Using SPECT with [123I]IBVM, Kuhl et al. [16] demonstrated that whilst in PD without dementia, VAChT levels are reduced only in the parietal and occipital cortices, in PDD, major losses are seen throughout the entire cortex, suggesting a greater and more widespread presynaptic cholinergic dysfunction in PDD patients. Here, SLC18A3 is linked to dementia.