The flow and disintegration of sensory information in the spinal circuitry

A.H. Stienen, A.C. Schouten

    Research output: Contribution to conferencePoster

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    Abstract

    Bashor (1998) created a large-scale biological neural network model and used it to study the dynamic interactions in neuron populations. We adapted the model to control a single-joint musculoskeletal model during a postural task (Stienen et al., 2007). The biological neural network controls the motoneuron firing rate by combining the tonic descending excitation and the muscle spindle and Golgi tendon organ proprioceptor signals.

    The network with a total of 2298 neurons consists of motoneurons and several types of interneurons in six antagonistic population pairs: the motoneurons (169 neurons per pair-half) directly drive the muscles; the interneurons (five types, 196 neurons per pair-half) are exciting or inhibiting---and possibly recurrent or reciprocal---intermediates for passing the Ia (muscle length and velocity), Ib (muscle force) and II afferent (muscle length) information received from the proprioceptors on to the motoneurons. The model parameters are based on spinal recordings in cats, which are assumed to be functionally comparable with humans. With this model we showed that the model mimics the findings of human postural experiments using presynaptic inhibition of the Ia-afferents to modulate the feedback gains, with both human and model able to achieve negative feedback gains. In a pathological example, disabling one specific interneural connection simulates the experimental results in complex regional pain syndrome patients. We have further investigated the flow of sensory information in the spinal circuitry. Two aspects seem to dominate the outcome: the number of synapses the information crosses and the total stimulation effect of all inhibitory and excitatory connections.

    The proprioceptive feedback reaches the motoneurons directly or via one or more intermediating interneurons. The number of synaptic connections classifies these paths. For instance, for the monosynaptic stretch reflex the spinal information crosses only one synapse between muscle spindle and motoneuron. Paths that cross two or three synapses between sensor and motoneurons are called di- and trisynaptic. The influence decreases with the number of synapses due to information dilution. We found that paths that cross more than three synapses can be ignored.

    Paths can provide positive or negative stimulation to the motoneurons. Crossing one reciprocal or one inhibitory synapse will make the stimulus negative; crossing another makes the stimulus positive again. The total stimulation effect of the path on the motoneuron can be calculated. Note that positive stimulation results in a negative feedback path with positive gain components in feedback control diagrams.

    With a modeling study we investigated the effect of the sensorimotor interaction on the phase-frequency relationship of the CMC. The model includes two systems, representing the efferent and afferent pathways modeled as gains and realistic neural time delays. We found that the closed-loop formed by the sensorimotor interaction has a huge effect on the phase-frequency relationship, depending on the relative strength of the afferent pathways. Within the beta band the slope of the phase-frequency relation is reduced (i.e. is less negative than expected for a pure efferent pathway) and has a nonzero intersect. If the afferent pathways are stronger than the efferent pathways a phase advance will result, i.e. the slope can become positive. In conclusion, the phase-frequency relation emerges from the interaction in the sensorimotor loop and here we demonstrated how the relation depends on a complex interaction between the afferent and efferent pathways.
    Original languageEnglish
    Number of pages1
    Publication statusPublished - 16 Oct 2012
    EventSociety for Neuroscience Annual Meeting, Neuroscience 2012 - New Orleans, United States
    Duration: 13 Oct 201217 Oct 2012

    Conference

    ConferenceSociety for Neuroscience Annual Meeting, Neuroscience 2012
    Abbreviated titleNeuroscience 2012
    CountryUnited States
    CityNew Orleans
    Period13/10/1217/10/12

    Keywords

    • Network
    • Model
    • Sensory

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  • Cite this

    Stienen, A. H., & Schouten, A. C. (2012). The flow and disintegration of sensory information in the spinal circuitry. Poster session presented at Society for Neuroscience Annual Meeting, Neuroscience 2012, New Orleans, United States.