# Determining the role of muscle afferent signals in cortical proprioceptive representation

> **NIH NIH F32** · NORTHWESTERN UNIVERSITY · 2021 · $54,658

## Abstract

Project Summary
The overall premise of this proposal is to understand how the transformation of the signals from proprioceptive
afferents within muscles leads to the representation of movements in somatosensory cortex. Proprioception is a
fundamental part of the neural control of movement, evidenced by extreme movement impairments in individuals
with proprioceptive loss. However, proprioception has been the topic of far less research compared to motor
outputs and other sensory modalities, so how muscle afferent signals arising from muscle spindles and Golgi
tendon organs, the peripheral afferents primarily responsible for proprioception, are transformed in the nervous
system to represent movements in S1 remains a critical, unsolved mystery.
 In the proposed work, active and passive movements of the upper limb will be utilized in order to elicit
different response characteristics from muscle spindles and Golgi tendon organs, which drive cortical
proprioceptive signals in area 3a (S1). Simultaneously, neural activity from area 3a will be recorded using a multi-
electrode array, as well as arm segment kinematics, and EMGs of proximal and distal arm muscles. Monkeys
will be trained to perform a center-out reaching task while grasping the handle of a two-link planar manipulandum.
In the horizontal plane, monkey’s arms will move via unperturbed reaches (ACT condition), passive perturbations
applied at-rest (PAS condition), or passive perturbations applied during reaches (COMB condition). These
movement conditions will elicit different muscle afferent feedback by altering combinations of movement
kinematics, forces, and gamma motor drive. Muscle spindle afferent signals will be modeled using a biophysical
model (previously developed by the PI) that accounts for both classical and paradoxical firing characteristics of
muscle spindle afferents in active and passive conditions. Golgi tendon organ afferent signals will be modeled
using the existing Mileusnic model.
 How these muscle afferent signals are transformed into movement representations in area 3a will be
analyzed in two Specific Aims. In Aim 1, a combination of the modeled afferent signals and data collected from
area 3a will be used determine how these signals are represented by area 3a neurons in all three movement
conditions. Additionally, network activity recorded from across the array in 3a will be decoded to determine what
class of movement variables are encoded in this brain area. In Aim 2, these modeled afferent inputs will be used
to drive neural network models of proprioceptive transformations to determine to compare which model produces
the most similar neural responses to area 3a. In total, these two aims provide two complimentary approaches
for determining the role of proprioceptive afferent signals in cortical proprioceptive representation. This work will
provide important foundational knowledge of how cortical proprioception arises from muscle afferents and is
important for further u...

## Key facts

- **NIH application ID:** 10213612
- **Project number:** 5F32MH120893-03
- **Recipient organization:** NORTHWESTERN UNIVERSITY
- **Principal Investigator:** Kyle Blum
- **Activity code:** F32 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2021
- **Award amount:** $54,658
- **Award type:** 5
- **Project period:** 2019-08-01 → 2022-03-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10213612

## Citation

> US National Institutes of Health, RePORTER application 10213612, Determining the role of muscle afferent signals in cortical proprioceptive representation (5F32MH120893-03). Retrieved via AI Analytics 2026-05-22 from https://api.ai-analytics.org/grant/nih/10213612. Licensed CC0.

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