Author's School

School of Medicine

ORCID

https://orcid.org/0009-0006-9755-8933

Author's Department/Program

Rehabilitation and Participation Science

Language

English (en)

Date of Award

8-15-2026

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Chair and Committee

Lisa T. Connor

Committee Members

Benjamin A. Philip, Ian Dobbins, Keith R. Lohse, Muriah D. Wheelock

Abstract

Peripheral nerve injury (PNI) in the upper extremity results in significant sensorimotor impairment. Nearly 40-50% of patients affected by PNI fail to restore normal hand and arm function and recovery remains variable. Recovery related cortical plasticity is recognized as an important factor, though its relationship to meaningful outcomes remains unclear. This dissertation examined how cortical activity patterns relate to functional recovery after PNI through a systematic review and three subsequent cross-sectional studies.

The systematic review of multimodal neuroimaging studies on cortical plasticity after upper extremity nerve transfer found that good recovery is generally linked to restoration of contralateral or typical cortical representations, but this relationship was inconsistent. Also, variability across studies, methodological differences, and the focus on impairment-level outcomes limited understanding of how neural plasticity was related to functional recovery. Despite the limitations, three knowledge gaps were identified: limited assessment of activity-level outcomes, insufficient evidence on functional connectivity during real world motor tasks, and limited understanding of how individual differences in neural representation are linked to individual differences in motor behavior. These gaps were addressed in the three empirical studies that followed.

To address the first gap, a cross-sectional study examined participation outcomes in adults with unilateral PNI. Participation was quantified as activity retention (percentage of pre-injury activities retained) using the Activity Card Sort (ACS), with activities categorized according to their motor demand dimensions. Results showed that activity retention was not explained by motor demands alone; participants retained fewer gross motor than fine motor activities, unimanual activities were retained more than bimanual activities, and hand dexterity measures were not associated with fine motor activities retention. These findings indicate that participation following PNI is influenced by factors beyond motor impairment alone.

To address the second gap, a cross-sectional study investigated task-based functional connectivity (FC) during an ecologically valid fine motor drawing task in patients following peripheral nerve surgery compared with healthy controls. Seed based functional connectivity analysis with the left primary motor cortex (M1) during right hand drawing was used. Results showed that patients exhibited greater functional connectivity with right visual and premotor cortices compared to healthy controls. Differences in FC with M1 were also observed by surgical groups: individuals who underwent nerve transfer demonstrated greater connectivity between left M1 and right inferior parietal regions relative to those who had nerve repair. FC was not linearly associated with months since surgery. However, exploratory analyses suggested involvement of inferior parietal regions in earlier stages of recovery that diminishes over time. These findings indicate that recovery following PNI surgery is supported by distinct, task-dependent patterns of FC and point to the importance of incorporating functionally relevant training in rehabilitation.

To address the third gap, a cross-sectional study examined how individual differences in neural representational structure during fine motor drawing task relate to the representational structure of drawing variables and real world hand use following PNI surgery. Neural representational structure in the left primary motor cortex (M1) and dorsal premotor region (PMd) was significantly associated with the representational structure of both behavioral measures in the full study sample. An exploratory (group specific) analysis revealed that patients showed the same significant neural–behavioral associations observed in the full sample, compared to healthy controls. A second exploratory analysis using a regression based weighted model further demonstrated that parietal and cerebellar regions contributed the most to the representational structure of the two behavioral measures (draw, Use) which supports the involvement of distributed sensorimotor networks. These findings indicate that neural and behavioral recovery can be meaningfully linked and highlight the value of multidimensional behavioral assessments for understanding cortical plasticity after PNI.

DOI

https://doi.org/10.48765/28jp-gq37

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