Countermanding in Rats as a Practical Model for Investigation of Adaptive Control of Behaviour, Lifespan Changes in Behavioural Control and Neurotransmitter Function

........................................................................................................................................................ ii Co-Authorship.............................................................................................................................................. iv Acknowledgements ....................................................................................................................................... v List of Figures .............................................................................................................................................. ix List of Tables ................................................................................................................................................ x List of Abbreviations ................................................................................................................................... xi Chapter 1 General Introduction..................................................................................................................... 1 1.1 The study of executive function and behavioural inhibition ............................................................... 3 1.2 The countermanding task .................................................................................................................... 5 1.3 Adaptive RT adjustments in the countermanding task ....................................................................... 5 1.4 Countermanding task performance throughout the lifespan ............................................................... 7 1.5 Neuromodulatory control of countermanding task behaviour ............................................................ 8 1.6 The countermanding task in rats ....................................................................................................... 11 1.7 Objectives ......................................................................................................................................... 15 Chapter 2 Investigating a race model account of executive control in rats with the countermanding paradigm ..................................................................................................................................................... 18 2.1 Abstract ............................................................................................................................................. 19 2.2 Introduction ....................................................................................................................................... 20 2.3 Experimental Procedures .................................................................................................................. 23 2.3.1 Animals ...................................................................................................................................... 23 2.3.2 Apparatus ................................................................................................................................... 23 2.3.3 Training Procedures ................................................................................................................... 24 2.3.4 Countermanding task ................................................................................................................. 26 2.3.5 Data Analysis ............................................................................................................................. 27 2.3.6 Amphetamine treatment ............................................................................................................. 29 2.4 Results ............................................................................................................................................... 32 2.4.1 Race model analysis ................................................................................................................... 32 2.4.2 Race model predictions .............................................................................................................. 35 2.4.3 Response adjustment .................................................................................................................. 39 2.4.4 Amphetamine treatment ............................................................................................................. 41 2.5 Discussion ......................................................................................................................................... 46 2.5.1 Acknowledgements .................................................................................................................... 51 vii 2.6 References ......................................................................................................................................... 51 Chapter 3 Behavioural response time adaptation for rats performing the countermanding task: Influence of stop trials and timeout interval ............................................................................................................... 59 3.1 Abstract ............................................................................................................................................. 60 3.2 Introduction ....................................................................................................................................... 61 3.3 Experimental procedures .................................................................................................................. 64 3.3.1 Animals ...................................................................................................................................... 64 3.3.2 Apparatus ................................................................................................................................... 64 3.3.3 Procedures .................................................................................................................................. 65 3.3.4 Data Analysis ............................................................................................................................. 68 3.4 Results ............................................................................................................................................... 72 3.4.1 10-s vs. 1-s timeout interval ....................................................................................................... 72 3.4.2 Simple RT task vs. the countermanding task ............................................................................. 76 3.5 Discussion ......................................................................................................................................... 82 3.5.1 Acknowledgements .................................................................................................................... 90 3.6 References ......................................................................................................................................... 91 Chapter 4 Lifespan changes in the countermanding performance of young and middle aged adult rats .... 98 4.1 Abstract ............................................................................................................................................. 99 4.2 Introduction ..................................................................................................................................... 100 4.3 Methods........................................................................................................................................... 104 4.3.1 Subjects .................................................................................................................................... 104 4.3.2 Apparatus ................................................................................................................................. 104 4.3.3 Procedures ................................................................................................................................ 105 4.3.4 Data analysis ............................................................................................................................ 108 4.4 Results ............................................................................................................................................. 110 4.5 Discussion ....................................................................................................................................... 117 4.5.1 Acknowledgements .................................................................................................................. 125 4.6 References ....................................................................................................................................... 125 Chapter 5 Yohimbine encourages motivated responding for food reward and reveals baseline-dependent effects on stopping for rats performing the countermanding task ............................................................. 136 5.1 Abstract ........................................................................................................................................... 137 5.2 Introduction ..................................................................................................................................... 138 5.3 Methods........................................................................................................................................... 141 5.3.1 Animals .................................................................................................................................... 141 viii 5.3.2 Apparatus ................................................................................................................................. 142 5.3.3 Drugs ........................................................................................................................................ 142 5.3.4 Procedures ................................................................................................................................ 143 5.3.5 Data analysis ............................................................................................................................ 146 5.4 Results ............................................................................................................................................. 149 5.5 Discussion ....................................................................................................................................... 155 5.5.1 Acknowledgements .................................................................................................................. 163 5.6 References ....................................................................................................................................... 163 Chapter 6 General Discussion ................................................................................................................... 172 6.1 References ....................................................................................................................................... 189