Language Disorders

As noted above, memory deficits are among the earliest hallmarks of the onset of probable Alzheimer's disease (AD). In the language domain, individuals with suspected early AD have predominantly lexical-semantic impairments. For example, they may have particular difficulty naming pictures, naming items that are described to them (e.g., "what do you use to tell time?"), and generating more than a few common examples of words that start with a given letter of the alphabet. They may also wander from the topic of a conversation and be vague in what they say. Syntax, morphology, and phonology are relatively preserved until the later stages of the disease. Thus, early in the course of AD, language production may be perfectly structured, but "empty" or lacking in content (e.g., "The thing is over there, you know").

Progressive aphasia is a poorly understood condition in which language deteriorates over time, but which only infrequently is identified at autopsy as AD (Mesulam). Like AD, symptom onset and decline are gradual, but in contrast to most cases of AD, language difficulties are the earliest and the primary signs of trouble. While non-language aspects of cognition reportedly are retained for several years after the onset of language symptoms, deficits may be evident with careful testing. Once clearly identified, non-language cognitive abilities may decline less rapidly than language skills.

Again, progressive aphasia may manifest in various ways. Language expression may be effortless and well-formed but low in content, as in early AD, or it may be effortful and "telegraphic" in quality, consisting primarily of nouns and verbs (e.g., "Boy - girl - cookie - falling"). Likewise, language comprehension may be relatively good or poor. According to Mesulam, progressive aphasia often is associated with a loss of nerve cells in relatively focal cortical areas of the brain, but precise causal factors are unclear.