Biology subjects

Pozzo, T.

Publications and source records attributed to Pozzo, T..

6 recordsLinked to original sources

bioRxiv2023

Evidence for a sensorimotor prediction process in action observation

The mirror neurons network in the human brain is activated both during the observation of action and the execution of the same action, facilitating thus the transformation of visual information into motor representations, to understand the actions and intentions of others. How this transformation takes place, however, is still under debate. One prevailing theory, direct matching, assumes a direct correspondence between the visual information of the actors movement and the activation of the motor representations in the observers motor cortex that would produce the same movement. Alternatively, the predictive coding theory postulates that, during action observation, motor predictions (e.g., position, velocity) are generated and compared to the visual information of the actors movement. Here, we experimentally interrogate these two hypotheses during a locomotion task. The motor prediction process was assessed by measuring the timing of imagined movements: the participants had to imagine walking, forward or backward, for 9 m (linear path). Action observation was assessed by measuring time estimation in an inference locomotor task (the same 9 m linear path): after perceiving an actor walking forward or backward for 3 m, the vision of the observer was occluded and he/she had to estimate when the actor would reach the end of the 9 m path. We manipulated the timing processes during the two tasks by creating sensory illusions via peripheral mechanical muscle vibration on leg muscles, which has provided consistent results in the literature (acceleration of forward and deceleration of backward locomotion). We found that sensory illusions specifically affected the timing processes of both locomotion inference and mental locomotion, suggesting the involvement of sensorimotor predictions, common to both tasks. These findings seem to support the predictive coding hypothesis.

neuroscience↗

bioRxiv2023

Evidence for subjective values guiding cognitive integration of gravity in a free speed manifold pointing task

Studies of regularities in human movement control have led to the idea that our brains incorporate generic motor laws that guide our behaviors and thus these regularities. Among these, it has been argued that a generic internal model of gravity minimizes the bodys energy expenditure during actions performed in the vertical plane. According to this hypothesis, the energy criterion would represent the factor dominating motor planning. However, a growing body of experimental evidence indicates the presence of significant individual sensorimotor differences that suggest the use of various motor decision criteria. We asked 41 voluntary participants to perform a free speed manifold pointing task (i.e., at three free different speeds and toward non-salient targets), in the vertical plane designed to avoid situation-specific responses and favor the expression of singularities. We found that temporal parameters (duration of motion and vigor) were idiosyncratic and not affected by mechanical effects induced by changes in velocity and gravitational force (i.e., assistive or resistive forces). Upward motions had a shorter time to reach maximum velocity than downward motions confirming the presence of asymmetric movement timing. Finally, synchronization of up-down movements was not correlated with energy minimization, indicating that movements performed in the vertical plane do not rely exclusively on a standard representation of gravity reducing effort. Rather, we concluded that individual values and the subjective rewards associated with each of these values could influence the planning of movements executed along the vertical plane as well as the cognitive integration of the gravitational force field.

neuroscience↗

bioRxiv2020

Diazotrophic bacteria from maize exhibit multifaceted plant growth promotion traits in multiple hosts

Sierra Mixe maize is a geographically remote landrace variety grown on nitrogen-deficient fields in Oaxaca, Mexico that meets its nutritional requirements without synthetic fertilizer by associating with free-living diazotrophs comprising the microbiota of its aerial root mucilage. We selected nearly 500 diazotrophic bacteria isolated from Sierra Mixe maize mucilage and sequenced their genomes. Comparative genomic analysis demonstrated that isolates represented diverse genera and possessed multiple marker genes for mechanisms of direct plant growth promotion (PGP). In addition to nitrogen fixation, we examined deamination of 1-amino-1-cyclopropanecarboxylic acid, biosynthesis of indole-3-acetic acid, and phosphate solubilization. Implementing in vitro colorimetric assays revealed each isolates potential to confer the alternative PGP activities that corroborated genotype and pathway content. We examined the ability of mucilage diazotrophs to confer PGP by direct inoculation of clonally propagated potato plants in planta, which led to the identification of bio-stimulant candidates that were tested for PGP by inoculating a conventional maize variety. The results indicate that, while many diazotrophic isolates from Sierra Mixe maize possessed genotypes and in vitro phenotypes for targeted PGP traits, a subset of these organisms promoted the growth of potato and conventional maize using multiple promotion mechanisms.

microbiology↗

bioRxiv2020

Genomic characterization of a diazotrophic microbiota associated with maize aerial root mucilage

A geographically isolated maize landrace cultivated on nitrogen-depleted fields without synthetic fertilizer in the Sierra Mixe region of Oaxaca, Mexico utilizes nitrogen derived from the atmosphere and develops an extensive network of mucilage-secreting aerial roots that harbors a diazotrophic microbiota. Targeting these diazotrophs, we selected nearly 600 microbes from a collection isolated from these plants and confirmed their ability to incorporate heavy nitrogen (15N2) metabolites in vitro. Sequencing their genomes and conducting comparative bioinformatic analyses showed that these genomes had substantial phylogenetic diversity. We examined each diazotroph genome for the presence of nif genes essential to nitrogen fixation (nifHDKENB) and carbohydrate utilization genes relevant to the mucilage polysaccharide digestion. These analyses identified diazotrophs that possessed canonical nif gene operons, as well as many other operon configurations with concomitant fixation and release of >700 different 15N labeled metabolites. We further demonstrated that many diazotrophs possessed alternative nif gene operons and confirmed their genomic potential to derive chemical energy from mucilage polysaccharide to fuel nitrogen fixation. These results confirm that some diazotrophic bacteria associated with Sierra Mixe maize were capable of incorporating atmospheric nitrogen into their small molecule extracellular metabolites through multiple nif gene configurations while others were able to fix nitrogen without the canonical (nifHDKENB) genes. Data SummaryGenetic resources, including biological materials and nucleic acid sequences, were accessed under an Access and Benefit Sharing (ABS) Agreement between the Sierra Mixe community and the Mars Corporation, and with authorization from the Mexican government. An internationally recognized certificate of compliance has been issued by the Mexican government under the Nagoya Protocol for such activities (ABSCH-IRCC-MX-207343-3). Any party seeking access to the nucleic acid sequences underlying the analysis reported here is subject to the full terms and obligations of the ABS agreement and the authorization from the government of Mexico. Individuals wishing to access nucleic acid sequence data for scientific research activities should contact Mars Incorporated Chief Science Officer at CSO@effem.com.

genomics↗

bioRxiv2019

Gravity highlights a dual role of the insula in internal models

Movements rely on a mixture of predictive and reactive mechanisms. With experience, the brain builds internal representations of actions in different contexts. Many factors are taken into account in this process among which the immutable presence of gravity. Any displacement of a massive body in the gravitational field generates forces and torques that must be predicted and compensated by appropriate motor commands. Studies have shown that the insular cortex is a key brain area for graviception. However, none attempted to address whether the same internal representation of gravity is shared between reactive and predictive mechanisms. Here, participants either mentally simulated (only predictive) or performed (predictive and reactive) vertical movements of the hand. We found that the posterior part of the insular cortex was engaged when feedback was processed. The anterior insula, however, was activated only in mental simulation of the action. A psychophysical experiment shows participants ability to integrate the effects of gravity. Our results demonstrate a dual internal representation of gravity within the insula and discuss how they can conceptually be linked.

neuroscience↗

bioRxiv2017

Spatiotemporal organization of whole-body muscle activity during upright reaching movements in various directions: modularity or not modularity?

The modular control hypothesis suggests that motor commands are built from precoded modules whose specific combined recruitment can allow the performance of virtually any motor task. Despite considerable experimental support, this hypothesis remains tentative as classical findings of reduced dimensionality in muscle activity may also result from other constraints (biomechanical couplings, data averaging or low dimensionality of motor tasks). Here we assessed the effectiveness of modularity in describing muscle activity in a comprehensive experiment comprising 72 distinct point-to-point whole-body movements during which the activity of 30 muscles was recorded. To identify invariant modules of a temporal and spatial nature, we used a space-by-time decomposition of muscle activity that has been shown to encompass classical modularity models. To examine the decompositions, we focused not only on the amount of variance they explained but also on whether the task performed on each trial could be decoded from the single-trial activations of modules. For the sake of comparison, we confronted these scores to the scores obtained from alternative non-modular descriptions of the muscle data. We found that the space-by-time decomposition was effective in terms of data approximation and task discrimination at comparable reduction of dimensionality. These findings show that few spatial and temporal modules give a compact yet approximate representation of muscle patterns carrying nearly all task-relevant information for a variety of whole-body reaching movements.

neuroscience↗