Characterising trait anxiety in the common marmoset

274 Pages·2013·5.8 MB·English

by  Yoshiro Shiba

Characterising trait anxiety in
the common marmoset (Callithrix jacchus):
Investigations into behavioural, psychophysiological and
cognitive phenotypes

Yoshiro Shiba
Darwin College
University of Cambridge

A dissertation submitted for the degree of
Doctor of Philosophy

2012
To my grandparents,
Tashichi and Fumi Shiba
Preface

The following work was carried out at the Department of Physiology, Development and
Neuroscience, University of Cambridge, during the years 2008 to 2012, under the
supervision of Dr Angela C. Roberts.

I hereby declare that this dissertation has not been submitted, in whole or in part, for any
other degree, diploma or qualification at any other university. This dissertation is the result of
my own work and includes nothing that is the outcome of work done in collaboration. I have
attempted to reference appropriately any idea or finding which is not my own.

This dissertation does not exceed the limit of length specified by the Degree Committee of
Biology, as stated in the Memorandum to Graduate Students.

Yoshiro Shiba

28th September 2012
Acknowledgment

First and foremost I would like to express my sincerest gratitude to my supervisor, Professor
Angela Roberts, who has supported me at every step throughout my PhD project with her
patience, encouragement and knowledge. I would also like to thank my advisors Professor
Wolfram Schultz and Dr Jeff Dalley for their support and guidance.

I would like to acknowledge Dr Carmen Agustin-Pavon and Dr Mei-See Man from whom I
received critical support at the initiation of the project. I am also hugely grateful to Dr Katrin
Braesicke for all her help on the autonomic data analysis. Behavioural scoring of a large
sample of animals was an enormous task. Especially I would like to thank Ms Gemma
Cockcroft and Ms Charrisa Kim for many hours of their contribution. In addition to the help
with the scoring, Dr Andrea Santangelo and Dr Hannah Clarke provided me with many useful
intellectual inputs. I would also like to acknowledge Dr Nicole Horst, Dr Rafal Rygula, Ms
Yevheniia Mikheenko, Ms Evelien Schut and Ms Faaiza Asma for their support and
friendship. I would like to express special thanks to Professor Mark Haggard for valuable
advice on statistic issues.

I would like to thank Mr Colin Windle for his informative comments on marmoset’s life in
general and occasional help with testing equipment. My gratitude also goes to our
veterinarian, Dr Jo Keeley and animal technicians, Ms Jodie Smith, Mr Mark Wing, Ms Sian
Drage and Ms Lindis Bergland, without whom this project was not possible. I received
enormous assistance from the engineers at Biotronix, Mr John Baldwin, Mr John Osborne
and Mr Mike Morgan for setting up experimental machineries.

Thanks to Tedi, who incessantly and patiently supported me throughout four years of my
PhD student life from both near and far. I am grateful to my parents and family who
occasionally cheered me up with nifty packages from Japan.

I must thank all the monkeys who participated in my project. This thesis was certainly not
possible without their contribution.

Finally, I would like to thank the Ministry of Education, Culture, Sports, Science and
Technology of Japan and Osaka University for funding my PhD studentship at Cambridge.
Abstract

The major aim of my thesis project has been to develop a non-human primate model of trait
anxiety, using a new world monkey, the common marmoset. The first step was to identify
animals high or low in trait anxiety. Based on the findings that high trait-anxious individuals
display over-generalization of fear responses, a pathogenic marker of elevated trait anxiety in
humans, a new aversive discriminative conditioning paradigm was designed. Testing a
normal cohort of marmosets revealed that 26% of the animals displayed both behavioural
and physiological signs of fear generalization, i.e. failure to discriminate safety from danger
cues (‘failed’ group). The remaining 74% showed successful discrimination (‘passed’ group).
Additional regression analysis on several behavioural and physiological responses early in
training revealed two potential biomarkers of high trait anxiety in marmosets: suppressed
baseline blood pressure, indicative of contextual effects, and hyper cue-specific vigilance.
These measures predicted the animal’s likelihood of passing or failing the discrimination. The
finding that the ‘failed’ group showed intact discriminative performance in the appetitive
domain rules out an interpretation of the results in terms of a general impairment in learning,
per se. To further determine whether these hypothetically high trait-anxious animals would
display enhanced anxiety-related responses in more classical primate models of anxiety,
human intruder and rubber snake tests were performed on a large sample of marmosets.
Principal component analysis on multiple behavioural measures revealed two components
underlying performance: ‘emotionality’ and ‘coping strategy’. Although no difference was
found in the human intruder test, the ’failed’ group displayed significantly elevated levels of
‘emotionality’ in comparison to the ‘passed’ group in the rubber snake test. Moreover, the two
biomarkers of fear over-generalisation also reliably predicted the ‘emotionality’ scores. Finally,
having developed a marmoset model of trait anxiety, investigations into the neural
underpinnings, especially prefrontal involvement in trait anxiety mechanisms, were carried
out by testing the animals on two cognitive flexibility tests: an orbitofrontal cortex (OFC)-
dependent incongruent object discrimination test and a lateral prefrontal cortex (lPFC)-
dependent detour reaching rule transfer test. Whilst group differences did not reach
significance, the two biomarkers of fear over-generalisation, the suppressed baseline blood
pressure and hyper cue-specific vigilance, were inversely and differentially correlated with
perseverative performance on the two tests, the lPFC- and OFC-dependent tests,
respectively. This not only indicates that high trait anxiety can lead to improvements in
certain aspects of prefrontal cognitive function but also suggests that changes in the activity
of at least two distinct prefronto-subcortical neural circuits, a cue-sensitive amygdala-OFC
and a context-sensitive hippocampus-lPFC circuit, may contribute to trait anxiety.
Contents

Chapter 1: General introduction ··········································································· 1
1.1 Trait Anxiety: Definition ················································································ 5
1.2 Anxiety Disorders ························································································ 8
1.3 Animal Models of Trait Anxiety ····································································· 19
1.4 Neurobiology of Anxiety ·············································································· 31
1.5 Genetics of Anxiety ···················································································· 43

Chapter 2: A novel test for assessing trait anxiety in marmosets: The aversive
discriminative conditioning paradigm ················································· 54
Abstract ······································································································· 55
2.1 Introduction ······························································································ 56
2.2 Mild Aversive Pavlovian Discriminative Conditioning Paradigm ··························· 62
2.2.1 Methods and Materials ········································································· 62
2.2.1.1 Subjects ····················································································· 62
2.2.1.2 Telemetry ··················································································· 62
2.2.1.2.1 Telemetric Physiologic Monitors ················································ 62
2.2.1.2.2 Implantation of Telemetry Transmitter ········································ 66
2.2.1.3 Mild Aversive Discrimination Test Apparatus ······································ 69
2.2.1.4 Behavioural Procedures ································································· 71
2.2.1.5 Data Acquisition and Analysis ························································· 72
2.2.2 Results ····························································································· 76
2.2.2.1 Individual Differences in the Acquisition of Aversive Discriminative
Conditioning ·············································································· 76
2.2.2.2 Measures in Early Sessions as Predictors of the Discriminative Outcome
································································································ 83
2.3 Appetitive Discrimination Paradigm ······························································· 87
2.3.1 Methods and Materials ········································································· 87
2.3.1.1 Subjects ····················································································· 87
2.3.1.2 Appetitive Discrimination Test Apparatus ··········································· 87
2.3.1.3 Behavioural Procedure ·································································· 89
2.3.1.4 Data Acquisition and Analysis ························································· 91
2.3.2 Results ····························································································· 93
2.3.2.1 Performance of the ‘Failed’ Group in Appetitive Discriminative Conditioning
································································································ 93
2.4 Discussion ······························································································· 97

Chapter 3: Is failure to show discriminative fear conditioning a marker of high trait
anxiety in marmosets? ····································································· 104
Abstract ······································································································ 105
3.1 Introduction ···························································································· 106
3.2 Human Intruder Test ················································································ 113
3.2.1 Methods and Materials ······································································· 113
3.2.1.1 Subjects ···················································································· 113
3.2.1.2 Test Apparatus ··········································································· 113
3.2.1.3 Behavioural Procedure ································································ 114
3.2.1.4 Data Acquisition and Analysis ······················································· 116
3.2.2 Results ··························································································· 122
3.2.2.1 Effect of Intruder Presence on an Animal’s Behaviour ························ 122
3.2.2.2 PCA Reveals Two Psychological Dimensions: ‘Emotionality’ and ‘Coping
Strategy’ ···················································································· 126
3.3 Rubber Snake Test ·················································································· 130
3.3.1 Methods and Materials ······································································· 130
3.3.1.1 Subjects ···················································································· 130
3.3.1.2 Test Apparatus ··········································································· 130
3.3.1.3 Behavioural Procedure ································································ 131
3.3.1.4 Data Acquisition and Analysis ······················································· 133
3.3.2 Results ··························································································· 136
3.3.2.1 Effect of Rubber Snake on an Animal’s Behaviour ····························· 136
3.3.2.2 PCA Reveals Two Psychological Dimensions: ‘Emotionality’ and ‘Coping
Strategy’ ···················································································· 141
3.4 How Comparable are the Human Intruder and Rubber Snake Tests of Anxiety? ··· 145
3.4.1 Subjects ·························································································· 145
3.4.2 Statistical Analysis ············································································· 145
3.4.3 Results ··························································································· 146
3.4.3.1 Comparison of the ‘Emotionality’ and ‘Coping Strategy’ Component Scores
Derived from the Human Intruder Test and Rubber Snake Tests ··········· 146
3.4.3.2 Correlation of Individual Variables Common to both the Human Intruder and
Rubber Snake Tests ···································································· 150
3.5 Comparison of the ‘Passed’ and ‘Failed’ Groups in the Human Intruder Test and the
Rubber Snake Test ················································································· 151
3.5.1 Subjects ·························································································· 151
3.5.2 Statistical Analysis ············································································· 151
3.5.3 Results: Human Intruder Test ······························································ 152
3.5.3.1 Comparison of the ‘Passed’ and ‘Failed’ groups on the ‘Emotionality’ and
‘Coping Strategy’ Component Scores ·············································· 152
3.5.3.2 Comparison of the ‘Passed’ and ‘Failed’ Groups on the Individual
Behavioural Measurements ··························································· 152
3.5.3.3 Correlation with the Predictors of Aversive Discriminative Conditioning ·· 153
3.5.4 Results: Rubber Snake Test ································································ 155
3.5.4.1 Comparison of the ‘Passed’ and ‘Failed’ groups on the ‘Emotionality’ and
‘Coping Strategy’ Component Scores ·············································· 155
3.5.4.2 Comparison of the ‘Passed’ and ‘Failed’ Groups on the Individual
Behavioural Measurements ··························································· 155
3.5.4.3 Correlation with the Predictors of Aversive Discriminative Conditioning ·· 159
3.5.4.4 Prediction of the Rubber Snake Test Component Scores ···················· 159
3.6 Discussion ····························································································· 161

Chapter 4: How does trait anxiety affect prefrontal cognitive functionalities?
Comparison of high and low anxious groups’ performances on the OFC-
and lPFC-dependent cognitive flexibility tests ···································· 175
Abstract ······································································································ 176
4.1 Introduction ···························································································· 177
4.2 Incongruent Object Discrimination Test ························································ 187
4.2.1 Methods and Materials ······································································· 187
4.2.1.1 Subjects ···················································································· 187
4.2.1.2 Test Apparatus ··········································································· 188
4.2.1.3 Behavioural Procedure ································································ 190
4.2.1.4 Data Acquisition and Analysis ······················································· 192
4.2.2 Results ··························································································· 194
4.2.2.1 Comparison of the ‘Passed’ and ‘Failed’ Groups during Preliminary Training
······································································································ 194
4.2.2.2 Comparison of the ‘Passed’ and ‘Failed’ Group on Performance of the
Incongruent Object Discrimination Task ··········································· 195
4.2.2.3 Relationship of the Performance on the Incongruent Object Discrimination
Task with the Predictors of Aversive Discriminative Conditioning ··········· 196
4.2.2.4 Correlation with the ‘Emotionality’ and ‘Coping Strategy’ Components of the
Human Intruder Test and the Rubber Snake Test ······························ 198
4.3 Detour Reaching Rule Transfer Test ···························································· 200
4.3.1 Methods and Materials ······································································· 200
4.3.1.1 Subjects ···················································································· 200
4.3.1.2 Test Apparatus ··········································································· 200
4.3.1.3 Behavioural Procedure ································································ 201
4.3.1.4 Data Acquisition and Analysis ······················································· 206
4.3.2 Results ··························································································· 207
4.3.2.1 Comparison of the ‘Passed’ and ‘Failed’ Groups during Preliminary Training
······································································································ 207
4.3.2.2 Comparison of the ‘Passed’ and ‘Failed’ Groups on the Over-training on the
Detour Reach Rule ······································································ 207
4.3.2.3 Comparison of the ‘Passed’ and ‘Failed’ Groups on Performance of the
Detour Reach Rule Transfer Task ·················································· 208
4.3.2.4 Relationship of the Performance on the Detour Reach Rule Transfer Task
with the Predictors of Aversive Discriminative Conditioning ·················· 210
4.3.2.5 Correlation with the ‘Emotionality’ and ‘Coping Strategy’ Components of the
Human Intruder Test and the Rubber Snake Test ······························ 212
4.4 Discussion ····························································································· 214

Chapter 5: Conclusion ····················································································· 223
5.1 Summary ······························································································· 224
5.2 Limitations ····························································································· 230
5.2 Future Directions ····················································································· 232

References ···································································································· 235
Chapter 1
General introduction

1