Spinal Interneurons: Diversity and Connectivity in Motor Control

Sengupta, Mohini; Bagnall, Martha W.

doi:10.1146/annurev-neuro-083122-025325

Cited by 16 publications

(9 citation statements)

References 167 publications

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“…8A, bottom ). In our model, we include the two specific types of V2a neurons and single generic sources of recurrent and reciprocal inhibition, each of which has the potential to form connections with the other types (Sengupta and Bagnall, 2023). We do not include conserved sources of commissural excitation here (e.g., V0v and V3 neurons), but these will be important to include in any future models exploring intersegmental coordination and signal amplification (Bohm et al, 2022; Kawano et al, 2022; Wiggin et al, 2022).…”

Section: Discussionmentioning

confidence: 99%

Cell-type-specific origins of locomotor rhythmicity at different speeds in larval zebrafish

Agha,

Kishore,

McLean

2024

Preprint

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Different speeds of locomotion require heterogeneous spinal populations, but a common mode of rhythm generation is presumed to exist. Here, we explore the cellular versus synaptic origins of spinal rhythmicity at different speeds by performing electrophysiological recordings from premotor excitatory interneurons in larval zebrafish. Chx10-labeled V2a neurons are divided into at least two subtypes proposed to play distinct roles in timing and intensity control. Consistent with distinct rhythm generating and output patterning functions within the spinal V2a population, we find that one subtype is recruited exclusively at slow or fast speeds and exhibits intrinsic cellular properties suitable for rhythmogenesis at those speeds, while the other subtype is recruited more reliably at all speeds and lacks appropriate rhythmogenic cellular properties. Unexpectedly, however, phasic firing patterns during locomotion in rhythmogenic and non-rhythmogenic subtypes are best explained by distinct modes of synaptic inhibition linked to cell-type and speed. At fast speeds reciprocal inhibition in rhythmogenic V2a neurons supports phasic firing, while recurrent inhibition in non-rhythmogenic V2a neurons helps pattern motor output. In contrast, at slow speeds recurrent inhibition in rhythmogenic V2a neurons supports phasic firing, while non-rhythmogenic V2a neurons rely on reciprocal inhibition alone to pattern output. Our findings suggest cell-type-specific, not common, modes of rhythmogenesis generate and coordinate different speeds of locomotion.

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Section: Discussionmentioning

confidence: 99%

Cell-type-specific origins of locomotor rhythmicity at different speeds in larval zebrafish

Agha,

Kishore,

McLean

2024

Preprint

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“…A large body of literature, developed over a century, provides a wealth of detail on spinal cord anatomy and cell type distributions (Roome and Levine, 2023; Sengupta and Bagnall, 2023). Emerging technologies for large-scale, chronic recording and stimulation of spinal populations (Berg et al, 2009; Metuh et al, 2024; Wu et al, 2023), as well as the advancements in approaches to monitor and manipulate the well-defined spinal inputs (i.e., tactile, proprioceptive, nociceptive neurons) and outputs (i.e., motorneurons (Chung et al, 2023)) are rapidly being realized.…”

Section: Discussionmentioning

confidence: 99%

Spinal interneuron population dynamics underlying flexible pattern generation

Wimalasena,

Pandarinath,

Yong

2024

Preprint

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The mammalian spinal locomotor network is composed of diverse populations of interneurons that collectively orchestrate and execute a range of locomotor behaviors. Despite the identification of many classes of spinal interneurons constituting the locomotor network, it remains unclear how the network’s collective activity computes and modifies locomotor output on a step-by-step basis. To investigate this, we analyzed lumbar interneuron population recordings and multi-muscle electromyography from spinalized cats performing air stepping and used artificial intelligence methods to uncover state space trajectories of spinal interneuron population activity on single step cycles and at millisecond timescales. Our analyses of interneuron population trajectories revealed that traversal of specific state space regions held millisecond-timescale correspondence to the timing adjustments of extensor-flexor alternation. Similarly, we found that small variations in the path of state space trajectories were tightly linked to single-step, microvolt-scale adjustments in the magnitude of muscle output.One sentence summaryFeatures of spinal interneuron state space trajectories capture variations in the timing and magnitude of muscle activations across individual step cycles, with precision on the scales of milliseconds and microvolts respectively.

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“…In this review, we will focus on the premotor INs contained in motor circuits and how they react after different kinds of TSCI. For a broader information about the spinal circuitry responsible for the locomotion in the ventral spinal cord and central pattern generators, the authors strongly recommend reviewing the indicated publications [23][24][25][26][27][28]. neurons (MNs), which receive inputs from supraspinal centers and sensory afferents (in a direct or indirect way) and send their output to muscles and premotor interneurons (INs).…”

Section: Introductionmentioning

confidence: 99%

Potential Roles of Specific Subclasses of Premotor Interneurons in Spinal Cord Function Recovery after Traumatic Spinal Cord Injury in Adults

Dominguez-Bajo,

Clotman

2024

Cells

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The differential expression of transcription factors during embryonic development has been selected as the main feature to define the specific subclasses of spinal interneurons. However, recent studies based on single-cell RNA sequencing and transcriptomic experiments suggest that this approach might not be appropriate in the adult spinal cord, where interneurons show overlapping expression profiles, especially in the ventral region. This constitutes a major challenge for the identification and direct targeting of specific populations that could be involved in locomotor recovery after a traumatic spinal cord injury in adults. Current experimental therapies, including electrical stimulation, training, pharmacological treatments, or cell implantation, that have resulted in improvements in locomotor behavior rely on the modulation of the activity and connectivity of interneurons located in the surroundings of the lesion core for the formation of detour circuits. However, very few publications clarify the specific identity of these cells. In this work, we review the studies where premotor interneurons were able to create new intraspinal circuits after different kinds of traumatic spinal cord injury, highlighting the difficulties encountered by researchers, to classify these populations.

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Spinal Interneurons: Diversity and Connectivity in Motor Control

Cited by 16 publications

References 167 publications

Cell-type-specific origins of locomotor rhythmicity at different speeds in larval zebrafish

Cell-type-specific origins of locomotor rhythmicity at different speeds in larval zebrafish

Spinal interneuron population dynamics underlying flexible pattern generation

Potential Roles of Specific Subclasses of Premotor Interneurons in Spinal Cord Function Recovery after Traumatic Spinal Cord Injury in Adults

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