Effect of binocular visual cue availability on fruit and insect grasping performance in two cheirogaleids: Implications for primate origins hypotheses.

Forward-facing eyes with parallel optic axes, which provide a wide field of binocular vision and precise depth perception, are among the diagnostic features of crown primates; however, the adaptive significance of this feature remains contentious. Two of the most prominent primate-origins hypotheses propose that either foraging for fruit or nocturnal predation on insects created selective pressures that led to the evolution of diagnostic primate traits, including a wide binocular field. To determine whether either of these hypotheses provides a viable explanation for the evolution of primates' derived eye orientation, the importance of binocular depth cues for the two tasks invoked by these hypotheses was evaluated experimentally in Microcebus murinus and Cheirogaleus medius, cheirogaleids' considered reasonable living analogs of the earliest euprimates. Performance in grasping insects and fruit was evaluated when the animals made use of their full binocular visual field and when their binocular visual field was restricted using a helmet-mounted blinder. Restriction of the binocular field had no effect on fruit grasping performance; however, restriction of the binocular field resulted in a significant deficit in insect predation performance. Differences in behavioral variables also suggest that insect predation is a more visually demanding task than fruit foraging. These results support the role of insect predation, but not fruit foraging, in contributing to the selective pressures that led to the evolution of parallel optic axes and a wide binocular field in crown primates.

Postural Stability When Grasping an Object While Standing: Younger and Older Adults (Fallers and Non-Fallers).

We investigated postural stability through the margin of stability (MoS) while reaching and grasping an object with increasing difficulty levels in younger, fallers and non-fallers. Forty-five individuals distributed into three groups participated in this study: younger adults (YA), non-fallers (OA), and fallers (FOA). They stood upright and reached and grasped a dowel. Six conditions combining the stability of the dowel's base and obstacles close to the dowel were manipulated to characterize different difficulty levels. We computed the MoS in both anterior-posterior (AP) and medial-lateral (ML) directions in the interval between reaching onset and dowel contact. From the MoS time series, we analyzed the minimum and maximum, including the time of occurrence of these events. The MoS was smaller for OA than for YA in both directions. In the ML direction, the minimum MoS was smaller for FOA than for YA. The minimum MoS took place earlier for FOA than YA in the AP direction. FOA and OA exhibited similar behavior with reduced MoS, suggesting impaired postural control during reaching-to-grasping in a standing posture. FOA used a more cautious strategy by reverting the MoS earlier than YA, allowing them to increase their MoS before YA when preparing to grasp the dowel.

Effect of the habitat and tusks on trunk grasping techniques in African savannah elephants.

Among tetrapods, grasping is an essential function involved in many vital behaviours. The selective pressures that led to this function were widely investigated in species with prehensile hands and feet. Previous studies namely highlighted a strong effect of item properties but also of the species habitat on manual grasping behaviour. African savannah elephants (Loxodonta africana) are known to display various prehensile abilities and use their trunk in a large diversity of habitats. Composed of muscles and without a rigid structure, the trunk is a muscular hydrostat with great freedom of movement. This multitasking organ is particularly recruited for grasping food items while foraging. Yet, the diet of African savannah elephants varies widely between groups living in different habitats. Moreover, they have tusks alongside the trunk which can assist in grasping behaviours, and their tusk morphologies are known to vary considerably between groups. Therefore, in this study, we investigate the food grasping techniques used by the trunk of two elephant groups that live in different habitats: an arid study site in Etosha National Park in Namibia, and an area with consistent water presence in Kruger National Park in South Africa. We characterised the tusks profiles and compared the grasping techniques and their frequencies of use for different foods. Our results show differences in food-grasping techniques between the two groups. These differences are related to the food item property and tusk profile discrepancies highlighted between the two groups. We suggest that habitat heterogeneity, particularly aridity gaps, may induce these differences. This may reveal an optimisation of grasping types depending on habitat, food size and accessibility, as well as tusk profiles.

Back to the water: Tongue morphology associated to contrasting lifestyles in two Andean frogs of the genus Telmatobius.

The evolution of the tongue in tetrapods is associated with feeding in the terrestrial environment. This study analyzes the tongue morphology of two closely related frog species, Telmatobius oxycephalus and T. rubigo, which exhibit contrasting feeding mechanisms. Telmatobius oxycephalus, a semi-aquatic species, relies on its tongue to capture terrestrial prey whereas T. rubigo, a secondarily aquatic species, uses suction feeding not involving the tongue. Through anatomical, histological and scanning electron microscopy analyses, we revealed remarkable differences in tongue morphology between these species. Telmatobius oxycephalus exhibits a well-developed tongue whose dorsal epithelium has numerous and slender filiform papillae. The epithelial cells of the papillae are protruded and have a complex array of microridges. In contrast, T. rubigo possesses a reduced tongue with flat and less numerous filiform papillae. The epithelial cells are completely flat and lack microridges. These findings highlight the remarkable adaptability of lingual morphology in Telmatobius to respond to the contrasting ecological niches and prey capture mechanisms. This study sheds light on the relationship between tongue shape and the different functional demands, contributing to our understanding of the evolution of prey capture mechanisms in amphibians.

A novel tool for characterising upper limb function in progressive multiple sclerosis through kinematic assessment.

INTRODUCTION: Current upper limb assessment methods in MS rely on measuring duration in tasks like the nine-hole peg test (9HPT). Kinematic techniques may provide a more useful measure of functional change in clinical and research practice. The aim of this study was to assess upper limb function prospectively in people with progressive MS using a kinematic 3D motion capture system and compare with current measures. METHODS: 42 people with progressive MS (PwPMS) and 15 healthy controls reached-and-grasped different objects whilst recorded by a kinematic assessment system. 9HPT, Expanded Disability Status Scale (EDSS), and patient reported outcome measures (PROs) were collected. All measures were taken at baseline for PwPMS and controls, and again at six months for PwPMS. RESULTS: Relative to controls, PwPMS had significantly longer reaction (0.11 s, p < 0.05) and reach (0.25 s, p < 0.05) times. PwPMS took longer to pick-up (0.34 s, p < 0.05), move (0.14 s, p < 0.05), and place (0.18 s, p < 0.05) objects. PwPMS had lower peak velocities when reaching (7.4 cm/s, p < 0.05) and moving (7.3 cm/s, p < 0.05) objects. Kinematic assessment demonstrated consistent differences between PwPMS with mild and severe upper limb dysfunction as defined by PROs, which were not captured by 9HPT or EDSS in this group. PwPMS demonstrated altered grip apertures profiles, as measured by their ability to complete individual parts of the reach and grasp task, between the baseline and follow-up timepoints. CONCLUSIONS: We have created and tested a novel upper limb function assessment tool which has detected changes and characteristics in hand function, not currently captured by the EDSS and 9HPT.

Time-independent relationship between digits closure velocity and hand transport acceleration during reach-to-grasp movements.

Prehension movements in primates have been extensively studied for decades, and hand transport and hand grip adjustment are usually considered as the main components of any object reach-to-grasp action. Evident temporal patterns were found for the velocity of the hand during the transport phase and for the digits kinematics during pre-shaping and enclosing phases. However, such kinematics were always analysed separately in regard to time, and never studied in terms of dependence one from another. Nevertheless, if a reliable one-to-one relationship is proven, it would allow reconstructing the digit velocity (and position) simply by knowing the hand acceleration during reaching motions towards the target object, ceasing the usual dependence seen in literature from time of movement and distance from the target. In this study, the aim was precisely to analyse reach-to-grasp motions to explore if such relationship exists and how it can be formulated. Offline and real-time results not only seem to suggest the existence of a time-independent, one-to-one relationship between hand transport and hand grip adjustment, but also that such relationship is quite resilient to the different intrinsic and extrinsic properties of the target objects such as size, shape and position.

Kinematic Assessment of Fine Motor Skills in Children: Comparison of a Kinematic Approach and a Standardized Test.

Deficits in fine motor skills have been reported in some children with neurodevelopmental disorders such as amblyopia or strabismus. Therefore, monitoring the development of motor skills and any potential improvement due to therapy is an important clinical goal. The aim of this study was to test the feasibility of performing a kinematic assessment within an optometric setting using inexpensive, portable, off-the-shelf equipment. The study also assessed whether kinematic data could enhance the information provided by a routine motor function screening test (the Movement Assessment Battery for Children, MABC). Using the MABC-2, upper limb dexterity was measured in a cohort of 47 typically developing children (7-15 years old), and the Leap motion capture system was used to record hand kinematics while children performed a bead-threading task. Two children with a history of amblyopia were also tested to explore the utility of a kinematic assessment in a clinical population. For the typically developing children, visual acuity and stereoacuity were within the normal range; however, the average standardized MABC-2 scores were lower than published norms. Comparing MABC-2 and kinematic measures in the two children with amblyopia revealed that both assessments provide convergent results and revealed deficits in fine motor control. In conclusion, kinematic assessment can augment standardized tests of fine motor skills in an optometric setting and may be useful for measuring visuomotor function and monitoring treatment outcomes in children with binocular vision anomalies.

Postural control during gait termination and prehension.

BACKGROUND: Challenges to postural stability emerge in the transition from locomotion to a standing posture as during gait termination, often accompanied by another task (e.g., opening a door), which may complicate control. However, less is known about postural control during terminating gait while engaged in a secondary manual task. RESEARCH QUESTION: What are the changes in postural control when terminating gait with and without a prehension task? METHODS: In a cross-sectional design, 15 healthy young adults (M=8, F=7; 27±2 years; 69±13 kg; 171±8 cm) underwent both a single task gait termination (GTO) and dual task (gait termination plus reaching; GTR). Postural Time-to-Contact (TtC) was measured using Center of Pressure (CoP) and the sternum position in anterior-posterior (AP) and medial-lateral (ML) directions over two different phases: preparatory phase and stabilization phase. Five successful trials were recorded to obtain a mean TtC. For statistical analysis of TtC, a two-tailed paired t-test was used (p =.05) as normality was satisfied. RESULTS: For the preparatory phase, there were no differences for the CoP, but TtC of the sternum position in AP was shorter in GTR than GTO (p =.001). Meanwhile, for the stabilization phase, TtCs of both the CoP and sternum position were longer in GTR in both AP and ML directions (p's <.001). SIGNIFICANCE: We suggest that for the preparatory phase, the shorter TtC of the sternum position with intact TtC of the CoP in GTR indicates that healthy young individuals are flexible, in that they smoothly integrate CoP control with the upper body demands required to also perform the prehension task. Meanwhile, for the stabilization phase, the longer TtC in dual termination and prehension task indicates that the perturbation imposed by the prehension movement did not result in reduced stabilization when returning to an upright posture.

Effects of the motivation focus on manual grasping

We have shown before that grasping movements from a given starting position to a given object differ substantially when performed as a typical laboratory task (L) and when they are embedded in an everyday-like context (E). The present study investigates whether this context-dependence is related to the subjects' motivation focus. We manipulated subjects' motivation focus and observed significant effects of Context on performance, as in previous work, but also significant effects of Motivation and Context x Motivation on performance. The interaction term could not be interpreted as generally higher or lower motivation sensitivity in L than in E, and therefore it doesn't support the hypothesis that context-dependence of grasping can be reduced to motivation-dependence. We conclude that some brain areas contribute differently to L and to E, thus producing context-dependence, and that those areas are differently sensitive to motivation...

As durações do devir: como construir objetos-problema com a cartografia / The durations of the becoming: how to building problem-objects with cartography

Como podemos falar de objetos, duração e estabilidade em um mundo feito de vertigem e puro fluxo? Este artigo propõe a problematização do conceito de objeto na prática cartográfica para pensar a formação do cartógrafo. Para tanto, necessitamos ultrapassar o dualismo entre estável e instável. Por meio de conceitos como os de tensão e complexidade podemos produzir uma ontologia metaestável. Para produzir esta ontologia relacional, criativa e complexa, vamos usar uma caixa de ferramentas conceitual advinda de dois autores. De Henri Bergson tomaremos os conceitos de duração, intuição, seleção e sentido. De A. N. Whitehead tomaremos os conceitos de preensão, sentires e criação. A partir desses conceitos produziremos um conceito de objeto adequado ao empirismo transcendental e suas virtualidades, um conceito de objeto que ultrapasse os dualismos entre os fluidos e os sólidos: objeto-acontecimento, objeto-problema.

How can you talk about objects, during and stability and a world made of vertigo and pure fluxes? This article proposes a question about the concept of object in the cartography, to work the formation of the researcher. We need to go beyond the dualism between stable and instable. With concepts like tension and complexity we can produce a metastable ontology. To elaborate this relational, complex and creativity ontology we will use some concepts that can be very useful like a tool box. From Henri Bergson we will catch the following concepts: duration, intuition, selection and felt. From Alfred North Whitehead, we will catch the concepts of prehension, feelings, creation. Working a complexity and relational ontology with this concepts, we will be producing an object without form and substance, beyond the dualism and the necessary essential. An object with a virtual dimension, on a transcendental empiricism: the event-object, the problem-object.