Title: Modulation of Motor Unit Behaviour During Standing Balance
Thesis Supervisors: Dr. Mark Carpenter
Committee Member: Dr. J Timothy Inglis, Dr. Brian Dalton
Chair: Dr. Romeo Chua
Abstract:
Balance control relies on the continuous integration of sensory input with spinal and supraspinal motor commands, yet it remains unclear how additional sensory perturbations and psychological states modulate motor unit behaviour during standing. Previous research has characterized global muscle activity and mechanical strategies for maintaining posture. However, these measures cannot fully explain the neural mechanisms underlying balance. Examining individual motor units offers insight into these mechanisms, revealing how neural control adapts to altered sensory input, dynamic postural demands, or postural threat.
This thesis aims to investigate how motor unit behaviour is modulated during standing balance across four different experimental contexts. Study 1 will examine whether cutaneous vibration alters motor unit recruitment strategies in postural muscles during quiets standing. Study 2 will extend on this work by testing if vibration influences motor unit behaviour during dynamic balance perturbations. Together, these studies will address how additional somatosensory input affects sensorimotor integration in static and dynamic postural tasks. Study 3 will investigate how anxiety related changes in brain stem systems modulate intrinsic motoneuron properties, leading to altered motor unit behaviour under postural threat. Study 4 explores the neural mechanisms underlying increased sensory gain during threat by addressing how additional somatosensory input modifies motor unit activity.
Overall, this thesis aims to extend our current understanding of balance behaviour by examining neural mechanisms at the motor unit level in which sensory feedback, intrinsic motoneuron excitability, and psychological state shape postural control.