Neurodegeneration and the structure of time: clinical evidence for philosophical reasoning.

Alzheimer’s disease (AD) has become the model disease for the whole dementia syndrome with predominant memory deficits (World Health Organization, 1994). Other forms of neurodegenerative dementias – dementia with Lewy bodies (DLB) and frontotemporal degeneration (FTD) – are characterized by different patterns of neuropsychological performance and behavioral disturbances (Neary et al., 1998; McKeith et al., 2004). AD, DLB and FTD affect specific neuronal systems underlying different memory functions (Gabrieli et al., 1994; Moscovitch et al., 2005). Such differential effects on memory are associated with distinct effects on the perception of time. Concepts of time and their pathological change have not been considered as central issues in dementia research and care. This paper suggests that the altered perception of time in patients with different forms of dementia is largely neglected, and that clinical observations in dementia may improve our understanding of how the past, the present and the future are psychologically connected, a problem which philosophers have addressed repeatedly.