Biology subjects

Chiappe, M. E.

Publications and source records attributed to Chiappe, M. E..

4 recordsLinked to original sources

bioRxiv2023

A competitive disinhibitory network for robust optic flow processing in Drosophila

Many animals rely on optic flow for navigation, using differences in eye image velocity to detect deviations from their intended direction of travel. However, asymmetries in image velocity between the eyes are often overshadowed by strong, symmetric translational optic flow during navigation. Yet, the brain efficiently extracts these asymmetries for course control. While optic flow sensitive-neurons have been found in many animal species, far less is known about the postsynaptic circuits that support such robust optic flow processing. In the fly Drosophila melanogaster, a group of neurons called the horizontal system (HS) are involved in course control during high-speed translation. To understand how HS cells facilitate robust optic flow processing, we identified central networks that connect to HS cells using full brain electron microscopy datasets. These networks comprise three layers: convergent inputs from different, optic flow-sensitive cells, a middle layer with reciprocal, and lateral inhibitory interactions among different interneuron classes, and divergent output projecting to both the ventral nerve cord (equivalent to the vertebrate spinal cord), and to deeper regions of the fly brain. By combining two-photon optical imaging to monitor free calcium dynamics, manipulating GABA receptors and modeling, we found that lateral disinhibition between brain hemispheres enhance the selectivity to rotational visual flow at the output layer of the network. Moreover, asymmetric manipulations of interneurons and their descending outputs induce drifts during high-speed walking, confirming their contribution to steering control. Together, these findings highlight the importance of competitive disinhibition as a critical circuit mechanism for robust processing of optic flow, which likely influences course control and heading perception, both critical functions supporting navigation.

neuroscience↗

bioRxiv2021

Walking strides direct rapid and flexible recruitment of visual circuits for course control in

Flexible mapping between activity in sensory systems and movement parameters is a hallmark of successful motor control. This flexibility depends on continuous comparison of short-term postural dynamics and the longer-term goals of an animal, thereby necessitating neural mechanisms that can operate across multiple timescales. To understand how such body-brain interactions emerge to control movement across timescales, we performed whole-cell patch recordings from visual neurons involved in course control in Drosophila. We demonstrate that the activity of leg mechanosensory cells, propagating via specific ascending neurons, is critical to provide a clock signal to the visual circuit for stride-by-stride steering adjustments and, at longer timescales, information on speed-associated motor context to flexibly recruit visual circuits for course control. Thus, our data reveal a stride-based mechanism for the control of high-performance walking operating at multiple timescales. We propose that this mechanism functions as a general basis for adaptive control of locomotion.

neuroscience↗

bioRxiv2019

Motor context coordinates visually guided walking in Drosophila

Course control is critical for the acquisition of spatial information during exploration and navigation, and it is thought to rely on neural circuits that process locomotive-related multimodal signals. However, which circuits underlie this control, and how multimodal information contributes to the control system are questions poorly understood. We used Virtual Reality to examine the role of self-generated visual signals (visual feedback) on the control of exploratory walking in flies. Exploratory flies display two distinct motor contexts, characterized by low speed and fast rotations, or by high speed and slow rotations, respectively. Flies use visual feedback to control body rotations, but in a motor-context specific manner, primarily when walking at high speed. Different populations of visual motion-sensitive cells estimate body rotations via congruent, multimodal inputs, and drive compensatory rotations. However, their effective contribution to course control is dynamically tuned by a speed-related signal. Our data identifies visual networks with a multimodal circuit mechanism for adaptive course control and suggests models for how visual feedback is combined with internal signals to guide exploratory course control.

neuroscience↗

bioRxiv2019

A single microRNA system controls complex movement in morphologically distinct forms of Drosophila

Movement is the main output of the nervous system. It emerges during development to become a highly coordinated physiological process essential to the survival and adaptation of the organism to the environment. Similar movements can be observed in morphologically-distinct developmental stages of an organism, but it is currently unclear whether these movements have a common or diverse molecular basis. Here we explore this problem in Drosophila focusing on the roles played by the microRNA (miRNA) locus miR-iab4/8 which was previously shown to be essential for the fruit fly larva to correct its orientation if turned upside down (self-righting) (Picao-Osorio et al., 2015). Our study shows that miR-iab4 is required for normal self-righting across all three Drosophila larval stages. Unexpectedly, we also discover that this miRNA is essential for normal self-righting behaviour in the Drosophila adult, an organism with radically different morphological and neural constitution. Through the combination of gene-expression, optical imaging and quantitative behavioural approaches we provide evidence that miR-iab4 exerts its effects on adult self-righting behaviour through repression of the Hox gene Ultrabithorax (Ubx) (Morgan, 1923; Sanchez-Herrero et al., 1985) in a specific set of motor neurons that innervate the adult Drosophila leg. Our results show that this miRNA-Hox module affects the function, rather than the morphology of motor neurons and indicate that post-developmental changes in Hox gene expression can modulate behavioural outputs in the adult. Altogether our work reveals that a common miRNA-Hox genetic module can control complex movement in morphologically-distinct organisms and describes a novel post-developmental role of the Hox genes in adult neural function.

neuroscience↗