A method for selective stimulation of leg chemoreceptors in whole crustaceans

The integration of sensory information with adequate motor outputs is critical for animal survival. Here, we present an innovative technique based on a non-invasive closed-circuit device consisting of a perfusion/stimulation chamber chronically applied on a single leg of the crayfish Procambarus clarkii. Using this technique, we focally stimulated the leg inside the chamber and studied the leg-dependent sensory-motor integration involving other sensory appendages, such as antennules and maxillipeds, which remain unstimulated outside the chamber. Results show that the stimulation of a single leg with chemicals, such as disaccharides, is sufficient to trigger a complex search behaviour involving locomotion coupled with the reflex activation of antennules and maxillipeds. This technique can be easily adapted to other decapods and/or other sensory appendages. Thus, it has opened possibilities for studying sensory-motor integration evoked by leg stimulation in whole aquatic animals under natural conditions to supplement, with a direct approach, current ablation/silencing techniques.

Deliberate practice

A large volume of research has shown that acquiring expertise in any domain is heavily influenced by the amount of deliberate practice (DP) the performer engages in over time. This chapter provides an overview of Ericsson’s highly influential theory of deliberate practice (DP) and argues that DP is essential if performers are to maintain and improve their skill levels over time. One of the primary goals is to distinguish between mechanical practice and DP. In doing so, the chapter posits that mechanical practice involves mindless repetition of well-learned skills while DP involves the use of reflective and self-regulatory processes to identify and correct errors (movement patterns that produce undesirable motor outputs) and to inspire exploratory behaviour. The chapter also argues that DP activities are often characterized by experimentation, playfulness, and enjoyment and that these are important components of expertise because they increase one’s motivation or desire to stick with difficult tasks.

An Extended Model for Ripple Analysis of 2–4 Phase Resonant Electrostatic Induction Motors

Electrostatic motors are promising forms of actuation for future robotic devices. The study of their different implementations should accelerate their adoption. Current models for resonant electrostatic induction motors were found not to be able to properly describe their behavior, namely, with regard to changes with position. This paper reports a new analytical model for these motors, aiming to address this issue. The model is based on identification of all capacitance harmonics, through a simplified method. Using these, equations for different motor parameters, notably, thrust force, were obtained and compared to previous literature. The new equations model position dependent properties, such as force ripple. The outputs of this model were validated through experimentation with a prototype, with the results confirming the new model better describes motor behavior. An analysis into how to decrease this ripple was also discussed and tested. We concluded that the use of a higher number of harmonics resulted in a much more accurate model, capable of adequately characterizing motor outputs with changes in position.

A distributed circuit for associating environmental context with motor choice in retrosplenial cortex

During navigation, animals often use recognition of familiar environmental contexts to guide motor action selection. The retrosplenial cortex (RSC) receives inputs from both visual cortex and subcortical regions required for spatial memory and projects to motor planning regions. However, it is not known whether RSC is important for associating familiar environmental contexts with specific motor actions. We test this possibility by developing a task in which motor trajectories are chosen based on the context. We find that mice exhibit differential predecision activity in RSC and that optogenetic suppression of RSC activity impairs task performance. Individual RSC neurons encode a range of task variables, often multiplexed with distinct temporal profiles. However, the responses are spatiotemporally organized, with task variables represented along a posterior-to-anterior gradient along RSC during the behavioral performance, consistent with histological characterization. These results reveal an anatomically organized retrosplenial cortical circuit for associating environmental contexts with appropriate motor outputs.

Modeling Post-Scratching Locomotion with Two Rhythm Generators and a Shared Pattern Formation

This study aimed to present a model of post-scratching locomotion with two intermixed central pattern generator (CPG) networks, one for scratching and another for locomotion. We hypothesized that the rhythm generator layers for each CPG are different, with the condition that both CPGs share their supraspinal circuits and their motor outputs at the level of their pattern formation networks. We show that the model reproduces the post-scratching locomotion latency of 6.2 ± 3.5 s, and the mean cycle durations for scratching and post-scratching locomotion of 0.3 ± 0.09 s and 1.7 ± 0.6 s, respectively, which were observed in a previous experimental study. Our findings show how the transition of two rhythmic movements could be mediated by information exchanged between their CPG circuits through routes converging in a common pattern formation layer. This integrated organization may provide flexible and effective connectivity despite the rigidity of the anatomical connections in the spinal cord circuitry.

Understanding the Prefrontal Cortex

The primate prefrontal cortex sits at the top of the sensory, motor, and outcome processing hierarchies of the neocortex. It transforms sensory inputs into motor outputs, determining the response that is appropriate given the current context and desired outcome. This transformation involves conditional rules. The dorsal prefrontal cortex supports the learning of behavioural sequences, where the next action is conditional on the previous one. The ventral prefrontal cortex supports associations between objects, where the choice of one object is conditional on the presence of another object. However, because hierarchical processing supports the extraction of abstract representations, the primate prefrontal cortex is able to represent conditional rules that are abstract, meaning that they apply irrespective of the specific inputs. The selective advantage is that by learning these rules, primates can solve new problems rapidly when they have the same conditional logic as prior problems. The human prefrontal cortex has the same fundamental organization as in other primates. The dorsal prefrontal cortex supports the understanding of sequences and the ventral prefrontal cortex supports the ability to learn semantic associations. Thus the human prefrontal cortex has co-opted and elaborated mechanisms that were present in ancestral primates. These mechanisms can be used for new ends. For example, words have been associated with objects so as to communicate with others. This means that to understand human intelligence it is necessary to take into account the fact that the abstract rules are transmitted verbally from one generation to another.

Haltere and visual inputs sum linearly to predict wing (but not gaze) motor output in tethered flying Drosophila

In the true flies (Diptera), the hind wings have evolved into specialized mechanosensory organs known as halteres, which are sensitive to gyroscopic and other inertial forces. Together with the fly's visual system, the halteres direct head and wing movements through a suite of equilibrium reflexes that are crucial to the fly's ability to maintain stable flight. As in other animals (including humans), this presents challenges to the nervous system as equilibrium reflexes driven by the inertial sensory system must be integrated with those driven by the visual system in order to control an overlapping pool of motor outputs shared between the two of them. Here, we introduce an experimental paradigm for reproducibly altering haltere stroke kinematics and use it to quantify multisensory integration of wing and gaze equilibrium reflexes. We show that multisensory wing-steering responses reflect a linear superposition of haltere-driven and visually driven responses, but that multisensory gaze responses are not well predicted by this framework. These models, based on populations, extend also to the responses of individual flies.

A Distributed Circuit for Associating Environmental Context to Motor Choice in Retrosplenial Cortex

ABSTRACTDuring navigation, animals often use recognition of familiar environmental contexts to guide motor action selection. The retrosplenial cortex (RSC) receives inputs from both visual cortex and subcortical regions required for spatial memory, and projects to motor planning regions. However, it is not known whether RSC is important for associating familiar environmental contexts with specific motor actions. Here, we test this possibility by developing a task in which trajectories are chosen based on the context. We find that mice exhibit differential pre-decision activity in RSC, and that optogenetic suppression of RSC activity impairs task performance. Individual RSC neurons encode a range of task variables, often multiplexed with distinct temporal profiles. However, the responses are spatiotemporally organized, with task variables represented along a posterior-to-anterior gradient along RSC during the behavioral performance, consistent with histological characterization. These results reveal an anatomically-organized retrosplenial cortical circuit for associating environmental contexts to appropriate motor outputs.