Confrontation Naming Errors in Alzheimer’s Disease
Dement Geriatr Cogn Disord. 2014;37(1-2):86-94. doi: 10.1159/000354359.
Lin CY1,2, Chen TB1,2, Lin KN1,3, Yeh YC2,4, Chen WT1,2, Wang KS5, Wang PN1,2.
1Department of Neurology, Neurological Institute, Taipei Veterans General Hospital, Taipei, Taiwan
2Department of Neurology, National Yang-Ming University School of Medicine, Taipei, Taiwan
3Department of Psychology, Soo-Chow University, Taipei, Taiwan
4Department of Neurology, Kuo General Hospital, Tainan, Taiwan
5Graduate Institute of Linguistics, National Taiwan University, Taipei, Taiwan
Correspondence author: Prof. Pei-Ning Wang, firstname.lastname@example.org
BACKGROUND/AIMS: Impairment in visual interpretation, semantic conception, or word retrieval may contribute to the naming errors identified in the Boston Naming Test (BNT). We investigated the possible cognitive mechanism of the naming difficulty in Alzheimer’s disease (AD) by analyzing the error patterns presented in the BNT.
METHODS: The Chinese version of the 30-item BNT (BNT-30) was performed on 115 normal control (NC) subjects and 104 mild-to-moderate AD patients. Accurate rates after semantic and phonemic cues were analyzed. The frequencies of 7 types of error patterns in the AD patients and the NC subjects were compared.
RESULTS: The accurate rate after semantic cues was significantly lower in the AD than in the NC groups, but phonemic cues were more helpful than semantic cues to achieve accurate naming in both groups. The AD patients made more errors in all error patterns. Particularly, the frequency of nonresponse errors (n = 806) in the AD group significantly exceeded that in the NC group (n = 382). However, the distribution of the error patterns did not differ between the two groups.
CONCLUSION: Naming difficulties in AD might be attributed to progressive semantic knowledge degradation. The AD and the NC groups differ quantitatively but not qualitatively in the error patterns in confrontation naming.
Naming difficulty may result from dysfunction of presemantic visual perception, semantic knowledge deterioration, or word retrieval . By performing the Chinese version of the 30-item BNT (BNT-30) , we investigated the differences in naming error patterns between Alzheimer’s disease (AD) and normal controls (NC). The aim of this study was to inspect which step of the cognitive processes could account for the possible causes of naming difficulties in AD by analyzing the effects of cues and error patterns.
We classified the naming errors into 7 patterns: (1) Nonresponse: ‘I don’t know’ or no response, (2) Visual errors: visually similar to the target but belong to a different semantic category (‘mountain’ for pyramid), (3) Semantic coordinate errors: semantic ambiguous visual errors and semantic within-category errors. The former refer to responses visually similar to the item and from the same semantic category (‘gecko’ for seahorse); the latter are responses from the same semantic category but visually different (‘brush’ for broom), (4) Semantic superordinate errors: general class (‘animal’ for seahorse), (5) Semantic circumlocutory errors: statements of action or function, physical attributes, and contextual associates (‘in the desert’ for cactus, ‘for residence in the North Pole’ for igloo) or multiword responses which could point towards the target items (‘it is used at elementary school…and to measure angles’ for protractor), (6) Phonemic/phonological errors: mispronunciations or distortions of the target name, (7) Other errors: perseveration, reutterance of a response which has been previously used to name 1 of the previous 5 pictures (‘broom’ for dart), and unrelated errors, that is the responses show no clear connection to the target items (‘thermometer’ for protractor). We compared the number and frequency (the ratio of the number of each error pattern to the number of total errors that every individual made on the BNT-30) of each error pattern.
The result showed naming impairment was obviously presented in AD patients. Only 3 items (harp, igloo, and protractor) were incorrectly responded by more than 50% of the NC, compared to 14 items by the AD patients. Phonemic cue was more helpful than semantic cue for AD patients. In error pattern analysis, we found the numbers of nonresponse, visual, semantic coordinate, and semantic circumlocutory errors were more in the AD than the NC groups. The most common error pattern was the nonresponse error. Apart from the nonresponse error, the semantic coordinate error was the highest and the phonemic error was the lowest (fig.1). However, the distributions of the error pattern frequencies do not differ between the AD and NC groups.
Successful semantic and phonemic cues: more of our NC was semantically cued with correct answers than AD. This indicated that NC had a more intact semantic structure than AD. Phonemic cues assist word retrieval in the lexical access. If the patient’s semantic concept was partially preserved , phonemic cues provides extra clues and messages in accessing the underspecified lexical-semantic information. In our study, phonemic cues were helpful (25%) to AD, which implies that our mild to moderate AD patient have partial semantic degradation.
Nonresponse error indicates a severe semantic breakdown in naming [4, 5]. As the disease progresses, dysnomia in AD would gradually shift from semantic superordinate errors to ‘I don’t know’ responses . Our results corresponded to this hypothesis. Interestingly, NC frequently presented nonresponse errors in some items but the average number of the nonresponse error in NC was only 3.3, much less than that in AD (fig. 1). We infer that in NC, most of the nonresponse errors are caused by unfamiliarity with the items (i.e. harp and igloo are not familiar in Taiwanese culture and protractor was not used by Taiwanese elderly when they were in schooling) but not as a consequence of a semantic breakdown.
Semantic errors: many researchers claim that AD tends to list more shared features among category members rather than distinctive features . Our result supported this postulation: the order from the highest to the lowest was semantic coordinate, semantic circumlocutory, and finally semantic superordinate. This indicated that semantic knowledge was partially but not totally broken down in mild to moderate AD.
Visual errors: the visual acuity is relatively intact in AD, as proven by various visual discrimination tasks . However, the visually related naming difficulty increases while dementia worsens . Thus, visual disturbance on picture naming might not occur more frequently in mild AD patients.
Phonological and other errors: phonological error is a rare naming error pattern in our study. We speculate that it was because fewer syllables are required to name an object in Chinese, and therefore mispronunciation is less likely to occur. Furthermore, unlike in an alphabetic language, even very mildly distorting the pronunciation of a logographic language such as Chinese might lead to a totally distinct word.
To our knowledge, it is the first article using Chinese version of the BNT-30 to compare the error pattern differences between AD and NC and to investigate the cognitive mechanism of AD’s naming difficulty. Our study highlights the following important points: (1) cultural differences or any factors that lead to unfamiliarity with the picture naming items might influence the test result, (2) AD and NC differ quantitatively, but not qualitatively in picture naming errors, and (3) the naming difficulty in AD might be attributed to semantic breakdown, rather than word retrieval or visual problems.
Fig. 1. Distribution and average numbers of the 7 error patterns of the BNT-30 in AD patients and NC subjects. Non. = Nonresponse error; Coord. = semantic coordinate error; Circum. = semantic circumlocutory error; Super. = semantic superordinate error; Phon. = phonemic/phonological error. The frequency of each error pattern was calculated from the ratio of the number of each error pattern to the number of total errors of every individual. The numbers below the columns present the mean items of each error pattern in the AD and the NC groups.
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