A Contribution of Area 5 of the Posterior Parietal Cortex to the Planning of Visually Guided Locomotion: Limb-Specific and Limb-Independent Effects

Andujar, Jacques-Étienne; Lajoie, Kim; Drew, Trevor

doi:10.1152/jn.00912.2009

Cited by 51 publications

(72 citation statements)

References 96 publications

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“…Several studies have reported that gaze is normally directed about two step lengths ahead during walking behaviour in humans [23,26] and cats [24,25], and subjects are better able to step over a single obstacle in their path when they become visible two steps in advance [46]. In addition, certain neurons in area five of the posterior parietal cortex in cats show an increase in activity two to three steps prior to stepping over an obstacle [47]. However, no explanation has been offered for what is special about this distance.…”

Section: Discussionmentioning

confidence: 99%

Humans exploit the biomechanics of bipedal gait during visually guided walking over complex terrain

Matthis

Fajen

2013

Proc. R. Soc. B.

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How do humans achieve such remarkable energetic efficiency when walking over complex terrain such as a rocky trail? Recent research in biomechanics suggests that the efficiency of human walking over flat, obstacle-free terrain derives from the ability to exploit the physical dynamics of our bodies. In this study, we investigated whether this principle also applies to visually guided walking over complex terrain. We found that when humans can see the immediate foreground as little as two step lengths ahead, they are able to choose footholds that allow them to exploit their biomechanical structure as efficiently as they can with unlimited visual information. We conclude that when humans walk over complex terrain, they use visual information from two step lengths ahead to choose footholds that allow them to approximate the energetic efficiency of walking in flat, obstacle-free environments.

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Section: Discussionmentioning

confidence: 99%

Humans exploit the biomechanics of bipedal gait during visually guided walking over complex terrain

Matthis

Fajen

2013

Proc. R. Soc. B.

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“…Fourteen subjects [5 females, 9 males; mean age = 18.7 (18)(19)(20)(21) years] participated in experiment 1, 18 subjects [7 females, 11 males; mean age = 19.1 (18)(19)(20)(21) years] participated in experiment 2, and 12 subjects [5 females, 7 males; mean age = 20.0 (18)(19)(20)(21)(22) years] participated in experiment 3. Data from two subjects in experiment 1 were excluded because their average stepping accuracy across all conditions was more than 2 SDs from the mean.…”

Section: Methodsmentioning

confidence: 99%

“…This area has been implicated in the control of reaching to remembered locations in primates (24,25) and may play an analogous role in stepping behavior during locomotion. In vivo recordings from cats walking on a treadmill revealed that neurons from this region increase their firing rates in the 2-3 steps before the step over an obstacle (22), suggesting that this area could be involved in encoding the position of upcoming obstacles relative to the moving observer. This estimate may then be used by the motor cortex to generate the descending signals that modulate the activity of synergistic muscle groups in the limbs to enact the gait adjustment necessary to account for the upcoming obstacle (or target foothold) (23).…”

Section: Significancementioning

confidence: 99%

“…Nevertheless, humans are not locked into rigid patterns of movement. The spinal and subcortical activity underlying the basic rhythmic pattern of the preferred gait cycle that humans adopt during steady-state walking over flat terrain can be modulated by descending signals from the cortex to accommodate variations in task demands and variations in the environment (3,21,22). Such descending signals are essential when walking over complex terrain, where it may not be an option to place the feet in the position that is ideal for the exploitation of the body's inverted pendulum dynamics.…”

Section: Significancementioning

confidence: 99%

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The critical phase for visual control of human walking over complex terrain

Matthis

Barton

Fajen

2017

Proc. Natl. Acad. Sci. U.S.A.

103

104

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To walk efficiently over complex terrain, humans must use vision to tailor their gait to the upcoming ground surface without interfering with the exploitation of passive mechanical forces. We propose that walkers use visual information to initialize the mechanical state of the body before the beginning of each step so the resulting ballistic trajectory of the walker's center-of-mass will facilitate stepping on target footholds. Using a precision stepping task and synchronizing target visibility to the gait cycle, we empirically validated two predictions derived from this strategy: (1) Walkers must have information about upcoming footholds during the second half of the preceding step, and (2) foot placement is guided by information about the position of the target foothold relative to the preceding base of support. We conclude that active and passive modes of control work synergistically to allow walkers to negotiate complex terrain with efficiency, stability, and precision.H umans and other animals are remarkable in their ability to take advantage of what is freely available in the environment to the benefit of efficiency, stability, and coordination in movement. This opportunism can take on at least two forms, both of which are evident in human locomotion over complex terrain: (i) harnessing external forces to minimize the need for self-generated (i.e., muscular) forces (1), and (ii) taking advantage of passive stability to simplify the control of a complex movement (e.g., ref. 2). In the ensuing section, we explain how walkers exploit external forces and passive stability while walking over flat, obstacle-free terrain.* We then generalize this account to walking over irregular surfaces by explaining how walkers can adapt gait to terrain variations while still reaping the benefits of the available mechanical forces and inherent stability. This account leads to hypotheses about how and when walkers use visual information about the upcoming terrain and where that information is found. We derive several predictions from these hypotheses and then put them to the test in three experiments. Passive Control in Human WalkingThe basic movement pattern of the human gait cycle arises primarily from the phasic activation of flexor and extensor muscle groups by spinal-level central pattern generators, regulated by sensory signals from lower limb proprioceptors and cutaneous feedback from the plantar surface of the foot. This low-level neuromuscular circuitry serves to maintain the rhythmic physical oscillations that define locomotor behavior (see ref. 3 for review). This section will provide an overview of the basic biomechanics of the bipedal gait cycle to show how these inherent physical dynamics contribute to the passive stability and energetic efficiency of human locomotion.During the single support phase of the bipedal gait cycle, when only one foot is in contact with the ground, a walker shares the physical dynamics of an inverted pendulum. The body's center of mass (COM) acts as the bob of the pendulum and is support...

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“…Precuneus, parahippocampal cortex, hippocampus, and lingual gyrus have been shown to be involved in cognitive aspects of movement in space (Rosenbaum et al, 2004;Epstein, 2008;Schinazi and Epstein, 2010;Wegman and Janzen, 2011;Drew and Marigold, 2015). Based on animal studies, some of these regions appear to be critical for coordinating motor activity during complex motor tasks involving object avoidance, which may involve control of foot placement and toe muscle activity (Andujar et al, 2010).…”

Section: -130mentioning

confidence: 99%

Brain Connectivity Associated with Muscle Synergies in Humans

et al. 2015

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The human brain is believed to simplify the control of the large number of muscles in the body by flexibly combining muscle coordination patterns, termed muscle synergies. However, the neural connectivity allowing the human brain to access and coordinate muscle synergies to accomplish functional tasks remains unknown. Here, we use a surprising pair of synergists in humans, the flexor hallucis longus (FHL, a toe flexor) and the anal sphincter, as a model that we show to be well suited in elucidating the neural connectivity underlying muscle synergy control. First, using electromyographic recordings, we demonstrate that voluntary FHL contraction is associated with synergistic anal sphincter contraction, but voluntary anal sphincter contraction occurs without FHL contraction. Second, using fMRI, we show that two important medial wall motor cortical regions emerge in relation to these tasks: one located more posteriorly that preferentially activates during voluntary FHL contraction and one located more anteriorly that activates during both voluntary FHL contraction as well as voluntary anal sphincter contraction. Third, using transcranial magnetic stimulation, we demonstrate that the anterior region is more likely to generate anal sphincter contraction than FHL contraction. Finally, using a repository resting-state fMRI dataset, we demonstrate that the anterior and posterior motor cortical regions have significantly different functional connectivity with distinct and distant brain regions. We conclude that specific motor cortical regions in humans provide access to different muscle synergies, which may allow distinct brain networks to coordinate muscle synergies during functional tasks.

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A Contribution of Area 5 of the Posterior Parietal Cortex to the Planning of Visually Guided Locomotion: Limb-Specific and Limb-Independent Effects

Cited by 51 publications

References 96 publications

Humans exploit the biomechanics of bipedal gait during visually guided walking over complex terrain

Humans exploit the biomechanics of bipedal gait during visually guided walking over complex terrain

The critical phase for visual control of human walking over complex terrain

Brain Connectivity Associated with Muscle Synergies in Humans

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