The protection is likely to relate, in part, to an increased capillary density and tissue oxygen levels. This observation supports considering pre-activation of genes as a method of providing hypoxia tolerance and, in so doing, reducing stroke severity. A wealth of literature shows that both healthy ageing and Alzheimer’s disease are associated with accompanying decrements in sensory and cognitive performance. Moreover, there is an assumption that functions which involve more complex processing are more likely to be vulnerable, presumably because age-related decline accumulates across multiple-component processes, or because compensation mechanisms become less effective as complexity increases, e.g.. One function which is considered particularly complex is the ability to distinguish “material” from “light” within the visual input ; that is, to distinguish “real objects” from shadows. A given physical object is associated with very different retinal input depending upon the strength and direction of lighting, and whether or not the illumination is occluded by other items to create cast shadows. Successful object recognition requires, in part, that the brain can ignore any light-related variability in the visual input. Despite decades of research on the subject, it remains unclear exactly how this distinction is made. A Tofacitinib frequent assumption is that colour vision evolved in order to solve this kind of problem – colour is constant across many illumination changes. However, the visual system can be confronted with scenes largely devoid of colour information, and then faces a major challenge in computing surface information. It seems likely that numerous complex higher-level heuristics are used for identifying light-related variability, and these determine the extent to which basic lower-level features of the input are accessible, with the features relating to object properties being the most comprehensively processed. The underlying mechanisms are likely to be complicated and to involve information circulating between multiple cortical levels. In this paper we examine whether these complex mechanisms appear to be disrupted by cognitively healthy ageing and AD. Evidence is emerging that some of the more complex aspects of visual processing, including those contributing to object recognition, may become disrupted by pathological and even by healthy ageing. The optical properties of the eye change as people get older, resulting in alterations to basic visual sensitivities, together with some of the processes on which these depend, e.g.. In addition, recent reports indicate that older people perform less well than the young at integrating certain types of basic visual information over time or space to identify structure. One crucial factor to the identification of structure is to correctly distinguish lighting from material, and there is evidence in various neurological conditions that this specific ability can be disrupted, causing difficulties with object recognition. Becchio et al, for example, found cast shadow information to interfere with object recognition for autistic children, but assist performance in typically developing children. Similarly, visual neglect can disrupt shadow processing. While not suggesting any parallels between those neurological dysfunctions and ageing or AD, we wondered whether ageing might also reduce the ability to appropriately process lighting-related visual information? This has been little investigated, although Norman & Wiesemann found judgements of surface orientation.