The role of the primary motor cortex (M1) in volitional and reflexive pharyngeal swallowing.

2 DEDICATION . 7 ACKNOWLEDGMENT . 8 TABLE OF CONTENT. 10 PREFACE . 18 LIST OF ABBREVIATIONS . 20 PART I: INTRODUCTION . 22 INTRODUCTION . 23 CHAPTER 1: PART II: LITERATURE REVIEW . 27 LITERATURE REVIEW . 28 CHAPTER 2: PART A: SWALLOWING BIOMECHANICS AND NEURAL CONTROL: . 28 2.1. Biomechanics of normal swallowing: . 29 2.1.1 Pre-oral phase: . 30 2.1.1.1 Oral phase: . 30 2.1.1.2 Pharyngeal phase: . 33 2.1.1.3 Esophageal phase:. 35 2.1.1.4 Summary: . 36 Discrete versus continuous swallowing: . 37 2.1.2 Summary: . 39 Peripheral control of swallowing: . 40 2.1.3 The neural control of swallowing: . 44 2.1.4 The role of brainstem in swallowing: . 45 2.1.4.1 Dorsal Swallowing Group: . 46 The Role of M1 in pharyngeal swallowing 11 Ventral Swallowing Group: . 47 Brainstem networks involved in swallowing control other than the CPG:. 47 Role of sensory input in altering swallowing program in CPG: . 48 Summary: . 49 The role of the cortex in swallowing: . 50 2.1.4.2 The functional contribution of M1 in swallowing: . 55 Asymmetry of swallowing representation in the brain: . 57 2.1.4.3 Neural control of voluntary corticobulbar movements:. 61 2.1. 5 Role of M1 in the execution of voluntary corticobulbar tasks: . 61 2.1. 5.1 Role of S1 and sensory feedback in modulating the neural control of corticobulbar tasks: 2.1. 5.2 . 63 Asymmetry of cortical control of voluntary corticobulbar movements: . 64 2.1. 5.3 Neural control of corticospinal tasks: . 65 2.1. 6 Hemispheric specialization in the control of corticospinal motor behaviours: . 67 2.1. 6.1 Summary: . 69 PART B: METHODS TO INVESTIGATE NEURAL CONTROL AND BIOMECHANICAL CHANGES OF MOTOR 2.2. BEHAVIOURS: . 71 Experimental methods to investigate neurophysiology: . 71 2.2.1 Neuroimaging techniques: . 71 2.2.1.1 Transcranial magnetic stimulation (TMS): . 72 2.2.1.2 Behavioural methods to investigate neural control: the dual-task (DT) paradigm: . 77 2.2.2 Theories underlying the effect of DT paradigm on functional infrastructure: . 79 2.2.2.1 Theories underlying the demand in attention during DT paradigm . 80 2.2.2.2 Factors influencing DT paradigm results: . 81 2.2.2.3 Hemispheric specialization versus manual dominance: . 81 Tapping rate: . 83 Divided attentional demands between tasks: . 83 Summary: . 84 Methods to investigate biomechanics of swallowing: . 85 2.2.3 The Role of M1 in pharyngeal swallowing 12 Imaging techniques: . 85 2.2.3.1 Pharyngeal manometry: . 86 2.2.3.2 Electroencephalography (EMG): . 88 2.2.3.3 Summary: . 89 SUMMARY, LIMITATIONS AND FUTURE DIRECTIONS: . 89 2.3. HYPOTHESES . 92 CHAPTER 3: HYPOTHESES . 92 3.1. The effect of trials on the performance of corticospinal and corticobulbar motor 3.1.1 behaviours. (Chapter 5) . 92 The effect of dual-task interference on pharyngeal swallowing. (Chapter 6) . 94 3.1.2 The effect of electrophysiological disruption to corticobulbar pathways on pharyngeal 3.1.3 swallowing. (Chapter 7) . 98 Pharyngeal pressure differences between four conditions of swallowing in healthy 3.1.4 participants. (Chapter 8) . 102 PART III: METHODOLOGY . 105 METHODOLOGY . 106 CHAPTER 4: POWER ANALYSIS: . 106 4.1. PARTICIPANTS . 106 4.2. INSTRUMENTATION . 107 4.3. Finger tapping device: . 107 4.3.1 Surface EMG instrumentation: . 109 4.3.2 Reflexive swallowing instrumentation: . 111 4.3.3 Pharyngeal manometry instrumentation: . 112 4.3. 4 TMS disruption instrumentation . 113 4.3. 5 PROCEDURE: .