| Summary: | The ability to respond rapidly with spatial precision is required in a number of facets of everyday life, whether catching a falling object, reacting to other drivers on a busy freeway or recovering one’s balance following an unexpected perturbation. The sophisticated central nervous system (CNS) control of these reactions is often overlooked until the speed of such reactions becomes delayed, either due to ageing or brain injury, wherein the individual becomes at risk of injury. Surprisingly, little is known regarding the control of these ‘temporally urgent’ movements. Therefore, the primary objectives of this dissertation were to develop an understanding of the control of these movements by exploring the factors that may be involved in the generation of temporally urgent movements in the healthy CNS, locating the areas within the CNS that such modulation occurs and identifying the relative weighted importance of those modulators based on the initial conditions of stimulus delivery. Specific characteristics of stimulus properties, such as intensity and modality were particularly influential in the latency of motor reactions and physiological electrodermal skin responses fluctuated in accordance with input stimulus parameters. Importantly, outcomes from this dissertation identified that rapid reactions likely utilize a CNS network that includes higher cortical regions such as somatosensory cortex and primary motor cortex, which may be modulated by physiological arousal, rather than the solitary involvement of subcortical structures. The findings from this dissertation have important implications for individuals with disordered speed of processing and indicate the potential modifiability of factors that influence reaction time.
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