Figure 1.

Examples of data collected in the programme from Parkinson’s participants with normal cognition (PDN), mild cognitive impairment (PD-MCI), and dementia (PDD). The top row shows group-level progression across groups in the extent of cortical thinning relative to controls. The consequences of this are shown in this selection of neuropsychological tests from three representative male participants (PDN: age 68, 8 years symptom duration; PD-MCI: age 72, 6 years duration; PDD: age 60, 5 years duration; all with 10–11 years of education). The PDN participant shows good performance in the trail-making test of executive function, and the visuo-spatial tests of drawing a clock and copying a complex figure. The memory ability that allows drawing that figure again after delays of 3 and 30 min is also relatively preserved. The PD-MCI participant shows good trail making and only mildly disorganised clock drawing and figure copying. The ability to redraw the complex figure from memory, however, is somewhat degraded. The participant with dementia is severely impaired on all of the tasks. Figure available under an open CC-BY licence (MacAskill and Horne 2021).