Do the waves begin to waver? ERP studies of language processing in the elderly

Abstract

Until recently, relatively little research had been done on language processing in the elderly except as an adjunct to the study of aphasia. While language processes have usually been thought to be fairly impervious to aging, it is now clear that some changes do occur. Moreover, many of these changes often seem to be directly linked to changes in the efficacy of other cognitive operations affected by aging, particularly the active suppression of irrelevant information and the management of working memory (WM). One way to study these changes is to record event-related brain potentials (ERPs) from the scalp in response to individual words either in isolation or in sentences. In this chapter, we review what is currently known about the electrophysiology of visual language processing in the elderly, and what ERPs may tell us about age-related changes in the neural substrates of reading. ERP STUDIES OF LANGUAGE PROCESSING IN THE ELDERLYMuch more research has been focused on the development of language abilities from infancy through early adulthood than on changes in language processing over the next forty to fifty years. Notable exceptions are the investigations of individuals with gross disturbances in language caused by certain strokes or dementing illnesses and their age-matched controls. But a variety of subtle changes do occur within the normal aging brain that can have noticeable effects on language processing. In this chapter, we review some of our results from studies of language processing in presumably normal, healthy, elderly individuals employing event-related brain potentials (ERPs). ERPs provide us with a brain imaging technique that is well-suited for mapping processes at the psychological and linguistic level onto the relevant neural physiology. They are especially useful for our purposes because they provide a potentially continuous measure of on-going brain activity which is sensitive to many of the same variables that influence language processing. Further, ERPs give us a useful measure that does not require

Age‐related changes in the impact of contextual strength on multiple aspects of sentence comprehension

“…Between 0 and 250 ms poststimulus onset, both age groups show the characteristic series of evoked potentials elicited by visual stimuli, as displayed in Figure 1. Consistent with past studies of word-by-word reading examining sentence-final critical words, visual inspection reveals that posterior potentials are slightly reduced in size for older adults, whereas, anteriorly, the N1 is much larger in older compared to younger adults and the P2 is notably reduced (King & Kutas, 1995;Wlotko, Lee, & Federmeier, 2010). ERPs are overlapped for the two age groups at two frontal, central, and occipital sites in Figure 2.…”

Language of the Aging Brain: Event‐Related Potential Studies of Comprehension in Older Adults

“…Research on other kinds of processes needed to build a message-level representation has not been as well developed as in the use of semantic information during comprehension. However, King and Kutas (1995) show similar use of syntactic information by younger and older adults (modulated by working memory) and relate these findings to behavioral work (see, e.g., Kemper and Herman 2006). Similarly, Kemmer et al (2004) observed that older adults showed no difference in the size or timing of the P600 response, an ERP effect sensitive to grammaticality.…”

“…The characteristics of ERPs that make them so suitable for studying language also make them particularly useful for studying age-related changes in comprehension (see also King and Kutas 1995). It is clear that aging has differential effects on cognitive subprocesses, and ERPs provide specific indices that allow these effects to be examined independently but in tandem.…”

“…One explanation for this pattern is that a reduced working memory size means that sentence context information can be retained over smaller intervals, and, thus, is less likely to bear on the processing of upcoming words. The decline in working memory for older adults is sometimes offered as a cause of changes in comprehension (see King andKutas 1995 andBurke andShafto 2008 for discussions), and Federmeier and Kutas (2005) indeed found that reading span (along with verbal fluency) was a reliable predictor of the N400 constraint effect. However, working memory capacity alone can't explain all the findings, as sometimes young adults low on working memory span still differ from older adults -such as in their tendency to use predictive processing mechanisms.…”

Cognitive Event-Related Potentials: Biomarkers of Synaptic Dysfunction Across the Stages of Alzheimer's Disease

“…The N400 response to written words is sensitive to normal aging: N400 latency increases at ~2 ms/year and N400 amplitude decreases at ~0.07 μV/year across the adult lifespan [64, 65]. From ERP studies of semantic memory (reviewed below), it is apparent that the N400 is usually abnormal in AD, typically reduced in amplitude and delayed in latency beyond that seen in normal aging.…”