- Title
- The neural basis of stop-signal inhibition in healthy individuals and in schizophrenia patients
- Creator
- Hughes, Matthew
- Relation
- University of Newcastle Research Higher Degree Thesis
- Resource Type
- thesis
- Date
- 2010
- Description
- Research Doctorate - Doctor of Philosophy (PhD)
- Description
- The capacity to inhibit planned or on-going action enables individuals to flexibly control behaviour in response to changing task demands or a change in goals. This capacity, termed response inhibition, is a core function of the executive control system and is often studied in laboratory settings using the stop-signal paradigm, which was used for studying response inhibition throughout this thesis. The stop-signal paradigm (Logan & Cowan, 1984) is increasingly being used by research groups to study response inhibition largely due to the indices of behavioural control afforded by stop-signal procedures, notably the speed of response inhibition processes and the capacity to trigger these processes. Lesion, transcranial magnetic stimulation and neuroimaging experiments have linked stopping to activity in the right inferior frontal gyrus (IFG), and some evidence indicates a role for the subthalamic nucleus (STN). These brain areas are thought to form a network which acts by suppressing thalamo-cortical output to motor cortex. Event-related potential studies have linked stopping to amplitude enhancement of an N1-P3 complex during successful inhibition trials compared to unsuccessful inhibition trials. The primary aim of this thesis was to investigate the spatio-temporal dynamics of stop-signal inhibition in healthy individuals using electrophysiological and neuroimaging methods, and secondly, to investigate the neural basis of impaired stopping in patients with a diagnosis of schizophrenia – the first of its kind using the stop-signal paradigm. Several previous behavioural studies have reported slowed stop-signal response inhibition processes in patients with schizophrenia, but an impaired capacity to trigger response inhibition processes has also been reported. In each of the three neuroimaging studies detailed herein, stopping was related to activation in right IFG and STN, and in one study a model for the difficulty of inhibition was proposed, which predicted activity in this network. Consistent with previous reports, stopping processes in patients with schizophrenia were slower compared to controls, and right IFG and STN were uniquely underactivated in the patient group. Additionally, one study revealed a link between response inhibition speed and both Stop-P3 amplitude, and the latency difference between N1 and P3 potential peaks elicited on stop-signal trials.
- Subject
- stop-signal paradigm; response inhibition; fMRI; ERPs; schizophrenia
- Identifier
- uon:6881
- Identifier
- http://hdl.handle.net/1959.13/805511
- Rights
- Copyright 2010 Matthew Hughes
- Language
- eng
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