-
Philosophical Transactions of the Royal... Aug 1997This paper presents several approaches to the machine perception of motion and discusses the role and levels of knowledge in each. In particular, different techniques of... (Review)
Review
This paper presents several approaches to the machine perception of motion and discusses the role and levels of knowledge in each. In particular, different techniques of motion understanding as focusing on one of movement, activity or action are described. Movements are the most atomic primitives, requiring no contextual or sequence knowledge to be recognized; movement is often addressed using either view-invariant or view-specific geometric techniques. Activity refers to sequences of movements or states, where the only real knowledge required is the statistics of the sequence; much of the recent work in gesture understanding falls within this category of motion perception. Finally, actions are larger-scale events, which typically include interaction with the environment and causal relationships; action understanding straddles the grey division between perception and cognition, computer vision and artificial intelligence. These levels are illustrated with examples drawn mostly from the group's work in understanding motion in video imagery. It is argued that the utility of such a division is that it makes explicit the representational competencies and manipulations necessary for perception.
Topics: Motion Perception; Motor Activity; Movement; Neural Networks, Computer
PubMed: 9304692
DOI: 10.1098/rstb.1997.0108 -
Journal of Neurophysiology Jul 2020Conventional explanations of the vestibulo-ocular reflex (VOR) and eye and head movements are revisited by considering two alternative frameworks addressing the question... (Review)
Review
Conventional explanations of the vestibulo-ocular reflex (VOR) and eye and head movements are revisited by considering two alternative frameworks addressing the question of how the brain controls motor actions. Traditionally, biomechanical and/or computational frameworks reflect the views of several prominent scholars of the past, including Helmholtz and von Holst, who assumed that the brain directly specifies the desired motor outcome and uses efference copy to influence perception. However, empirical studies resulting in the theory of referent control of action and perception (an extension of the equilibrium-point hypothesis) revealed that direct specification of motor outcome is inconsistent with nonlinear properties of motoneurons and with the physical principle that the brain can control motor actions only indirectly, by changing or maintaining the values of neurophysiological parameters that influence, but can remain independent of, biomechanical variables. Some parameters are used to shift the origin (referent) points of spatial frames of reference (FRs) or system of coordinates in which motor actions emerge without being predetermined. Parameters are adjusted until the emergent motor actions meet the task demands. Several physiological parameters and spatial FRs have been identified, supporting the notion of indirect, referent control of movements. Instead of integration of velocity-dependent signals, position-dimensional referent signals underlying head motion can likely be transmitted to motoneurons of extraocular muscles. This would produce compensatory eye movement preventing shifts in gaze during head rotation, even after bilateral destruction of the labyrinths. The referent control framework symbolizes a shift in the paradigm for the understanding of VOR and eye and head movement production.
Topics: Eye Movements; Head Movements; Humans; Motor Activity; Motor Neurons; Oculomotor Muscles; Reflex, Vestibulo-Ocular; Superior Colliculi
PubMed: 32490708
DOI: 10.1152/jn.00076.2020 -
Journal of Neurophysiology Oct 2018If a whole body reaching task is produced when standing or adopting challenging postures, it is unclear whether changes in attentional demands or the sensorimotor...
If a whole body reaching task is produced when standing or adopting challenging postures, it is unclear whether changes in attentional demands or the sensorimotor integration necessary for balance control influence the interaction between visuomotor and postural components of the movement. Is gaze control prioritized by the central nervous system (CNS) to produce coordinated eye movements with the head and whole body regardless of movement context? Considering the coupled nature of visuomotor and whole body postural control during action, this study aimed to understand how changing equilibrium constraints (in the form of different postural configurations) influenced the initiation of eye, head, and arm movements. We quantified the eye-head metrics and segmental kinematics as participants executed either isolated gaze shifts or whole body reaching movements to visual targets. In total, four postural configurations were compared: seated, natural stance, with the feet together (narrow stance), or while balancing on a wooden beam. Contrary to our initial predictions, the lack of distinct changes in eye-head metrics; timing of eye, head, and arm movement initiation; and gaze accuracy, in spite of kinematic differences, suggests that the CNS integrates postural constraints into the control necessary to initiate gaze shifts. This may be achieved by adopting a whole body gaze strategy that allows for the successful completion of both gaze and reaching goals. NEW & NOTEWORTHY Differences in sequence of movement among the eye, head, and arm have been shown across various paradigms during reaching. Here we show that distinct changes in eye characteristics and movement sequence, coupled with stereotyped profiles of head and gaze movement, are not observed when adopting postures requiring changes to balance constraints. This suggests that a whole body gaze strategy is prioritized by the central nervous system with postural control subservient to gaze stability requirements.
Topics: Adult; Arm; Eye Movements; Female; Head Movements; Humans; Male; Posture; Psychomotor Performance
PubMed: 30020836
DOI: 10.1152/jn.00200.2018 -
Philosophical Transactions of the Royal... Aug 2009In this article we discuss both merits and limitations of the ideomotor approach to action control and action imitation. In the first part, we give a brief outline of... (Review)
Review
In this article we discuss both merits and limitations of the ideomotor approach to action control and action imitation. In the first part, we give a brief outline of ideomotor theory and its functional implications for imitation and related kinds of behaviours. In the subsequent sections, we summarize pertinent experimental studies on action imitation and action induction. These studies show that action perception modulates action planning in a number of ways, of which imitation is but one. In the last part, we move from regular actions to tool-use actions, raising the issue of whether and how watching others' tool-use actions leads to corresponding behaviours in observers. Here, we discuss experiments aimed at dissociating the relative roles of environmental targets, bodily movements and target-to-movement-mappings (action rules) in the observation of tool-use actions. Our findings indicate a strong role for action rules in the observation and imitation of tool-use actions. We argue that, in order to account for these findings, ideomotor theory needs to be extended to take mappings between bodily movements and environmental effects into account.
Topics: Humans; Imitative Behavior; Motor Activity; Movement; Tool Use Behavior
PubMed: 19620106
DOI: 10.1098/rstb.2009.0059 -
PLoS Computational Biology May 2024On any given day, we make countless reaching movements to objects around us. While such ubiquity may suggest uniformity, each movement's speed is unique-why is this?...
On any given day, we make countless reaching movements to objects around us. While such ubiquity may suggest uniformity, each movement's speed is unique-why is this? Reach speed is known to be influenced by accuracy; we slow down to sustain high accuracy. However, in other forms of movement like walking or running, metabolic cost is often the primary determinant of movement speed. Here we bridge this gap and ask: how do metabolic cost and accuracy interact to determine speed of reaching movements? First, we systematically measure the effect of increasing mass on the metabolic cost of reaching across a range of movement speeds. Next, in a sequence of three experiments, we examine how added mass affects preferred reaching speed across changing accuracy requirements. We find that, while added mass consistently increases metabolic cost thereby leading to slower metabolically optimal movement speeds, self-selected reach speeds are slower than those predicted by an optimization of metabolic cost alone. We then demonstrate how a single model that considers both accuracy and metabolic costs can explain preferred movement speeds. Together, our findings provide a unifying framework to illuminate the combined effects of metabolic cost and accuracy on movement speed and highlight the integral role metabolic cost plays in determining reach speed.
Topics: Humans; Movement; Male; Energy Metabolism; Female; Adult; Models, Biological; Young Adult; Computational Biology; Psychomotor Performance
PubMed: 38820571
DOI: 10.1371/journal.pcbi.1012169 -
Journal of Neuroengineering and... Sep 2023Characterizing human movement is essential for understanding movement disorders, evaluating progress in rehabilitation, or even analyzing how a person adapts to the use... (Review)
Review
Characterizing human movement is essential for understanding movement disorders, evaluating progress in rehabilitation, or even analyzing how a person adapts to the use of assistive devices. Thanks to the improvement of motion capture technology, recording human movement has become increasingly accessible and easier to conduct. Over the last few years, multiple methods have been proposed for characterizing inter-joint coordination. Despite this, there is no real consensus regarding how these different inter-joint coordination metrics should be applied when analyzing the coordination of discrete movement from kinematic data. In this work, we consider 12 coordination metrics identified from the literature and apply them to a simulated dataset based on reaching movements using two degrees of freedom. Each metric is evaluated according to eight criteria based on current understanding of human motor control physiology, i.e, each metric is graded on how well it fulfills each of these criteria. This comparative analysis highlights that no single inter-joint coordination metric can be considered as ideal. Depending on the movement characteristics that one seeks to understand, one or several metrics among those reviewed here may be pertinent in data analysis. We propose four main factors when choosing a metric (or a group of metrics): the importance of temporal vs. spatial coordination, the need for result explainability, the size of the dataset, and the computational resources. As a result, this study shows that extracting the relevant characteristics of inter-joint coordination is a scientific challenge and requires a methodical choice. As this preliminary study is conducted on a limited dataset, a more comprehensive analysis, introducing more variability, could be complementary to these results.
Topics: Humans; Movement; Movement Disorders; Biomechanical Phenomena
PubMed: 37777814
DOI: 10.1186/s12984-023-01252-2 -
Age and Ageing May 2021Overly cautious gait is common in older adults. This is characterised by excessively slow gait, shortened steps, broadened base of support and increased double limb...
BACKGROUND
Overly cautious gait is common in older adults. This is characterised by excessively slow gait, shortened steps, broadened base of support and increased double limb support. The current study sought to (1) evaluate if overly cautious gait is associated with attempts to consciously process walking movements, and (2) explore whether an individual's ability to rapidly inhibit a dominant motor response serves to mitigate this relationship.
METHODS
A total of 50 older adults walked at a self-selected pace on an instrumented walkway containing two raised wooden obstacles (height = 23 cm). Trait conscious movement processing was measured with the Movement-Specific Reinvestment Scale. Short-latency inhibitory function was assessed using a validated electronic go/no-go ruler catch protocol. We used linear regressions to explore the relationship between these variables and gait parameters indicative of overly cautious gait.
RESULTS
When controlling for general cognitive function (MoCA), and functional balance (Berg Balance Scale), the interaction between trait conscious movement processing and short-latency inhibition capacity significantly predicted gait velocity, step length and double limb support. Specifically, older adults with higher trait conscious movement processing and poorer inhibition were more likely to exhibit gait characteristics indicative of cautious gait (i.e. reduced velocity, shorter step lengths and increased double limb support). Neither conscious movement processing nor inhibition independently predicted gait performance.
CONCLUSION
The combination of excessive movement processing tendencies and poor short-latency inhibitory capacity was associated with dysfunctional or 'overly cautious' gait. It is therefore plausible that improvement in either factor may lead to improved gait and reduced fall risk.
Topics: Aged; Cognition; Consciousness; Gait; Humans; Movement; Walking
PubMed: 33951155
DOI: 10.1093/ageing/afaa230 -
Social Cognitive and Affective... Mar 2023Although the ability to detect the actions of other living beings is key for adaptive social behavior, it is still unclear if biological motion perception is specific to...
Although the ability to detect the actions of other living beings is key for adaptive social behavior, it is still unclear if biological motion perception is specific to human stimuli. Biological motion perception involves both bottom-up processing of movement kinematics ('motion pathway') and top-down reconstruction of movement from changes in the body posture ('form pathway'). Previous research using point-light displays has shown that processing in the motion pathway depends on the presence of a well-defined, configural shape (objecthood) but not necessarily on whether that shape depicts a living being (animacy). Here, we focused on the form pathway. Specifically, we combined electroencephalography (EEG) frequency tagging with apparent motion to study how objecthood and animacy influence posture processing and the integration of postures into movements. By measuring brain responses to repeating sequences of well-defined or pixelated images (objecthood), depicting human or corkscrew agents (animacy), performing either fluent or non-fluent movements (movement fluency), we found that movement processing was sensitive to objecthood but not animacy. In contrast, posture processing was sensitive to both. Together, these results indicate that reconstructing biological movements from apparent motion sequences requires a well-defined but not necessarily an animate shape. Instead, stimulus animacy appears to be relevant only for posture processing.
Topics: Humans; Photic Stimulation; Movement; Motion Perception; Posture; Social Behavior
PubMed: 36905406
DOI: 10.1093/scan/nsad014 -
The European Journal of Neuroscience Sep 2019The posterior parietal cortex (PPC) serves as a sensorimotor interface by integrating multisensory signals with motor related information for generating and updating...
Ascending vestibular pathways to parietal areas MIP and LIPv and efference copy inputs from the medial reticular formation: Functional frameworks for body representations updating and online movement guidance.
The posterior parietal cortex (PPC) serves as a sensorimotor interface by integrating multisensory signals with motor related information for generating and updating body representations and movement plans. Using retrograde transneuronal transfer of rabies virus combined with a conventional tracer, we identified direct and polysynaptic pathways to two PPC areas, the rostral medial intraparietal area (MIP) and the ventral part of the lateral intraparietal area (LIPv) in macaque monkeys. We found that rostral MIP and LIPv receive ascending vestibular pathways, and putative efference copy inputs disynaptically from the medullary medial reticular formation (MRF) where reticulospinal pathways to neck and arm motoneurons originate. LIPv receives minor disynaptic vestibular inputs, and substantial projections from the head movement-related rostral MRF, consistent with head gain modulation of LIPv activity and a role in planning gaze shifts. Rostral MIP is the target of prominent disynaptic pathways from reaching- and head movement-related MRF domains, and major ascending vestibular pathways trisynaptically from both labyrinths, explaining prominent vestibular responses and discrimination between active and passive movements demonstrated in rostral MIP and in the neighboring ventral intraparietal area, which are heavily interconnected. The findings that rostral MIP (belonging to the 'parietal reach region'), receives vestibular inputs as directly as classical vestibular areas, via a parallel channel, and efference copy signals pathways from MRF reticulospinal domains that belong to reach and head movement networks have important implications for the understanding of the role of the PPC in updating body representations and internal models for online guidance of movement.
Topics: Animals; Body Image; Head Movements; Macaca fascicularis; Macaca mulatta; Motor Neurons; Movement; Neural Pathways; Neurons; Parietal Lobe; Reticular Formation
PubMed: 31012519
DOI: 10.1111/ejn.14426 -
Sensors (Basel, Switzerland) Feb 2024To understand human behavior, it is essential to study it in the context of natural movement in immersive, three-dimensional environments. Virtual reality (VR), with...
To understand human behavior, it is essential to study it in the context of natural movement in immersive, three-dimensional environments. Virtual reality (VR), with head-mounted displays, offers an unprecedented compromise between ecological validity and experimental control. However, such technological advancements mean that new data streams will become more widely available, and therefore, a need arises to standardize methodologies by which these streams are analyzed. One such data stream is that of head position and rotation tracking, now made easily available from head-mounted systems. The current study presents five candidate algorithms of varying complexity for classifying head movements. Each algorithm is compared against human rater classifications and graded based on the overall agreement as well as biases in metrics such as movement onset/offset time and movement amplitude. Finally, we conclude this article by offering recommendations for the best practices and considerations for VR researchers looking to incorporate head movement analysis in their future studies.
Topics: Humans; Head Movements; Movement; Algorithms; Virtual Reality; Smart Glasses; Rotation
PubMed: 38400418
DOI: 10.3390/s24041260