for the population. Same format as in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0093020#pone-0093020-g002" target="_blank">Figure 2B</a>.</p
Raw data related to "Visuomotor Interactions and Perceptual Judgments in Virtual Reality Sim... more Raw data related to "Visuomotor Interactions and Perceptual Judgments in Virtual Reality Simulating Different Levels of Gravity"
X and Y raw centroid and tail positions of individual Drosophila melanogaster larvae (n=41) in th... more X and Y raw centroid and tail positions of individual Drosophila melanogaster larvae (n=41) in the dispersal condition (foraging in the absence of olfactory cues) tracked at 7Hz and at the spatial resolution specified in the file— see manuscript for more details
We report the discovery that the locomotor trajectories of <i>Drosophila</i> larvae f... more We report the discovery that the locomotor trajectories of <i>Drosophila</i> larvae follow the power-law relationship between speed and curvature previously found in the movements of human and non-human primates. Using high-resolution behavioural tracking in controlled but naturalistic sensory environments, we tested the law in maggots tracing different trajectory types, from reaching-like movements to scribbles. For most but not all flies, we found that the law holds robustly, with an exponent close to third-fourth rather than to the usual two-third found in almost all human situations, suggesting dynamic effects adding on purely kinematic constraints. There are different hypotheses for the origin of the law in primates, one invoking cortical computations, another viscoelastic muscle properties coupled with central pattern generators. Our findings are consistent with the latter view and demonstrate that the law is possible in animals with nervous systems orders of magnitude simpler than in primates. Scaling laws might exist, because natural selection favours processes that remain behaviourally efficient across a wide range of neural and body architectures in distantly related species.
Gravity is a physical constraint all terrestrial species have adapted to through evolution. Indee... more Gravity is a physical constraint all terrestrial species have adapted to through evolution. Indeed, gravity effects are taken into account in many forms of interaction with the environment, from the seemingly simple task of maintaining balance to the complex motor skills performed by athletes and dancers. Graviceptors, primarily located in the vestibular otolith organs, feed the Central Nervous System with information related to the gravity acceleration vector. This information is integrated with signals from semicircular canals, vision, and proprioception in an ensemble of interconnected brain areas, including the vestibular nuclei, cerebellum, thalamus, insula, retroinsula, parietal operculum, and temporo-parietal junction, in the so-called vestibular network. Classical views consider this stage of multisensory integration as instrumental to sort out conflicting and/or ambiguous information from the incoming sensory signals. However, there is compelling evidence that it also contr...
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