1
|
Larbi MC, Messa G, Jalal H, Koutsikou S. An early midbrain sensorimotor pathway is involved in the timely initiation and direction of swimming in the hatchling Xenopus laevis tadpole. Front Neural Circuits 2022; 16:1027831. [PMID: 36619662 PMCID: PMC9810627 DOI: 10.3389/fncir.2022.1027831] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2022] [Accepted: 11/25/2022] [Indexed: 12/24/2022] Open
Abstract
Vertebrate locomotion is heavily dependent on descending control originating in the midbrain and subsequently influencing central pattern generators in the spinal cord. However, the midbrain neuronal circuitry and its connections with other brainstem and spinal motor circuits has not been fully elucidated. Vertebrates with very simple nervous system, like the hatchling Xenopus laevis tadpole, have been instrumental in unravelling fundamental principles of locomotion and its suspraspinal control. Here, we use behavioral and electrophysiological approaches in combination with lesions of the midbrain to investigate its contribution to the initiation and control of the tadpole swimming in response to trunk skin stimulation. None of the midbrain lesions studied here blocked the tadpole's sustained swim behavior following trunk skin stimulation. However, we identified that distinct midbrain lesions led to significant changes in the latency and trajectory of swimming. These changes could partly be explained by the increase in synchronous muscle contractions on the opposite sides of the tadpole's body and permanent deflection of the tail from its normal position, respectively. We conclude that the tadpole's embryonic trunk skin sensorimotor pathway involves the midbrain, which harbors essential neuronal circuitry to significantly contribute to the appropriate, timely and coordinated selection and execution of locomotion, imperative to the animal's survival.
Collapse
|
2
|
From decision to action: Detailed modelling of frog tadpoles reveals neuronal mechanisms of decision-making and reproduces unpredictable swimming movements in response to sensory signals. PLoS Comput Biol 2021; 17:e1009654. [PMID: 34898604 PMCID: PMC8699619 DOI: 10.1371/journal.pcbi.1009654] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2021] [Revised: 12/23/2021] [Accepted: 11/17/2021] [Indexed: 01/30/2023] Open
Abstract
How does the brain process sensory stimuli, and decide whether to initiate locomotor behaviour? To investigate this question we develop two whole body computer models of a tadpole. The "Central Nervous System" (CNS) model uses evidence from whole-cell recording to define 2300 neurons in 12 classes to study how sensory signals from the skin initiate and stop swimming. In response to skin stimulation, it generates realistic sensory pathway spiking and shows how hindbrain sensory memory populations on each side can compete to initiate reticulospinal neuron firing and start swimming. The 3-D "Virtual Tadpole" (VT) biomechanical model with realistic muscle innervation, body flexion, body-water interaction, and movement is then used to evaluate if motor nerve outputs from the CNS model can produce swimming-like movements in a volume of "water". We find that the whole tadpole VT model generates reliable and realistic swimming. Combining these two models opens new perspectives for experiments.
Collapse
|
3
|
Roberts A, Borisyuk R, Buhl E, Ferrario A, Koutsikou S, Li WC, Soffe SR. The decision to move: response times, neuronal circuits and sensory memory in a simple vertebrate. Proc Biol Sci 2020; 286:20190297. [PMID: 30900536 DOI: 10.1098/rspb.2019.0297] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
All animals use sensory systems to monitor external events and have to decide whether to move. Response times are long and variable compared to reflexes, and fast escape movements. The complexity of adult vertebrate brains makes it difficult to trace the neuronal circuits underlying basic decisions to move. To simplify the problem, we investigate the nervous system and responses of hatchling frog tadpoles which swim when their skin is stimulated. Studying the neuron-by-neuron pathway from sensory to hindbrain neurons, where the decision to swim is made, has revealed two simple pathways generating excitation which sums to threshold in these neurons to initiate swimming. The direct pathway leads to short, and reliable delays like an escape response. The other includes a population of sensory processing neurons which extend firing to introduce noise and delay into responses. These neurons provide a brief, sensory memory of the stimulus, that allows tadpoles to integrate stimuli occurring within a second or so of each other. We relate these findings to other studies and conclude that sensory memory makes a fundamental contribution to simple decisions and is present in the brainstem of a basic vertebrate at a surprisingly early stage in development.
Collapse
Affiliation(s)
- Alan Roberts
- 1 School of Biological Sciences, University of Bristol , Bristol BS8 1TQ , UK
| | - Roman Borisyuk
- 2 School of Computing, Electronics and Mathematics, University of Plymouth , Plymouth PL4 8AA , UK
| | - Edgar Buhl
- 1 School of Biological Sciences, University of Bristol , Bristol BS8 1TQ , UK.,3 School of Physiology, Pharmacology and Neuroscience, University of Bristol , Bristol BS8 1TD , UK
| | - Andrea Ferrario
- 2 School of Computing, Electronics and Mathematics, University of Plymouth , Plymouth PL4 8AA , UK
| | - Stella Koutsikou
- 1 School of Biological Sciences, University of Bristol , Bristol BS8 1TQ , UK.,4 Medway School of Pharmacy, University of Kent , Chatham Maritime ME4 4TB , UK
| | - Wen-Chang Li
- 5 School of Psychology and Neuroscience, University of St Andrews , St Andrews KY16 9JP , UK
| | - Stephen R Soffe
- 1 School of Biological Sciences, University of Bristol , Bristol BS8 1TQ , UK
| |
Collapse
|
4
|
Li WC, Soffe SR. Stimulation of Single, Possible CHX10 Hindbrain Neurons Turns Swimming On and Off in Young Xenopus Tadpoles. Front Cell Neurosci 2019; 13:47. [PMID: 30873004 PMCID: PMC6401594 DOI: 10.3389/fncel.2019.00047] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2018] [Accepted: 02/01/2019] [Indexed: 11/13/2022] Open
Abstract
Vertebrate central pattern generators (CPGs) controlling locomotion contain neurons which provide the excitation that drives and maintains network rhythms. In a simple vertebrate, the developing Xenopus tadpole, we study the role of excitatory descending neurons with ipsilateral projecting axons (descending interneurons, dINs) in the control of swimming rhythms. In tadpoles with both intact central nervous system (CNS) and transections in the hindbrain, exciting some individual dINs in the caudal hindbrain region could start swimming repeatedly. Analyses indicated the recruitment of additional dINs immediately after such evoked dIN spiking and prior to swimming. Excitation of dINs can therefore be sufficient for the initiation of swimming. These "powerful" dINs all possessed both ascending and descending axons. However, their axon projection lengths were not different from those of other excitatory dINs at similar locations. The dorsoventral position of dINs, as a population, significantly better matched that of cells marked by immunocytochemistry for the transcription factor CHX10 than other known neuron types in the ventral hindbrain and spinal cord. The comparison suggests that the excitatory interneurons including dINs are CHX10-positive, in agreement with CHX10 as a marker for excitatory neurons with ipsilateral projections in the spinal cord and brainstem of other vertebrates. Overall, our results further demonstrate the key importance of dINs in driving tadpole swimming rhythms.
Collapse
Affiliation(s)
- Wen-Chang Li
- School of Psychology and Neuroscience, University of St Andrews, St Andrews, United Kingdom
| | - Stephen R Soffe
- School of Biological Sciences, Tyndall Avenue, University of Bristol, Bristol, United Kingdom
| |
Collapse
|
5
|
Koutsikou S, Merrison‐Hort R, Buhl E, Ferrario A, Li W, Borisyuk R, Soffe SR, Roberts A. A simple decision to move in response to touch reveals basic sensory memory and mechanisms for variable response times. J Physiol 2018; 596:6219-6233. [PMID: 30074236 PMCID: PMC6292811 DOI: 10.1113/jp276356] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2018] [Accepted: 07/13/2018] [Indexed: 01/28/2023] Open
Abstract
KEY POINTS Short-term working memory and decision-making are usually studied in the cerebral cortex; in many models of simple decision making, sensory signals build slowly and noisily to threshold to initiate a motor response after long, variable delays. When touched, hatchling frog tadpoles decide whether to swim; we define the long and variable delays to swimming and use whole-cell recordings to uncover the neurons and processes responsible. Firing in sensory and sensory pathway neurons is short latency, and too brief and invariant to explain these delays, while recordings from hindbrain reticulospinal neurons controlling swimming reveal a prolonged and variable build-up of synaptic excitation which can reach firing threshold and initiate swimming. We propose this excitation provides a sensory memory of the stimulus and may be generated by small reverberatory hindbrain networks. Our results uncover fundamental network mechanisms that allow animals to remember brief sensory stimuli and delay simple motor decisions. ABSTRACT Many motor responses to sensory input, like locomotion or eye movements, are much slower than reflexes. Can simpler animals provide fundamental answers about the cellular mechanisms for motor decisions? Can we observe the 'accumulation' of excitation to threshold proposed to underlie decision making elsewhere? We explore how somatosensory touch stimulation leads to the decision to swim in hatchling Xenopus tadpoles. Delays measured to swimming in behaving and immobilised tadpoles are long and variable. Activity in their extensively studied sensory and sensory pathway neurons is too short-lived to explain these response delays. Instead, whole-cell recordings from the hindbrain reticulospinal neurons that drive swimming show that these receive prolonged, variable synaptic excitation lasting for nearly a second following a brief stimulus. They fire and initiate swimming when this excitation reaches threshold. Analysis of the summation of excitation requires us to propose extended firing in currently undefined presynaptic hindbrain neurons. Simple models show that a small excitatory recurrent-network inserted in the sensory pathway can mimic this process. We suggest that such a network may generate slow, variable summation of excitation to threshold. This excitation provides a simple memory of the sensory stimulus. It allows temporal and spatial integration of sensory inputs and explains the long, variable delays to swimming. The process resembles the 'accumulation' of excitation proposed for cortical circuits in mammals. We conclude that fundamental elements of sensory memory and decision making are present in the brainstem at a surprisingly early stage in development.
Collapse
Affiliation(s)
- Stella Koutsikou
- School of Biological SciencesUniversity of Bristol24 Tyndall AvenueBristolBS8 1TQUK
- Medway School of PharmacyUniversity of KentAnson Building, Central AvenueChatham MaritimeME4 4 TBUK
| | - Robert Merrison‐Hort
- School of ComputingElectronics and MathematicsUniversity of PlymouthDrake CircusPlymouthPL4 8AAUK
| | - Edgar Buhl
- School of Biological SciencesUniversity of Bristol24 Tyndall AvenueBristolBS8 1TQUK
| | - Andrea Ferrario
- School of ComputingElectronics and MathematicsUniversity of PlymouthDrake CircusPlymouthPL4 8AAUK
| | - Wen‐Chang Li
- School of Psychology and NeuroscienceUniversity of St Andrews9 South StreetSt AndrewsFifeKY16 9JPUK
| | - Roman Borisyuk
- School of ComputingElectronics and MathematicsUniversity of PlymouthDrake CircusPlymouthPL4 8AAUK
| | - Stephen R. Soffe
- School of Biological SciencesUniversity of Bristol24 Tyndall AvenueBristolBS8 1TQUK
| | - Alan Roberts
- School of Biological SciencesUniversity of Bristol24 Tyndall AvenueBristolBS8 1TQUK
| |
Collapse
|
6
|
Ferrario A, Merrison-Hort R, Soffe SR, Borisyuk R. Structural and functional properties of a probabilistic model of neuronal connectivity in a simple locomotor network. eLife 2018; 7:33281. [PMID: 29589828 PMCID: PMC5910024 DOI: 10.7554/elife.33281] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2017] [Accepted: 03/25/2018] [Indexed: 11/13/2022] Open
Abstract
Although, in most animals, brain connectivity varies between individuals, behaviour is often similar across a species. What fundamental structural properties are shared across individual networks that define this behaviour? We describe a probabilistic model of connectivity in the hatchling Xenopus tadpole spinal cord which, when combined with a spiking model, reliably produces rhythmic activity corresponding to swimming. The probabilistic model allows calculation of structural characteristics that reflect common network properties, independent of individual network realisations. We use the structural characteristics to study examples of neuronal dynamics, in the complete network and various sub-networks, and this allows us to explain the basis for key experimental findings, and make predictions for experiments. We also study how structural and functional features differ between detailed anatomical connectomes and those generated by our new, simpler, model (meta-model).
Collapse
Affiliation(s)
- Andrea Ferrario
- School of Computing, Electronics and Mathematics, University of Plymouth, Plymouth, United Kingdom
| | - Robert Merrison-Hort
- School of Computing, Electronics and Mathematics, University of Plymouth, Plymouth, United Kingdom
| | - Stephen R Soffe
- School of Biological Sciences, University of Bristol, Bristol, United Kingdom
| | - Roman Borisyuk
- School of Computing, Electronics and Mathematics, University of Plymouth, Plymouth, United Kingdom
| |
Collapse
|
7
|
Borodinsky LN. Xenopus laevis as a Model Organism for the Study of Spinal Cord Formation, Development, Function and Regeneration. Front Neural Circuits 2017; 11:90. [PMID: 29218002 PMCID: PMC5704749 DOI: 10.3389/fncir.2017.00090] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2017] [Accepted: 11/08/2017] [Indexed: 11/13/2022] Open
Abstract
The spinal cord is the first central nervous system structure to develop during vertebrate embryogenesis, underscoring its importance to the organism. Because of its early formation, accessibility to the developing spinal cord in amniotes is challenging, often invasive and the experimental approaches amenable to model systems like mammals are limited. In contrast, amphibians, in general and the African-clawed frog Xenopus laevis, in particular, offer model systems in which the formation of the spinal cord, the differentiation of spinal neurons and glia and the establishment of spinal neuron and neuromuscular synapses can be easily investigated with minimal perturbations to the whole organism. The significant advances on gene editing and microscopy along with the recent completion of the Xenopus laevis genome sequencing have reinvigorated the use of this classic model species to elucidate the mechanisms of spinal cord formation, development, function and regeneration.
Collapse
Affiliation(s)
- Laura N Borodinsky
- Department of Physiology & Membrane Biology and Institute for Pediatric Regenerative Medicine, Shriners Hospital for Children, University of California Davis School of Medicine, Sacramento, CA, United States
| |
Collapse
|
8
|
Borisyuk R, Merrison-Hort R, Soffe SR, Koutsikou S, Li WC. To swim or not to swim: A population-level model of Xenopus tadpole decision making and locomotor behaviour. Biosystems 2017; 161:3-14. [PMID: 28720508 PMCID: PMC5669369 DOI: 10.1016/j.biosystems.2017.07.004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2017] [Revised: 06/14/2017] [Accepted: 07/10/2017] [Indexed: 11/04/2022]
Abstract
We present a detailed computational model of interacting neuronal populations that mimic the hatchling Xenopus tadpole nervous system. The model includes four sensory pathways, integrators of sensory information, and a central pattern generator (CPG) network. Sensory pathways of different modalities receive inputs from an “environment”; these inputs are then processed and integrated to select the most appropriate locomotor action. The CPG populations execute the selected action, generating output in motor neuron populations. Thus, the model describes a detailed and biologically plausible chain of information processing from external signals to sensors, sensory pathways, integration and decision-making, action selection and execution and finally, generation of appropriate motor activity and behaviour. We show how the model produces appropriate behaviours in response to a selected scenario, which consists of a sequence of “environmental” signals. These behaviours might be relatively complex due to noisy sensory pathways and the possibility of spontaneous actions.
Collapse
Affiliation(s)
- Roman Borisyuk
- School of Computing, Electronics and Mathematics, University of Plymouth, Drake Circus, Plymouth, PL4 8AA, UK; Institute of Mathematical Problems of Biology, The Branch of Keldysh Institute of Applied Mathematics of Russian Academy of Sciences, Pushchino, 142290, Russia.
| | - Robert Merrison-Hort
- School of Computing, Electronics and Mathematics, University of Plymouth, Drake Circus, Plymouth, PL4 8AA, UK
| | - Steve R Soffe
- School of Biological Sciences, 24 Tyndall Avenue, University of Bristol, Bristol, BS8 1TQ, UK
| | - Stella Koutsikou
- School of Biological Sciences, 24 Tyndall Avenue, University of Bristol, Bristol, BS8 1TQ, UK
| | - Wen-Chang Li
- School of Psychology & Neuroscience, Westburn Lane, University of St Andrews, St Andrews KY16 9JP, UK
| |
Collapse
|
9
|
Koyama M, Minale F, Shum J, Nishimura N, Schaffer CB, Fetcho JR. A circuit motif in the zebrafish hindbrain for a two alternative behavioral choice to turn left or right. eLife 2016; 5. [PMID: 27502742 PMCID: PMC4978520 DOI: 10.7554/elife.16808] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2016] [Accepted: 06/30/2016] [Indexed: 11/16/2022] Open
Abstract
Animals collect sensory information from the world and make adaptive choices about how to respond to it. Here, we reveal a network motif in the brain for one of the most fundamental behavioral choices made by bilaterally symmetric animals: whether to respond to a sensory stimulus by moving to the left or to the right. We define network connectivity in the hindbrain important for the lateralized escape behavior of zebrafish and then test the role of neurons by using laser ablations and behavioral studies. Key inhibitory neurons in the circuit lie in a column of morphologically similar cells that is one of a series of such columns that form a developmental and functional ground plan for building hindbrain networks. Repetition within the columns of the network motif we defined may therefore lie at the foundation of other lateralized behavioral choices. DOI:http://dx.doi.org/10.7554/eLife.16808.001 Humans and other vertebrate animals constantly make choices about whether to respond to the left or to the right. Do they look left or right; turn left or right; reach left or right? In humans, the distinction between left and right is so fundamental that it has entered our collective thinking. Many societies define their political positions, for example, in terms of leaning to the left or to the right. However, we know little about the wiring of the brain that accomplishes the task of making physical left-right choices. Koyama et al. therefore set out to identify the neural circuit responsible for the decision to turn either left or right. Zebrafish larvae were chosen as subjects because they execute rapid left or right turns to escape predators. Given that one wrong turn can result in the death of the zebrafish, a correct choice matters more than in most of the other decisions that animals make. Experiments revealed that a process of competition between neurons on the left and right sides of the brain underlies this decision-making. Neurons on the right collect evidence that an attack is coming from the right, and drive turns to the left, away from the threat. These neurons also attempt to silence competing neurons on the left that act to produce turns to the right. By weighing up the evidence from left and right sides, the circuit as a whole comes to a decision about the best direction in which to turn. The region of the brain that controls the left versus right escape response in zebrafish is present in all vertebrates. Moreover, it appears to have a similar structure across species, consisting of repeating columns of neurons. This raises the possibility that other left-right choices in fish and other animals occur in a similar way – a principle that can be tested in future work. DOI:http://dx.doi.org/10.7554/eLife.16808.002
Collapse
Affiliation(s)
- Minoru Koyama
- Department of Neurobiology and Behavior, Cornell University, Ithaca, United States.,Howard Hughes Medical Institute, Janelia Research Campus, Ashburn, United States
| | - Francesca Minale
- Meinig School of Biomedical Engineering, Cornell University, Ithaca, United States
| | - Jennifer Shum
- Meinig School of Biomedical Engineering, Cornell University, Ithaca, United States
| | - Nozomi Nishimura
- Meinig School of Biomedical Engineering, Cornell University, Ithaca, United States
| | - Chris B Schaffer
- Meinig School of Biomedical Engineering, Cornell University, Ithaca, United States
| | - Joseph R Fetcho
- Department of Neurobiology and Behavior, Cornell University, Ithaca, United States
| |
Collapse
|
10
|
Bui TV, Roussel Y. Choosing sides: making decisions in an escape response. J Physiol 2015; 593:4303-4. [PMID: 26423211 DOI: 10.1113/jp271271] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2015] [Accepted: 07/31/2015] [Indexed: 11/08/2022] Open
Affiliation(s)
- Tuan V Bui
- Department of Biology, University of Ottawa, Ottawa, ON, Canada
| | - Yann Roussel
- Department of Biology, University of Ottawa, Ottawa, ON, Canada
| |
Collapse
|