BIOBRIEFPAPER
Parkinson's and related Lewy body diseases often bring depression, and a small new MRI study finds a candidate signal in the hippocampus, not the usual mood circuits.
Depression, anxiety, and apathy are among the most disabling symptoms of Parkinson's and the related Lewy body diseases, and no brain scan can yet flag them. A small new high-resolution MRI study points at one candidate signal, sitting in the hippocampus, a memory structure, rather than the mood circuits most readers would expect.
Published in Hippocampus and indexed on PubMed (PMID 42717433), the work scanned 38 people across the Lewy body disease spectrum (Parkinson's with mild cognitive impairment, Parkinson's with dementia, and dementia with Lewy bodies) and 35 healthy controls. Diffusion tensor imaging, which traces water movement through tissue, was applied at higher resolution than most clinical MRI.
Two findings stand out. Hippocampal fractional anisotropy, a measure of microscopic wiring organization, was lower across the Lewy body group than in controls. Within that group, the same measure tracked with depression severity: more depression, higher wiring score. There was no group difference in hippocampal volume or mean diffusivity.
The direction is counterintuitive. Higher fractional anisotropy usually signals more intact tissue, so tying it to more depression hints at something other than simple white-matter loss. The authors interpret it as a possible shift in synaptic density, Lewy neurite organization, or neuroplasticity. None of that is established.
Single-site, modest sample, and no imaging split between cognitively impaired and unimpaired participants. The signal is a candidate, not a diagnostic.