Can literacy change brain anatomy?

Abstract

Several studies have postulated that education and/or literacy may not only protect against the effects of biological ageing (Albert et al., 1995; Christensen & Henderson, 1991; Orrell & Sahakian, 1995), but also against the clinical manifestation of cerebral neuropathology (Katzman, 1993; Stern, 2002; Stern, Gurland, Tatemichi, Tang, Wilder, & Mayeux, 1994; Zhang et al., 1990). In clinical neuropsychology, much debate has centred on whether the brain is more likely to degenerate as a result of overuse or underuse; while some epidemiological studies have suggested that active engagement in intellectual, social, and physical activities may delay the cognitive deterioration associated with normal ageing (Scarmeas, Levy, Tang, Manly, & Stern, 2001), other studies have emphasized that the protective effect of education is not always observed but depends upon the specific cognitive ability that is measured (Ardila, Ostrosky-Solis, Rosselli, & Gomez, 2000; Ostrosky-Solis, Ardila, Rosselli, Lopez, & Mendoza, 1998). Ostrosky-Solis (2002) points out that protection or age-related decline attenuation in well-educated subjects is highly related to verbal abilities; thus, education and verbal advantage could serve as a means of compensatory strategies, such as using verbal cues to aid recall or encoding visuospatial tasks with language. These are the strategies provided by formal education. The use of these strategies could mask otherwise similar rates of biological ageing among different educational groups, and this advantage, coupled with the effects of several important variables such as good health, appropriate occupation, and active engagement with the surrounding environment, could explain why cognitive stimulation can provide some moderating influence on the complex changes in cognitive performance associated with ageing. It has also been reported that Alzheimer’s disease not only has a later onset but that it is less severe in highly educated people (Katzman, 1993; Stern et al., 1994). This association of high education with late age of onset of dementia has been considered as an evidence of cognitive and/or brain reserve (Katzman, 1993; Mortimer, 1988; Satz, 1993; Stern, 2002). The articles presented in this Special Issue analyse the impact of literacy on the anatomic and functional organization of the adult brain. Cognitive neuroimaging studies, event-related potentials, neuropsychological data of literate and illiterate subjects, and discussion regarding the origins and evolution of reading and writing are presented. Stern, Scarmeas, and Habeck point out that the cognitive reserve model suggests that variables such as education and IQ are associated with cognitive reserve (CR) and may mediate differential susceptibility to age-related memory changes. They propose two complementary facets to CR: reserve—individual differences in the capacity to perform task—and compensation—the use of alternate brain networks or cognitive processes to cope with brain pathology. However, up to now the neurophysiologic substrate of CR has not been established. Therefore in order to explore the anatomical basis for CR in healthy young and old individuals, they used H215O PET to analyse the relationship between CR and task-related activation during the performance of a nonverbal recognition memory test. The first two studies focused on young subjects, and found either brain areas or brain networks where the amount of increased activation correlated with CR. The third study compared activation patterns of young and elderly individuals and found locations where the relation between activation and CR differed