Presynaptic spinal reflex modulation in children and adolescents

Children with neurodevelopmental disorders like Cerebral Palsy (CP) show improperly developed motor responses including hyperreflexia and spasticity, greatly impacting their quality of life. Investigations for treatment and improvement for quality of life in young populations need to be appropriately adjusted to assess the development of reflexes in pediatric stages. Findings in adults with spinal cord injuries (SCI) implicate changes in primary afferent depolarization (PAD), a GABAA dependent modality of presynaptic modulation of motor activity as partly responsible for these effects. PAD-mediated reflex modulation phenomena which are present in healthy children and adolescents have not been characterized. This thesis characterized how measures of PAD-mediated reflex excitability in children and adolescents compare with the same in adults. Experiments investigated soleus muscle H-reflex facilitation following tonic PAD induction via cutaneous and sub-motor threshold flexor-afferent stimulation, and post-activation depression from rate-dependent depression and supra-motor threshold flexor-afferent conditioning, in awake human subjects. Reflex facilitation and suppression in children and adolescents, reflecting excitability, resembled previous findings from neurologically healthy adults, with post-activation depression following rate-dependent depression, as well as trends indicating tonic PAD build-up in response to cutaneous conditioning. A greater level of reflex facilitation following cutaneous conditioning was observed in children than adults. Differences between younger subjects and adults in the specific protocols of post-activation depression used in these experiments were not statistically significant. The findings of this thesis have implications for research on neurodevelopmental disorders affecting motor function in children and adolescents.

Name thesis:degree_name

Master of Science (M.Sc.)

Level thesis:degree_level

Masters

Discipline thesis:degree_discipline

Health Sciences

Grantor

University of Saskatchewan

Year dc:date.issued

2025

Author dc:creator

• Dalkilic, Sara S

Advisor dc:contributor.advisor

• Norton, Jonathan A

Committee members dc:contributor.committeemember

• Donkers, Sarah J
• Farthing, Jonathan P
• Mang, Cameron S

• spinal reflex
• H-reflex
• neurophysiology
• EMG

Language dc:language.iso

en

Handle dc:identifier.uri

https://hdl.handle.net/10388/17383

OAI identifier oai:identifier

oai:harvest.usask.ca:10388/17383