Signed Dopaminergic Asymmetry Tracks Contralateral Motor Laterality in Parkinsons Disease

Abstract

Parkinson's disease is asymmetric, but representations that collapse left--right measurements discard that direction. We separated overall dopamine-transporter availability from hemispheric distribution: mean putamen specific-binding ratio (SBR) indexed overall DaT signal, whereas signed asymmetry retained which hemisphere was relatively more affected. Signed asymmetry aligned with contralateral MDS-UPDRS Part III laterality in PPMI (n=1,367; r=0.676) and S4 (n=56; r=0.551). In 1,204 PPMI landmarks, each 0.1 asymmetry corresponded to a 0.0507 increase in 12-month laterality (95\% CI 0.0387--0.0626); held-out R² improved 0.0176 over non-directional imaging but was uncertain under a bounded link. Exploratory imaging--clinical disagreement marked lower side persistence (OR=0.491 per IQR-standardized unit; 0.297--0.711). Signed direction therefore distinguishes mirror-image and conflicting dopaminergic--motor states erased by mean-only summaries. This is a reproducible biological coordinate, not global progression, treatment benefit or clinical utility.

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BibTeX RIS

BibTeX

@misc{tirhekar2026signed,
  title = {{Signed Dopaminergic Asymmetry Tracks Contralateral Motor Laterality in Parkinsons Disease}},
  author = {H. Tirhekar and P. Yadav and C. Bajaj},
  howpublished = {bioRxiv},
  year = {2026},
  month = sep,
  doi = {10.64898/2026.09.23.753983},
  url = {https://www.biorxiv.org/content/10.64898/2026.09.23.753983v1},
  note = {CC BY-NC-ND},
}

RIS

TY  - UNPB
TI  - Signed Dopaminergic Asymmetry Tracks Contralateral Motor Laterality in Parkinsons Disease
AU  - H. Tirhekar
AU  - P. Yadav
AU  - C. Bajaj
PY  - 2026
DA  - 2026/09/23
PB  - bioRxiv
DO  - 10.64898/2026.09.23.753983
UR  - https://www.biorxiv.org/content/10.64898/2026.09.23.753983v1
AB  - Parkinson's disease is asymmetric, but representations that collapse left--right measurements discard that direction. We separated overall dopamine-transporter availability from hemispheric distribution: mean putamen specific-binding ratio (SBR) indexed overall DaT signal, whereas signed asymmetry retained which hemisphere was relatively more affected. Signed asymmetry aligned with contralateral MDS-UPDRS Part III laterality in PPMI (n=1,367; r=0.676) and S4 (n=56; r=0.551). In 1,204 PPMI landmarks, each 0.1 asymmetry corresponded to a 0.0507 increase in 12-month laterality (95\% CI 0.0387--0.0626); held-out R^2 improved 0.0176 over non-directional imaging but was uncertain under a bounded link. Exploratory imaging--clinical disagreement marked lower side persistence (OR=0.491 per IQR-standardized unit; 0.297--0.711). Signed direction therefore distinguishes mirror-image and conflicting dopaminergic--motor states erased by mean-only summaries. This is a reproducible biological coordinate, not global progression, treatment benefit or clinical utility.
ER  -

Abstract

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