Semantic Fluency in Mild and Moderate Alzheimer's Disease Seija Pekkala 2004

265 Pages·2004·3.93 MB·English

Semantic Fluency in Mild and
Moderate Alzheimer’s Disease
Seija Pekkala
2004
Department of Phonetics
University of Helsinki
P.O. Box 35 (Vironkatu 1B)
00014 University of Helsinki
ISSN 0357-5217
ISBN 952-10-1645-0 (paperback)
ISBN 952-10-1646-9 (PDF, http://ethesis.helsinki.fi/)
Hakapaino Oy, Helsinki 2004
Copyright Seija Pekkala 2004
To my parents

ABSTRACT
Semantic Fluency in Mild and Moderate Alzheimer’s Disease
Seija Pekkala
University of Helsinki, FIN
Alzheimer’s disease (AD) is characterized by an impairment of the semantic memory
responsible for processing meaning-related knowledge. This study was aimed at
examining how Finnish-speaking healthy elderly subjects (n = 30) and mildly (n=20)
and moderately (n = 20) demented AD patients utilize semantic knowledge to perform
a semantic fluency task, a method of studying semantic memory. In this task subjects
are typically given 60 seconds to generate words belonging to the semantic category
of animals. Successful task performance requires fast retrieval of subcategory
exemplars in clusters (e.g., farm animals: ‘cow’, ‘horse’, ‘sheep’) and switching
between subcategories (e.g., pets, water animals, birds, rodents). In this study, the
scope of the task was extended to cover various noun and verb categories.
The results indicated that, compared with normal controls, both mildly and moder-
ately demented AD patients showed reduced word production, limited clustering
and switching, narrowed semantic space, and an increase in errors, particularly
perseverations. However, the size of the clusters, the proportion of clustered words,
and the frequency and prototypicality of words remained relatively similar across
the subject groups. Although the moderately demented patients showed a poorer
overall performance than the mildly demented patients in the individual categories,
the error analysis appeared unaffected by the severity of AD. The results indicate a
semantically rather coherent performance but less specific, effective, and flexible
functioning of the semantic memory in mild and moderate AD patients.
The findings are discussed in relation to recent theories of word production and
semantic representation.
Semantic fluency, clustering, switching, semantic category, nouns, verbs,
Alzheimer’s disease

Contents
Acknowledgements ................................................................................................i
List of Tables ........................................................................................................iii
List of Figures.......................................................................................................iv
Abbreviations.........................................................................................................v
1 Introduction ......................................................................................................1
2 Alzheimer’s disease...........................................................................................5
2.1 Etiology and pathogenesis of Alzheimer’s disease..........................................7
2.2 Clinical findings of Alzheimer’s disease .........................................................8
2.3 Staging the severity of dementia in Alzheimer’s disease...............................12
2.4 Semantic impairment in Alzheimer’s disease................................................16
2.4.1 Impaired knowledge of the meaning representation ...........................17
2.4.2 Impaired naming .................................................................................18
3 Frameworks of semantic knowledge.............................................................23
3.1 Principles of categorization...........................................................................26
3.1.1 Categorization of objects.....................................................................28
3.1.2 Subcategories and hierarchical structure of nouns..............................32
3.2 Feature-based models as accounts of the semantic representation of nouns.34
3.3 Accounts of semantic representation of verbs...............................................39
3.3.1 Categorization of actions.....................................................................41
3.3.2 Subcategories and hierarchical structure of verbs...............................43
3.3.3 Feature-based models as accounts of the semantic
representation of verbs........................................................................47
3.3.4 Scripts as the account of semantic
representation of verbs........................................................................49
4 Spoken word production................................................................................51
4.1 Theories of spoken word production.............................................................51
4.2 Two-stage interactive activation models........................................................53
5 Semantic fluency performance in
elderly adults and Alzheimer’s patients.......................................................55
5.1 Word production during the semantic fluency task.......................................56
5.2 Clustering and switching...............................................................................66
5.3 Activation of different associations and semantic dimensions......................68
5.4 Error analysis.................................................................................................70
5.4.1 Intrusions.............................................................................................71
5.4.2 Perseverations......................................................................................73
5.5 Performance in different semantic categories................................................74
6 Causes of the semantic impairment in
Alzheimer’s disease........................................................................................77
6.1 Breakdown and loss of semantic structures...................................................77
6.2 Impaired processing.......................................................................................79
6.3 A multifactorial deficit...................................................................................80
7 Aims of the study ............................................................................................83
8 Method.............................................................................................................85
8.1 Subjects..........................................................................................................85
8.2 Method...........................................................................................................86
8.2.1 Procedure of the semantic fluency tasks .............................................86
8.2.2 Analysis of the overall performance on the semantic fluency tasks....87
8.2.3 Clustering rules ...................................................................................89
8.2.4 Analysis of the contents of the responses on the semantic
fluency tasks........................................................................................90
8.2.5 Inter-rater judgements .........................................................................92
8.2.6 Control tasks........................................................................................93
8.2.7 Statistical analysis ...............................................................................94
9 Results..............................................................................................................97
9.1 Overall performance on the noun fluency tasks............................................97
9.1.1 Number of correct nouns.....................................................................99
9.1.2 Clustering and switching...................................................................100
9.1.3 Summary of the results and discussion .............................................103
9.2 Analysis of the contents of the responses on the noun fluency tasks..........109
9.2.1 Proportion of correct nouns...............................................................109
9.2.2 Proportion of intrusions and perseverations......................................109
9.2.3 Clustering strategies..........................................................................112
9.2.4 Number and variety of different semantic subcategories..................114
9.2.5 Degree of prototypicality and frequency of the nouns produced......118
9.2.6 Summary of the results and discussion .............................................120
9.3 Overall performance on the verb fluency tasks...........................................128
9.3.1 Number of correct verbs....................................................................128
9.3.2 Clustering and switching...................................................................131
9.3.3 Summary of the results and discussion .............................................133
9.4 Analysis of the contents of the responses on the verb fluency tasks...........135
9.4.1 Proportion of correct verbs................................................................136
9.4.2 Proportion of intrusions and perseverations......................................138
9.4.3 Number and variety of different semantic subcategories..................140
9.4.4 Degree of prototypicality and frequency of the verbs produced.......144
9.4.5 Summary of the results and discussion .............................................144
9.5 Summary of the overall semantic fluency performance..............................152
9.6 Performance on the control tasks.................................................................154
9.6.1 Performance on the control tasks requiring verbal responses...........154
9.6.2 Performance on the control tasks requiring non-verbal responses....155
9.6.3 Correlations among scores on the semantic tasks.............................156
9.6.4 Discussion on the semantic tasks ......................................................157
10 General discussion......................................................................................161
10.1 Semantic fluency performance in mild and moderate Alzheimer’s disease162
10.1.1 Decreased semantic fluency performance.......................................162
10.1.2 Errors as indicators of impaired semantic memory functioning .....165
10.1.3 Causes of the semantic impairment in Alzheimer’s disease............167
10.2 Methodological considerations of the study..............................................171
10.2.1 Subjects ...........................................................................................171
10.2.2 Considerations of the semantic fluency task...................................173
10.2.3 Limitations of the study...................................................................177
10.3 Clinical implications..................................................................................179
10.4 Implications for further study....................................................................180
11 Conclusions .................................................................................................183
References.........................................................................................................187
Appendix 1A. Cluster division for the noun categories ....................................225
Appendix 1B. Cluster division for the verb categories......................................228
Appendix 2 A sample of prototypicality ratings of the words produced
for the semantic fluency tasks ......................................................................231
Appendix 3 A sample of frequency ratings of the words produced
for the semantic fluency tasks ......................................................................233
Appendix 4A. Examples of the semantic fluency performance
given by a participant in each subject group : clothes..................................235
Appendix 4B. Examples of the semantic fluency performance
given by a participant in each subject group: vegetables .............................236
Appendix 4C. Examples of the semantic fluency performance
given by a participant in each subject group: vehicles.................................237
Appendix 4D. Examples of the semantic fluency performance
given by a participant in each subject group: animals..................................238
Appendix 4E. Examples of the semantic fluency performance
given by a participant in each subject group: preparing food.......................239
Appendix 4F. Examples of the semantic fluency performance
given by a participant in each subject group: playing sports........................240
Appendix 4G. Examples of the semantic fluency performance
given by a participant in each subject group: construction ..........................241
Appendix 4H. Examples of the semantic fluency performance
given by a participant in each subject group: cleaning up............................242
Appendix 5. Results of the post-hoc pair-wise analyses of
the noun fluency tasks..................................................................................243
Appendix 6. Results of the post-hoc pair-wise analyses of
the verb fluency tasks...................................................................................246
Appendix 7. Results of the post-hoc pair-wise analyses of the control tasks....249