Optimising the training-induced changes of inhibitory control

In four studies, this thesis examined the effect of task difficulty and brief training on inhibitory processing in the Go/Nogo task, and transfer to the Stop-signal and Eriksenflanker tasks. It also aimed to clarify how the event-related potential (ERP) of the N2 and P3, as well as the earlier N1 and P2 components, reflect training-related modulations in the underlying neural processes. This was achieved by (1) the use of three task difficulty levels (Low, Medium, High) using incremental reaction time deadlines (RTDs), (2) the effect of these three RTDs on task performance and the early (N1, P2) and inhibition-related (N2, P3) ERP components after brief training, (3) the use of another form of task difficulty – stimulus prepotency – to investigate whether training effects may be enhanced, and (4) the use of single Go/Nogo training (planned inhibition) vs. combined training of Go/Nogo (planned inhibition) and Stop-signal (action cancellation) inhibition. The main results were that the Nogo N2 effect was robustly observed to increase with greater task difficulty (i.e. RTDs), but that it reduced irrespective with time-on-task or training condition. It does not appear to reflect neural processing related to motor or pre-motor inhibition, but may instead represent the detection of conflict between responses. The Nogo P3, however, behaved in a fashion consistent with an inhibitory interpretation, being reduced with greater task difficulty (concurrent with lower levels of task performance), but showing increased amplitudes over frontal brain regions with training and improved task performance – an effect that showed near-transfer to an untrained Stop-signal task. Reduced N1, but enhanced P2 amplitudes, occurred regardless of training condition, indicating a generalised change in sensory processing with repeated task administration. The results cast doubt on the current inhibitory interpretation of the N2. Instead they suggest that, not only does the amplitude of the frontocentral Nogo P3 represent neural processing related to inhibitory control, but that it shows clear training-induced quantitative changes coinciding with performance improvements - furthering both the theoretical and applied knowledge of the key task parameters required to effectively train inhibitory control

Investigating predictive coding in younger and older children using MEG and a multi-feature auditory oddball paradigm

There is mounting evidence for predictive coding theory from computational, neuroimaging, and psychological research. However, there remains a lack of research exploring how predictive brain function develops across childhood. To address this gap, we used pediatric magnetoencephalography to record the evoked magnetic fields of 18 younger children (M = 4.1 years) and 19 older children (M = 6.2 years) as they listened to a 12-min auditory oddball paradigm. For each child, we computed a mismatch field "MMF": an electrophysiological component that is widely interpreted as a neural signature of predictive coding. At the sensor level, the older children showed significantly larger MMF amplitudes relative to the younger children. At the source level, the older children showed a significantly larger MMF amplitude in the right inferior frontal gyrus relative to the younger children, P < 0.05. No differences were found in 2 other key regions (right primary auditory cortex and right superior temporal gyrus) thought to be involved in mismatch generation. These findings support the idea that predictive brain function develops during childhood, with increasing involvement of the frontal cortex in response to prediction errors. These findings contribute to a deeper understanding of the brain function underpinning child cognitive development

The role of configurality in the Thatcher illusion: an ERP study.

The Thatcher illusion (Thompson in Perception, 9, 483-484, 1980) is often explained as resulting from recognising a distortion of configural information when 'Thatcherised' faces are upright but not when inverted. However, recent behavioural studies suggest that there is an absence of perceptual configurality in upright Thatcherised faces (Donnelly et al. in Attention, Perception & Psychophysics, 74, 1475-1487, 2012) and both perceptual and decisional sources of configurality in behavioural tasks with Thatcherised stimuli (Mestry, Menneer et al. in Frontiers in Psychology, 3, 456, 2012). To examine sources linked to the behavioural experience of the illusion, we studied inversion and Thatcherisation of faces (comparing across conditions in which no features, the eyes, the mouth, or both features were Thatcherised) on a set of event-related potential (ERP) components. Effects of inversion were found at the N170, P2 and P3b. Effects of eye condition were restricted to the N170 generated in the right hemisphere. Critically, an interaction of orientation and eye Thatcherisation was found for the P3b amplitude. Results from an individual with acquired prosopagnosia who can discriminate Thatcherised from typical faces but cannot categorise them or perceive the illusion (Mestry, Donnelly et al. in Neuropsychologia, 50, 3410-3418, 2012) only differed from typical participants at the P3b component. Findings suggest the P3b links most directly to the experience of the illusion. Overall, the study showed evidence consistent with both perceptual and decisional sources and the need to consider both in relation to configurality

Training-induced improvements in inhibitor control

Abstract presented at the 17th World Congress of Psychophysiology (IOP2014) of the International Organization of Psychophysiology (IOP) Hiroshima, Japan, September 23rd to 27th, 201

Arousal-state modulation in children with AD/HD

Objective: To investigate the effect of arousal-state modulation, via manipulation of stimulus event-rate,on response inhibition in children with Attention-Deficit/Hyperactivity disorder (AD/HD) using behaviouraland ERP measures.Methods: Eighteen children with AD/HD, aged 7–14 years, and 18 age-and sex-matched controls performeda cued visual Go/Nogo task (70% Go) with stimuli presented at fast, medium and slow event-rates.Task performance and ERPs to Warning, Go and Nogo stimuli, as well as preparation between the S1–S2interval, were examined for group differences.Results: AD/HD subjects displayed poorer response inhibition during the fast condition, accompanied bya reduced Nogo P3. Group differences during the fast rate extended to Warning cues, with the AD/HDgroup showing ERP evidence of atypical orienting/preparation, as indexed by the early and late CNV,and early sensory/attentive processing prior to S2.Conclusions: Although deficient response inhibition has been proposed as the core deficit in AD/HD, theresults of the present study highlight the key role of energetic factors. Furthermore, group differencesfound to cues suggest that this effect extends to the processing of task-irrelevant stimuli.Significance: This was the first ERP Go/Nogo task investigation using three event-rates, and the resultssupport the theory that state factors may contribute to response inhibition deficits in AD/HD

Short-term training in the Go/Nogo task: behavioural and neural changes depend on task demands

Neural activity underlying executive functions is subject to modulation as a result of increasing cognitive demands and practice. In the present study, we examined these modulatory effects by varying task difficulty, as manipulated by reaction time deadline (RTD), on inhibitory control during a single Go/Nogo training session (8 blocks; 70% Go). Sixty adults were randomly assigned to one of three task difficulty conditions: High (n=20), Medium (n=20) and Low (n=20), with RTDs of 300, 500 or 1000ms, respectively. Task performance, Event-related potentials (ERPs) and task-related arousal (indexed by skin conductance level) were examined for training effects. Results indicated that improvements in behavioural Go/Nogo proficiency were optimised during conditions of moderate rather than low or high inhibitory demands. An across-session increase in task-related arousal did not differ between conditions, indicating a generalised increase in the mobilisation of mental resources with time-on-task. In contrast, training-related changes in ERPs were dependent on task demands such that the Low task difficulty condition showed an enhanced centroparietal Nogo P2, while a training-induced augmentation in the Nogo&gt;Go P3 effect was greater in the High than Medium condition. The High condition also showed the greatest reduction in the Nogo N1. Although further research is needed in this area, these findings implicate the potential key role of task difficulty in training inhibitory control and suggest that practice-related changes are reflected by qualitative changes in brain activity