Word‐stem completion task to investigate semantic network in patients with Alzheimer's disease

Abstract

Semantic impairment in patients with Alzheimer's disease (AD) is revealed by tasks of verbal naming, verbal fluency, and semantic knowledge. Causes of the deficit remain unclear in spite of many studies to investigate whether AD patients suffer from the inability to have voluntary access to an almost intact semantic store or from its break down. Word-stem completion (WSC) tasks have been utilized in healthy subjects in order to study semantic memory and network by exploiting the possibility of the involuntary access to them. Available conflicting data refer to the presence of semantic prime in AD patients. To explore the semantic network in AD, patients were requested to complete with the first word that sprang to their mind a stem submitted immediately after presentation of the word prime, as a WSC task. Stems consisted of the three beginning letters of words that were semantically related to primes. We compared data obtained with this task from patients with mild to moderate AD with those from normal controls (NC). AD patients completed less stems (P<0.001) with the expected words than NC, suggesting a break down of the semantic network rather than a deficit in the access to the semantic store.

Lexical Priming in Alzheimer's Disease and Aphasia

“…Besides, similar results have been reported previously [38,40,41,42,43,44,45,46,47,48]. However, our results concerning AD are not concordant with those of certain other studies [31,33,34,35,36,37]. The AD patients in the study of Partridge et al [43] were more severely demented than those investigated by Shimamura et al [33] or by Salmon et al [31], but nevertheless demonstrated less severe impairment.…”

“…These discrepancies may be due to the choice of words used in the tests. Passafiume et al [36] did not indicate the criteria used for the selection of words and other studies failed to describe the frequency of the words used [31,33]. Keane et al [63] used words of frequent occurrence, but derived from the study published in 1967 [64].…”

“…Future investigations should evaluate the influence of word usage frequency on lexical priming, and should be carried out on larger groups of participants than those published up to the present. Our study contains the largest number of patients published (30): 8 patients [33], 13 [31], 16 [32], 15 [43] and 23 [36]. …”

“…Some investigators have reported a priming deficit in AD [30,31,32,33,34,35,36,37], whereas others have found no differences in priming effects between patients with AD and normal control participants [38,39,40,41,42,43,44,45,46,47,48]. Thus, Fleischman and Gabrieli [29] found that 65% of AD studies reported that priming was normal.…”

Word Processing Is Faster than Picture Processing in Alzheimer’s Disease

“…Yang et al [7] suggested that loss of semantic structure and an inability to access semantic knowledge occur in the pathogenesis of AD. Passafiume et al [8] suggested a breakdown of the semantic network rather than a deficit in the access to the semantic store. Hodges et al [9] indicated that AD patients consistently perform poorly across different semantic tasks identifying the same item and argued for semantic storage degradation.…”